Internet-Draft	SATP Core	September 2025
Hargreaves, et al.	Expires 21 March 2026	[Page]

Workgroup:: Secure Asset Transfer Protocol
Internet-Draft:: draft-ietf-satp-core-latest
Published:: 17 September 2025
Intended Status:: Informational
Expires:: 21 March 2026
Authors:: M. Hargreaves

Quant Network

T. Hardjono

MIT

R. Belchior

INESC-ID, Técnico Lisboa, Blockdaemon

V. Ramakrishna

IBM

A. Chiriac

Quant Network

Secure Asset Transfer Protocol (SATP) Core

Abstract

This memo describes the Secure Asset Transfer (SAT) Protocol for digital assets. SAT is a protocol operating between two gateways that conducts the transfer of a digital asset from one gateway to another, each representing their corresponding digital asset networks. The protocol establishes a secure channel between the endpoints and implements a 2-phase commit (2PC) to ensure the properties of transfer atomicity, consistency, isolation and durability.¶

About This Document

This note is to be removed before publishing as an RFC.¶

The latest revision of this draft can be found at https://ietf-satp.github.io/draft-ietf-satp-core/draft-ietf-satp-core.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-satp-core/.¶

Discussion of this document takes place on the Secure Asset Transfer Protocol Working Group mailing list (mailto:sat@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/sat/. Subscribe at https://www.ietf.org/mailman/listinfo/sat/.¶

Source for this draft and an issue tracker can be found at https://github.com/ietf-satp/draft-ietf-satp-core.¶

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶

This Internet-Draft will expire on 21 March 2026.¶

Copyright Notice

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

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1. Introduction

This memo proposes a secure asset transfer protocol (SATP) that is intended to be deployed between two gateway endpoints to transfer a digital asset from an origin asset network to a destination asset network. Readers are directed first to [ARCH] for a description of the architecture underlying the current protocol.¶

Both the origin and destination asset networks are assumed to be opaque in the sense that the interior construct of a given network is not read/write accessible to unauthorized entities.¶

The protocol utilizes the asset burn-and-mint paradigm whereby the asset to be transferred is permanently disabled or destroyed (burned) at the origin asset network and is re-generated (minted) at the destination asset network. This is achieved through the coordinated actions of the peer gateways handling the unidirectional transfer at the respective networks.¶

A gateway is assumed to be trusted to perform the tasks involved in the asset transfer.¶

The overall aim of the protocol is to ensure that the state of assets in the origin and destination networks remain consistent, and that asset movements into (out of) networks via gateways can be accounted for.¶

There are several desirable technical properties of the protocol. The protocol must ensure that the properties of atomicity, consistency, isolation, and durability (ACID) are satisfied.¶

The requirement of consistency implies that the asset transfer protocol always leaves both asset networks in a consistent state (that the asset is located in one system/network only at any time).¶

Atomicity means that the protocol must guarantee that either the transfer commits (completes) or entirely fails, where failure is taken to mean there is no change to the state of the asset in the origin (sender) asset network.¶

The property of isolation means that while a transfer is occurring to a digital asset from an origin network, no other state changes can occur to the asset.¶

The property of durability means that once the transfer has been committed by both gateways, that this commitment must hold regardless of subsequent unavailability (e.g. crash) of the gateways implementing the SAT protocol.¶

All messages exchanged between gateways are assumed to run over TLS1.2 or higher, and the endpoints at the respective gateways are associated with a certificate indicating the legal owner (or operator) of the gateway. HTTPS/S must be used intead of plain HTTP.¶

2. Conventions used in this document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [REQ-LEVEL].¶

In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying significance described in RFC 2119.¶

3. Terminology

The following are some terminology used in the current document, some borrowed from [NIST]:¶

Digital asset: digital representation of a value or of a right that is able to be transferred and stored electronically using distributed ledger technology or similar technology [MICA].¶
Asset network: A monolithic system or a set of distributed systems that manage digital assets.¶
Client application: This is the application employed by a user to interact with a gateway.¶
Gateway: The computer system functionally capable of acting as a gateway in an asset transfer.¶
Sender gateway: The gateway that initiates a unidirectional asset transfer.¶
Recipient gateway: The gateway that is the recipient side of a unidirectional asset transfer.¶
Claim: An assertion made by an Entity [JWT].¶
Claim Type: Syntax used for representing a Claim Value [JWT].¶
Gateway Claim: An assertion made by a Gateway regarding the status or condition of resources (e.g. assets, public keys, etc.) accessible to that gateway (e.g. within its asset network or system).¶

In the remainder of this document, for brevity of description the term “asset network” will often be shorted to "network".¶

4. The Secure Asset Transfer Protocol

4.1. Overview

The Secure Asset Transfer Protocol (SATP) is a gateway-to-gateway protocol used by a sender gateway with a recipient gateway to perform a unidirectional transfer of a digital asset.¶

The protocol defines a number of API endpoints, resources and identifier definitions, and message flows corresponding to the asset transfer between the two gateways.¶

The current document pertains to the interaction between gateways through API2 [ARCH].¶

+----------+ +----------+ | Client | | Off-net | ------ | (App) | | Resource | | +----------+ +----------+ | | | API3 | | | +----------+ | | ^ | V | | +---------+ | V | API1 | | +-----+ +---------+----+ +----+---------+ +-----+ | | | | | | | | | | | Net.| | Gateway |API2| |API2| Gateway | | Net.| | NW1 |---| G1 | |<------>| | G2 |---| NW2 | | | | | | | | | | | +-----+ +---------+----+ +----+---------+ +-----+ Figure 1¶

4.2. SAT Model

The model for SATP is shown in Figure 1 [ARCH]. The Client (application) interacts with its local gateway (G1) over an interface (API1) in order to provide instructions to the gateway with regards to actions to assets and related resources located in the local system or network (NW1).¶

Gateways interact with each other over a gateway interface (API2). A given gateway may be required to access resources that are not located in network NW1 or network NW2. Access to these types of resources are performed over an off-network interface (API3).¶

4.3. Stages of the Protocol

The SAT protocol defines three (3) stages for a unidirectional asset transfer:¶

Transfer Initiation stage (Stage-1): These flows deal with commencing a transfer from one gateway to another. In this stage the sender gateway delivers a proposal containing the parameters agreed upon in Stage-0.¶
Lock-Assertion stage (Stage-2): These flows deal with the conveyance of signed assertions from the sender gateway to the receiver gateway regarding the locked status of an asset at the origin network.¶
Commitment Preparation and Finalization stage (Stage-3): These flows deal with the asset transfer and commitment establishment between two gateways.¶

In order to clarify discussion, the interactions between the peer gateways prior to the transfer initiation stage is referred to as the setup stage (Stage-0), which is outside the scope of the current specification.¶

The Stage-1, Stage-2 and Stage-3 flows will be discussed below.¶

4.4. Gateway Cryptographic Keys

SATP recognizes the following cryptographic keys which are intended for distinct purposes within the different stages of the protocol.¶

Gateway signature public key-pair: This is the key-pair utilized by a gateway to digitally sign assertions and receipts.¶
Gateway secure channel establishment public key-pair: This is the key-pair utilized by peer gateways to establish a secure channel (e.g. TLS) for a transfer session.¶
Gateway identity public key pair: This is the key-pair that uniquely identifies a gateway.¶
Gateway-owner identity public key pair: This is the key-pair that identifies the owner (e.g. legal entity) who is the legal owner of a gateway.¶

This document assumes that the relevant X.509 certificates are associated with these keys. However, the mechanisms to obtain X.509 certificates is outside the scope of this specification.¶

5. SATP Message Format, identifiers and Descriptors

5.1. Overview

This section describes the SATP message-types, the format of the messages exchanged between two gateways, the format for resource descriptors and other related parameters.¶

The mandatory fields are determined by the message type exchanged between the two gateways (see Section 7).¶

5.2. SATP Message Digital Signatures

All SATP messages exchanged between gateways must be signed, using JSON Web Signatures mechanism (RFC7515).¶

All gateways implementing SATP must support the "ES256" from the IANA "JSON Web Signature and Encryption Algorithms" registry [JWA], which is the ECDSA signature algorithm with the P-256 curve and the SHA-256 hash function.¶

Additional signature algorithms and keying parameters may be negotiated by peer gateways. However, the negotiation protocol is outside the scope of this specification.¶

5.3. SATP Message Format and Payloads

SATP messages are exchanged between peer gateways, where depending on the message type one gateway may act as a client of the other (and vice versa).¶

All SATP messages exchanged between gateways are in JSON format [JSON]. Unless otherwise noted, all values are encoded as JSON Strings. Values not representable as JSON strings (such as binary data), unless otherwise noted, will be encoded as base64 [BASE64].¶

5.3.1. Protocol version

This refers to SATP protocol Version, encoded as "major.minor" (separated by a period symbol).¶

The current version is "1.0" defined in this specification. Implementations not understanding a future option value should return an appropriate error response and cease the negotiation.¶

5.3.2. Message Type

This refers to the type of request or response to be conveyed in the message.¶

The possible values are defined in the IANA SATP Message Types Registry Section 14.3, Paragraph 1:¶

transfer-proposal-msg: This is the transfer proposal message from the sender gateway carrying the set of proposed parameters for the transfer.¶
proposal-receipt-msg: This is the signed receipt message indicating acceptance of the proposal by the receiver gateway.¶
reject-msg: This is a reject message from a gateway to the peer gateway in the session, indication the reason and the resulting action.¶
transfer-commence-msg: Request to begin the commencement of the asset transfer.¶
ack-commence-msg: Response to accept the commencement of the asset transfer.¶
lock-assert-msg: Sender gateway has performed the lock of the asset in the origin network.¶
assertion-receipt-msg: Receiver gateway acknowledges receiving the signed lock-assert-msg.¶
commit-prepare-msg: Sender gateway requests the start of the commitment stage.¶
ack-prepare-msg: Receiver gateway acknowledges receiving the previous commit-prepare-msg and agrees to start the commitment stage.¶
commit-final-msg: Sender gateway has performed the extinguishment (burn) of the asset in the origin network.¶
ack-commit-final-msg: Receiver gateway acknowledges receiving the signed commit-final-msg and has performed the asset creation and assignment in the destination network.¶
commit-transfer-complete-msg: Sender gateway indicates closure of the current transfer session.¶
error-msg: This message is used to indicate that an error has occured at the SATP layer. It can be transmitted by either gateways.¶
session-abort-msg: This message is used by a gateway to abort the current session.¶

5.3.3. Digital Asset Identifier

This is the identifier that uniquely identifies the digital asset in the origin network which is to be transferred to the destination network.¶

The digital asset identifier is a value that is derived by the applications utilized by the originator and the beneficiary prior to starting the asset transfer.¶

The mechanism used to derive the digital asset identifier is outside the scope of the current document.¶

5.3.4. Asset Profile Identifier

This is the unique identifier of the asset schema or asset profile which defines the class or type of asset in question. The asset profile is relevant from a regulatory perspective.¶

In some cases the profile identifier may be needed by the receiver gateway at the destination network in order to evaluate whether the asset is permitted to enter the destination network.¶

The formal specification of asset profiles and their identification is outside the scope of this document.¶

5.3.5. Transfer-Context ID:

This is the unique immutable identifier representing the application layer context of a single unidirectional transfer. The method to generate the transfer-context ID is outside the scope of the current document.¶

The transfer-context may be a complex data structure that contains all information related to a SATP execution instance. Examples of information contained in a transfer-context may include identifiers of sessions, gateways, networks or assets related to the specific SATP execution instance.¶

The sender gateway provides this value to the receiver gateway. Mechanisms to establish this value between the sender and receiver gateways may be utilized prior commencing the SAT protocol. Specifically, these are expected to be negated prior to the establishment of the SAT protocol and are out of scope for this document.¶

5.3.6. Session ID:

This is the unique identifier representing a session between two gateways handling a single unidirectional transfer. This may be derived from the Transfer-Context ID at the application level. There may be several session IDs related to a SATP execution instance. Only one Session ID may be active for a given SATP execution instance. Session IDs may be stored in the transfer-context for audit trail purposes.¶

The sender gateway provides this value to the receiver gateway.¶

5.3.7. Gateway Credential Type

This is the type of authentication mechanism supported by the gateway (e.g. SAML, OAuth, X.509)¶

5.3.8. Gateway Credential

This payload is the actual credential of the gateway (token, certificate, string, etc.) with a string based encoding based on the corresponding Gateway Credential Type.¶

5.3.9. Gateway Identifier

This is the unique identifier of the gateway service. The gateway identifier MUST be uniquely bound to its SAT endpoint (e.g. via X.509 certificates).¶

This gateway identifier is distinct from the gateway operator business identifier (e.g., legal entity identifier (LEI) number). A gateway operator may operate multiple gateways. Each of the gateways within an asset network MUST be identified by a unique gateway identifier.¶

The mechanisms to establish the gateway identifier or the operator identifier is outside the scope of this specification.¶

5.3.10. Payload Hash

This is the hash of the current message payload.¶

5.3.11. Signature Algorithms Supported

This is a JSON list of digital signature algorithms supported by a gateway. Each entry in the list should either an Algorithm Name value registered in the IANA "JSON Web Signature and Encryption Algorithms" registry established by [JWA] or be a value that contains a Collision-Resistant Name.¶

All implementations MUST support a common default of "ES256", which is the ECDSA signature algorithm with the P-256 curve and the SHA-256 hash function.¶

5.3.12. Lock assertion Claim Format

This is the format of the claim regarding the state of the asset in the origin network.¶

The claim is network-dependent in the sense that different asset networks or systems may utilize a different asset locking (disablement) mechanism.¶

The sender gateway provides the choice of the format to the receiver gateway. Mechanisms to establish this value between the sender and receiver gateways may be utilized prior commencing the SAT protocol. Specifically, these are expected to be negated prior to the establishment of the SAT protocol and are out of scope for this document.¶

5.3.13. Lock assertion Claim

The actual encoded JSON string representation of the claim using the format as specified by the corresponding Lock assertion Claim Format.¶

5.4. Negotiation of Security Protocols and Parameters

The peer gateways in SATP must establish a TLS session between them prior to starting the transfer initiation stage (Stage-0). The TLS session continues until the transfer is completed at the end of the commitment establishment stage (Stage-3).¶

In the following steps, the sender gateway is referred to as the client while the received gateway as the server.¶

5.4.1. TLS Secure Channel Establishment

TLS 1.2 or higher MUST be implemented to protect gateway communications. TLS 1.3 or higher SHOULD be used where both gateways support TLS 1.3 or higher.¶

5.4.2. Client offers supported credential schemes

Prior to commecing the TLS 1.3 secure channel establishment, the client (sender gateway) may choose to send a JSON block containing information regarding the client's supported credential schemes.¶

The purpose of the credential scheme is to enable the client to deliver to server the relevant identity information in that scheme regarding the gateway-identity and gateway-owner identity information.¶

5.4.3. Server selects supported credential scheme

If the client (sender gateway) transmits a list of supported credential schemes, the server (recipient gateway) selects one acceptable credential scheme from the offered schemes.¶

If no acceptable credential scheme was offered, a "unsupported gatewayCredentialProfile" (err_1.1.34) reject message is returned by the server Section 8.5, Paragraph 1.¶

5.4.4. Client asserts or proves identity

The details of the assertion/verification step are specific to the chosen credential scheme and are outside the scope of this document.¶

5.4.5. Messages can now be exchanged

Handshaking is complete at this point, and the client and server can begin exchanging SATP messages.¶

6. Overview of Message Flows

The SATP message flows are logically divided into three (3) stages [ARCH], with the preparatory stage denoted as Stage-0. How the tasks are achieved in Stage-0 is out of the scope of this specification.¶

The Stage-1 flows pertains to the initialization of the transfer between the two gateways.¶

After both gateways agree to commence the transfer at the start of Stage-2, the sender gateway G1 must deliver a signed assertion that it has correctly performed the relevant action on the asset within the origin network (NW1). Examples of actions by G1 include performing a temporary lock on the asset, or performing a permanent disablement (burn) of the asset in NW1.¶

If that signed assertion is accepted by gateway G2, it must in return transmit a signed receipt to gateway G1 that it has correctly performed the relevant corresponding action on destination network (NW2). Examples of actions by G2 include creating (minting) a temporary asset under its control in NW2.¶

The Stage-3 flows commit gateways G1 and G2 to the burn and mint in Stage-2. The sender gateway G1 must make the lock on the asset in the origin network NW1 to be permanent (burn). The receiver gateway G2 must assign (mint) the asset in the destination network NW2 to the correct beneficiary.¶

The reader is directed to [ARCH] for further discussion of this model.¶

App1 NW1 G1 G2 NW2 App2 ..|.....|............|......................|............|.....|.. | | | Stage 1 | | | | | | | | | | | (1.1)|--Transf. Proposal -->| | | | | | | | | | | |<--Proposal Receipt---|(1.2) | | | | | | | | | | (1.3)|---Transf. Commence-->| | | | | | | | | | | |<----ACK Commence-----|(1.4) | | | | | | | | ..|.....|............|......................|............|.....|.. | | | Stage 2 | | | | | | | | | | |<---Lock----|(2.1) | | | | | | | | | | | (2.2)|----Lock-Assertion--->| | | | | | | | | | | | (2.3)|--Record--->| | | | | | | | | | |<--Assertion Receipt--|(2.4) | | | | | | | | ..|.....|............|......................|............|.....|.. | | | Stage 3 | | | | | | | | | | | (3.1)|----Commit Prepare--->| | | | | | | | | | | | (3.2)|----Mint--->| | | | | | | | | | |<----Commit Ready-----|(3.3) | | | | | | | | | |<---Burn----|(3.4) | | | | | | | | | | | (3.5)|-----Commit Final---->| | | | | | | | | | | | (3.6)|---Assign-->| | | | | | | | | | |<-----ACK Final-------|(3.7) | | | | | | | | | | | | | | | |<--Record---|(3.8) | | | | | | | | | | | (3.9)|--Transfer Complete-->| | | ..|.....|............|......................|............|.....|.. Figure 2¶

7. Identity and Asset Verification Stage (Stage 0)

Prior to commencing the asset transfer from the sender gateway (client) to the recipient gateway (server), both gateways must perform a number of verification steps. The types of information required by both the sender and recipient are use-case dependent and asset-type dependent.¶

The verifications include, but not limited to, the following:¶

Verification of the gateway signature public key: The sender gateway and receiver gateway must validate their respective signature public keys that will later be used to sign assertions and claims. This may include validating the X509 certificates of these keys.¶
Gateway owner verification: This is the verification of the identity (e.g. LEI) of the owners of the gateways.¶
Gateway device and state validation: This is the device attestation evidence [RFC9334] that a gateway must collect and convey to each other, where a verifier is assumed to be available to decode, parse and appraise the evidence.¶
Originator and beneficiary identity verification: This is the identity and public-key of the entity (originator) in the origin network seeking to transfer the asset to another entity (beneficiary) in the destination network.¶

These are considered out of scope in the current specification, and are assumed to have been successfully completed prior to the commencement of the transfer initiation flow. The reader is directed to [ARCH] for further discussion regarding Stage-0.¶

8. Transfer Initiation Stage (Stage 1)

This section describes the transfer initiation stage, where the sender gateway and the receiver gateway prepare for the start of the asset transfer.¶

The sender gateway proposes the set of transfer parameters and asset-related artifacts for the transfer to the receiver gateway. These are contained in the Transfer Initiation Claim.¶

If the receiver gateway accepts the proposal, it returns a signed receipt message for the proposal indicating it agrees to proceed to the next stage. If the receiver gateway rejects any parameters or artifacts in the proposal, it can provide a counteroffer to the sender gateway by responding with a proposal reject message carrying alternative parameters.¶

Gateways MUST support the use of the HTTP GET and POST methods defined in RFC 2616 [RFC2616] for the endpoint.¶

Clients (sender gateway) MAY use the HTTP GET or POST methods to send messages in this stage to the server (recipient gateway). If using the HTTP GET method, the request parameters may be serialized using URI Query String Serialization.¶

(NOTE: Flows occur over TLS. Nonces are not shown).¶

8.1. Transfer Initialization Claim

This is set of artifacts pertaining to the asset that must be agreed upon between the client (sender gateway) and the server (recipient gateway).¶

The format of the identity fields in this message, unless otherwise stated, is a JSON string that contains a [X.500] Distinguished Name.¶

The Transfer Initialization Claim consists of the following:¶

digitalAssetId REQUIRED: This is the globally unique identifier for the digital asset located in the origin network. The format of this JSON string is dependent on the assetProfileId that indicates the asset network in which the asset is originating.¶
assetProfileId REQUIRED: This is the globally unique identifier for the asset-profile definition (document) on which the digital asset was issued.¶
verifiedOriginatorEntityId REQUIRED: This is the identity data of the originator entity (person or organization) in the origin network. This information must be verified by the sender gateway.¶
verifiedBeneficiaryEntityId REQUIRED: This is the identity data of the beneficiary entity (person or organization) in the destination network. This information must be verified by the receiver gateway.¶
originatorPubkey REQUIRED. This is the public key of the asset owner (originator) in the origin network or system.¶
beneficiaryPubkey REQUIRED. This is the public key of the beneficiary in the destination network.¶
senderGatewaySignaturePublicKey REQUIRED. This is the public key of the key-pair used by the sender gateway to sign assertions and receipts.¶
receiverGatewaySignaturePublicKey REQUIRED. This is the public key of the key-pair used by the recevier gateway to sign assertions and receipts.¶
senderGatewayId REQUIRED. This is the identifier of the sender gateway.¶
recipientGatewayId REQUIRED. This is the identifier of the receiver gateway.¶
senderGatewayNetworkId REQUIRED. This is the identifier of the origin network or system behind the client.¶
recipientGatewayNetworkId REQUIRED. This is the identifier of the destination network or system behind the server.¶
senderGatewayDeviceIdentityPubkey OPTIONAL. The device public key of the sender gateway (client).¶
receiverGatewayDeviceIdentityPubkey OPTIONAL. The device public key of the receiver gateway¶
senderGatewayOwnerId OPTIONAL: This is the identity information of the owner or operator of the sender gateway.¶
receiverGatewayOwnerId OPTIONAL: This is the identity information of the owner or operator of the recipient gateway.¶

Here is an example representation in JSON format:¶

{ "digitalAssetId": "2c949e3c-5edb-4a2c-9ef4-20de64b9960d",\ "assetProfileId": "38561",\ "verifiedOriginatorEntityId": "CN=Alice, OU=Example Org Unit, O=Example, L=New York, C=US",\ "verifiedBeneficiaryEntityId": "CN=Bob, OU=Case Org Unit, O=Case, L=San Francisco, C=US",\ "originatorPubkey": "0304b9f34d3898b27f85b3d88fa069a879abe14db5060dde466dd1e4a31ff75e44",\ "beneficiaryPubkey": "02a7bc058e1c6f3a79601d046069c9b6d0cb8ea5afc99e6074a5997284756fc9ae",\ "senderGatewaySignaturePublicKey": "02a7bc058e1c6f3a79601d046069c9b6d0cb8ea5afc99e6074a5997284756fc9ae",\ "receiverGatewaySignaturePublicKey": "0243b12ada6515ada3bf99a7da32e84f00383b5765fd7701528e660449ba5ef260",\ "senderGatewayId": "GW1",\ "recipientGatewayId": "GW2",\ "senderGatewayNetworkId": "1",\ "recipientGatewayNetworkId": "43114",\ "senderGatewayDeviceIdentityPubkey": "0245785e34b4a7b457dd4683a297ea3d78bab35f8b2583df55d9df8c69604d0e73",\ "receiverGatewayDeviceIdentityPubkey": "03763f0bc48ff154cff45ea533a9d8a94349d65a45573e4de6ad6495b6e834312b",\ "senderGatewayOwnerId": "CN=GatewayOps, OU=GatewayOps Systems, O=GatewayOps LTD, L=Austin, C=US",\ "receiverGatewayOwnerId": "CN=BridgeSolutions, OU=BridgeSolutions Engineering, O=BridgeSolutions LTD, L=Austin, C=US"\ }¶

8.2. Conveyance of Gateway and Network Capabilities

This is the set of parameters pertaining to the origin network and the destination network, and the technical capabilities supported by the peer gateways. Some of these parameters must be previously agreed to during the Stage-0 negotiations, which is outside the scope of this document.¶

Some network-specific parameters regarding the origin network may be relevant for a receiver gateway to evaluate its ability to process the proposed transfer.¶

For example, the average duration of time of a lock to be held by a sender gateway may inform the receiver gateway about delay expectations.¶

The gateway and network capabilities list is as follows:¶

gatewayDefaultSignatureAlgorithm REQUIRED: The default digital signature algorithm (algorithm-id) from the IANA "JSON Web Signature and Encryption Algorithms" registry used by a gateway to sign claims.¶
gatewaySupportedSignatureAlgorithms OPTIONAL: The list of other digital signature algorithms (algorithm-id) from the IANA "JSON Web Signature and Encryption Algorithms" registry supported by a gateway to sign claims¶
networkLockType REQUIRED: The default locking mechanism used by a network. The values allowed are "TIME_LOCK", "HASH_LOCK", "HASH_TIME_LOCK". Future updates to this specification may define new values and implementations not supporting a value or not understanding a value for this field must return an appropriate error and cease the negotiation.¶
networkLockExpirationTime REQUIRED: The duration of time (in integer seconds) for a lock to expire in the network.¶
gatewayCredentialProfile REQUIRED: Specify type of auth (e.g., SAML, OAuth, X.509).¶
gatewayLoggingProfile REQUIRED: contains the profile of the logging procedure. "LOCAL_STORE" is the only defined allowed value at this time, but others may be defined in future updates to this specification. Implementations not understanding a future option value should return an appropriate error response and cease the negotiation.¶
gatewayAccessControlProfile REQUIRED: the profile regarding the confidentiality of the log entries being stored. "RBAC" is the only defined allowed value at this time, but others may be defined in future updates to this specification. Implementations not understanding a future option value should return an appropriate error response and cease the negotiation. Default is only the gateway that created the logs can access them.¶

Here is an example representation in JSON format:¶

json { "gatewayDefaultSignatureAlgorithm": "ES256", "gatewaySupportedSignatureAlgorithms": ["ES256", "RSA"], "networkLockType": "HASH_TIME_LOCK", "networkLockExpirationTime": 120, "gatewayCredentialProfile": "OAUTH", "gatewayLoggingProfile": "LOCAL_STORE", "gatewayAccessControlProfile": "RBAC" }¶

8.3. Transfer Proposal Message

The purpose of this message is for the sender gateway as the client to initiate an asset transfer session with the receiver gateway as the server.¶

The client transmits a proposal message that carries the claim related to the asset to be transferred. This message must be signed by the client.¶

This message is sent from the client to the Transfer Initialization Endpoint at the server.¶

The parameters of this message consist of the following:¶

version REQUIRED: SAT protocol Version (see Section 5.3.1, Paragraph 1) as a string "major.minor".¶
messageType REQUIRED: urn:ietf:satp:msgtype:transfer-proposal-msg.¶
sessionId REQUIRED: A unique identifier chosen by the client to identify the current session.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
transferInitClaimFormat REQUIRED: The format of the transfer initialization claim.¶
transferInitClaim REQUIRED: The set of artifacts and parameters as the basis for the current transfer.¶
gatewayAndNetworkCapabilities REQUIRED: The set of origin gateway and network parameters reported by the client to the server.¶

Here is an example of the message request body:¶

json { "version": "1.0", "messageType": "urn:ietf:satp:msgtype:transfer-proposal-msg", "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1", "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0", "transferInitClaimFormat": "TRANSFER_INIT_CLAIM_FORMAT_1", "transferInitClaim": { "digitalAssetId": "2c949e3c-5edb-4a2c-9ef4-20de64b9960d", "assetProfileId": "38561", "verifiedOriginatorEntityId": "CN=Alice, OU=Example Org Unit, O=Example, L=New York, C=US", "verifiedBeneficiaryEntityId": "CN=Bob, OU=Case Org Unit, O=Case, L=San Francisco, C=US", "originatorPubkey": "0304b9f34d3898b27f85b3d88fa069a879abe14db5060dde466dd1e4a31ff75e44", "beneficiaryPubkey": "02a7bc058e1c6f3a79601d046069c9b6d0cb8ea5afc99e6074a5997284756fc9ae", "senderGatewaySignaturePublicKey": "02a7bc058e1c6f3a79601d046069c9b6d0cb8ea5afc99e6074a5997284756fc9ae", "receiverGatewaySignaturePublicKey": "0243b12ada6515ada3bf99a7da32e84f00383b5765fd7701528e660449ba5ef260", "senderGatewayId": "GW1", "recipientGatewayId": "GW2", "senderGatewayNetworkId": "1", "recipientGatewayNetworkId": "43114", "senderGatewayDeviceIdentityPubkey": "0245785e34b4a7b457dd4683a297ea3d78bab35f8b2583df55d9df8c69604d0e73", "receiverGatewayDeviceIdentityPubkey": "03763f0bc48ff154cff45ea533a9d8a94349d65a45573e4de6ad6495b6e834312b", "senderGatewayOwnerId": "CN=GatewayOps, OU=GatewayOps Systems, O=GatewayOps LTD, L=Austin, C=US", "receiverGatewayOwnerId": "CN=BridgeSolutions, OU=BridgeSolutions Engineering, O=BridgeSolutions LTD, L=Austin, C=US" }, "gatewayAndNetworkCapabilities": { "gatewayDefaultSignatureAlgorithm": "ES256", "gatewaySupportedSignatureAlgorithms": ["ES256", "RSA"], "networkLockType": "HASH_TIME_LOCK", "networkLockExpirationTime": 120, "gatewayCredentialProfile": "OAUTH", "gatewayLoggingProfile": "LOCAL_STORE", "gatewayAccessControlProfile": "RBAC" } }¶

8.4. Transfer Proposal Receipt Message

The purpose of this message is for the server to indicate explicit acceptance of the parameters in the claim part of the transfer proposal message.¶

The message must be signed by the server.¶

The message is sent from the server to the Transfer Proposal Endpoint at the client.¶

The parameters of this message consist of the following:¶

version REQUIRED: SAT protocol Version see {satp-protocol-version}} as a string "major.minor".¶
messageType REQUIRED: urn:ietf:satp:msgtype:proposal-receipt-msg.¶
sessionId REQUIRED: A unique identifier chosen by the client to identify the current session.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashTransferInitClaim REQUIRED: Hash of the Transfer Initialization Claim received in the Transfer Proposal Message.¶
timestamp REQUIRED: timestamp referring to when the Initialization Request Message was received.¶

Here is an example of the message request body:¶

{\ "version": "1.0",\ "messageType": "urn:ietf:satp:msgtype:proposal-receipt-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashTransferInitClaim": "154dfaf0406038641e7e59509febf41d9d5d80f367db96198690151f4758ca6e",\ "timestamp": "2024-10-03T12:02+00Z",\ }\¶

8.5. Reject Message

The purpose of this message is for the server to indicate explicit rejection of the the previous message receuved from the client. This message can be sent at any time in the session. The server MUST include an error code (see Section 15, Paragraph 1) in this message. A reject message is taken to mean an immediate termination of the session.¶

The message must be signed by the server.¶

The parameters of this message consist of the following:¶

version REQUIRED: SAT protocol Version see {satp-protocol-version}} as a string "major.minor".¶
messageType REQUIRED: urn:ietf:satp:msgtype:reject-msg¶
sessionId REQUIRED: A unique identifier chosen by the client to identify the current session.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED: The hash of the last message that caused the rejection to occur.¶
reasonCode REQUIRED: the error code (see Section 15, Paragraph 1) causing the rejection.¶
timestamp REQUIRED: timestamp of this message.¶

Here is an example of the message request body:¶

{\ "version": "1.0",\ "messageType": "urn:ietf:satp:msgtype:reject-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "154dfaf0406038641e7e59509febf41d9d5d80f367db96198690151f4758ca6e",\ "reasonCode": "err_2.1",\ "timestamp": "2024-10-03T12:02+00Z",\ }\¶

8.6. Transfer Commence Message

The purpose of this message is for the client to signal to the server that the client is ready to start the transfer of the digital asset. This message must be signed by the client.¶

This message is sent by the client as a response to the Transfer Proposal Receipt Message previously received from the server.¶

This message is sent by the client to the Transfer Commence Endpoint at the server.¶

The parameters of this message consist of the following:¶

messageType REQUIRED. MUST be the value urn:ietf:satp:msgtype:transfer-commence-msg.¶
sessionId REQUIRED: A unique identifier chosen earlier by the client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashTransferInitClaim REQUIRED: Hash of the Transfer Initialization Claim in the Transfer Proposal message.¶
hashPrevMessage REQUIRED. The hash of the last message, in this case the Transfer Proposal Receipt message.¶

For example, the client makes the following HTTP request using TLS:¶

{\ "messageType": "urn:ietf:satp:msgtype:transfer-commence-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashTransferInitClaim": "154dfaf0406038641e7e59509febf41d9d5d80f367db96198690151f4758ca6e",\ "hashPrevMessage": "0b0aecc2680e0d8a86bece6b54c454fba67068799484f477cdf2f87e6541db66",\ }\¶

8.7. Commence Response Message (ACK-Commence)

The purpose of this message is for the server to indicate agreement to proceed with the asset transfer, based on the artifacts found in the previous Transfer Proposal Message.¶

This message is sent by the server to the Transfer Commence Endpoint at the client.¶

The message must be signed by the server.¶

The parameters of this message consist of the following: The parameters of this message consist of the following:¶

messageType REQUIRED urn:ietf:satp:msgtype:ack-commence-msg¶
sessionId REQUIRED: A unique identifier chosen earlier by the client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED.The hash of the last message, in this case the the Transfer Commence Message.¶

An example of a success response could be as follows:¶

{\ "messageType": "urn:ietf:satp:msgtype:ack-commence-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "dd5a61a26fc8f5d72e5ca6052c2a1fca1613115e5582d9417d336375c196db89",\ }\¶

9. Lock Assertion Stage (Stage 2)

The messages in this stage pertain to the sender gateway providing the recipient gateway with a signed assertion that the asset in the origin network has been locked or disabled and under the control of the sender gateway.¶

In the following steps, the sender gateway takes the role of the client while the recipient gateway takes the role of the server.¶

The flow follows a request-response model. The client makes a request (POST) to the Lock-Assertion Endpoint at the server.¶

Gateways MUST support the use of the HTTP GET and POST methods defined in RFC 2616 [RFC2616] for the endpoint.¶

Clients MAY use the HTTP GET or POST methods to send messages in this stage to the server. If using the HTTP GET method, the request parameters may be serialized using URI Query String Serialization.¶

(NOTE: Flows occur over TLS. Nonces are not shown).¶

9.1. Lock Assertion Message

The purpose of this message is for the client (sender gateway) to convey a signed claim to the server (receiver gateway) declaring that the asset in question has been locked or escrowed by the client in the origin network (e.g. to prevent double-spending).¶

The format of the claim is dependent on the network or system of the client and is outside the scope of this specification.¶

This message is sent from the client to the Lock Assertion Endpoint at the server.¶

The server must validate the claim (payload) in this message prior to the next step.¶

The message must be signed by the client.¶

The parameters of this message consist of the following:¶

messageType REQUIRED urn:ietf:satp:msgtype:lock-assert-msg.¶
sessionId REQUIRED: A unique identifier chosen earlier by the client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
lockAssertionClaimFormat REQUIRED. The format of the claim.¶
lockAssertionClaim REQUIRED. The lock assertion claim or statement by the client.¶
lockAssertionExpiration REQUIRED. The expiration date and time [DATETIME] of the lock or escrow upon the asset.¶
hashPrevMessage REQUIRED. The hash of the previous message.¶

Example:¶

{\ "messageType": "urn:ietf:satp:msgtype:lock-assert-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "lockAssertionClaimFormat": "LOCK_ASSERTION_CLAIM_FORMAT_1",\ "lockAssertionClaim": {},\ "lockAssetionExpiration": "2024-12-23T23:59:59.999Z",\ "hashPrevMessage": "b2c3e916703c4ee4494f45bcf52414a2c3edfe53643510ff158ff4a406678346",\ }\¶

9.2. Lock Assertion Receipt Message

The purpose of this message is for the server (receiver gateway) to indicate acceptance of the claim in the lock-assertion message delivered by the client (sender gateway) in the previous message.¶

This message is sent from the server to the Assertion Receipt Endpoint at the client.¶

The message must be signed by the server.¶

The parameters of this message consist of the following:¶

messageType REQUIRED urn:ietf:satp:msgtype:assertion-receipt-msg.¶
sessionId REQUIRED: A unique identifier chosen earlier by the client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED. The hash of the previous message.¶

Example:¶

{\ "messageType": "urn:ietf:satp:msgtype:assertion-receipt-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "16c983122d7506c78f906c15ca1dcc7142a0fa94552cdea9578fe87419c2c5d0",\ }\¶

10. Commitment Preparation and Finalization (Stage 3)

This section describes the transfer commitment agreement between the client (sender gateway) and the server (receiver gateway).¶

This stage must be completed within the time specified in the lockAssertionExpiration value in the lock-assertion message.¶

In the following steps, the sender gateway takes the role of the client while the recipient gateway takes the role of the server.¶

The flow follows a request-response model. The client makes a request (POST) to the Transfer Commitment endpoint at the server.¶

Gateways MUST support the use of the HTTP GET and POST methods defined in RFC 2616 [RFC2616] for the endpoint.¶

The client and server may be required to sign certain messages in order to provide standalone proof (for non-repudiation) independent of the secure channel between the client and server. This proof may be required for audit verifications post-event.¶

(NOTE: Flows occur over TLS. Nonces are not shown).¶

10.1. Commit Preparation Message (Commit-Prepare)

The purpose of this message is for the client to indicate its readiness to begin the commitment of the transfer.¶

This message is sent from the client to the Commit Prepare Endpoint at the server.¶

The message must be signed by the client.¶

The parameters of this message consist of the following:¶

messageType REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-prepare-msg¶
sessionId REQUIRED: A unique identifier chosen earlier by the client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED. The hash of the previous message.¶

Example:¶

{\ "messageType": "urn:ietf:satp:msgtype:commit-prepare-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "399bdadc07fe0bd57c4dfdd6cc176ceeca50a5e744f774154eccbeee8908fbaa",\ }\¶

10.2. Commit Ready Message (Commit-Ready)

The purpose The purpose of this message is for the server to indicate to the client that: (i) the server has created (minted) an equivalent asset in the destination network; (ii) that the newly minted asset has been self-assigned to the server; and (iii) that the server is ready to proceed to the next step.¶

This message is sent from the server to the Commit Ready Endpoint at the client.¶

The message must be signed by the server.¶

The parameters of this message consist of the following:¶

messageType REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-ready-msg.¶
sessionId REQUIRED: A unique identifier chosen earlier by client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED. The hash of the previous message.¶
mintAssertionFormat REQUIRED. The format of the assertion payload.¶
mintAssertionClaim REQUIRED. The mint assertion claim or statement by the server.¶

Example:¶

{\ "messageType": "urn:ietf:satp:msgtype:commit-ready-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "8dcc8dc4e6c2c979474b42d24d3747ce4607a92637d1a7b294857ff7288b8e46",\ "mintAssertionClaimFormat": "MINT_ASSERTION_CLAIM_FORMAT_1",\ "mintAssertionClaim": {},\ }\¶

10.3. Commit Final Assertion Message (Commit-Final)

The purpose of this message is for the client to indicate to the server that the client (sender gateway) has completed the extinguishment (burn) of the asset in the origin network.¶

The message must contain a standalone claim related to the extinguishment of the asset by the client. The standalone claim must be signed by the client.¶

This message is sent from the client to the Commit Final Assertion Endpoint at the server.¶

The message must be signed by the server.¶

The parameters of this message consist of the following:¶

messageType REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-final-msg.¶
sessionId REQUIRED: A unique identifier chosen earlier by the client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED. The hash of the previous message.¶
burnAssertionClaimFormat REQUIRED. The format of the claim.¶
burnAssertionClaim REQUIRED. The burn assertion signed claim or statement by the client.¶

Example:¶

{\ "messageType": "urn:ietf:satp:msgtype:commit-final-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "b92f13007216c58f2b51a8621599c3aef6527b02c8284e90c6a54a181d898e02",\ "burnAssertionClaimFormat": "BURN_ASSERTION_CLAIM_FORMAT_1",\ "burnAssertionClaim": {},\ }\¶

10.4. Commit-Final Acknowledgement Receipt Message (ACK-Final-Receipt)

The purpose of this message is to indicate to the client that the server has completed the assignment of the newly minted asset to the intended beneficiary at the destination network.¶

This message is sent from the server to the Commit Final Receipt Endpoint at the client.¶

The message must be signed by the server.¶

The parameters of this message consist of the following:¶

messageType REQUIRED. It MUST be the value urn:ietf:satp:msgtype:ack-commit-final-msg.¶
sessionId REQUIRED: A unique identifier chosen earlier by client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED. The hash of the previous message.¶
assignmentAssertionClaimFormat REQUIRED. The format of the claim.¶
assignmentAssertionClaim REQUIRED. The claim or statement by the server that the asset has been assigned by the server to the intended beneficiary.¶

Example:¶

{\ "messageType": "urn:ietf:satp:msgtype:ack-commit-final-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "9c8f07c22ccf6888fc0306fee0799325efb87dfd536d90bb47d97392f020e998",\ "assignmentAssertionClaimFormat": "ASSIGNMENT_ASSERTION_CLAIM_FORMAT_1",\ "assignmentAssertionClaim": {},\ }\¶

10.5. Transfer Complete Message

The purpose of this message is for the client to indicate to the server that the asset transfer session (identified by sessionId) has been completed and no further messages are to be expected from the client in regards to this transfer instance.¶

The message closes the first message of Stage 2 (Transfer Commence Message).¶

This message is sent from the client to the Transfer Complete Endpoint at the server.¶

The message must be signed by the client.¶

The parameters of this message consist of the following:¶

messageType REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-transfer-complete-msg.¶
sessionId REQUIRED: A unique identifier chosen earlier by the client in the Initialization Request Message.¶
transferContextId REQUIRED: A unique identifier used to identify the current transfer session at the application layer.¶
hashPrevMessage REQUIRED. The hash of the previous message.¶
hashTransferCommence REQUIRED. The hash of the Transfer Commence message at the start of Stage 2.¶

Example:¶

{\ "messageType": "urn:ietf:satp:msgtype:commit-transfer-complete-msg",\ "sessionId": "d66a567c-11f2-4729-a0e9-17ce1faf47c1",\ "transferContextId": "89e04e71-bba2-4363-933c-262f42ec07a0",\ "hashPrevMessage": "9c8f07c22ccf6888fc0306fee0799325efb87dfd536d90bb47d97392f020e998",\ "hashTransferCommence": "4ba76c69265f4215b4e2d2f24fe56e708512fdb49e27f50d2ac0095928e1531b",\ }\¶

10.6. Error Message

The purpose of this message is for either the sender or the receiver gateways to indicate to its peer that an error has occurred within the transfer protocol flow.¶

This message must contain the error type (see the appendix) and the course of action indicated by the severity level. Typicaly, the action taken will be the immediate termination of the session.¶

messageType REQUIRED. It MUST be the value urn:ietf:satp:msgtype:error-msg.¶
sessionId REQUIRED: This is the current session in which the error pertains.¶
errorMsgType: The pevious msg-type that was erronous.¶
errorType REQUIRED: This is the error code being reported (Section 15, Paragraph 1).¶
errorSeverity REQUIRED: This is the severity level of the error, leading to the action.¶

Futher discussion on protocol errors can be found below (Section 15, Paragraph 1).¶

10.7. Session abort message

The purpose of this message is to indicate that one of the peer gateways has decided not to proceed with the session. No further messages will be delivered after the abort message.¶

messageType REQUIRED. It MUST be the value urn:ietf:satp:msgtype:session-abort-msg.¶
sessionId REQUIRED: This is the current session in which the abort occurs.¶

The effect of session aborts on the state of the asset is discussed below.¶

11. SATP Session Resumption

This section answers the question of how can a backup gateway build trust with the counterparty gateway to resume the execution of the protocol, in the presence of errors and crashes?¶

Gateways may enter a faulty state at any time while executing the protocol. The faulty state can manifest itself in incorrect behavior, leading to gateways emitting alerts and errors.¶

In some instances, gateways may crash. We employ either the primary-backup or self-healing paradigm, meaning that the crashed gateway will eventually be replaced by a functioning one, or recover, respectively.¶

When a crash occurs, we initiate a recovery procedure by the backup gateway or the recovered gateway, as defined in the crash recovery draft [I-D.draft-belchior-satp-gateway-recovery]. In either case, if the recovery happens within a time period defined as max_timeout (in Stage 2), the recovered gateway triggers a session resumption. The schema and order of the recovered messages are specified in the crash recovery draft.¶

In the case where there is no answer from the gateway within the specified max_timeout, the counterparty gateway rollbacks the process until that stage. Upon recovery, the crashed gateway learns that the counterparty gateway has initiated a rollback, and it proceeds accordingly (by also initiating a rollback). Note that rollbacks can also happen in case of unresolved errors.¶

The non-crashed gateway that conducts the rollback tries to communicate with the crashed gateway from time to time (self-healing) or to contact the backup gateways (primary-backup). In any case, upon the completion of a rollback, the non-crashed gateway sends a ROLLBACK message to the recovered gateway to notify that a rollback happened. The recovered gateway should answer with ROLLBACK-ACK.¶

Since the self-healing recovery process does not require changes to the protocol (since from the counterparty gateway perspective, the sender gateway is just taking longer than normal; there are no new actions done or logs recorded), we focus on the primary-backup paradigm.¶

11.1. Primary-Backup Session Resumption

Upon a gateway recovering using primary-backup, a new gateway (recovered gateway) takes over the crashed gateway. The counterparty gateway assures that the recovered gateway is legitimate (according to the crash recovery specification).¶

After the recovery, the gateways exchange information about their current view of the protocol, since the crashed gateway may have been in the middle of executing the protocol when it crashed.¶

After that, the gateways MUST agree on the current state of the protocol.¶

11.2. Recovery Messages

We have omitted the logging procedure, as that it implementation dependent to properly log a set of recovery steps needed to reconstruct state upon a gateway failure. As defined in the crash recovery draft [I-D.draft-belchior-satp-gateway-recovery], there is a set of messages that are exchanged between the recovered gateway and counterparty gateway:¶

RECOVER: when a gateway crashes and recovers, it sends a RECOVER message to the counterparty gateway, informing them of its most recent state. The message contains various parameters such as the session ID, message type, SATP stage, context ID, a flag indicating if the sender is a backup gateway, the new public key if the sender is a backup, the timestamp of the last known log entry, and the sender's digital signature.¶
RECOVER-UPDATE: Upon receiving the RECOVER message, the counterparty gateway sends a RECOVER-UPDATE message. The message includes parameters such as the session ID, message type, the hash of the previous message, the list of log messages that the recovered gateway needs to update, and the sender's digital signature.¶
RECOVER-SUCCESS: The recovered gateway responds with a RECOVER-SUCCESS message if its logs have been successfully updated. If there are inconsistencies detected, the recovered gateway initiates a dispute with a RECOVER-DISPUTE message. The message parameters include session ID, message type, the hash of the previous message, a boolean indicating success, a list of hashes of log entries that were appended to the recovered gateway log, and the sender's digital signature.¶

In case the recovery procedure has failed and a rollback process is needed, the following messages are used:¶

ROLLBACK: A gateway that initiates a rollback sends a ROLLBACK message. The message parameters include session ID, message type, a boolean indicating success, a list of actions performed to rollback a state (e.g., UNLOCK, BURN), a list of proofs specific to the DLT, and the sender's digital signature.¶
ROLLBACK-ACK: Upon successful rollback, the counterparty gateway sends a ROLLBACK-ACK message to the recovered gateway acknowledging that the rollback has been performed successfully. The message parameters are similar to those of the ROLLBACK message.¶

12. Error Messages

SATP distinguishes between session termination initiated by the user at the application layer from session termination cased by errors at the SATP protocol layer.¶

A gateway can transmit an error message at any point in the SATP protocol flow to its peer gateway.¶

The default action to be taken by the transitting gateway is to terminate the session immediately.¶

Error messages at the SATP protocol layer is distinct from time-outs due to gateway crashes.¶

12.1. Session Termination Notification

Session closure initiated at the application layer is not considered to be an error at the SATP protocol layer.¶

The message type used for application-initiated session termination: session-abort-msg.¶

The message type used to indicate protocols errors: error-msg.¶

A gateway can transmit the session abort message at any point in the SATP protocol flow. No further messages will be sent by the gateway.¶

Any data received after the session termination message MUST be ignored.¶

12.2. Connection Errors

Errors may occur at the connection layer, independent of the flows at the SATP layer and errors there.¶

(a) connectionError: There is an error in the TLS session establishment (TLS error codes should be reported-up to the gateway level)¶

(b) badCertificate: The gateway TLS certificate was corrupt, contained signatures, that did not verify correctly, etc. (Some common TLS level errors: unsupported_certificate, certificate_revoked, certificate_expired, certificate_unknown, unknown_ca).¶

12.3. SATP Protocol Errors

The errors at the SATP level pertain to protocol flow and the information carried within each message. These are enumerated in the appendix.¶

12.4. Effectiveness of Session Aborts

The effectiveness of a session-abort message on the state of the asset depends on where the abort message occurs in the SATP protocol flow in Figure 2.¶

Note that a session-abort message by be lost and never be received by the peer gateway. Gateways can crash prior to receiving an abort message.¶

If gateway G2 transmits a session-abort message after gateway G1 performs a lock (msgtype:lock-assert-msg) on the asset in network NW1, the gateway G1 can always unlock the asset and restore its state.¶

If either gateway G1 or gateway G2 transmits a session-abort message after gateway G1 sends a lock-assert message (msgtype:lock-assert-msg) but before G2 sends the commit ready message (msgtype:commit-ready-msg), the gateway G1 can always unlock the asset and restore its state in network NW1.¶

Similarly, if either gateway G1 or gateway G2 transmits a session-abort message immediately after gateway G1 sends a commit-prepare message (msgtype:commit-prepare-msg) but before G2 sends the commit ready message (msgtype:commit-ready-msg), the gateway G2 can always reverse the changes made by G2 to NW2 (i.e. reverse the assignment-to-self of the minted asset).¶

However, an abort message (occurring in either direction) after gateway G1 transmits the commit final message (msgtype:commit-final-msg) will not be effective. This is because G1 has already burned the asset in NW1 and G2 has already minted the asset in NW2 and has legally agreed to assign the asset to the appropriate beneficiary in NW2.¶

In general, the termination of sessions or aborts occurring before the sender gateway G1 disables (burns) the asset in NW1 (in flow 3.4 in Figure 2) will incur a minimal cost in terms of computing resources or fees on the part of both gateways G1 and G2.¶

13. Security Consideration

Gateways may be of interest to attackers because they enable the transferal of digital assets across networks and therefore are an important function in the digital economy.¶

Disruptions in transfers and denial of service: Disruptions to a transfer session may cause not only resource waste (e.g. CPU usage), but in some cases may result in financial loss on the part of the gateway operator (e.g. fees charged by network). Denial-of-service attacks by third parties to a run of the protocol may result in the termination of the current run (e.g. time-outs at the SATP layer), and for new attempts to be conducted. If the gateway selection mechanisms are utilized by networks NW1 and NW2, such attacks may incur more delays because new gateways may have to be elected at either network.¶
Dishonest gateways: The SATP protocol requires gateways to sign messages related to the transfer layer, not only to provide message source authentication and integrity but also to maintain honesty on the part of the gateways. Gateway-operators may take-on legal and financial liabilities in certain jurisdictions by digitally signing messages. Dishonest gateways may intentionally delay the delivery of certain messages or intentionally fail (abort) the protocol run at certain crucial points [ARCH]. Two such crucial points in the message flows are the following: (i) the commit-final-msg, where the sender G1 asserts it has extinguished (burned) the asset in the origin network, and (ii) the ack-prepare-msg where the receiver gateway G2 asserts it is ready to proceed with the final commitment. If gateway G1 intentionally drops the commit-final-msg (commit-final) such that gateway G2 times-out, then G2 may suffer financial loss due to roll-back costs in network NW2. Similarly, if G2 intentionally drops the ack-prepare-msg to signal that it is ready to proceed with the commitment (commit-ready), then gateway G1 may time-out and terminate the protocol run, causing resource waste at G1. Operators of gateways should utlize relevant tools to detect possible dishonest behavior of certain gateways, and select to have their gateways peer with other reliable gateways.¶
Protection of gateway keys: It is crucial to protect the cryptographic keys utilized by gateways. This includes keys for secure session establishment (TLS1.3) and keys utilized for signing SATP messages. Loss of gateway keys may incur financial loss on the part of the gateway-operator. Implementation of gateways should consider utilizing tamper-resistant hardware to store and manage the relevant keys for gateways operational functions.¶
Gateway identification: Mechanisms must be utilized to provide unique identifiers to gateway implementations to ensure global uniqueness and reachability. Existing identification mechanisms such a X509 certificates and Verifiable Credentials (VC) and Selective Disclosure CBOR Web Tokens (SD-CWT) may be applied for gateway identification.¶
Identification of networks: There needs to be mechanism for gateways to declare or disclose the asset networks it current serves. Combined with strong gateway identification, this allows remote gateways to quickly locate suitable gateways to peer with for the purposes of asset transfers.¶

14. IANA Consideration

The following request is being made to IANA.¶

14.1. SATP Error Codes Registry

This registry defines the error codes used in SATP protocol messages. Each entry consists of:¶

Code: The enumeration string (e.g., err_3.3.1)¶
Category: The protocol stage or message type (e.g., Commit Ready errors)¶
Type: The error type (e.g., badly formed message)¶
Description: A brief description (e.g., mismatch transferContextId)¶

Table 1
Code	Category	Type	Description
err_1.1.1	Transfer Proposal/Receipt errors	badly formed message	invalid transferContextId
err_1.1.2	Transfer Proposal/Receipt errors	badly formed message	invalid sessionId
err_1.1.3	Transfer Proposal/Receipt errors	badly formed message	incorect transferInitClaimFormat
err_1.1.4	Transfer Proposal/Receipt errors	badly formed message	bad signature
err_1.1.11	Transfer Proposal/Receipt errors	badly formed claim	invalid digitalAssetId
err_1.1.12	Transfer Proposal/Receipt errors	badly formed claim	invalid assetProfileId
err_1.1.13	Transfer Proposal/Receipt errors	badly formed claim	invalid verifiedOriginatorEntityId
err_1.1.14	Transfer Proposal/Receipt errors	badly formed claim	invalid verifiedBeneficiaryEntityId
err_1.1.15	Transfer Proposal/Receipt errors	badly formed claim	invalid originatorPubkey
err_1.1.16	Transfer Proposal/Receipt errors	badly formed claim	invalid beneficiaryPubkey
err_1.1.17	Transfer Proposal/Receipt errors	badly formed claim	invalid senderGatewaySignaturePublicKey
err_1.1.18	Transfer Proposal/Receipt errors	badly formed claim	invalid receiverGatewaySignaturePublicKey
err_1.1.19	Transfer Proposal/Receipt errors	badly formed claim	invalid senderGatewayId
err_1.1.20	Transfer Proposal/Receipt errors	badly formed claim	invalid recipientGatewayId
err_1.1.31	Transfer Proposal/Receipt errors	badly formed parameter	unsupported gatewayDefaultSignatureAlgorithm
err_1.1.32	Transfer Proposal/Receipt errors	badly formed parameter	unsupported networkLockType
err_1.1.33	Transfer Proposal/Receipt errors	badly formed parameter	unsupported networkLockExpirationTime
err_1.1.34	Transfer Proposal/Receipt errors	badly formed parameter	unsupported gatewayCredentialProfile
err_1.1.35	Transfer Proposal/Receipt errors	badly formed parameter	unsupported gatewayLoggingProfile
err_1.1.36	Transfer Proposal/Receipt errors	badly formed parameter	unsupported gatewayAccessControlProfile
err_1.2.1	Transfer Proposal/Receipt errors	badly formed message	mismatch transferContextId
err_1.2.2	Transfer Proposal/Receipt errors	badly formed message	mismatch sessionId
err_1.2.3	Transfer Proposal/Receipt errors	badly formed message	mismatch hashTransferInitClaim
err_1.2.4	Transfer Proposal/Receipt errors	badly formed message	bad signature
err_1.3.1	Transfer Commence errors	badly formed message	mismatch transferContextId
err_1.3.2	Transfer Commence errors	badly formed message	mismatch sessionId
err_1.3.3	Transfer Commence errors	badly formed message	mismatch hashTransferInitClaim
err_1.3.4	Transfer Commence errors	badly formed message	mismatch hashPrevMessage
err_1.3.5	Transfer Commence errors	badly formed message	bad signature
err_1.4.1	ACK Commence errors	badly formed message	mismatch transferContextId
err_1.4.2	ACK Commence errors	badly formed message	mismatch sessionId
err_1.4.3	ACK Commence errors	badly formed message	mismatch hashPrevMessage
err_1.4.4	ACK Commence errors	badly formed message	bad signature
err_2.2.1	Lock Assertion errors	badly formed message	mismatch transferContextId
err_2.2.2	Lock Assertion errors	badly formed message	mismatch sessionId
err_2.2.3	Lock Assertion errors	badly formed message	unsupported lockAssertionClaimFormat
err_2.2.4	Lock Assertion errors	badly formed message	unsupported lockAssertionExpiration
err_2.2.5	Lock Assertion errors	badly formed message	mismatch hashPrevMessage
err_2.2.6	Lock Assertion errors	badly formed message	bad signature
err_2.4.1	Lock Assertion Receipt errors	badly formed message	mismatch transferContextId
err_2.4.2	Lock Assertion Receipt errors	badly formed message	mismatch sessionId
err_2.4.3	Lock Assertion Receipt errors	badly formed message	mismatch hashPrevMessage
err_2.4.4	Lock Assertion Receipt errors	badly formed message	bad signature
err_3.1.1	Commit Preparation errors	badly formed message	mismatch transferContextId
err_3.1.2	Commit Preparation errors	badly formed message	mismatch sessionId
err_3.1.3	Commit Preparation errors	badly formed message	mismatch hashPrevMessage
err_3.1.4	Commit Preparation errors	badly formed message	bad signature
err_3.3.1	Commit Ready errors	badly formed message	mismatch transferContextId
err_3.3.2	Commit Ready errors	badly formed message	mismatch sessionId
err_3.3.3	Commit Ready errors	badly formed message	mismatch hashPrevMessage
err_3.3.4	Commit Ready errors	badly formed message	unsupported mintAssertionFormat
err_3.3.5	Commit Ready errors	badly formed message	bad signature
err_3.5.1	Commit Final Assertion errors	badly formed message	mismatch transferContextId
err_3.5.2	Commit Final Assertion errors	badly formed message	mismatch sessionId
err_3.5.3	Commit Final Assertion errors	badly formed message	mismatch hashPrevMessage
err_3.5.4	Commit Final Assertion errors	badly formed message	unsupported burnAssertionClaimFormat
err_3.5.5	Commit Final Assertion errors	badly formed message	bad signature
err_3.7.1	Commit Final Ack Receipt errors	badly formed message	mismatch transferContextId
err_3.7.2	Commit Final Ack Receipt errors	badly formed message	mismatch sessionId
err_3.7.3	Commit Final Ack Receipt errors	badly formed message	mismatch hashPrevMessage
err_3.7.4	Commit Final Ack Receipt errors	badly formed message	unsupported assignmentAssertionClaimFormat
err_3.7.5	Commit Final Ack Receipt errors	badly formed message	bad signature
err_3.9.1	Transfer Complete errors	badly formed message	mismatch transferContextId
err_3.9.2	Transfer Complete errors	badly formed message	mismatch sessionId
err_3.9.3	Transfer Complete errors	badly formed message	mismatch hashPrevMessage
err_3.9.4	Transfer Complete errors	badly formed message	mismatch hashTransferCommence
err_3.9.5	Transfer Complete errors	badly formed message	bad signature

14.2. URN Registration

URN: Request to be assigned by IANA.¶

Common Name: urn:ietf:satp¶

Registrant Contact: IESG¶

Description: The secure asset transfer protocol (SATP) requires message types, endpoints and parameters to be defined within a unique namespace to prevent collision.¶

14.3. SATP Message Types Registry

This specification establishes the SATP Message Types registry. The purpose of this registry is to define the various message types utilized in the secure asset transfer protocol (SATP).¶

14.4. Initial Registry Contents

The SATP Message Types registry's initial contents are as follows:¶

14.4.1. Parameter name: transfer-proposal-msg

Parameter usage location: Transfer Proposal¶
Change controller: IETF¶
Specification document(s): Section 8.3 of draft-ietf-satp-core.¶

14.4.2. Parameter name: proposal-receipt-msg

Parameter usage location: Transfer Proposal Receipt Message¶
Change controller: IETF¶
Specification document(s): Section 8.4 of draft-ietf-satp-core.¶

14.4.3. Parameter name: reject-msg

Parameter usage location: Transfer Reject¶
Change controller: IETF¶
Specification document(s): Section 8.5 of draft-ietf-satp-core.¶

14.4.4. Parameter name: transfer-commence-msg

Parameter usage location: Transfer Commence¶
Change controller: IETF¶
Specification document(s): Section 8.6 of draft-ietf-satp-core.¶

14.4.5. Parameter name: ack-commence-msg

Parameter usage location: Transfer Commence Response¶
Change controller: IETF¶
Specification document(s): Section 8.7 of draft-ietf-satp-core.¶

14.4.6. Parameter name: lock-assert-msg

Parameter usage location: Lock Assertion¶
Change controller: IETF¶
Specification document(s): Section 9.1 of draft-ietf-satp-core.¶

14.4.7. Parameter name: assertion-receipt-msg

Parameter usage location: Lock Assertion Receipt¶
Change controller: IETF¶
Specification document(s): Section 9.2 of draft-ietf-satp-core.¶

14.4.8. Parameter name: commit-prepare-msg

Parameter usage location: Commit Preparation¶
Change controller: IETF¶
Specification document(s): Section 10.1 of draft-ietf-satp-core.¶

14.4.9. Parameter name: commit-ready-msg

Parameter usage location: Commit Ready¶
Change controller: IETF¶
Specification document(s): Section 10.2 of draft-ietf-satp-core.¶

14.4.10. Parameter name: commit-final-msg

Parameter usage location: Commit Final Assertion¶
Change controller: IETF¶
Specification document(s): Section 10.3 of draft-ietf-satp-core.¶

14.4.11. Parameter name: ack-commit-final-msg

Parameter usage location: Commit-Final Acknowledgement Receipt¶
Change controller: IETF¶
Specification document(s): Section 10.4 of draft-ietf-satp-core.¶

14.4.12. Parameter name: commit-transfer-complete-msg

Parameter usage location: Transfer Complete¶
Change controller: IETF¶
Specification document(s): Section 10.5 of draft-ietf-satp-core.¶

14.4.13. Parameter name: error-msg

Parameter usage location: Error message¶
Change controller: IETF¶
Specification document(s): Section 10.6 of draft-ietf-satp-core.¶

14.4.14. Parameter name: session-abort-msg

Parameter usage location: Session Abort¶
Change controller: IETF¶
Specification document(s): Section 10.7 of draft-ietf-satp-core.¶

15. Error Types and Codes

This appendix defines the error codes that may be returned in SATP protocol messages.¶

15.1. Protocol Error Codes

The following error codes are defined for SATP protocol errors:¶

err_1.1: Invalid message type¶
err_1.2: Invalid session ID¶
err_1.3: Invalid transfer context ID¶
err_1.4: Invalid signature¶
err_1.5: Invalid hash value¶
err_2.1: Asset not found¶
err_2.2: Asset already locked¶
err_2.3: Asset lock expired¶
err_2.4: Insufficient permissions¶
err_3.1: Network connection failure¶
err_3.2: Gateway unavailable¶
err_3.3: Timeout exceeded¶
err_4.1: Unsupported credential profile¶
err_4.2: Invalid credential format¶
err_4.3: Credential verification failed¶

16. Acknowledgements

The authors would like to thank the following people for their input and support:¶

Andre Augusto, Denis Avrilionis, Rafael Belchior, Alexandru Chiriac, Anthony Culligan, Claire Facer, Martin Gfeller, Wes Hardaker, David Millman, Krishnasuri Narayanam, Anais Ofranc, Luke Riley, John Robotham, Orie Steele, Yaron Scheffer, Peter Somogyvari, Weijia Zhang.¶

17. References

17.1. Normative References

[BASE64]: Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, <https://www.rfc-editor.org/rfc/rfc4648>.
[DATETIME]: Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, <https://www.rfc-editor.org/rfc/rfc3339>.
[JSON]: Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, <https://www.rfc-editor.org/rfc/rfc8259>.
[JWA]: Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, DOI 10.17487/RFC7518, May 2015, <https://www.rfc-editor.org/rfc/rfc7518>.
[JWS]: Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, <https://www.rfc-editor.org/rfc/rfc7515>.
[JWT]: Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, <https://www.rfc-editor.org/rfc/rfc7519>.
[REQ-LEVEL]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC2616]: Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, DOI 10.17487/RFC2616, June 1999, <https://www.rfc-editor.org/rfc/rfc2616>.
[X.500]: ITU-T, "The Directory: Overview of concepts, models and services", 2005.

17.2. Informative References

[ARCH]: Hardjono, T., Hargreaves, M., Smith, N., and V. Ramakrishna, "Secure Asset Transfer (SAT) Interoperability Architecture", June 2024, <https://datatracker.ietf.org/doc/draft-ietf-satp-architecture/>.
[ECDSA]: "Digital Signature Standard (FIPS 186-5)", February 2023, <https://doi.org/10.6028/NIST.FIPS.186-5>.
[I-D.draft-belchior-satp-gateway-recovery]: Belchior, R., Correia, M., Augusto, A., and T. Hardjono, "Secure Asset Transfer Protocol (SATP) Gateway Crash Recovery Mechanism", Work in Progress, Internet-Draft, draft-belchior-satp-gateway-recovery-03, 20 January 2025, <https://datatracker.ietf.org/doc/html/draft-belchior-satp-gateway-recovery-03>.
[MICA]: European Commission, "EU Directive on Markets in Crypto-Assets Regulation (MiCA)", June 2023, <https://www.esma.europa.eu/esmas-activities/digital-finance-and-innovation/markets-crypto-assets-regulation-mica>.
[NIST]: Yaga, D., Mell, P., Roby, N., and K. Scarfone, "NIST Blockchain Technology Overview (NISTR-8202)", October 2018, <https://doi.org/10.6028/NIST.IR.8202>.
[RFC5939]: Andreasen, F., "Session Description Protocol (SDP) Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939, September 2010, <https://www.rfc-editor.org/rfc/rfc5939>.
[RFC9334]: Birkholz, H., Thaler, D., Richardson, M., Smith, N., and W. Pan, "Remote ATtestation procedureS (RATS) Architecture", RFC 9334, DOI 10.17487/RFC9334, January 2023, <https://www.rfc-editor.org/rfc/rfc9334>.