Internet Engineering Task Force M. Hargreaves Internet-Draft Quant Network Intended status: Informational T. Hardjono Expires: 10 January 2024 MIT R. Belchior Technico Lisboa 9 July 2023 Secure Asset Transfer Protocol (SATP) draft-ietf-satp-core-02 Abstract This memo 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. The protocol establishes a secure channel between the endpoints and implements a 2-phase commit to ensure the properties of transfer atomicity, consistency, isolation and durability. 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 10 January 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. 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 Hargreaves, et al. Expires 10 January 2024 [Page 1] Internet-Draft SATP Core July 2023 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. The Secure Asset Transfer Protocol . . . . . . . . . . . . . 5 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 5 4.2. SAT Model . . . . . . . . . . . . . . . . . . . . . . . . 6 4.3. Types of APIs . . . . . . . . . . . . . . . . . . . . . . 6 4.4. Types of Flows . . . . . . . . . . . . . . . . . . . . . 7 4.5. Resources and Identifiers . . . . . . . . . . . . . . . . 7 5. SATP Message Format, identifiers and Descriptors . . . . . . 7 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 8 5.2. SATP Message Format . . . . . . . . . . . . . . . . . . . 8 5.3. Digital Asset Resource Descriptors . . . . . . . . . . . 9 5.3.1. Organization Identifier . . . . . . . . . . . . . . . 9 5.3.2. Gateway / Endpoint ID . . . . . . . . . . . . . . . . 9 5.3.3. Network or system Identifier . . . . . . . . . . . . 9 5.3.4. Resource . . . . . . . . . . . . . . . . . . . . . . 10 5.3.5. Examples . . . . . . . . . . . . . . . . . . . . . . 10 5.4. Digital Asset Resource Client Descriptors . . . . . . . . 10 5.4.1. Organization Identifier . . . . . . . . . . . . . . . 10 5.4.2. Gateway / Endpoint ID . . . . . . . . . . . . . . . . 10 5.4.3. Organizational Unit . . . . . . . . . . . . . . . . . 11 5.4.4. Name . . . . . . . . . . . . . . . . . . . . . . . . 11 5.4.5. Examples . . . . . . . . . . . . . . . . . . . . . . 11 5.5. Gateway Level Access Control . . . . . . . . . . . . . . 11 5.6. Negotiation of Security Protocols and Parameters . . . . 12 5.6.1. TLS Established . . . . . . . . . . . . . . . . . . . 12 5.6.2. Client offers supported credential schemes . . . . . 12 5.6.3. Server selects supported credential scheme . . . . . 12 5.6.4. Client asserts or proves identity . . . . . . . . . . 12 5.6.5. Sequence numbers initialized . . . . . . . . . . . . 12 5.6.6. Messages can now be exchanged . . . . . . . . . . . . 13 5.7. Asset Profile Identification . . . . . . . . . . . . . . 13 5.8. Application Profile Negotiation . . . . . . . . . . . . . 13 5.9. Discovery of Digital Asset Resources . . . . . . . . . . 14 6. Identity and Asset Verification Flow (Stage 0) . . . . . . . 14 7. Transfer Initiation and Commencement Flows (Stage 1) . . . . 15 7.1. Transfer Initialization Claims . . . . . . . . . . . . . 15 7.2. Conveyance of Network Capabilities and Parameters . . . . 16 7.3. Transfer Proposal Message . . . . . . . . . . . . . . . . 17 7.4. Transfer Proposal Receipt Message . . . . . . . . . . . . 18 Hargreaves, et al. Expires 10 January 2024 [Page 2] Internet-Draft SATP Core July 2023 7.5. Transfer Proposal Reject and Conditional Reject Message . . . . . . . . . . . . . . . . . . . . . . . . . 19 7.6. Transfer Commence Message . . . . . . . . . . . . . . . . 20 7.7. Commence Response Message (ACK-Commence) . . . . . . . . 21 8. Lock Assertion and Receipt (Stage 2) . . . . . . . . . . . . 22 8.1. Lock Assertion Message . . . . . . . . . . . . . . . . . 23 8.2. Lock Assertion Receipt Message . . . . . . . . . . . . . 24 9. Commitment Preparation and Finalization (Stage 3) . . . . . . 24 9.1. Commit Preparation Message (Commit-Prepare) . . . . . . . 25 9.2. Commit Ready Message (Commit-Ready) . . . . . . . . . . . 26 9.3. Commit Final Assertion Message (Commit-Final) . . . . . . 27 9.4. Commit-Final Acknowledgement Receipt Message (ACK-Final-Receipt) . . . . . . . . . . . . . . . . . . . 28 9.5. Transfer Complete Message . . . . . . . . . . . . . . . . 29 10. SATP Session Resumption . . . . . . . . . . . . . . . . . . . 29 10.1. Primary-Backup Session Resumption . . . . . . . . . . . 30 10.2. Recovery Messages . . . . . . . . . . . . . . . . . . . 31 11. Error Messages . . . . . . . . . . . . . . . . . . . . . . . 32 11.1. Closure Alerts . . . . . . . . . . . . . . . . . . . . . 32 11.2. Error Alerts . . . . . . . . . . . . . . . . . . . . . . 33 12. Security Consideration . . . . . . . . . . . . . . . . . . . 33 13. IANA Consideration . . . . . . . . . . . . . . . . . . . . . 33 14. Appendix A: Error Types . . . . . . . . . . . . . . . . . . . 34 14.1. Transfer Commence and Response errors . . . . . . . . . 34 14.2. Lock Assertion errors . . . . . . . . . . . . . . . . . 34 14.3. Lock Assertion Receipt errors . . . . . . . . . . . . . 34 14.4. Commit Preparation errors . . . . . . . . . . . . . . . 35 14.5. Commit Preparation Acknowledgement errors . . . . . . . 35 14.6. Commit Ready errors . . . . . . . . . . . . . . . . . . 35 14.7. Commit Final Assertion errors . . . . . . . . . . . . . 35 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 36 15.1. Normative References . . . . . . . . . . . . . . . . . . 36 15.2. Informative References . . . . . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36 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 network to a destination network. Both the origin and destination networks are assumed to be opaque in the sense that the interior constructs 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 network and is re-generated (minted) at the destination Hargreaves, et al. Expires 10 January 2024 [Page 3] Internet-Draft SATP Core July 2023 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 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) 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, and the endpoints at the respective gateways are associated with a certificate indicating the legal owner (or operator) of the gateway. 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 [RFC2119]. 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. Hargreaves, et al. Expires 10 January 2024 [Page 4] Internet-Draft SATP Core July 2023 3. Terminology The following are some terminology used in the current document: 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 network or system). 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. Hargreaves, et al. Expires 10 January 2024 [Page 5] Internet-Draft SATP Core July 2023 +----------+ +----------+ | Client | | Off-net | | (App) | | Resource | +----------+ +----------+ | |API Type-3| | +----------+ | ^ V | +----------+ | |API Type-1| | +------+ +----------+----+ +----+----------+ +------+ | | | | | | | | | | | Net. | | Gateway |API | |API | Gateway | | Net. | | NW1 |---| G1 |Type|<------>|Type| G2 |---| NW2 | | | | | 2 | | 2 | | | | +------+ +----------+----+ +----+----------+ +------+ Figure 1 4.2. SAT Model The model for SATP is shown in Figure 1. The Client (application) interacts with its local gateway (G1) over an interface (API Type-1) 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 (API Type- 2). 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 (API Type-3). 4.3. Types of APIs The following are the types of APIs in SATP: * Gateway APIs for client (API Type-1): This the REST APIs that permit a Client (application) to interact with a local gateway, and issue instructions for actions pertaining to resources accessible to the gateway. * Gateway APIs for peer gateways (API Type-2): This is the REST APIs employed by two (2) peer gateways in performing unidirectional asset transfers. Hargreaves, et al. Expires 10 January 2024 [Page 6] Internet-Draft SATP Core July 2023 * APIs for validation of off-network resources (API Type-3): This is the REST APIs made available by a resource server (resource owner) at which a gateway can access resources. The use of these APIs is dependent on the mode of access and the type of flow in question. 4.4. Types of Flows The SAT protocol defines the following three (3) flows: * Transfer Initiation flow: This flow deals with commencing a transfer from one gateway to another. Several tasks are involved, including (but not limited to): (i) gateway identification and mutual authentication; (ii) exchange of asset type (definition) information; (iii) verification of the asset definition, and others. * Lock-Assertion flow: This flow deals 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 Establishment flow: This flow deals with the asset transfer and commitment establishment between two gateways. These flow will be discussed below. 4.5. Resources and Identifiers (a) Resource addressing for systems or networks, using the URL syntax. (b) Client identification based on the URN format. These are for identifying clients (developers and applications) who access these resources, and which in some use-cases require access authorization. (c) Protocol message family for negotiating authentication, authorisation, and parameters for confidential channel establishment. (d) Resource discovery mechanism for developers and applications to discover resources hosted at a gateway. The gateway response is subject to the level of access granted to that developer or application. 5. SATP Message Format, identifiers and Descriptors Hargreaves, et al. Expires 10 January 2024 [Page 7] Internet-Draft SATP Core July 2023 5.1. Overview This section describes (i) the phases of SATP; (ii) the format of SATP messages; (iii) the format for resource descriptors; (iv) a method for gateways to implement access controls; (iv) protocol for negotiating security capabilities; (v) discovery and accessing resources and provisions for backward compatibility with existing systems. 5.2. SATP Message Format SATP messages are exchanged between applications (clients) and gateways (servers). They consist of protocol negotiation and functional messages. Messages are in JSON format, with protocol specific mandatory fields, support for several authentication and authorization schemes and support for a free format field for plaintext or encrypted payloads directed at the gateway. JSON format message, mandatory fields are shown below: * Version: SATP protocol Version (major, minor). * Message Type: This refers to the type of request or response to be conveyed in this message. * Session ID: unique identifier (UUIDv2) representing a session between two gateways handling a single unidirectional transfer. * Transfer-Context ID: unique optional identifier (UUIDv2) representing the application layer context. * Sequence Number: Monotonically increasing counter that uniquely represents a message from a session. * Resource URL: Location of Resource to be accessed. * Developer URN: Assertion of developer / application identity. * Action/Response: GET/POST and arguments (or Response Code) * Credential Profile: Specify type of auth (e.g. SAML, OAuth, X.509) * Credential Block: Credential token, certificate, string * Payload Profile: Asset profile and capabilities Hargreaves, et al. Expires 10 January 2024 [Page 8] Internet-Draft SATP Core July 2023 * Application Profile: Vendor or Application specific profile * Payload: Payload for POST, responses, and local networks. The payload is specific to the current SAT phase. * Payload Hash: hash of the current message payload. * Message signature: Gateway EDCSA signature over the message Other relevant attributes may exists that need to be captured for logging purposes. 5.3. Digital Asset Resource Descriptors Resources are identified by URL [RFC 1738] as described below: * The type is new: application/satres * The access protocol is SATP. Data included in the URL includes the folowing: 5.3.1. Organization Identifier This MAY be a Legal Entity Identifier (LEI) or other identifier linking resource ownership to a real world entity. Any scheme for identifying gateway owners may be implemented (e.g. LEI directory, closed user group membership, SWIFT BIC, etc.). The developer or application MAY validate the identity with the issuing authority. The identifier is not a trusted identity, but MAY be relied on where trust has been established between the two parties (e.g. in a closed user group). The mechanisms to determine organizations identifiers is out of scope for the current specification. 5.3.2. Gateway / Endpoint ID FQDN of the SATP compliant gateway. Required to establish IP connectivity. This MUST resolve to a valid IP address. 5.3.3. Network or system Identifier Specific to the gateway behind which the target network operates. This field is local to the gateway and is used to direct SATP interactions to the correct underlying network. This value maybe alphanumeric or a hexadecimal value. Hargreaves, et al. Expires 10 January 2024 [Page 9] Internet-Draft SATP Core July 2023 For example: "tradelens-network", "EU-supply-chain". 5.3.4. Resource Specifies a resource held on the underlying network. This field must be meaningful to the network in question but is otherwise an arbitrary string. The underlying object it points to may be a network address, data block, transaction ID, alias, etc. or a future object type not yet defined. 5.3.5. Examples satpres://quant/api.gateway1.com/swift 5.4. Digital Asset Resource Client Descriptors Resources are identified by URN as described below: * The type is new: application/satpclient The URN format does not imply availability of access protocol. Data included in the URN includes the following: 5.4.1. Organization Identifier Legal Entity Identifier (LEI) or other identifier linking resource ownership to a real-world entity. Any scheme for identifying Gateway owners may be implemented (e.g. LEI directory, closed user group membership, BIC, etc.). The Gateway MAY validate the identity with the issuing authority. The identifier is not a trusted identity, but MAY be relied on where trust has been established between the two parties (e.g. in a closed user group). 5.4.2. Gateway / Endpoint ID Applications which interact with multiple networks can operate in a mode whereby the application connects to its local gateway, which then forwards application traffic to local networks and to remote networks via other SATP gateways. Where this is the case, this field identifies the "home" gateway for this application. This may be required to carry out gateway to gateway handshaking and protocol negotiation, or for the server to look up use case specific data relating to the client. Hargreaves, et al. Expires 10 January 2024 [Page 10] Internet-Draft SATP Core July 2023 5.4.3. Organizational Unit The organization unit within the organization that the client (application or developer) belongs to. This assertion should be backed up with authentication via the negotiated protocol. The purpose of this field is to allow gateways to maintain access control mapping between applications and resources that are independent of the authentication and authorization schemes used, supporting future changes and supporting counterparties that operate different schemes. 5.4.4. Name A locally unique (within the OU) identifier, which can identify the application, project or individual developer responsible for this client connection. This is the most granular unit of access control, and gateways should ensure appropriate identifiers are used for the needs of the application or use case. 5.4.5. Examples satclient:quant/api.overledger.quant.com/research/luke.riley 5.5. Gateway Level Access Control Gateways can enforce access rules based on standard naming conventions using novel or existing mechanisms such as AuthZ protocols using the resource identifiers above, for example: satpclient://hsbc/api.overledger.hsbc.com/lending/eric.devloper can READ/WRITE satpres://quant/api.gateway1.com/tradelens AND satpres://quant/api.gateway1.com/ripple These rules would allow a client so identified to access resources directly, for example: satpres://quant/api.gateway1.com/tradelens/xxxxxADDRESSxxxxx Hargreaves, et al. Expires 10 January 2024 [Page 11] Internet-Draft SATP Core July 2023 This method allows resource owners to easily grant access to individuals, groups and organizations. Individual gateway implementations may implement access controls, including subsetting and supersetting or applications or resources according to their own requirements. 5.6. Negotiation of Security Protocols and Parameters 5.6.1. TLS Established TLS 1.2 or higher MUST be implemented to protect gateway communications. TLS 1.3 or higher SHOULD be implemented where both gateways support TLS 1.3 or higher. 5.6.2. Client offers supported credential schemes Capability negotiation prior to data exchange, follows a scheme similar to the Session Description Protocol [RFC 5939]. Initially the client (application) sends a JSON block containing acceptable credential schemes, e.g. OAuth2.0, SAML in the "Credential Scheme" field of the SATP message. 5.6.3. Server selects supported credential scheme The server (recipient Gateway) selects one acceptable credential scheme from the offered schemes, returning the selection in the "Credential Scheme" field of the SATP message. If no acceptable credential scheme was offered, an HTPP 511 "Network Authentication Required" error is returned in the Action/Response field of the SATP message. 5.6.4. Client asserts or proves identity The details of the assertion / verification step are specific to the chosen credential scheme and are out of scope of this document. 5.6.5. Sequence numbers initialized Sequence numbers are used to allow the server to correctly order operations from the client, some of which may be asynchronous, synchronous, idempotent with duplicate requests handled in different ways according to the use case. The initial sequence number is proposed by the client (sender gateway) after the finalization of credential verification. The server (recipient gateway) MUST respond with the same sequence number to indicate acceptance. Hargreaves, et al. Expires 10 January 2024 [Page 12] Internet-Draft SATP Core July 2023 The client (sender gateway) increments the sequence number with each new request. Sequence numbers can be reused for retries in the event of a gateway timeout. 5.6.6. Messages can now be exchanged Handshaking is complete at this point, and the client can send SAT messages to perform actions on resources, which MAY reference the SAT Payload field. 5.7. Asset Profile Identification The client and server must mutually agree as to the asset type or profile that is the subject to the current transfer from the client and server. The client must provide the server with the asset- identification number, or the server may provide the client with the asset-identification numbers for the digital asset supported by the server. Formal specification of asset identification is out of scope of this document. Global numbering of digital asset types or profiles is expected to be performed by a legally recognized entity. 5.8. Application Profile Negotiation Where an application relies on specific extensions for operation, these can be represented in an Application Profile. For example, a payments application tracks payments through the use of a cloud based API and will only interact with gateways that log messages to that API, a resource profile can be established: Application Name: TRACKER X-Tracker_URL: https://api.tracker.com/updates X-Tracking-Policy: Always As gateways implement this functionality, they support the TRACKER application profile, and the application is able to expand its reach by periodically polling for the availability of the profile. This is an intentionally generalized extension mechanism for application or vendor specific functionality. Hargreaves, et al. Expires 10 January 2024 [Page 13] Internet-Draft SATP Core July 2023 5.9. Discovery of Digital Asset Resources Applications located outside a network or system SHOULD be able to discover which resources they are authorized to access in a network or system. Resource discovery is handled by the gateway in front of the network. For instance using a GET request against the gateway URL with no resource identifier could return a list of URLs available to the requester. This list is subject to the access controls above. Gateways MAY allow applications to discover resources they do not have access to. This should be indicated in the free text field, and gateways SHOULD implement a process for applications to request access. Formal specification of supported resource discovery methods is out of scope of this document. 6. Identity and Asset Verification Flow (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 verifications 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: * Gateway identity mutual verification: This is the identity of the gateway at the protocol and network layer. This may include validating the X509 certificates of the gateways. * 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 [RATS] 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. Hargreaves, et al. Expires 10 January 2024 [Page 14] Internet-Draft SATP Core July 2023 These are considered out of scope in the current specifications, and are assumed to have been successfully completed prior to the commencement of the transfer initiation flow. 7. Transfer Initiation and Commencement Flows (Stage 1) This section describes the SATP Set-up stage, where a sender gateway interacts with a recipient gateway, proposing a session. These artifacst are contained in the Transfer Initiation Claims. 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 phase to the server (recipient gateway). If using the HTTP GET method, the request parameters may be serialized using URI Query String Serialization. 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 (e.g. post-event). (NOTE: Flows occur over TLS. Nonces are not shown). 7.1. Transfer Initialization Claims 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 Transfer Initialization Claims consists of the following: * digital_asset_id: This is the globally unique identifier for the digital asset located in the origin network. * asset_profile_id: This is the globally unique identifier for the asset-profile definition (document) on which the digital asset was issued. * verified_originator_entity_id: 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. Hargreaves, et al. Expires 10 January 2024 [Page 15] Internet-Draft SATP Core July 2023 * verified_beneficiary_entity_id: 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. * originator_pubkey REQUIRED. This is the public key of the asset owner (originator) in the origin network or system. * beneficiary_pubkey REQUIRED. This is the public key of the beneficiary in the destination network. * sender_gateway_network_id REQUIRED. This is the identifier of the origin network or system behind the client. * recipient_gateway_network_id REQUIRED. This is the identifier of the destination network or system behind the server. * client_identity_pubkey REQUIRED. The public key of client who sent this message. * server_identity_pubkey REQUIRED. The public key of server for whom this message is intended. * sender_gateway_owner_id: This is the identity information of the owner or operator of the sender gateway. * receiver_gateway_owner_id: This is the identity information of the owner or operator of the recipient gateway. 7.2. Conveyance of Network Capabilities and Parameters This is set of artifacts pertaining to the origin network behind the client (sender gateway) that MAY be communicated to the server (recipient gateway). A server may accept the asset-related claims but reject the transfer request based on parameters of the origin network. Some of these parameters maybe gateway-specific (e.g. chosen signature algorithm), while others are inherent in the origin network (e.g. lock type; average lock duration time; etc.). The network capabilities list is as follows: * sender_gateway_network_id REQUIRED. This is the identifier of the origin network or system behind the client. * signature_algorithm REQUIRED: The digital signature algorithm chosen by the client (sender gateway) for signing claims. Hargreaves, et al. Expires 10 January 2024 [Page 16] Internet-Draft SATP Core July 2023 * supported_signature_algorithm OPTIONAL: The list of algorithm-id that is supported by the client from which the server MAY select. * Lock_type REQUIRED: faucet, timelock, hashlock, hashtimelock, multi-claim PC, destroy/burn (escrowed cross-claim). * Lock_expiration_time REQUIRED: when will the lock or escrow expire. * Permissions OPTIONAL: list of identities (public-keys or X.509 certificates) that can perform operations on the escrow or lock on the asset in the origin network. * developer_URN OPTIONAL: Assertion of developer / application identity. * credential_profile REQUIRED: Specify type of auth (e.g. SAML, OAuth, X.509). * application_profile OPTIONAL: Vendor or Application specific profile. * logging_profile REQUIRED: contains the profile regarding the logging procedure. Default is local store * Access_control_profile REQUIRED: the profile regarding the confidentiality of the log entries being stored. Default is only the gateway that created the logs can access them. * Subsequent calls OPTIONAL: details possible escrow actions. * History OPTIONAL: provides an history of the escrow, in case it has previously been initialized. 7.3. Transfer Proposal Message The purpose of this message is for the client to initiate an asset Transfer and propose the set of claims related to the asset to be transferred. This message must be signed by the client. Depending on the proposal, multiple rounds of communication between the client and the server may occur. This message is sent from the client to the Transfer Initialization Endpoint at the server. The parameters of this message consists of the following: Hargreaves, et al. Expires 10 January 2024 [Page 17] Internet-Draft SATP Core July 2023 * version REQUIRED: SAT protocol Version (major, minor). * message_type REQUIRED: urn:ietf:satp:msgtype:init-proposal-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen by the client to identify the current session. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * transfer_init_claims: The set of artifacts and parameters as the basis for the current transfer. * transfer_init_claims_format OPTIONAL: The format of the transfer initialization claims. * network_capabilities_list REQUIRED: The set of origin network parameters reported by the client to the server. * client_identity_pubkey REQUIRED. The public key of client who sent this message. * server_identity_pubkey REQUIRED. The public key of server for whom this message is intended. * multiple_claims_allowed OPTIONAL: true/false. * multiple_cancels_allowed OPTIONAL: true/false. * client signature REQUIRED: The client's signature over the message. 7.4. Transfer Proposal Receipt Message The purpose of this message is for the server to indicate explicit acceptance of the Transfer Initialization Claims in 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 consists of the following: * version REQUIRED: SAT protocol Version (major, minor). * message_type REQUIRED: urn:ietf:satp:msgtype:init-receipt-msg Hargreaves, et al. Expires 10 January 2024 [Page 18] Internet-Draft SATP Core July 2023 * session_id REQUIRED: A unique identifier (UUIDv2) chosen by the client to identify the current session. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * hash_transfer_init_claims REQUIRED: Hash of the Transfer Initialization Claims received in the Transfer Proposal Message. * Timestamp REQUIRED: timestamp referring to when the Initialization Request Message was received. Example: TBD. 7.5. Transfer Proposal Reject and Conditional Reject Message The purpose of this message is for the server to indicate a rejection or conditional rejection of the Transfer Initialization Claims. In the case of a conditional rejection, the server may propose a different set of claims (counter-proposal claims) to the client. If the server wishes to indicate a conditional rejection, the server MUST include a counter-proposal set of claims. If the server does not wish to proceed, the server MUST include an empty (blank) counter-proposal. Depending on the proposal and counter-proposal, multiple rounds of communication between the client and the server may occur. 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 consists of the following: * version REQUIRED: SAT protocol Version (major, minor). * message_type REQUIRED: urn:ietf:satp:msgtype:init-reject-msg * session_id REQUIRED: A unique identifier (UUIDv2) chosen by the client to identify the current session. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. Hargreaves, et al. Expires 10 January 2024 [Page 19] Internet-Draft SATP Core July 2023 * hash_transfer_init_claims REQUIRED: Hash of the Transfer Initialization Claims received in the Transfer Proposal Message. * transfer_init_counter_claims: The set of artifacts and parameters as the counter-proposal to the client. * Timestamp REQUIRED: timestamp referring to when the Initialization Request Message was received. Example: TBD. 7.6. 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 receuved from the server. This message is sent by the client to the Transfer Commence Endpoint at the server. The parameters of this message consists of the following: * message_type REQUIRED. MUST be the value urn:ietf:satp:msgtype:transfer-commence-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The public key of client who sent this message. * server_identity_pubkey REQUIRED. The public key of server for whom this message is intended. * hash_transfer_init_claims REQUIRED: Hash of the Transfer Initialization Claims received in the Transfer Proposal Message. * hash_prev_message REQUIRED. The hash of the last message, in this case the Transfer Proposal Receipt message. Hargreaves, et al. Expires 10 January 2024 [Page 20] Internet-Draft SATP Core July 2023 * client_transfer_number OPTIONAL. This is the transfer identification number chosen by the client. This number is meaningful only the client. * client_signature REQUIRED. The digital signature of the client. For example, the client makes the following HTTP request using TLS (with extra line breaks for display purposes only): POST /token HTTP/1.1 Host: server.example.com Authorization: Basic awHCaGRSa3F0MzpnWDFmQmF0M2ZG Content-Type: application/x-www-form-urlencoded { "message_type": "urn:ietf:satp:msgtype:transfer-commence-msg", "session_id":"9097hkstgkjvVbNH", "originator_pubkey":"zGy89097hkbfgkjvVbNH", "beneficiary_pubkey": "mBGHJjjuijh67yghb", "sender_net_system": "originNETsystem", "recipient_net_system":"recipientNETsystem", "client_identity_pubkey":"fgH654tgeryuryuy", "server_identity_pubkey":"dFgdfgdfgt43tetr535teyrfge4t54334", "transfer_init_claims":"nbvcwertyhgfdsertyhgf2h3v4bd3v21", "hash_prev_message":"DRvfrb654vgreDerverv654nhRbvder4", "client_transfer_number":"ji9876543ewdfgh", "client_signature":"fdw34567uyhgfer45" } Figure 2 7.7. 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 consists of the following: * message_type REQUIRED urn:ietf:satp:msgtype:ack-commence-msg Hargreaves, et al. Expires 10 January 2024 [Page 21] Internet-Draft SATP Core July 2023 * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client for whom this message is intended. * server_identity_pubkey REQUIRED. The server who sent this message. * hash_prev_message REQUIRED. The hash of the last message, in this case the the Transfer Commence Message. * server_transfer_number OPTIONAL. This is the transfer identification number chosen by the server. This number is meaningful only to the server. * server_signature REQUIRED. The digital signature of the server. An example of a success response could be as follows: (TBD) 8. Lock Assertion and Receipt (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, 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 phase 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). Hargreaves, et al. Expires 10 January 2024 [Page 22] Internet-Draft SATP Core July 2023 8.1. 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 claims (payload) in this message prior to the next step. The message must be signed by the client. The parameters of this message consists of the following: * message_type REQUIRED urn:ietf:satp:msgtype:lock-assert-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client who sent this message. * server_identity_pubkey REQUIRED. The server for whom this message is intended. * lock_assertion_claim REQUIRED. The lock assertion claim or statement by the client. * lock_assertion_claim_format REQUIRED. The format of the claim. * lock_assertion_expiration REQUIRED. The duration of time of the lock or escrow upon the asset. * hash_prev_message REQUIRED. The hash of the previous message. * client_transfer_number OPTIONAL. This is the transfer identification number chosen by the client. This number is meaningful only to the client. Hargreaves, et al. Expires 10 January 2024 [Page 23] Internet-Draft SATP Core July 2023 * client_signature REQUIRED. The digital signature of the client. 8.2. Lock Assertion Receipt Message The purpose of this message is for the server (receiver gateway) to indicate acceptance of the claim(s) 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 consists of the following: * message_type REQUIRED urn:ietf:satp:msgtype:assertion-receipt-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client for whom this message is intended. * server_identity_pubkey REQUIRED. The server who sent this message. * hash_prev_message REQUIRED. The hash of previous message. * server_transfer_number OPTIONAL. This is the transfer identification number chosen by the server. This number is meaningful only to the server. * server_signature REQUIRED. The digital signature of the server. 9. Commitment Preparation and Finalization (Stage 3) This section describes the transfer commitment agreement between the client (sender gateway) and the server (receiver gateway). This phase must be completed within the time specified in the lock_assertion_expiration value in the lock-assertion message. In the following, the sender gateway takes the role of the client while the recipient gateway takes the role of the server. Hargreaves, et al. Expires 10 January 2024 [Page 24] Internet-Draft SATP Core July 2023 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. Clients MAY use the HTTP GET or POST methods to send messages in this phase to the server. If using the HTTP GET method, the request parameters maybe serialized using URI Query String Serialization. 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 maybe required for audit verifications post-event. (NOTE: Flows occur over TLS. Nonces are not shown). 9.1. 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 consists of the following: * message_type REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-prepare-msg * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client who sent this message. * server_identity_pubkey REQUIRED. The server for whom this message is intended. * hash_prev_message REQUIRED. The hash of previous message. Hargreaves, et al. Expires 10 January 2024 [Page 25] Internet-Draft SATP Core July 2023 * client_transfer_number OPTIONAL. This is the transfer identification number chosen by the client. This number is meaningful only the client. * client_signature REQUIRED. The digital signature of the client. 9.2. 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 consists of the following: * message_type REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-ready-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client for whom this message is intended. * server_identity_pubkey REQUIRED. The server who sent this message. * mint_assertion_claims REQUIRED. The mint assertion claim or statement by the server. * mint_assertion_format OPTIONAL. The format of the assertion payload. * hash_prev_message REQUIRED. The hash of previous message. * server_transfer_number OPTIONAL. This is the transfer identification number chosen by the server. This number is meaningful only the server. Hargreaves, et al. Expires 10 January 2024 [Page 26] Internet-Draft SATP Core July 2023 * server_signature REQUIRED. The digital signature of the server. 9.3. 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 standalone claims 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 consists of the following: * message_type REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-final-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client who sent this message. * server_identity_pubkey REQUIRED. The server for whom this message is intended. * burn_assertion_claim REQUIRED. The burn assertion signed claim or statement by the client. * burn_assertion_claim_format OPTIONAL. The format of the claim. * hash_prev_message REQUIRED. The hash of previous message. * client_transfer_number OPTIONAL. This is the transfer identification number chosen by the client. This number is meaningful only the client. * client_signature REQUIRED. The digital signature of the client. Hargreaves, et al. Expires 10 January 2024 [Page 27] Internet-Draft SATP Core July 2023 9.4. 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 consists of the following: * message_type REQUIRED. It MUST be the value urn:ietf:satp:msgtype:ack-commit-final-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client for whom this message is intended.. * server_identity_pubkey REQUIRED. The server who sent this message. * assignment_assertion_claim REQUIRED. The claim or statement by the server that the asset has been assigned by the server to the intended beneficiary. * assignment_assertion_claim_format OPTIONAL. The format of the claim. * hash_prev_message REQUIRED. The hash of previous message. * server_transfer_number OPTIONAL. This is the transfer identification number chosen by the server. This number is meaningful only the server. * server_signature REQUIRED. The digital signature of the server. Hargreaves, et al. Expires 10 January 2024 [Page 28] Internet-Draft SATP Core July 2023 9.5. Transfer Complete Message The purpose of this message is for the client to indicate to the server that the asset transer session (identified by session_id) has been completed and that 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 consists of the following: * message_type REQUIRED. It MUST be the value urn:ietf:satp:msgtype:commit-transfer-complete-msg. * session_id REQUIRED: A unique identifier (UUIDv2) chosen earlier by client in the Initialization Request Message. * transferContext_id OPTIONAL: An optional identifier (UUIDv2) used to identify the current transfer session at the application layer. * client_identity_pubkey REQUIRED. The client who sent this message. * server_identity_pubkey REQUIRED. The server for whom this message is intended. * hash_prev_message REQUIRED. The hash of previous message. * hash_transfer_commence REQUIRED. The hash of the Transfer Commence message at the start of Stage 2. * client_transfer_number OPTIONAL. This is the transfer identification number chosen by the client. This number is meaningful only the client. * client_signature REQUIRED. The digital signature of the client. 10. SATP Session Resumption This section answers the question how can a backup gateway build trust with the counter party gateway to resume the execution of the protocol, in the presence of errors and crashes? Hargreaves, et al. Expires 10 January 2024 [Page 29] Internet-Draft SATP Core July 2023 Gateways may enter faulty state at any time while execution the protocol. The faulty state can manifest itself by incorrect behaviour, 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 [draft-belchior-gateway-recovery-05]. In either case, if the recovery happens within a time period d efined as max_timeout (in Stage 2), the recovered gateway triggers a session resumption. The schema and order of the recovered messages is specified in the crash recovery draft. In the case where there is no answer from the gateway within the specified max_timeout, the counter-party gateway rollbacks the process until that stage. Upon recovery, the crashed gateway learns that the counterparty gateway has initated a rollback, and it proceeds accordingly (by also initating 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, and 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. 10.1. Primary-Backup Session Resumption Upon a gateway recovering using primary-backup, a new gateway (recovered gateway) takes over the crashed gateway. The counter- party 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. Hargreaves, et al. Expires 10 January 2024 [Page 30] Internet-Draft SATP Core July 2023 After that, the gateways agree on the current state of the protocol. 10.2. Recovery Messages We have omitted the logging procedure (only focusing the different messages). As defined in the crash recovery draft [draft-belchior- gateway-recovery-05], there are 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 phase, sequence number, 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. This message carries the difference between the log entry corresponding to the received sequence number from the recovered gateway and the latest sequence number (corresponding to the latest log entry). 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 [SATP], and the sender's digital signature. Hargreaves, et al. Expires 10 January 2024 [Page 31] Internet-Draft SATP Core July 2023 * 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. 11. Error Messages SATP SATP distinguishes between application driven closures (terminations) and those caused by errors at the SATP protocol level. The list of errors and desciption can be found in the Appendix. enum { session_closure(1), nonfatal_error (2) fatal_error(3), (255) } AlertLevel; enum { close_notify(0), bad_certificate(42), unsupported_certificate(43), certificate_revoked(44), certificate_expired(45), certificate_unknown(46), illegal_parameter(47), TBD (255) } AlertDescription; struct { AlertLevel level; AlertDescription description; } Alert; Figure 3 11.1. Closure Alerts The SATP client and server (gateways) must share knowledge that the transfer connection is ending in order to avoid third party attacks. (a) close_notify: This alert notifies the recipient that the sender gateway will not send any more messages on this transfer connection. Any data received after a closure alert has been received MUST be ignored. Hargreaves, et al. Expires 10 January 2024 [Page 32] Internet-Draft SATP Core July 2023 (b) user_canceled: This alert notifies the recipient that the sender gateway is canceling the transfer connection for some reason unrelated to a protocol failure. 11.2. Error Alerts When an error is detected by a SATP gateway, the detecting gateway sends a message to its peer. Upon transmission or receipt of a fatal alert message, both gateways MUST immediately close the connection. Whenever a SATP implementation encounters a fatal error condition, it SHOULD send an appropriate fatal alert and MUST close the connection without sending or receiving any additional data. The following error alerts are defined: * connection_error: There is an error in the TLS session establishment (TLS error codes should be reported-up to gateway level) * bad_certificate: The gateway 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). * protocol_version_error: The SATP protocol version the peer has attempted to negotiate is recognized but not supported. * (Others TBD) 12. Security Consideration Gateways are of particular interest to attackers because they are a kind of end-to-end pipeline that enable the transferral of digital assets to external networks or systems. Thus, attacking a gateway may be attractive to attackers instead of the network behind a gateway. As such, hardware hardening technologies and tamper-resistant crypto- processors (e.g. TPM, Secure Enclaves, SGX) should be considered for implementations of gateways. 13. IANA Consideration (TBD) Hargreaves, et al. Expires 10 January 2024 [Page 33] Internet-Draft SATP Core July 2023 14. Appendix A: Error Types The following lists the error associated with each message in SATP. (Note: these have been laid out for convenience, and may be grouped together more efficiently later). 14.1. Transfer Commence and Response errors The following are the list of errors related to Transfer Commence and Response: * [err_2.1] Badly formed message. * [err_2.2] Incorrect parameter. * [err_2.3] ACK mismatch. 14.2. Lock Assertion errors The following are the list of errors related to Lock Assertion: * [err_2.4.1] Badly formed message: badly formed Claim. * [err_2.4.2] Badly formed message: bad signature. * [err_2.4.3] Badly formed message: wrong transaction ID. * [err_2.4.4] Badly formed message: Mismatch hash values. * [err_2.4.5] Expired signing-key certificate. * [err_2.4.6] Expired Claim. 14.3. Lock Assertion Receipt errors The following are the list of errors related to Lock Assertion Receipt: * [err_2.6.1] Badly formed message: badly formed Claim. * [err_2.6.2] Badly formed message: bad signature. * [err_2.6.3] Badly formed message: wrong transaction ID. * [err_2.6.4] Badly formed message: Mismatch hash values. * [err_2.6.5] Expired signing-key certificate. Hargreaves, et al. Expires 10 January 2024 [Page 34] Internet-Draft SATP Core July 2023 * [err_2.6.6] Expired Claim. 14.4. Commit Preparation errors The following are the list of errors related to Commit Preparation: * [err_3.1.1] Badly formed message: wrong transaction ID. * [err_3.1.2] Badly formed message: mismatch hash value (i.e. from msg 2.6). * [err_3.1.3] Incorrect parameter. * [err_3.1.4] Message out of sequence. 14.5. Commit Preparation Acknowledgement errors The following are the list of errors related to Commit Preparation Acknowledgement: * [err_3.2.1] Badly formed message: wrong transaction ID. * [err_3.2.2] Badly formed message: mismatch hash value. * [err_3.2.3] Incorrect parameter. * [err_3.2.4] Message out of sequence. 14.6. Commit Ready errors The following are the list of errors related to Commit Ready: * [err_3.4.1] Badly formed message: wrong transaction ID. * [err_3.4.2] Badly formed message: mismatch hash value. * [err_3.4.3] Incorrect parameter. * [err_3.4.4] Message out of sequence (ACK mismatch). 14.7. Commit Final Assertion errors The following are the list of errors related to Commit Final Assertion: * [err_3.6.1] Badly formed message: badly formed Claim. * [err_3.6.2] Badly formed message: bad signature. Hargreaves, et al. Expires 10 January 2024 [Page 35] Internet-Draft SATP Core July 2023 * [err_3.6.3] Badly formed message: wrong transaction ID. * [err_3.6.4] Badly formed message: Mismatch hash values. * [err_3.6.5] Expired signing-key certificate. * [err_3.6.6] Expired Claim. 15. References 15.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, DOI 10.17487/RFC2234, November 1997, . [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . 15.2. Informative References [draft-belchior-gateway-recovery-05] Belchior, R., Correia, M., Augusto, A., and T. Hardjono, "DLT Gateway Crash Recovery Mechanism", Work in Progress, Internet-Draft, draft-belchior-gateway-recovery-05, 19 April 2023, . [NIST] Yaga, D., Mell, P., Roby, N., and K. Scarfone, "NIST Blockchain Technology Overview (NISTR-8202)", October 2018, . [RFC5939] Andreasen, F., "Session Description Protocol (SDP) Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939, September 2010, . Authors' Addresses Martin Hargreaves Quant Network Email: martin.hargreaves@quant.network Hargreaves, et al. Expires 10 January 2024 [Page 36] Internet-Draft SATP Core July 2023 Thomas Hardjono MIT Email: hardjono@mit.edu Rafael Belchior Technico Lisboa Email: rafael.belchior@tecnico.ulisboa.pt Hargreaves, et al. Expires 10 January 2024 [Page 37]