Internet Engineering Task Force M. Hargreaves Internet-Draft Quant Network Intended status: Informational T. Hardjono Expires: April 13, 2021 MIT October 10, 2020 Open Digital Asset Protocol draft-hargreaves-odap-00 Abstract This memo describes the Open Digital Asset Protocol (ODAP). ODAP is intended for describing assets held on distributed ledgers in an open and interoperable format, session negotiation and message passing between gateways connecting disparate blockchain systems. 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/. 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Hargreaves & Hardjono Expires April 13, 2021 [Page 1] Internet-Draft ODAP October 2020 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Open Digital Asset Protocol . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 4 3. ODAP: Elements of the proposal . . . . . . . . . . . . . . . 4 3.1. ODAP Message Flow Context . . . . . . . . . . . . . . . . 4 3.2. ODAP Message Format . . . . . . . . . . . . . . . . . . . 4 3.3. Digital Asset Resource Descriptors . . . . . . . . . . . 5 3.3.1. Organisation Identifier . . . . . . . . . . . . . . . 5 3.3.2. DLT Gateway / Endpoint ID . . . . . . . . . . . . . . 5 3.3.3. DLT Identifier . . . . . . . . . . . . . . . . . . . 5 3.3.4. Resource . . . . . . . . . . . . . . . . . . . . . . 6 3.3.5. Examples . . . . . . . . . . . . . . . . . . . . . . 6 3.4. Digital Asset Resource Client Descriptors . . . . . . . . 6 3.4.1. Organization Identifier . . . . . . . . . . . . . . . 6 3.4.2. DLT Gateway / Endpoint ID . . . . . . . . . . . . . . 6 3.4.3. Organizational Unit . . . . . . . . . . . . . . . . . 7 3.4.4. Name . . . . . . . . . . . . . . . . . . . . . . . . 7 3.4.5. Examples . . . . . . . . . . . . . . . . . . . . . . 7 3.5. Gateway Level Access Control . . . . . . . . . . . . . . 7 3.6. Negotiation of Security Protocols and Parameters . . . . 8 3.6.1. TLS Established . . . . . . . . . . . . . . . . . . . 8 3.6.2. Client offers supported credential schemes . . . . . 8 3.6.3. Server selects supported credential scheme . . . . . 8 3.6.4. Client asserts of proves identity . . . . . . . . . . 8 3.6.5. Sequence numbers initialized . . . . . . . . . . . . 8 3.6.6. Messages can now be exchanged . . . . . . . . . . . . 9 3.7. Digital Asset Resource Discovery . . . . . . . . . . . . 9 3.7.1. Format . . . . . . . . . . . . . . . . . . . . . . . 9 3.8. Accessing Resources via a DLT Gateway . . . . . . . . . . 9 3.8.1. Backward Compatibility . . . . . . . . . . . . . . . 9 4. Security Consideration . . . . . . . . . . . . . . . . . . . 9 5. IANA Consideration . . . . . . . . . . . . . . . . . . . . . 10 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. Normative References . . . . . . . . . . . . . . . . . . 10 6.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction There is a lack of interoperability between individual blockchains, but also a general difficulty building open DLT networks. Extant networks are custom built and relatively closed, usually limited to networks of a single DLT type Hargreaves & Hardjono Expires April 13, 2021 [Page 2] Internet-Draft ODAP October 2020 This memo proposes at blockchain-agnostic protocol in order to allow the creation of business applications that use and modify multiple blockchains or DLT systems, through a single programmatic interface. The target blockchain systems can be of any type, operated by different owners and managed using different DLT management platforms that implement ODAP interfaces. These platforms may act as gateways or relays for the application to interact with the blockchain systemn. They are referred to herein as blockchain or DLT Gateways. When correctly implemented and deployed, the protocol should provide the basis for solutions involving asset migration between two DLT systems, as well as use-cases when one side is a non-DLT system (e.g. legacy system). 1.1. Open Digital Asset Protocol This draft proposes a standard framework to address the following: o Resource addressing for DLTs, using the URL syntax. o 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. o Protocol message family for negotiating authentication, authorisation, and parameters for confidential channel establishment. o Resource discovery mechanism for developers and applications to discover DLT-based resources hosted at a DLT gateway. The gateway response is subject to the level of access granted to that developer or application. We propose a protocol for accessing DLT resources (read and modify) that are hosted behind gateways, either directly or via a local intermediate gateway. We propose a method to support pass-through of native DLT messaging where necessary for compatibility. Hargreaves & Hardjono Expires April 13, 2021 [Page 3] Internet-Draft ODAP October 2020 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. 3. ODAP: Elements of the proposal This section describes (i) the phases of the ODAP protocol; (ii) the format of ODAP messages; (iii) the format for resource descriptors; (iv) a method for gateways to implement access controls; (v) protocol for negotiating security capabilities; (vi) discovery and accessing resources and provisions for backward compatibility with existing systems. 3.1. ODAP Message Flow Context o OSimple Client to Gateway (Diagram to follow). o Client to Multiple Gateways (Diagram to follow). o Client to Local Gateway to Remote Gateway(s) (Diagram to follow). 3.2. ODAP Message Format ODAP messages are exchanged between applications (clients) and DLT gateways (servers). They consist of protocol negotiation and functional messages. Messages are JSON format, with protocol specific mandatory fields, support for arbitrary authentication and authorization schemes and support for a free format field for plaintext or encrypted payloads directed at the DLT gateway or an underlying DLT. JSON format message, mandatory fields are shown below: o Version: ODAP protocol Version (major, minor). o Resource URL: Location of Resource to be accessed. o Developer URN: Assertion of developer / application identity. o Credential Scheme: Specify type of authorization (e.g. SAML, OAuth, X.509). Hargreaves & Hardjono Expires April 13, 2021 [Page 4] Internet-Draft ODAP October 2020 o Credential Block: Credential token, certificate, string. o Payload: Payload for POST, responses, and native DLT txns. o Sequence Number: Sequence Number. 3.3. Digital Asset Resource Descriptors Resources are identified by URL [RFC 1738] as described below: o The type is new: application/odapres o The access protocol is ODAP. Data included in the URL includes the folowing: 3.3.1. Organisation Identifier This drafts supports a variety organization identification schemes. For example, the Legal Entity Identifier (LEI)scheme or other identifier linking resource ownership to real world entity can be used. Any scheme for identifying DLT 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. 3.3.2. DLT Gateway / Endpoint ID FQDN of the ODAP compliant DLT gateway. Required to establish IP connectivity. This MUST resolve to a valid IP address. 3.3.3. DLT Identifier Specify to gateway behind which the target DLTs operates. This field is local to the DLT gateway and is used to direct ODAP interactions to the correct underlying DLT. For example: "Hyperledger1", "Bitcoin, "EU-supply-chain". Hargreaves & Hardjono Expires April 13, 2021 [Page 5] Internet-Draft ODAP October 2020 3.3.4. Resource Specifies a resource held on the underlying DLT. This field must be meaningful to the DLT in question but is otherwise an arbitrary string. The underlying object it points to may be a DLT address, block, transaction ID, alias, etc. or a future object type not yet defined. 3.3.5. Examples odapres://quant/api.gateway1.com/ripple odapres://quant/api.gateway1.com/bitcoin/xxxxxADDRESSxxxxx 3.4. Digital Asset Resource Client Descriptors Resources are identified by URN as described below: o The type is new: application/odapclient The URN format does not imply availability or access protocol. Data included in the URN includes the folowing: 3.4.1. Organization Identifier Legal Entity Identifier (LEI) or other identifier linking resource ownership to real world entity. Any scheme for identifying DLT Gateway owners may be implemented (e.g. LEI directory, closed user group membership, BIC, etc.). The DLT 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). 3.4.2. DLT Gateway / Endpoint ID Multi-DLT applications can operate in a mode whereby the application connects to its local DLT gateway, which then forwards application traffic to local DLTS and to remote DLTs via other ODAP 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 & Hardjono Expires April 13, 2021 [Page 6] Internet-Draft ODAP October 2020 3.4.3. 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 DLT 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. 3.4.4. 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 DLT Gateways should ensure appropriate identifiers are used for the needs of the application or use case. 3.4.5. Examples odapclient:quant/api.overledger.quant.com/research/luke.riley 3.5. 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: odapclient://hsbc/api.overledger.hsbc.com/lending/eric.devloper can READ/WRITE odapres://quant/api.gateway1.com/bitcoin AND odapres://quant/api.gateway1.com/ripple These rules would allow a client so identified to access resources directly, for example: odapres://quant/api.gateway1.com/bitcoin/xxxxxADDRESSxxxxx This example could be an client subscribing to or writing to an address associated with a smart contract as part of its functionality. Hargreaves & Hardjono Expires April 13, 2021 [Page 7] Internet-Draft ODAP October 2020 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. 3.6. Negotiation of Security Protocols and Parameters 3.6.1. 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. 3.6.2. 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 ODAP message. 3.6.3. Server selects supported credential scheme The server (DLT Gateway) selects one acceptable credential scheme from the offered schemes, returning the selection in the "Credential Scheme" field of the ODAP message. If no acceptable credential scheme was offered, an HTPP 511 "Network Authentication Required" error is returned in the Action/Response field of the ODAP message. 3.6.4. Client asserts of proves identity The details of the assertion / verification step are specific to the chosen credential scheme and are out of scope of this document. 3.6.5. 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 (Application) after the finalization of credential verification. The server (DLT gateway) MUST respond with the same sequence number to indicate acceptance. Hargreaves & Hardjono Expires April 13, 2021 [Page 8] Internet-Draft ODAP October 2020 The client (application) increments the sequence number with each new request. Sequence numbers can be reused for retries in the event of a gateway timeout. 3.6.6. Messages can now be exchanged Handshaking is complete at this point, and the client (application) can send ODAP messages to perform actions of DLT resources, which MAY reference the ODAP Payload field. 3.7. Digital Asset Resource Discovery Resource discovery is handled by the DLT gateway, a GET request against the gateway URL with no DLT or resource MUST returns a list of URLs available to the requester to DLT level. This list is subject to the access controls above. DLT Gateways may allow applications to discover URLs they do not have access to, this should be indicated the free test field, and they should implement a process for applications to request access. 3.7.1. Format JSON structure, consisting of a set of responses, each is: URL, free text field, admin contact 3.8. Accessing Resources via a DLT Gateway The "Action" field is used to access resources via the gateway. We suggest these interactions use REST semantics however a detailed API specification is out of scope of this memo. In general, we suggest exposing a common subset of functionality via API using the Action field, augmented with DLT specific or smart contract specific functionality as needed. 3.8.1. Backward Compatibility It is also possible to send a fully formatted native message to the underlying DLT in the Payload field, directed to a resource URL. This allows existing DLT native code to be ported to ODAP infrastructures with minimal change. 4. Security Consideration Although the current interoperability architecture for blockchain gateways assumes the externalization of the value of assets, as a blockchain system holds an increasing number of virtual assets it Hargreaves & Hardjono Expires April 13, 2021 [Page 9] Internet-Draft ODAP October 2020 becomes attractive to attackers seeking to obtain cryptographic keys of its nodes and its end-users. Gateway nodes are of particular interest to attackers because they enable the transferal of virtual assets to external blockchain systems, which may or may not be regulated. As such, hardening technologies and tamper-resistant crypto-processors (e.g. TPM, SGX) should be used for implementations of gateways [HS19]. Due to the consensus-based nature of the underlying DLT technologies, gateway responses may be conditional and require verification, for instance if the DLT is undergoing a byzantine attack at the time of the request. The application must evaluate the correctness of responses from the gateway in context and may need to perform further verification steps with later ODAP calls. The application may base this evaluation on the number of DLT nodes the gateway has interacted with in order to fulfil the request. 5. IANA Consideration (TBD) 6. References 6.1. 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, . 6.2. Informative References [HS2019] Hardjono, T. and N. Smith, "Decentralized Trusted Computing Base for Blockchain Infrastructure Security, Frontiers Journal, Sepcial Issue on Blockchain Technology, Vol. 2, No. 24", December 2019, . [NIST] Yaga, D., Mell, P., Roby, N., and K. Scarfone, "NIST Blockchain Technology Overview (NISTR-8202)", October 2018, . Hargreaves & Hardjono Expires April 13, 2021 [Page 10] Internet-Draft ODAP October 2020 [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 Thomas Hardjono MIT Email: hardjono@mit.edu Hargreaves & Hardjono Expires April 13, 2021 [Page 11]