Serving an Authenticated Digital EMblem over UDP

Internet-Draft	ADEM over UDP	August 2023
Linker, et al.	Expires 29 February 2024	[Page]

Abstract

This document describes a mechanism using the User Datagram Protocol (UDP) to distribute Authenticated Digital EMblem (ADEM) tokens [ADEM-CORE]. ADEM tokens encode that an asset is protected under international humanitarian law.¶

About This Document

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

Status information for this document may be found at https://datatracker.ietf.org/doc/draft-adem-wg-adem-udp/.¶

Source for this draft and an issue tracker can be found at https://github.com/adem-wg/adem-spec.¶

Status of This Memo

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Copyright Notice

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1. Introduction

The ADEM Core document [ADEM-CORE] specifies how a set of tokens, encoded as JSON Web Signatures (JWSs) [RFC7515], can constitute signs of protection. Such signs of protection indicate that a digital asset is protected under international humanitarian law (IHL). This document describes a UDP-based distribution method for ADEM tokens, termed ADEM-UDP.¶

2. Conventions and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

3. UDP Distribution

Any digital, network-connected asset MAY distribute sets of ADEM tokens using the UDP protocol. Whenever an asset distributes tokens using UDP, it MUST set the destination port to 60. The data field encodes three elements (in that order): a uint16 sequence number, a uint16 stating the number of tokens in this sequence, and the token itself as a sequence of ASCII bytes representing the token's JWS compact serialization. Any UDP packet containing an ADEM token, MUST contain exactly one token. The sequence number identifies sets of related tokens. Therefore, sequence numbers SHOULD NOT repeat per recipient IP and within 300 seconds.¶

ADEM-UDP enabled assets SHOULD send a complete set of tokens allowing for the strongest verification possible (compare [ADEM-CORE], Section 6.1) whenever a client attempts to connect to the respectively protected asset. ADEM-UDP enabled assets MUST at the same apply rate-limiting mechanisms when sending out tokens to the same clients. Rate limitations SHOULD depend on the number of bytes sent per set of tokens, but assets MUST send a verifier a set of tokens at least every 300 seconds, should the verifier probe the protected asset repeatedly.¶

4. UDP Parsing

When listening on port 60, verifiers can distinguish different sets of tokens using the sequence number. When receiving any token on port 60, verifiers MUST apply a timeout of 300 seconds. That means, they MAY discard tokens from which they were not able to assemble a verifiable sign of protection after 300 seconds. But at the same time, verifiers MUST wait for at least 300 seconds after having probed a protected asset until they may classify this asset as unprotected.¶

Verifiers are RECOMMENDED to start verification procedures as specified in [ADEM-CORE] as soon as they received all internal endorsements belonging to an emblem. Independent endorsements can be verified individually once they are received.¶

7. References

7.1. Normative References

[ADEM-CORE]: Linker, F. E., Jackson, D., and D. Basin, "An Authenticated Digital EMblem - Core Specification", n.d., <./draft-adem-wg-adem-core.html>.
[RFC2119]: 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/info/rfc2119>.
[RFC8174]: Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2. Informative References

[REG-PORT]: "Service Name and Transport Protocol Port Number Registry", n.d., <https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml>.
[RFC7515]: Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, <https://www.rfc-editor.org/info/rfc7515>.