N-PAMP: Native Post-Quantum Agent Messaging Protocol

1.1. Goals

The design goals of N-PAMP are:¶

• Cryptographic agility within a stable wire format. The frame format does not change between profiles; the cryptographic primitives, modes, and operational requirements do.¶

• Defense in depth through hybrid post-quantum and classical key establishment, authenticated encryption, and a forward-secure key schedule.¶

• Channel multiplexing so that a single association can carry several classes of agent traffic with independent sequence spaces and per-channel keying.¶

• Interoperability across profiles, so that an endpoint operating at a higher profile MAY interoperate with a lower-profile peer when local policy permits.¶

1.2. Non-Goals

This document does NOT:¶

• Replace TLS for ordinary web traffic. N-PAMP is purpose-built for autonomous-agent, multi-channel traffic over long-lived associations.¶

• Define application-layer semantics for the data carried on its channels.¶

• Define a general-purpose IP-layer tunneling or VPN protocol.¶

1.3. Terminology

For the purposes of this document:¶

Association:

A long-lived, cryptographically authenticated session between two N-PAMP endpoints, identified by a stable Association ID.¶

Channel:

A semantic multiplexing lane within an association, identified by a 16-bit Channel ID, carrying one class of agent traffic with its own sequence space.¶

Frame:

The atomic unit of transmission, consisting of a fixed 36-octet header, optional extension TLVs, and an AEAD-protected payload.¶

Profile:

One of three negotiated levels of cryptographic strength and operational requirement (Standard, High, Sovereign).¶

4.1. Frame Structure

Every N-PAMP frame has the following structure:¶

+--------+-------------+-------------------+-----------+
| Header | Extension   | Payload           | AEAD Tag  |
| 36 B   | TLVs (var)  | (var, encrypted)  | (16 B)    |
+--------+-------------+-------------------+-----------+

The 36-octet header is fixed-size. Zero or more extension TLVs MAY accompany a frame. The payload is AEAD-sealed, and the associated data covers the 21-octet header prefix (octets 0-20, through the Payload Length field, the same octets protected by the header CRC32C) so that any modification to those header fields is detected on decryption.¶

4.2. Frame Header

The fixed header is 36 octets, laid out as follows. Multi-octet integers are encoded in network byte order (big-endian) unless stated otherwise.¶

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     'N'       |     'P'       |     'A'       |     'M'       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ver   | Flags |          Frame Type           |  Channel ID   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                   Sequence Number (64 bits)                   +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                   Payload Length (32 bits)                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                   CRC32C over octets 0-20                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+             Reserved + Padding (11 octets, zero)              +
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The fields are:¶

All multi-octet integers are big-endian. The Ver field carries the wire major version; the value 0x02 corresponds to the ALPN identifier "n-pamp/2".¶

4.3. Frame Flags

The low nibble of header octet 4 carries four flag bits:¶

4.4. Extension TLVs

Zero or more Type-Length-Value (TLV) extensions MAY accompany a frame. Each TLV is encoded as:¶

+---------+---------+-----------+
| Type    | Length  | Value     |
| 16 bits | 16 bits | Length B  |
+---------+---------+-----------+

Type and Length are 16-bit unsigned integers in network byte order; Length is the byte count of Value (0 to 65535). A receiver that encounters an unknown TLV whose Type has the high bit (0x8000) clear MUST ignore that TLV. A receiver that encounters an unknown TLV whose Type has the high bit (0x8000) set MUST treat it as a forward-incompatible extension and reject the frame. The TLV type registry maintained by this specification is given in Section 10.4.¶

4.5. Payload Encoding

The payload carries a frame-type-specific body. The body MAY be encoded in a binary serialization, in deterministic CBOR [RFC8949], or as raw octets. The selected encoding is signaled within the channel-local interpretation of the Frame Type field.¶

4.6. Reserved Frame Types

Each channel defines its own frame types in the 0x0000-0xFFFF space. The following frame types are reserved across all channels and have the same meaning on every channel:¶

Channel-specific frame types begin at 0x0100 within each channel's frame namespace. Frame-type code points at or above 0x0030 that are not reserved here, and in particular the ranges enumerated in Section 9, are reserved for extensions defined in companion specifications.¶

The Control channel (0x0000) assigns the following channel-specific frame types for the N-PAMP handshake (Section 8):¶

4.7. CLOSE Frame

A CLOSE frame is authenticated like any other frame. A receiver MUST verify the AEAD tag before honoring a close. An unauthenticated or forged CLOSE frame MUST be dropped and SHOULD be counted as a security event.¶

5.1. Core Channel Registry

The following channels are defined and maintained by this specification:¶

The Min Profile column gives the lowest profile at which a channel may be enabled; a channel is available at that profile and at every higher profile (for example, a "High" channel is available at High and Sovereign). The Audit channel is enabled by default only at Sovereign; other profiles MAY enable it. The Control and Immune channels SHOULD be scheduled at higher priority than bulk channels (Memory, Sensory, Telemetry) during congestion.¶

All N-PAMP channels are full-duplex: each peer maintains an independent send and receive sequence space and independent per-direction traffic keys, so both peers MAY transmit on a channel simultaneously. The Direction column classifies each channel as follows:¶

The Stream channel (0x000C) provides general-purpose multiplexed full-duplex streaming, carrying concurrent bidirectional sub-streams (for example token, audio, video, and file-transfer streams), each with independent flow control.¶

Channel IDs not listed in Section 5.1, and in particular the ranges enumerated in Section 9, are reserved for extensions defined in companion specifications.¶

7.1. Key Encapsulation Mechanisms

Both are hybrid KEMs combining X25519 ECDH with ML-KEM [FIPS203] (ML-KEM-768 and ML-KEM-1024, respectively). The two shared secrets are concatenated as (ML-KEM shared secret || X25519 shared secret) and supplied as input keying material to HKDF-Extract [RFC5869]. The ML-KEM shared secret is placed first so the FIPS-approved key-establishment output leads the HKDF input ([SP800-56C]), matching the X25519MLKEM768 construction of [I-D.ietf-tls-ecdhe-mlkem]. The suite name lists X25519 first, but the shared-secret concatenation and the on-wire KEMShare/KEMCiphertext layout are ML-KEM-first. The Sovereign profile MUST NOT accept X25519MLKEM768.¶

7.2. Authenticated Encryption

AES-256-GCM is used as specified for AEAD ciphers in [RFC5116]; ChaCha20-Poly1305 is used as specified in [RFC8439]. Endpoints operating at the High and Sovereign profiles MUST support both AEAD suites because per-frame AEAD diversification at those profiles selects between them. Endpoints operating at the Standard profile MUST support at least one of the two.¶

7.3. Signatures

Ed25519 is used as specified in [RFC8032]. ML-DSA-87 is the module-lattice-based digital signature algorithm standardized in [FIPS204]. The Sovereign profile uses ML-DSA-87 for identity and audit signatures.¶

7.4. Key Derivation and Hashing

All key derivation uses HKDF [RFC5869]. The KDF hash is SHA-256 at the Standard profile and SHA-384 at the High and Sovereign profiles. The HKDF-Expand-Label construction follows TLS 1.3 [RFC8446], with the literal label prefix "n-pamp " (with the trailing space) in place of TLS 1.3's "tls13 ", providing domain separation from TLS 1.3, from QUIC, and from earlier N-PAMP versions. A conforming implementation MUST use the "n-pamp " prefix; use of the "tls13 " prefix is non-conformant. The full key-schedule ladder is specified in Section 8.3.¶

7.5. Key Schedule and Nonces

Traffic secrets are derived per (direction, epoch, AEAD suite, channel) tuple, so that no two distinct contexts share a key. Each traffic secret yields an AEAD key, an AEAD initialization vector, and a header-protection key by HKDF-Expand-Label. The per-frame nonce is the AEAD IV exclusive-ORed with the left-zero-padded sequence number, identical in form to the construction used in TLS 1.3 [RFC8446] and QUIC [RFC9001]. This namespace partitioning prevents cross-direction, cross-suite, and cross-channel nonce reuse, and supports forward secrecy: on key update, traffic secrets for the new epoch are derived afresh and the prior epoch's secrets are zeroized.¶

7.6. Random Number Generation

All randomness that participates in security MUST come from a cryptographically secure random number generator. Implementations MUST NOT use a non-cryptographic source for any field that participates in security.¶

8.1. Message Flow

There is no separate Finished frame; the Finished MAC is a TLV inside each AUTH frame. Each frame is a standard 36-octet N-PAMP frame (Section 4) on channel 0x0000 with sequence 0; the AUTH frames set FlagENC and are AEAD-sealed (Section 8.4.3). A server reaches the Established state only after it has verified CLIENT_AUTH; the master secret is derived at the client-authentication boundary.¶

8.2. Transcript

The handshake transcript is a running byte buffer; a transcript hash is H over all bytes absorbed so far. Unlike TLS 1.3 [RFC8446] Section 4.4.1, which hashes whole handshake messages, N-PAMP absorbs at per-TLV granularity and absorbs only the 2-octet big-endian frame type of each frame: the remaining 34 header octets and the AEAD tag are NOT absorbed. For each frame, the 2-octet frame type is absorbed, followed by each of that frame's TLVs in canonical Type(2) || Length(2) || Value form, in order. Five transcript hashes are named:¶

Because both peers absorb the identical decoded on-wire TLV bytes, their transcripts are byte-identical.¶

8.3. Key Schedule

The key schedule is a single HKDF-Extract [RFC5869] followed by sibling HKDF-Expand-Label derivations (simpler than TLS 1.3 [RFC8446] Section 7.1's three-stage chain; N-PAMP defines no PSK or 0-RTT in this binding). HKDF-Expand-Label is as in TLS 1.3 Section 7.1 with the N-PAMP label prefix "n-pamp " (with the trailing space) in place of "tls13 ":¶

HKDF-Expand-Label(Secret, Label, Context, Length) =
    HKDF-Expand(Secret, HkdfLabel, Length)
HkdfLabel = uint16(Length) || opaque("n-pamp " || Label)
                           || opaque(Context)

The KEM output (Section 7) is the 64-octet value (ML-KEM shared secret || X25519 shared secret), fed directly as input keying material:¶

handshake_secret = HKDF-Extract(salt = HashLen zero octets,
                                IKM  = ML-KEM_SS || X25519_SS)
c_hs_secret = HKDF-Expand-Label(handshake_secret,
                                "c hs", TH_kem, HashLen)
s_hs_secret = HKDF-Expand-Label(handshake_secret,
                                "s hs", TH_kem, HashLen)
master      = HKDF-Expand-Label(handshake_secret,
                                "master", TH_cCV, HashLen)

The Extract salt is HashLen zero octets (the [RFC5869] default). The master secret is derived only at the client-authentication boundary, from TH_cCV. Handshake-phase traffic keys descend from c_hs_secret and s_hs_secret; application-phase traffic keys descend from master, using the traffic-secret construction of Section 7. Because the parents differ, an identical (direction, epoch, suite, channel) tuple yields different (key, iv) across the handshake and application phases, so no (key, nonce) pair is shared across phases.¶

8.4. Authentication

signing_input = (0x20 x 64) || context || 0x00 || transcript_hash
context (server) = "N-PAMP draft-00, server CertificateVerify"
context (client) = "N-PAMP draft-00, client CertificateVerify"

finished_key = HKDF-Expand-Label(BaseKey, "finished", "", HashLen)
verify_data  = HMAC(finished_key, transcript_hash)

9.1. Reserved Frame-Type Ranges

The following per-channel frame-type code points are reserved for extensions defined in companion specifications:¶

9.2. Reserved TLV Tags

The TLV types 0x0010, 0x0013, and 0x0014 are reserved for extension TLVs defined in companion specifications. TLV types in the range 0x8000-0xFFFF remain reserved as forward-incompatible extension points per Section 4.¶

9.3. Reserved Channel-ID Range

Channel IDs in the range 0x0014-0xFFFF are reserved. Channels 0x0014-0x001F are reserved for future core additions by this specification; 0x0020-0xEFFF are reserved for extension channels defined in companion specifications; 0xF000-0xFFFE are GREASE values that receivers MUST ignore; and 0xFFFF MUST NOT appear on the wire. The specific extension assignments are out of scope for this document.¶

No algorithms, parameters, or semantics for any reserved range are defined in this document.¶

10.1. ALPN Protocol Identifier

IANA has registered the following value in the "TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs" registry established by [RFC7301]. The registration was made under an earlier version of this document; IANA is requested to update its reference to the current version:¶

The identification sequence is the 8-octet UTF-8 string "n-pamp/2". The trailing digit "2" equals the N-PAMP wire major version (the value 0x02 carried in the Ver field of the frame header, Section 4). The registration policy for the ALPN registry is Expert Review [RFC8126].¶

The earlier identifier "n-pamp/1" is deprecated. Implementations SHOULD NOT negotiate "n-pamp/1" for new associations. Future wire major versions will use distinct ALPN identifiers (for example, "n-pamp/3").¶

10.2. URI Scheme Registration

The "npamp" URI scheme has been provisionally registered in the "Uniform Resource Identifier (URI) Schemes" registry, following the template and the provisional-registration procedure (First Come First Served) of [RFC7595], under an earlier version of this document; IANA is requested to update its reference to the current version. The registration template follows:¶

Scheme name: npamp¶

Status: Provisional¶

Applications/protocols that use this scheme: The protocol defined in this document (N-PAMP). An "npamp" URI names an N-PAMP endpoint and an optional resource path within that endpoint.¶

URI scheme syntax: The "npamp" scheme uses the generic URI syntax of [RFC3986]:¶

npamp-URI = "npamp://" authority path-abempty [ "?" query ]

where "authority", "path-abempty", and "query" are as defined in [RFC3986]. The "authority" component identifies the N-PAMP endpoint (host and optional port). N-PAMP does not reserve a fixed default port; the underlying transport is negotiated as described in Section 3.¶

Encoding considerations: "npamp" URIs are processed as defined in [RFC3986]; non-ASCII characters in the path or query components are percent-encoded UTF-8 octets.¶

Interoperability considerations: None beyond those of [RFC3986]. The scheme carries no protocol semantics of its own; all behavior is defined by N-PAMP.¶

Security considerations: See Section 11. An "npamp" URI is only an identifier. Connecting to an "npamp" endpoint invokes the N-PAMP handshake and its authentication, confidentiality, and downgrade protections; dereferencing an "npamp" URI MUST NOT bypass the security profile negotiated by N-PAMP.¶

Contact: Shawn Sammartano, BubbleFish Technologies, Inc.¶

Change controller: Shawn Sammartano, BubbleFish Technologies, Inc.¶

Reference: This document.¶

10.3. Registries Maintained by This Specification

The N-PAMP channel registry (Section 5.1), the frame-type registry (Section 4.6), and the TLV type registry (Section 10.4) are defined and maintained within this specification. Because this document is published through the Independent Submission stream, it does not request the creation of new IANA-hosted registries for these code points; the registries are normative within this document and are extended by companion specifications and by future revisions of this document, not by IANA registration actions.¶

10.4. TLV Type Registry

The following TLV tags are defined by this specification. Tags marked "reserved" are described in Section 9.¶

11.1. Hybrid Key Establishment

Every profile uses a hybrid KEM that concatenates an ML-KEM shared secret with an X25519 shared secret [FIPS203] (ML-KEM first) before key derivation. The confidentiality of an association is preserved as long as at least one of the two components remains unbroken; an adversary must defeat both the classical and the post-quantum component to recover traffic keys. N-PAMP makes no claim of unconditional or "quantum-proof" security; it provides post-quantum hybrid security against the adversaries addressed by its component primitives.¶

11.2. Downgrade, Unknown-Key-Share, and Identity Substitution

The negotiated profile, KEM, signature algorithm, AEAD suite(s), and both peer identities are bound into the handshake transcript and confirmed by the Finished MAC (Section 3, Section 6). Altering any negotiated parameter, stripping a profile from the offer, or substituting a peer identity invalidates the Finished MAC and aborts the handshake. The High and Sovereign profiles additionally refuse to complete at a profile below their configured minimum.¶

11.3. Authenticated Encryption and Nonce Management

All payloads are protected by AEAD [RFC5116]. Traffic keys are partitioned per (direction, epoch, suite, channel), which structurally prevents nonce reuse across directions, AEAD suites, and channels. AEAD tag verification MUST be performed before any payload is processed, and equality comparisons of authentication values MUST be constant-time to avoid timing side channels.¶

11.4. Replay

Each (channel, direction) pair maintains a sliding replay window over sequence numbers. Frames outside the window or already recorded within it MUST be rejected. Where 0-RTT data is permitted, it MUST be limited to idempotent operations and protected against replay by an anti-replay mechanism scoped to the current epoch; the Sovereign profile disables 0-RTT entirely.¶

11.5. Forward Secrecy and Key Update

Endpoints MUST perform key updates within profile-specific bounds on elapsed time, frames sent, and bytes protected, with the tightest bounds at the Sovereign profile. On key update, the prior epoch's traffic secrets MUST be zeroized so that compromise of the current epoch does not expose previously protected traffic. Rotation of the master secret requires a fresh handshake.¶

11.6. Connection Migration

When carried over QUIC, an endpoint MUST validate a peer's new path with a challenge-response exchange (PATH_CHALLENGE / PATH_RESPONSE) before accepting an address change, to prevent off-path migration spoofing.¶

11.7. Authenticated Close

CLOSE frames are AEAD-protected and MUST be verified before being honored, so that an off-path attacker cannot tear down an association with a forged CLOSE.¶

11.8. Extension Points

The reserved code-point ranges in Section 9 carry no algorithms or semantics in this document. Any security properties of extensions occupying those ranges are the responsibility of the companion specifications that define them and are out of scope here.¶

11.9. Implementation Considerations

Where the wire format requires deterministic encoding (for example, deterministic CBOR [RFC8949] or canonical integer encodings), implementations MUST produce byte-identical output for identical inputs, because non-deterministic encodings can invalidate transcript and integrity computations across peers.¶

12.1. Normative References

[FIPS203]

National Institute of Standards and Technology (NIST), "Module-Lattice-Based Key-Encapsulation Mechanism Standard", FIPS 203, 2024.

[FIPS204]

National Institute of Standards and Technology (NIST), "Module-Lattice-Based Digital Signature Standard", FIPS 204, 2024.

[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/rfc/rfc2119>.

[RFC3986]

Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, <https://www.rfc-editor.org/rfc/rfc3986>.

[RFC5116]

McGrew, D., "An Interface and Algorithms for Authenticated Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, <https://www.rfc-editor.org/rfc/rfc5116>.

[RFC5869]

Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 5869, DOI 10.17487/RFC5869, May 2010, <https://www.rfc-editor.org/rfc/rfc5869>.

[RFC7301]

Friedl, S., Popov, A., Langley, A., and E. Stephan, "Transport Layer Security (TLS) Application-Layer Protocol Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, July 2014, <https://www.rfc-editor.org/rfc/rfc7301>.

[RFC7595]

Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines and Registration Procedures for URI Schemes", BCP 35, RFC 7595, DOI 10.17487/RFC7595, June 2015, <https://www.rfc-editor.org/rfc/rfc7595>.

[RFC8032]

Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital Signature Algorithm (EdDSA)", RFC 8032, DOI 10.17487/RFC8032, January 2017, <https://www.rfc-editor.org/rfc/rfc8032>.

[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/rfc/rfc8174>.

[RFC8439]

Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018, <https://www.rfc-editor.org/rfc/rfc8439>.

[RFC8446]

Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, <https://www.rfc-editor.org/rfc/rfc8446>.

[RFC8949]

Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", STD 94, RFC 8949, DOI 10.17487/RFC8949, December 2020, <https://www.rfc-editor.org/rfc/rfc8949>.

[RFC9000]

Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, <https://www.rfc-editor.org/rfc/rfc9000>.

[RFC9001]

Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021, <https://www.rfc-editor.org/rfc/rfc9001>.

[SP800-56C]

National Institute of Standards and Technology (NIST), "Recommendation for Key-Derivation Methods in Key-Establishment Schemes", NIST Special Publication 800-56C Rev. 2, August 2020, <https://csrc.nist.gov/pubs/sp/800/56/c/r2/final>.

12.2. Informative References

[I-D.ietf-tls-ecdhe-mlkem]

Kwiatkowski, K., Kampanakis, P., Westerbaan, B., and D. Stebila, "Post-quantum hybrid ECDHE-MLKEM Key Agreement for TLSv1.3", Work in Progress, Internet-Draft, draft-ietf-tls-ecdhe-mlkem-05, 26 May 2026, <https://datatracker.ietf.org/doc/html/draft-ietf-tls-ecdhe-mlkem-05>.

[RFC3552]

Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on Security Considerations", BCP 72, RFC 3552, DOI 10.17487/RFC3552, July 2003, <https://www.rfc-editor.org/rfc/rfc3552>.

[RFC8126]

Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/rfc/rfc8126>.