TLS-DPA: An Identity-Bound Security Protocol for Traditional, Overlay, and Zero-Port Transports
draft-dpa-tls-dpa-01
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Benjamin Anthony Fisher | ||
| Last updated | 2026-03-16 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
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| Send notices to | (None) |
draft-dpa-tls-dpa-01
Network Working Group B.A. Fisher
Internet-Draft DPA R&D Ltd (https://www.dpa-cloud.co.uk)
Intended status: Informational 16 March 2026
Expires: 17 September 2026
TLS-DPA: An Identity-Bound Security Protocol for Traditional, Overlay,
and Zero-Port Transports
draft-dpa-tls-dpa-01
Abstract
TLS-DPA is an experimental, identity-bound security protocol inspired
by the design of TLS 1.3 ( [RFC8446] ). It is intended to operate
consistently across environments where conventional IP address and
port semantics are weak, unstable, or intentionally absent, including
zero-port transports such as UZP ( [UZP] ).
TLS-DPA generalises the handshake so it is not tied to server-side
listeners, binds authentication to Service Identities rather than
network coordinates, reduces metadata exposure to intermediaries
(including rendezvous nodes in UZP fabrics), provides a unified
hybrid-KEM post-quantum transition model ( [NIST-PQC] ), and supports
session continuity across overlay path changes (e.g., QUIC Connection
IDs; [RFC9000] ).
This document is part of an experimental, research-oriented
Independent Stream suite. It defines the current normative baseline
for trust objects, validation rules, and security semantics within
its scope. Hard interoperability is expected for shared object
semantics and validation rules. Full wire-level, clustering, and
proof-family interoperability is not claimed everywhere yet; the
remaining details are intentionally profile-defined or deferred where
noted.
Note to Reviewers
This document is part of an experimental, research-oriented suite
prepared for the Independent Stream. It is published to enable
structured technical review, interoperability discussion, and
disciplined specification development, and it remains a work-in-
progress research artefact rather than a finished specification.
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Within that suite, this revision defines the current normative
baseline for trust objects, validation rules, and security semantics
within TLS-DPA. Hard interoperability is expected for shared object
semantics and validation rules. Full wire-level, clustering, and
proof-family interoperability is not claimed everywhere yet; the
remaining details are intentionally profile-defined or deferred where
noted.
The name TLS-DPA is used to label this research protocol and avoid
confusion with the IETF TLS versioning and registry space. It is not
presented as a new version of the IETF TLS protocol, and no IANA
allocations are requested by this draft.
Where this document provides numeric guidance (for example, replay
windows, resumption behaviour, or profile parameters), the intent is
to offer recommended bounds suitable for experimentation; profile-
based behaviour and implementation discretion are explicitly expected
within stated limits.
Reducing metadata exposure in some roles does not imply complete
privacy or invisibility, and rendezvous or clustered deployments
still require explicit availability assumptions and operational
design.
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 17 September 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Table of Contents
1. Scope and Status . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Layering and Interoperability Baseline . . . . . . . . . . . 5
4. Conventions and Terminology . . . . . . . . . . . . . . . . . 6
5. Design Goals . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Core TLS-DPA Semantics . . . . . . . . . . . . . . . . . . . 7
7. Transport Binding Rules . . . . . . . . . . . . . . . . . . . 8
8. Identity Binding Model . . . . . . . . . . . . . . . . . . . 9
9. Identity Authority and Trust Model . . . . . . . . . . . . . 9
9.1. Revocation Model . . . . . . . . . . . . . . . . . . . . 10
9.1.1. Revocation Signal Object . . . . . . . . . . . . . . 11
9.1.2. Threshold-Consensus Evidence Format . . . . . . . . . 12
9.1.3. Revocation Signal Acquisition, Caching, and
Freshness . . . . . . . . . . . . . . . . . . . . . . 13
9.1.4. Baseline Revocation Processing . . . . . . . . . . . 14
10. Post-Quantum Key Exchange Model . . . . . . . . . . . . . . . 15
11. Key Schedule Summary . . . . . . . . . . . . . . . . . . . . 15
12. Transport Binding Extensions . . . . . . . . . . . . . . . . 16
12.1. tlsdpa_service_identity . . . . . . . . . . . . . . . . 16
12.2. tlsdpa_transport_binding . . . . . . . . . . . . . . . . 17
12.3. tlsdpa_pq_kem_params . . . . . . . . . . . . . . . . . . 17
13. Transcript Hashing Rules . . . . . . . . . . . . . . . . . . 18
14. Key Schedule and Exporters . . . . . . . . . . . . . . . . . 18
14.1. Exporter Binding Requirements . . . . . . . . . . . . . 18
14.2. Exporter Label Structure . . . . . . . . . . . . . . . . 19
14.3. Exporter Context Structure . . . . . . . . . . . . . . . 19
14.4. Example Exporter Computation . . . . . . . . . . . . . . 19
15. Handshake Diagrams . . . . . . . . . . . . . . . . . . . . . 19
15.1. Full UZP Flight Diagram . . . . . . . . . . . . . . . . 20
15.2. Generalised TLS-DPA Flow . . . . . . . . . . . . . . . . 20
15.3. RN Observation and Channel Truth . . . . . . . . . . . . 21
16. Service Identity Validation . . . . . . . . . . . . . . . . . 21
16.1. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . 21
16.2. UZP CID . . . . . . . . . . . . . . . . . . . . . . . . 21
16.3. UZP EID . . . . . . . . . . . . . . . . . . . . . . . . 21
16.4. UZPIF Selector . . . . . . . . . . . . . . . . . . . . . 22
16.5. Failure Handling . . . . . . . . . . . . . . . . . . . . 22
17. New Alerts . . . . . . . . . . . . . . . . . . . . . . . . . 22
18. UZP / UZPIF Applicability and Profile . . . . . . . . . . . . 22
19. Early Data (0-RTT) . . . . . . . . . . . . . . . . . . . . . 23
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19.1. RN Replay Detection . . . . . . . . . . . . . . . . . . 23
19.2. Endpoint Replay Detection . . . . . . . . . . . . . . . 23
19.3. Grant Nonce Interaction . . . . . . . . . . . . . . . . 24
19.4. 0-RTT over UZP Rebinds . . . . . . . . . . . . . . . . . 24
20. Optional and Experimental Extensions . . . . . . . . . . . . 24
20.1. tlsdpa_specification_origin_id . . . . . . . . . . . . . 24
21. Threat Model . . . . . . . . . . . . . . . . . . . . . . . . 25
22. Operational Considerations . . . . . . . . . . . . . . . . . 25
23. Security Considerations . . . . . . . . . . . . . . . . . . . 25
24. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
25. Normative References . . . . . . . . . . . . . . . . . . . . 26
26. Informative References . . . . . . . . . . . . . . . . . . . 26
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 27
1. Scope and Status
This Internet-Draft is part of an experimental, research-oriented
suite prepared for the Independent Stream. It specifies TLS-DPA for
identity-first and topology-independent deployments, including
rendezvous and zero-port fabrics, while remaining open to substantial
revision through review and implementation experiments.
Within that suite, this document defines the current normative
baseline for trust objects, validation rules, and security semantics
within TLS-DPA, especially identity binding, transcript construction,
and handshake authorisation. Hard interoperability is expected for
shared object semantics and validation rules.
Full wire-level, clustering, and proof-family interoperability is not
claimed everywhere yet; the remaining details are intentionally
profile-defined or deferred, so this draft should not be read as
claiming a fully closed wire image or proof model.
TLS-DPA is designed for environments where conventional port-
listening assumptions and IP:port-based identity binding do not hold.
It is designed for experimentation and profile-driven deployments
within its target environment. Privacy, decentralisation, and
availability remain deployment- and profile-dependent properties.
2. Introduction
TLS 1.3 ( [RFC8446] ) defines the current baseline for transport-
layer security on the Internet. However, its usage patterns remain
oriented around server-side listeners bound to IP address and port
tuples, and many deployments treat these network coordinates as
meaningful anchors for authentication and policy.
TLS-DPA extends the design principles of TLS 1.3 to support:
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* operation over identity-first, topology-independent transports
(for example UZP; [UZP] );
* authentication bound to Service Identities, rather than IP
addresses and ports;
* reduced metadata exposure to intermediaries, including rendezvous
nodes in UZP fabrics;
* hybrid classical/post-quantum KEM negotiation aligned with the
NIST PQC process ( [NIST-PQC] );
* session continuity across transport or overlay path changes (for
example QUIC Connection IDs; [RFC9000] ).
The eventual TLS-DPA wire image is intended to remain close to TLS
1.3, enabling reuse of existing implementation structure while adding
explicit identity and transport binding into the handshake transcript
and key schedule. This draft does not yet close every byte-level
encoding, extension layout, or deployment profile.
TLS-DPA also aligns with zero-trust guidance (NIST SP 800-207
[NIST-SP800-207]) and identity-centric designs such as HIP [RFC7401].
This draft should therefore be read as part of an experimental,
research-oriented Independent Stream suite and as the current
normative baseline for trust objects, validation rules, and security
semantics within TLS-DPA. Hard interoperability is expected for
shared object semantics and validation rules. Full wire-level,
clustering, and proof-family interoperability is not claimed
everywhere yet; the remaining details are intentionally profile-
defined or deferred. Reducing metadata exposure in some roles does
not imply complete privacy or invisibility, and rendezvous or
clustered deployment availability still depends on explicit
operational choices.
3. Layering and Interoperability Baseline
This document is organised into four specification strata: core
handshake semantics; transport binding rules; UZP / UZPIF
applicability and profile rules; and optional or experimental
extensions. The intent is to keep the core handshake and trust story
stable even where exact extension code points, deployment profiles,
or transport-specific optimisations remain open.
Sections Section 6, Section 8, Section 9, Section 10, Section 11,
Section 13, Section 14, Section 16, and Section 17 define the core
handshake semantics and trust decisions required for baseline
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interoperability. Sections Section 7 and Section 12 define the
transport binding rules that feed those semantics. Sections
Section 18 and Section 19 define the UZP / UZPIF applicability
profile. Section Section 20 is outside baseline interoperability
unless a later profile explicitly upgrades it.
Baseline interoperable behaviour in this revision requires the core
semantics for Service Identity binding, transcript construction, key
schedule inputs, minimum revocation processing, Service Identity
validation, and alert handling. Baseline interoperable transport
binding further requires processing of tlsdpa_service_identity and
tlsdpa_transport_binding. The tlsdpa_pq_kem_params extension is
required when a negotiated deployment profile enables post-quantum or
hybrid KEM operation.
Exact extension code points, final wire encodings, some revocation
acquisition paths beyond the baseline processing rules, UZP early-
data and rebind policy, and optional attribution metadata remain
profile-dependent or experimental in this revision. Optional
extensions MUST NOT alter authentication, authorisation, or trust
outcomes unless a later profile explicitly upgrades them.
Sections Section 5, Section 15, Section 21, and Section 22 are
explanatory or deployment-oriented unless they explicitly restate a
normative baseline rule from the sections above.
4. Conventions and Terminology
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
[RFC2119] and [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Terminology used throughout this document:
CID Canonical Identity (a long-term public key hash).
EID Ephemeral Identity (a session-level fingerprint).
UZP Zero-port transport as defined by the companion UZP Internet-
Draft ( [UZP] ).
ZPIT Zero-Port Interconnect Tunnel (a UZP fabric channel).
Pantheon A federated or deployment-scoped identity, attestation, and
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policy plane whose authorities bind identity, policy, and trust
metadata to keys or selectors accepted under local policy, may
validate or certify those bindings, and may issue credentials,
Grants, and delegations over them.
Service Identity The identity to which TLS-DPA authentication is
bound (for example a DNS name, CID, EID, or a UZPIF selector).
Specification-Origin Identifier An OPTIONAL non-authoritative
attribution metadata field carried by extension.
5. Design Goals
TLS-DPA is designed to:
1. decouple channel authentication from IP address and port
topology;
2. provide identity-first naming independent of network routing;
3. support hybrid classical and post-quantum KEM negotiation aligned
with NIST PQC guidance ( [NIST-PQC] );
4. reduce metadata in early handshake flights;
5. bind channels to transport-level identifiers (for example UZP
SessionIDs or QUIC Connection IDs; [RFC9000] );
6. remain closely aligned with the structure of TLS 1.3 ( [RFC8446]
);
7. operate efficiently over UZP and UZPIF rendezvous fabrics ( [UZP]
, [UZPIF] ).
Where this document specifies algorithms or parameter sets (for
example hybrid KEM combinations), these are intended as recommended
profiles and may evolve. Implementations may support additional
profiles and apply implementation-defined choices within any explicit
limits described in the relevant sections.
6. Core TLS-DPA Semantics
TLS-DPA retains the basic architecture of TLS 1.3 ( [RFC8446] ) but
introduces:
* transport-agnostic channel binding, via a dedicated extension that
carries a transport identifier and class;
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* Service Identity negotiation and binding into the transcript;
* mandatory transcript binding of identity and transport metadata;
* PQ-ready hybrid KEM negotiation using an explicit parameter
extension;
* stable session resumption across topology or path changes.
TLS-DPA defines the handshake over an abstract TLS-DPA Channel. The
channel only needs to provide:
* ordered or reliably framed delivery;
* a transport-level identifier (e.g., a TCP 4-tuple, QUIC Connection
ID; [RFC9000] , or a UZP SessionID);
* uniqueness sufficient for transcript binding.
Together with Sections Section 8, Section 9, Section 10, Section 11,
Section 13, Section 14, Section 16, and Section 17, this section
defines the core TLS-DPA handshake semantics for baseline
interoperability.
7. Transport Binding Rules
This section and Section Section 12 define the transport binding
rules consumed by the core TLS-DPA handshake. Baseline
interoperability requires consistent construction and verification of
Service Identity and transport-binding inputs; exact code points and
final byte-level encodings remain profile-defined in this revision.
TLS-DPA treats the underlying transport as providing one or more
channels:
* *TCP* : traditional byte stream;
* *QUIC* : stream over a QUIC connection, identified by QUIC
Connection ID ( [RFC9000] );
* *UZP* : stream inside a ZPIT, identified by a UZP SessionID (
[UZP] ).
The handshake binds to this transport using the
tlsdpa_transport_binding extension (see Section 12.2 ).
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+------------+ +---------------+ +------------+
| TLS-DPA |-->| Transport |-->| TLS-DPA |
| Client | | Channel | | Server |
| Handshake | | Handshake & | | |
| Protected | | Protected | | |
| Data | | Data | | |
+------------+ +---------------+ +------------+
Figure 1: TLS-DPA operating over an abstract transport channel.
This figure places TLS-DPA above a transport channel to highlight the
separation from the underlying relay.
8. Identity Binding Model
TLS-DPA authenticates peers using Service Identities, which may be:
* DNS names (validated per RFC 6125).
* UZP CIDs (canonical identities, derived from long-term public
keys).
* UZP EIDs (ephemeral, session-level identities).
* UZPIF selectors resolved via Pantheon services, federated identity
services, or local trust mappings [UZPIF].
The Service Identity MUST be included in the handshake transcript and
validated as described in Section Section 16.
CIDs are intended to be stable over meaningful operational time-
scales: changes in CID MUST be treated as key-rotation events and not
as transient transport artefacts.
9. Identity Authority and Trust Model
TLS-DPA identity issuance is intentionally decentralisable. Service
Identity credentials MAY be self-issued, multi-signed, federation-
signed, or organisationally issued. Deployments MAY use one or more
issuance models concurrently.
Where Pantheon is used in a UZPIF-aligned deployment, Pantheon
authorities bind identity, policy, and trust metadata to keys or
selectors accepted under policy; they may validate or certify those
bindings and issue credentials, Grants, or delegations over them, but
they need not generate or custody the underlying private keys.
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TLS-DPA implementations MUST NOT require a single global signing
authority. The protocol does not mandate a central certificate
authority.
If any root trust model is used by a deployment profile, that model
MUST be replaceable without protocol redesign.
9.1. Revocation Model
TLS-DPA revocation is policy-driven and decentralisable. The
protocol does not define a mandatory single revocation authority and
does not require any global CRL-equivalent service.
Baseline interoperable revocation in this revision is intentionally
narrow: signed Revocation Signal objects, optional Threshold-
Consensus Evidence, explicit acquisition and freshness rules, and
fail-closed handling of unknown status for new admission decisions.
Broader federation governance, quorum composition, and alternate
revocation transports remain deployment- or profile-defined.
Interoperable decentralised revocation in TLS-DPA is defined here
only when revocation is conveyed as explicit Revocation Signal
objects (Section 9.1.1), evaluated under a recognised threshold
policy and, where required, bound to Threshold-Consensus Evidence
(Section 9.1.2), and processed according to the client rules in this
section. Deployments that do not exchange such objects remain
deployment-local and MUST NOT assume interoperable revocation
semantics.
Revocation MAY be federation-scoped, multi-party threshold-based, and
client-enforced. For interoperable exchange, Revocation Signals MUST
be represented using the common signed artefact envelope defined by
UZPIF ([UZPIF]) with "object_type" set to "revocation" and with epoch
or sequence values suitable for conflict handling and freshness
checks. That object type inherits the UZPIF common envelope
unchanged, including canonical serialisation, exact signature
coverage, object_id derivation, unknown-extension handling, signature
ordering, algorithm identifier matching, epoch-versus-sequence
precedence, and the rule that detached signatures are not part of
baseline interoperability.
No single entity SHALL possess unilateral global revocation
authority.
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9.1.1. Revocation Signal Object
To support interoperable client behaviour, TLS-DPA defines a minimal
Revocation Signal object. A Revocation Signal MUST use the common
signed artefact envelope defined by UZPIF ([UZPIF]) with
"object_type" set to "revocation", plus the following minimum
revocation-specific body semantics:
* *subject_type:* identifies whether the revocation applies to a
service identity, a Grant, an authority key, or a selector.
* *subject_identifier:* identifies the specific service identity,
Grant, authority key, or selector being revoked.
* *issuer_authority_id:* identifies the authority context issuing
the revocation signal.
* *scope:* defines the operational scope of the revocation, such as
a tenant, service class, transport context, or selector namespace.
* *reason_code:* provides a deployment-defined reason such as key
compromise, administrative withdrawal, policy violation, or
supersession.
* *issue time:* states when the signal was issued.
* *expiry time:* indicates when the revocation signal ceases to
apply.
* *optional review_time:* indicates a non-expiry re-evaluation point
when deployments require review before the signal lapses.
* *threshold policy identifier:* identifies the quorum, threshold,
or federation rule under which the signal is to be evaluated.
* *common-envelope signature set:* one or more signatures sufficient
for the relying party to evaluate threshold satisfaction.
* *optional threshold-consensus evidence reference:* a pointer or
digest referring to a separate threshold-consensus evidence object
when quorum proof is carried out-of-line.
* *optional evidence reference:* a pointer or digest referring to
supporting evidence when the revocation is evidence-backed.
* *optional transparency-log checkpoint reference:* a pointer to a
transparency checkpoint or append-only log state relevant to the
signal.
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In terms of the common envelope, "subject_identifier" will normally
map to "subject_id", "issue time" to "issued_at", "expiry time" to
"not_after", and "threshold policy identifier" to "policy_id". If a
separate "review_time" is needed, it belongs in the revocation-
specific body and MUST NOT alter envelope validity semantics.
These fields extend only the revocation-specific body. TLS-DPA
inherits the UZPIF common envelope unchanged, including canonical
serialisation, exact signature coverage, object identifiers, unknown
extension handling, signature ordering, algorithm identifier
matching, epoch-versus-sequence precedence, and the rule that
detached signatures are not part of baseline interoperability.
9.1.2. Threshold-Consensus Evidence Format
When revocation depends on multi-party or threshold consensus and
interoperable exchange is required, implementations MUST represent
the quorum result as a Threshold-Consensus Evidence object. This
object MUST use the common signed artefact envelope defined by UZPIF
([UZPIF]), with "object_type" set to "threshold-consensus-evidence".
A minimal Threshold-Consensus Evidence object MUST carry:
* the referenced Revocation Signal identifier or digest;
* the threshold policy identifier;
* the required threshold or quorum rule;
* the participating authority identifiers or key identifiers;
* the signature set, signature digests, or equivalent verification
evidence used to satisfy the threshold;
* the consensus evaluation result, such as satisfied, unsatisfied,
or advisory;
* an evaluation timestamp;
* optional supporting evidence references; and
* optional transparency-log or checkpoint references anchoring the
threshold evidence.
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Threshold-Consensus Evidence MAY be embedded within the Revocation
Signal or carried as a separate artefact referenced by it. If it is
carried separately, the client MUST bind it to the exact Revocation
Signal via digest, object identifier, or another unambiguous
reference before using it for enforcement.
These fields populate the threshold-evidence body only and MUST NOT
redefine the suite envelope semantics. Threshold-Consensus Evidence
inherits the UZPIF common envelope unchanged, including canonical
serialisation, exact signature coverage, object identifiers, unknown
extension handling, signature ordering, algorithm identifier
matching, epoch-versus-sequence precedence, and the rule that
detached signatures are not part of baseline interoperability.
9.1.3. Revocation Signal Acquisition, Caching, and Freshness
A baseline interoperable client MUST be able to consume Revocation
Signal (Section 9.1.1) and Threshold-Consensus Evidence
(Section 9.1.2) objects presented by the peer during handshake or
resumption. A client SHOULD also support authenticated out-of-band
retrieval from authority, directory, or transparency channels so
freshness can be re-established when the peer does not present
current objects. Locally retained objects MAY be reused only within
the freshness bounds of this section. Regardless of acquisition
path, the client MUST authenticate the object under the common
envelope rules before using it.
An accepted Revocation Signal, Threshold-Consensus Evidence object,
or threshold-policy metadata item MUST be cached no longer than the
earliest of: its expiry time; its "review_time" if present;
replacement by a newer applicable object under epoch, sequence, or
object-identifier precedence; or a stricter local maximum-staleness
bound. In the absence of a stricter deployment profile, that local
maximum-staleness bound MUST NOT exceed 24 hours from the most recent
authenticated acquisition or freshness-confirmation event.
If current revocation state cannot be refreshed or its freshness
cannot be re-established within those bounds, the client MUST
classify the subject's revocation status as "unknown" rather than
silently treating the subject as clean or not revoked. For new
handshakes, session resumption, and any authorisation-expanding
transition, unknown status is fail-closed in the baseline model.
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9.1.4. Baseline Revocation Processing
A TLS-DPA client or relying service processing a Revocation Signal
(Section 9.1.1) or Threshold-Consensus Evidence (Section 9.1.2) MUST
verify the object's signatures, algorithm acceptability, issuer
authority context, validity interval, declared scope, freshness
state, supersession state, and any applicable threshold policy before
applying revocation effects. Minimum local processing MUST always
determine whether the outcome is enforced revocation, advisory
evidence, or unknown revocation state for the decision in question.
* If the locally recognised threshold is satisfied, the client MUST
enforce revocation for the stated scope.
* If the signal is authentic but below the locally recognised
threshold, it is advisory and MAY influence local risk policy,
warnings, or connection decisions.
* Authenticity alone is insufficient: an otherwise valid Revocation
Signal or Threshold-Consensus Evidence object MUST NOT be treated
as current revocation truth if it is stale, superseded, scope-
mismatched, or no longer policy-eligible for the decision being
made.
* If the threshold policy is unknown, or if required threshold-
consensus evidence is absent or cannot be bound to the Revocation
Signal, the client MUST classify the result as unknown revocation
state rather than as clean status.
* If a Revocation Signal or Threshold-Consensus Evidence object
carries a transparency-log or checkpoint reference, the client
SHOULD verify that reference before relying on the signal as
quorum-backed evidence.
* For already-established sessions whose revocation freshness later
becomes unknown, a deployment profile MAY define bounded fail-soft
handling, but that behaviour is outside baseline interoperability.
Absent such a profile, the endpoint MUST stop issuing resumption
state and MUST block authorisation-expanding actions until
freshness is re-established or the session is terminated.
* Clients MUST retain enough cached metadata to determine whether a
previously enforced or observed revocation has expired, requires
review, has been superseded by a newer signal, or has fallen into
unknown freshness state.
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* Conflicting revocation signals for the same subject and scope MUST
be processed under local policy unless a deployment profile
defines a stronger quorum or conflict-resolution rule.
This baseline does not attempt to solve global governance or
federation-wide dispute resolution. It defines enough shared
behaviour for interoperable handling of signed revocation artefacts,
threshold evidence, and checkpoint-anchored revocation claims while
leaving authority composition and quorum policy to deployment
profiles.
10. Post-Quantum Key Exchange Model
TLS-DPA introduces unified hybrid-KEM negotiation via the
tlsdpa_pq_kem_params extension. Supported KEM schemes include:
* X25519 (classical ECDH).
* Kyber768 (PQC KEM candidate).
* A hybrid X25519+Kyber768 mode.
The key schedule incorporates PQ KEM inputs prior to traffic secret
derivation, following general design principles for hybrid KEMs in
the NIST PQC process [NIST-PQC].
11. Key Schedule Summary
TLS-DPA modifies the TLS 1.3 key derivation [RFC8446] to include:
* Service Identity.
* Transport Binding.
* PQ KEM materials.
Exporter values MUST be bound to both identity and transport
(Section Section 14).
At a high level, PQ hybrid KEM inputs augment the TLS 1.3 key
schedule:
shared_secret = HKDF-Extract(kem_secret || ecdh_secret)
Figure 2: Hybrid shared secret extraction.
This equation shows the hybrid extraction step that combines KEM and
ECDH inputs.
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AEAD algorithms used with TLS-DPA MUST follow their specification-
defined tag lengths. Tags MUST NOT be truncated below 96 bits, and
128-bit tags SHOULD be preferred where supported.
12. Transport Binding Extensions
This section carries the handshake extensions that bind the core TLS-
DPA semantics into the transcript. Baseline interoperable behaviour
requires tlsdpa_service_identity and tlsdpa_transport_binding. The
tlsdpa_pq_kem_params extension is required when a negotiated
deployment profile enables post-quantum or hybrid KEM operation.
The extension semantics in this section are normative where baseline
interoperability requires them, but the example code points and
C-like structures are illustrative and intended for experimentation.
This draft does not request IANA allocations. Where appropriate,
implementations may use private-use ranges or negotiated profiles
while preserving the semantics defined here.
12.1. tlsdpa_service_identity
The tlsdpa_service_identity extension carries the Service Identity to
which the TLS-DPA handshake is bound. For experimentation, this
document uses an example private-use code point value (0xFE01);
deployments MAY select alternative values by profile.
extension_type = 0xFE01
struct {
ServiceIdentityType identity_type;
opaque identity_value<1..2^16-1>;
} ServiceIdentity;
enum {
dns_name(0),
uzp_cid(1),
uzp_eid(2),
uzpif_selector(3),
(255)
} ServiceIdentityType;
Figure 3: Service Identity extension structure (informative
C-like syntax).
This figure shows the fields carried in the Service Identity
extension.
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The client MUST send exactly one Service Identity. The server MUST
validate it according to its type (Section Section 16).
12.2. tlsdpa_transport_binding
The tlsdpa_transport_binding extension binds the handshake transcript
to an underlying transport identifier and transport class. For
experimentation, this document uses an example private-use code point
value (0xFE02); deployments MAY select alternative values by profile.
extension_type = 0xFE02
struct {
opaque transport_id<1..32>;
uint8 transport_class; /* 0=TCP, 1=QUIC, 2=UZP */
opaque transport_params<0..256>;
} TransportBinding;
Figure 4: Transport Binding extension structure (informative
C-like syntax).
This figure shows the fields used to bind the handshake to a
transport identifier and class.
For UZP, transport_id MUST contain the UZP SessionID. For QUIC, it
SHOULD contain the QUIC Connection ID [RFC9000].
12.3. tlsdpa_pq_kem_params
The tlsdpa_pq_kem_params extension carries the list of acceptable KEM
schemes and related profile parameters. For experimentation, this
document uses an example private-use code point value (0xFE03);
deployments MAY select alternative values by profile.
extension_type = 0xFE03
struct {
KEMScheme kem_list<2..2^8-1>;
} PQKemParams;
enum {
x25519(0),
kyber768(1),
hybrid_x25519_kyber768(2),
(255)
} KEMScheme;
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Figure 5: PQ KEM parameters extension structure (informative
C-like syntax).
This figure enumerates the acceptable KEM schemes and profile
parameters.
The client proposes a list of acceptable KEM schemes. The selected
scheme feeds into the key schedule.
13. Transcript Hashing Rules
New transcript components MUST be inserted as follows:
th = Hash(ClientHello
|| ServiceIdentity
|| TransportBinding
|| PQKemParams
|| ServerHello
|| ... )
Figure 6: Transcript hashing with identity and transport binding
(illustrative).
This figure shows where the new identity and transport inputs are
inserted into the transcript hash.
Hash mismatches MUST abort the handshake with
illegal_transport_binding or identity_mismatch (Section Section 17).
14. Key Schedule and Exporters
PQ hybrid KEM inputs augment the TLS 1.3 key schedule as:
shared_secret = HKDF-Extract(kem_secret || ecdh_secret)
Figure 7: Hybrid shared secret extraction (illustrative).
This figure shows the shared secret input used for exporter
derivation.
Exporter keys MUST incorporate identity and transport bindings.
14.1. Exporter Binding Requirements
TLS-DPA exporters MUST include:
* Service Identity (SID).
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* Transport Binding (TB).
* PQ KEM scheme identifier.
* UZP SessionID (if transport_class = UZP).
14.2. Exporter Label Structure
label = "tlsdpa exporter" || 0x00 ||
identity_type || transport_class
Figure 8: Exporter label structure (illustrative).
This figure shows the label composition that binds exporter output to
identity and transport.
where identity_type is from ServiceIdentityType, and transport_class
is from TransportBinding.
14.3. Exporter Context Structure
struct {
opaque sid_hash[32]; /* BLAKE3-256 of Service Identity */
opaque tb_hash[32]; /* BLAKE3-256 of TransportBinding */
opaque kem_id[1]; /* selected KEM scheme */
} ExporterContext;
Figure 9: ExporterContext structure (informative C-like syntax).
This figure shows the exporter context fields derived from Service
Identity, TransportBinding, and the selected KEM.
14.4. Example Exporter Computation
shared = HKDF-Extract(kem_secret || ecdh_secret);
ctx = ExporterContext(sid_hash, tb_hash, kem_id);
key = HKDF-Expand(shared, label, ctx, outlen);
Figure 10: Example exporter computation (illustrative).
This figure summarizes the exporter computation flow from shared
secret to derived key.
15. Handshake Diagrams
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15.1. Full UZP Flight Diagram
Figure 11 provides an illustrative end-to-end view of a TLS-DPA
handshake relayed via a rendezvous node (RN) in a UZP fabric. The RN
forwards handshake flights without decrypting them. Binding ensures
the RN cannot replay or modify flows undetected.
EP-Client RN EP-Server
| | |
|---- CH1: ClientHello(SID,TB,PQ) ------>| |
| |--- CH1' (fwd) ----------------------------->|
| |<-- SH1: ServerHello(PQ,TB) -----------------|
|<--- SH1' (fwd) -| |
|---- CH2: EncryptedExtensions --------->| |
| |--- CH2' (fwd) ----------------------------->|
| |<-- EE2/Cert/Finished -----------------------|
|<--- EE2'/Cert'/Finished' --------------| |
|<==== Finished + Encrypted App Data ===>|
Figure 11: TLS-DPA handshake relayed via an RN, with end-to-end
protection over the ZPIT (illustrative).
This figure traces the RN-relayed handshake flights while the
endpoints retain end-to-end protection.
Where:
* SID: Service Identity.
* TB: Transport Binding (UZP SessionID mandatory).
* PQ: PQ KEM parameters.
15.2. Generalised TLS-DPA Flow
Figure Figure 12 shows a generalised view of the handshake and the
role of a transport layer that relays flights but does not decrypt
them.
Client Transport Layer Server
|-- ClientHello(SID) -->| |
| |-- CH fwd --------->|
| |<-- ServerHello ----|
|<-- ServerHello -------| |
|-- EncryptedExtensions>| |
|<-- Certificate, Finished ------------------|
|-- Finished / App Data -------------------->|
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Figure 12: Generalised TLS-DPA handshake layers (illustrative).
This figure shows the transport relay separating TLS-DPA endpoints
while preserving end-to-end security.
* SID is carried in the ClientHello.
* The transport layer relays flights but does not decrypt them.
* End-to-end Finished confirms key schedule integrity.
15.3. RN Observation and Channel Truth
Even when TLS-DPA is carried over a rendezvous path or a stitched UZP
channel, authenticated channel truth is bound to endpoint identity
inputs, transcript hashing rules (Section Section 13), transport
binding, and Finished verification rather than to RN observation of
packets, flow identifiers, or relay placement.
A rendezvous node or other relay MAY observe encrypted flights,
timing, replay-related tuples, or local forwarding metadata, but it
MUST NOT be treated as an authoritative source for Service Identity
validation, transcript validity, or endpoint authentication state.
The only authoritative handshake truth is the endpoint-generated
material that validates under the transcript and Service Identity
rules in Section Section 16.
Consequently, relay presence, stitched-path continuity, or RN-local
telemetry MUST NOT upgrade, override, or substitute for endpoint-
authenticated TLS-DPA state. Such observations may be useful for
policy enforcement, replay suppression, or audit, but they are not
trust anchors.
16. Service Identity Validation
16.1. DNS
DNS-based identities MUST be validated according to [RFC6125].
16.2. UZP CID
The CID MUST equal BLAKE3-256(server_longterm_public_key).
16.3. UZP EID
The EID MUST match the server-presented ephemeral identity for this
session.
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16.4. UZPIF Selector
UZPIF selectors MUST be resolved via Pantheon services, federated
identity services, or local cached mappings consistent with local
trust policy, Section Section 9, and [UZPIF].
16.5. Failure Handling
If any validation fails, the implementation MUST abort the handshake
with an appropriate alert (Section Section 17):
* identity_mismatch;
* illegal_transport_binding;
* pq_required.
17. New Alerts
TLS-DPA defines the following experimental alert descriptions for use
in deployments and interoperability testing. The numeric values
shown are illustrative and are not requested for IANA allocation by
this draft.
enum {
illegal_transport_binding(200),
identity_mismatch(201),
pq_required(202),
grant_invalid(203),
grant_expired(204),
(255)
} AlertDescription;
Figure 13: Experimental alert descriptions (illustrative C-like
syntax).
This figure lists the experimental alert codes defined by TLS-DPA.
18. UZP / UZPIF Applicability and Profile
This section defines the UZP / UZPIF profile for TLS-DPA. It is
required only for deployments that carry TLS-DPA over UZP or consume
UZPIF trust artefacts; it does not redefine the core handshake
semantics.
TLS-DPA maps naturally to UZP by binding:
* tlsdpa_service_identity -> UZP CID/EID.
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* tlsdpa_transport_binding -> UZP SessionID.
* PQ capability and fallback -> Pantheon Grants.
UZP's multi-step rendezvous and authentication model, together with
the UZPIF framework defined in [UZP] and [UZPIF], provides:
* stronger pre-TLS identity establishment;
* reduced man-in-the-middle risk;
* deterministic channel binding for TLS-DPA.
This section and Section Section 19 are normative only for
deployments that carry TLS-DPA over UZP or consume UZPIF trust
artefacts. They do not redefine the core handshake semantics; they
constrain how those semantics are applied in zero-port fabrics.
19. Early Data (0-RTT)
Over UZP:
* early data is transmitted inside a ZPIT;
* replay protection uses CID/EID and Pantheon Grant metadata;
* early data MUST NOT be used if Pantheon Grants specify "no-
replay".
19.1. RN Replay Detection
The RN MUST maintain a sliding replay cache keyed on:
grant_nonce || CID || EID || SessionID
Figure 14: Replay cache key tuple (illustrative).
This figure shows the tuple the RN uses to index replay state.
Entries MUST be retained for at least twice the maximum ZPIT
propagation delay. Longer retention is permitted. If a duplicate
early-flight tuple is observed, the RN MUST drop it silently.
19.2. Endpoint Replay Detection
Endpoints MUST track Grant nonce values associated with early data.
For each:
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(grant_nonce, CID, EID, ticket_age)
Figure 15: Endpoint replay tuple (illustrative).
This figure shows the endpoint tuple tracked to detect early data
replay.
If an identical tuple is received twice within the resumption window,
the endpoint MUST abort with illegal_parameter.
19.3. Grant Nonce Interaction
Pantheon Grant issuers MUST issue or bind a fresh Grant nonce per
resumed or 0-RTT-enabled session. The nonce MUST be bound into the
handshake transcript.
19.4. 0-RTT over UZP Rebinds
If the UZP SessionID changes during path migration, 0-RTT data MUST
be rejected unless the new SessionID is verifiably linked to the
previous one via Pantheon metadata.
20. Optional and Experimental Extensions
The extensions in this section are not required for baseline
interoperability. They MUST NOT alter authentication, authorisation,
transcript truth, or trust-anchor decisions unless a later deployment
profile explicitly upgrades them.
20.1. tlsdpa_specification_origin_id
The tlsdpa_specification_origin_id extension carries an OPTIONAL
Specification-Origin Identifier for attribution metadata only. For
experimentation, this document uses an example private-use code point
value (0xFE04); deployments MAY select alternative values by profile.
extension_type = 0xFE04
struct {
opaque origin_id<1..255>;
opaque origin_uri<0..1024>;
} SpecificationOriginIdentifier;
Figure 16: Specification-Origin Identifier extension structure
(informative C-like syntax).
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This extension is non-authoritative and pure metadata. Endpoints
MUST NOT treat it as an authentication, authorisation, or trust-
anchor input.
Endpoints MAY log or display this metadata for attribution, but
handshake success and identity validation MUST be independent of this
extension.
21. Threat Model
TLS-DPA is designed to defend against:
* passive eavesdropping;
* active man-in-the-middle;
* downgrade attacks on both classical and PQ negotiation;
* identity spoofing;
* transport reattachment and rebinding attacks across overlays.
In UZP deployments, RN visibility is expected to be limited primarily
to flow identifiers, relay context, and encrypted envelopes.
Plaintext application data remains protected, but the exact
visibility of Service Identity and related metadata depends on the
transport profile and any additional confidentiality mechanisms in
use.
22. Operational Considerations
* Middleboxes SHOULD NOT assume fixed IP/port semantics for TLS-DPA
channels.
* Monitoring SHOULD use exporter-based identity hooks rather than
IP/port heuristics [NIST-SP800-207].
* Session resumption MUST accommodate overlay rebinds (e.g., QUIC
Connection IDs, UZP SessionIDs).
* PQ keys and related metadata SHOULD be logged where required for
compliance, in line with local policy.
23. Security Considerations
TLS-DPA implementations MUST:
1. ensure identity and transport bindings are transcript-authentic;
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2. authenticate PQ hybrid negotiation and detect downgrades;
3. suppress downgrade unless explicitly permitted by policy;
4. minimise metadata exposure, especially in early flights;
5. prevent unauthorised reattachment across transports or overlays.
6. apply revocation policy without assuming a single global
revocation authority.
The threat model for TLS-DPA is discussed in Section Section 21.
24. IANA Considerations
This document does not request any IANA actions.
The example code points used for extension_type values and alert
descriptions in this document are intended for experimentation (for
example in private-use or locally coordinated deployments). Any
future request for code point allocation is out of scope for this
draft.
25. 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,
<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>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
26. Informative References
[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/info/rfc8446>.
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[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/info/rfc9000>.
[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015,
<https://www.rfc-editor.org/info/rfc7401>.
[UZP] Fisher, B. A., "UZP: Universal Zero-Port Transport
Protocol", Work in Progress, Internet-Draft, draft-dpa-
uzp-transport, <https://datatracker.ietf.org/doc/html/
draft-dpa-uzp-transport>.
[UZPIF] Fisher, B. A., "Universal Zero-Port Interconnect Framework
(UZPIF)", Work in Progress, Internet-Draft, draft-dpa-
uzpif-framework, <https://datatracker.ietf.org/doc/html/
draft-dpa-uzpif-framework>.
[NIST-SP800-207]
Rose, S., Borchert, O., Mitchell, S., and S. Connelly,
"Zero Trust Architecture", NIST SP 800-207, 2019,
<https://doi.org/10.6028/NIST.SP.800-207>.
[NIST-PQC] Technology, N. I. O. S. A., "NIST Post-Quantum
Cryptography Standardization: Fourth Round Candidate
Algorithms", 2022, <https://csrc.nist.gov/Projects/post-
quantum-cryptography>.
Acknowledgements
The author thanks colleagues and early reviewers for discussions on
identity-first security, transport binding, and post-quantum
transition models. Any errors or omissions remain the author's
responsibility.
Author's Address
Benjamin Anthony Fisher
DPA R&D Ltd (https://www.dpa-cloud.co.uk)
Email: b.fisher@dpa-cloud.co.uk
URI: https://orcid.org/0009-0004-4412-2269
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