notes: research/papers/hardman-comparison-acdcs-and-merkle-tree-certificates

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research/papers/hardman-comparison-acdcs-and-merkle-tree-certificates Comparison: ACDCs and Merkle Tree Certificates summary v0.1 — 2026-10-15: drafted by Claude from the web page (version 1.1); unread by Mark; marked partner on Mark's word 2026-10-21, paraphrase only partner 535 # Comparison: ACDCs and Merkle Tree Certificates **Abstract.** A paper by Daniel Hardman comparing Authentic Chained Data Containers (ACDCs), with the Key Event Receipt Infrastructure (KERI), and Merkle Tree Certificates (MTCs), a proposed evolution of the web public key infrastructure (WebPKI). It is organized by function: what each commits to and proves, freshness and revocation, operational cost, post-quantum readiness and standardization. It states that it is not a bake-off and is written for readers fluent in one of the two worlds. ## Summary The introduction places KERI and ACDCs in identity and credential systems uneasy with static identifiers, brittle revocation and over-disclosure, and MTCs in the WebPKI, where certificate transparency (CT), unreliable revocation and post-quantum signature sizes strain the system. Both use hash commitments in Merkle-like structures, which invites comparison and misreading. A comparative table maps the two across twelve axes. Section 3 argues that the shared primitive works at different layers: in ACDCs a self-addressing identifier (SAID) commits to the meaning and structure of a claim; in MTCs a Merkle root or landmark commits to the position of a certificate in an append-only issuance log. Section 4 contrasts the proof obligations: ACDC graduated disclosure proves that a partial view corresponds to a specific claim, motivated by privacy and correlation; an MTC inclusion proof shows that a certificate belongs to a committed set, motivated by efficiency. Section 5 treats freshness: KERI emphasizes continuity of key state and permits offline verification, with revocation reconciled as events, while MTCs depend on relying parties having current landmarks and keep X.509 revocation semantics. KERI places its cost on reasoning about history; MTCs on distribution and synchronization. Section 6 says MTCs address post-quantum size pressure, and KERI and ACDCs address continuity across algorithm transitions through pre-rotation. Section 7 lists adoption paths: ISO 17442-3 for verifiable Legal Entity Identifiers (vLEIs), the GSMA Open Verifiable Calling project, and the Trust Over IP (ToIP) Dossier Task Force for ACDCs; an Internet Engineering Task Force (IETF) Internet-Draft, browser experiments and a September 2026 Apple root program draft policy for MTCs. The conclusion says the paths are orthogonal and offers clearer mental models, "not a verdict" (section 8). ## Key terms self-addressing identifier (SAID), graduated disclosure, Merkle Tree Certificates, inclusion proof, landmark, key state, freshness, cryptographic agility ## Claims and their evidence - A SAID commits to the identity of content, while a Merkle inclusion proof commits to placement in a history. [informative] - A fully expanded ACDC and a partially disclosed one verify the same way and anchor to the same claim. [normative] - MTC efficiency depends on clients being current on landmarks, falling back to heavier proofs otherwise. [informative] - ISO 17442-3 specifies ACDC use for verifiable LEIs, and the GSMA Open Verifiable Calling project uses ACDCs. [unverified] - In September 2026 Apple's root program published a draft MTC policy with an operator onboarding timeline. [unverified] ## Related Authentic Chained Data Containers (ACDC) specification; Key Event Receipt Infrastructure (KERI) specification; Where Trust Bottoms Out: X.509, Certificate Transparency, and KERI's DPKI Architecture; A Primer on KERI, ACDCs, and CESR. ## Provenance Drafted by Claude on 2026-10-15 from the web page at dhh1128.github.io/papers/acdc-and-mtc.html, read in full except the reference list. Not yet read by Mark.

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