notes: research/papers/hardman-analysis-of-did-cel-heartbeat-relevance-to-keri

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research/papers/hardman-analysis-of-did-cel-heartbeat-relevance-to-keri Analysis of did:cel Heartbeat: Relevance to KERI summary v0.1 — 2026-10-15: drafted by Claude from the HTML page (version 1.1); unread by Mark; marked partner on Mark's word 2026-10-21, paraphrase only partner 374 # Analysis of did:cel Heartbeat: Relevance to KERI **Abstract.** A short 2025 analysis by Daniel Hardman of the heartbeat mechanism in the did:cel decentralized identifier (DID) method, which defends against retrograde (history-rewriting) attacks, and of whether KERI (Key Event Receipt Infrastructure) needs one. It concludes that pre-rotation and witness-based duplicity detection already cover the threat, and is for readers comparing DID methods with KERI. ## Summary The analysis first describes the did:cel heartbeat: a periodic, timestamped signature from the identifier's controller. In a retrograde attack, someone holding a key that was valid in the past forges a history branching from that point; the heartbeat narrows the window, since a verifier facing competing histories rejects the one without a continuous stream of recent heartbeats. It then describes KERI's different approach. Pre-rotation commits each establishment event to a digest of the next key, so a compromised past key cannot produce a valid continuation. Witnesses hold replicas of the Key Event Log (KEL) and refuse conflicting events at the same sequence number; watchers query witnesses, and any fork is treated as duplicity, proof that the controller is compromised or dishonest, rather than a contest to pick a winner. A section on operations argues that a heartbeat makes identity infrastructure "hot", requiring keys online periodically, whereas KERI separates safety from liveness and supports cold identifiers whose pre-rotated keys can stay air-gapped for years. The conclusion states that a heartbeat would add complexity and operational risk to KERI without additional security. ## Key terms did:cel, heartbeat, retrograde attack, pre-rotation, witness, watcher, duplicity, Key Event Log (KEL), liveness, cold identifier ## Claims and their evidence - did:cel's heartbeat narrows the window for a successful fork to the most recent heartbeat interval. [informative] - KERI pre-rotation prevents extending a forged chain from a past point of compromise. [informative] - In KERI, detected duplicity marks the identifier untrustworthy rather than triggering selection of a winning history. [informative] - A mandatory heartbeat is redundant in a KERI ecosystem and would weaken cold-key storage. [informative] ## Related KERI specification; DID CEL Method Specification; Why Anchored Signatures?; A Primer on KERI, ACDCs, and CESR ## Provenance Drafted by Claude on 2026-10-15 from the HTML page at dhh1128.github.io/papers/heartbeat-and-witnesses.html, read in full. Not yet read by Mark.

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