Technical concepts
Hash Chain (append-only ledger)
A sequence of records where each entry contains the cryptographic hash of the previous entry. Tamper any past row, every later row breaks.
Definition
A hash chain is the simplest tamper-evident data structure. Each new entry stores the cryptographic hash of the immediately preceding entry alongside its own payload. Computing the chain forward is cheap; reversing it requires breaking the underlying hash function. If anyone alters a past entry (even a single byte), the stored next-entry hash no longer matches the actual content, and every entry that follows fails verification too. Concord by IaxaI's audit ledger is a hash chain implemented in Postgres with INSERT-only row-level security. Each row records the SHA-256 hash of its predecessor and an Ed25519 signature over its own content with a per-tenant key. Verifying the chain is a linear scan. Integrity is provable to a regulator without trusting Concord's runtime. This is the audit primitive. Compliance Evidence Auto-Packets read from it. Drift events, mapping changes, entity matches, and translation decisions all write to it.
See also
Related capabilities and terms
Auditability Ledger
An append-only, hash-chained, Ed25519-signed evidence chain threading every decision the engine makes.
Compliance Evidence Auto-Packets
FFIEC, SOC 2, HIPAA, and PCI evidence bundles assembled directly from the audit ledger. Not screenshotted into a PDF.
Drift Detection
Streaming statistical tests on input, output, and schema-shape that catch silent vendor changes before they break detection coverage.
Auto-Repair (self-healing pipeline)
When drift fires, Concord proposes a new mapping, runs it in shadow, calibrates it, and only promotes after operator approval. Every step is ledgered.
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