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05-scid-entryhash-prerotation.md

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Iteration 5 — SCID, entry-hash & pre-rotation generators

Status lives in ../PORTING-STATUS.md. Port faithfully from reference/didwebvh-java/; never commit.

Reference

crypto/ScidGenerator.java, crypto/EntryHashGenerator.java, crypto/PreRotationHashGenerator.java (spec §3.7.3, §3.7.4, §3.7.7; see ../ARCHITECTURE.md).

Produce (lib/src/crypto/)

  • scid_generator.dart, entry_hash_generator.dart, pre_rotation_hash_generator.dart.

Test

Vector-gated: known SCIDs and entry hashes from test-vectors/ and interop/ must match exactly.

Acceptance

  • Generated SCID/entry-hash/pre-rotation-hash equal the vector values byte-for-byte.

Implementation Notes

  • Ported the three Java classes 1:1 as abstract final class (static-only utilities, Dart's analog of the Java final class + private constructor). They reuse the iteration-2 primitives (Jcs.canonicalize, MultihashUtil.hashAndEncode, Base58Btc.encode); all three SCID/entry/pre-rotation outputs are bare base58btc with no z multibase prefix, matching Java's Base58Btc.encode.
  • EntryHashGenerator.generate: Java parses the entry JSON into a Gson JsonObject, removes proof, sets versionId, then Jcs.canonicalize(JsonObject) — whose object overload internally re-serializes and re-parses. The Dart port instead decodes to a Map, mutates (remove('proof'), ['versionId'] = predecessor), and canonicalizes the map directly via the new Jcs.canonicalizeValue — no encode→parse round-trip. This is the idiomatic Dart shape (we hold a decoded value) and is byte-identical to the string path (asserted by a Jcs unit test) and to the vectors (entry-hash-chain test). Decision recorded in PORTING-DECISIONS.md §8; the same change was applied to ProofGenerator (iteration 4) for consistency.
  • ScidGenerator.verify: mirrors Java's params.merge(new Parameters().setScid("{SCID}")). Java would NPE if getParameters() were null; the Dart port uses params! to reproduce that throw-on-null for invalid input (a real first entry always has parameters).
  • Kept the generators package-private (not re-exported by the barrel), consistent with how iteration 2 left the crypto primitives; tests import them via package:didwebvh/src/crypto/....
  • Gate: tool/verify.sh --coverage → VERIFY OK, 130 tests pass; all three new generator files appear in coverage/lcov.info. Includes the Jcs.canonicalizeValue work (see above) and its equivalence test.