aabbdev's comments

Shipped a timing leak via early-exit memcmp + secret branch. Flatline is a single-header toolbox for constant-time C (CT compare/select/lookup/div) guided by B.I.D.—no Branch on secrets, no secret Index, no variable-latency ops. DUDECT tests; feedback on LTO/autovec welcome

A Postgres extension is currently in development to provide transparent database optimization with custom type uuid45 and optional helpers ;)

You can always treat IDs as UUIDv4, while actually storing them as UUIDv7—combining the benefits of both. From your perspective, they’re just UUIDv4

Hi, I’m the author of uuidv47. The idea is simple: keep UUIDv7 internally for database indexing and sortability, but emit UUIDv4-looking façades externally so clients don’t see timing patterns.

How it works: the 48-bit timestamp is XOR-masked with a keyed SipHash-2-4 stream derived from the UUID’s random field. The random bits are preserved, the version flips between 7 (inside) and 4 (outside), and the RFC variant is kept. The mapping is injective: (ts, rand) → (encTS, rand). Decode is just encTS ⊕ mask, so round-trip is exact.

Security: SipHash is a PRF, so observing façades doesn’t leak the key. Wrong key = wrong timestamp. Rotation can be done with a key-ID outside the UUID.

Performance: one SipHash over 10 bytes + a couple of 48-bit loads/stores. Nanosecond overhead, header-only C11, no deps, allocation-free.

Tests: SipHash reference vectors, round-trip encode/decode, and version/variant invariants.

Curious to hear feedback!