Arxid

Details

External ID

49183506

Source

HN

Company

—

Product

Arxid

Website domain

github.com

Launched

Aug. 5, 2026

Cohort

—

Upvotes

8

Upvotes percentile

0.4731182795698925

Tags

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Fetched at

Sept. 10, 2026, 5:32 a.m.

Updated at

Sept. 10, 2026, 5:32 a.m.

Description

I kept reaching for Hashids/Sqids to keep sequential IDs out of URLs, but they don't use a real key — the alphabet is shuffled by a salt, and the Sqids FAQ says outright "there is no encryption of any kind."arxid is a keyed reversible permutation instead: a balanced Feistel network with an ARX (add-rotate-xor) round function over a 40-bit domain, mapping to a 7-char base62 code. Feed it an integer, get an unpredictable code back; same key reverses it. Runs ~16x faster than a structurally identical Feistel using HMAC-SHA256, because the round function is integer ops instead of a hash call.The round count (4) isn't a guess — it's calibrated by measuring strict avalanche. I'm also upfront in the README about what it is NOT: not encryption, not a MAC, not audited. It's a speed bump against enumeration, not access control.The part I care most about is portability: a frozen spec + canonical test vectors act as the contract, so any port in any language validates against the same vectors and is interoperable by construction. Rust reference + TypeScript port so far.Happy to answer questions on the construction, the calibration, or the cross-language design.

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