As of: 2026-10-17 07:29 CEST.
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Canonical page: https://postcutoff.com/p/2026-10-16-sweis-des-s-box-test-vectors/

# Steve Weis: Claude also traced the 1977 DES S-box test vectors to rand() on a PDP-11 running Unix V6

Steve Weis (@sweis), X, 2026-10-16.
Source: https://x.com/sweis/status/2111170587792208361

## Why it matters

First-hand claim by an Anthropic team member of a second historical-cryptography result not in the Anthropic post (~18k views).

## Summary

Posted Oct 16 19:01 UTC by Steve Weis (@sweis); 18,319 views, 224 likes, 26 reposts when read via api.fxtwitter.com on 2026-10-17. Quotes @sweis: "CLAUDE FOUND THE SEEDS https://www.anthropic.com/research/ecdsa-curve-origins".

## Archived text

> As a treat, Claude also reverse engineered the NBS's 1977 DES S-box test vectors and determined that it was generated on a PDP-11 Unix V6 using rand() .
> 
> > Quoting @sweis: CLAUDE FOUND THE SEEDS
> > https://www.anthropic.com/research/ecdsa-curve-origins

Archived 2026-10-17 via fxtwitter (unofficial).
Counts: 18,383 views, 225 likes, 26 reposts, 10 replies (at fetch time)

## Cited in

- 2026-10-16: [Claude explains where the NIST P-256 curve seeds came from](https://postcutoff.com/e/2026-10-16-claude-recovers-nist-ecdsa-curve-seeds/)