Skipjack's S-box and Seed 48571

Sun, 18 Oct 2026 08:00:00 +0400

One line of srand48 reproduces two-thirds of the NSA cipher’s lookup table. Here is what that shows, what it doesn’t, and an interactive way to see the difference.

In short. Seeding the POSIX drand48 generator with 48571 and running a simple shuffle produces a table that matches 173 of 256 bytes of Skipjack’s F-table. Neighbouring seeds match 1. The remaining 83 bytes can be fixed with 52 swaps, but those swaps are read off the official table, so they would “fix” any seed. The match is the evidence; the swaps are bookkeeping. One thing the swaps do reveal: they raise nonlinearity from 92 to 100 while differential uniformity gets slightly worse, from 10 to 12.

PRNG on

Skipjack's S-box and Seed 48571