Module util 

Small helpers: constant-time comparison and selection, hex for tests and diagnostics.

Functions

ct_eq

Constant-time equality of two slices. The lengths are not secret.

ct_eq_mask

All-ones if a == b, else zero, as an opaque mask.

ct_mask

An all-ones (flag = 1) or all-zero (flag = 0) mask, hidden from the optimizer so that it cannot turn masked selection back into a branch (LLVM’s cmov-to-branch conversion would otherwise make table lookups and swaps leak through the branch predictor).

hex

Lower-case hex.

unhex

Decodes hex, ignoring whitespace and :. Panics on bad input (constants and tests only).

zeroize

Best-effort zeroing of secret material (not elided: the writes go through black_box).