Module ct 

Constant-time primitives.

These routines avoid branches and table lookups on secret data (lengths are considered public). Input and output barriers using core::hint::black_box prevent known optimizer transformations back into branches. Compiled-code regression probes check fixed-size cases; this is not a guarantee for every compiler, optimization profile or caller.

Structs

Choice

A branch-free boolean whose value is never observable through control flow.

Functions

cmov

Copy src over dst only when c is true, in constant time.

cswap

Conditionally swap two equal-length buffers in constant time.

eq

Constant-time equality over two byte slices.

is_zero

Constant-time check that every byte of x is zero.

lt_be

Constant-time a < b over big-endian byte strings of equal length.

select_u8

Branch-free select: returns a when c is true, otherwise b.

select_u32

Branch-free select over u32.

select_u64

Branch-free select over u64.

verify

Constant-time byte-slice comparison returning a plain bool.