constant_time_eq

Compares two byte slices without stopping at the first difference.

The loop visits every byte and combines the differences with |, so the time it takes does not depend on where the slices differ, only on their length (a length mismatch returns at once, so the length is not secret). This is a best effort: Rust and LLVM give no hard guarantee that a compiler will not turn it back into an early exit, so for cryptographic code that needs one, use a dedicated crate such as subtle.

Import

use helpers4::bytes::constant_time_eq;

Cargo feature bytes (enabled by default). To compile only this module:

cargo add helpers4 --no-default-features --features bytes

or in Cargo.toml:

[dependencies]
helpers4 = { version = "0.0.6", default-features = false, features = ["bytes"] }

Signature

pub fn constant_time_eq(a: &[u8], b: &[u8]) -> bool

Parameters

Parameter	Type	Description
a	&[u8]	The first slice.
b	&[u8]	The second slice.

Returns

bool — true when both slices have the same length and the same content.

Examples

use helpers4::bytes::constant_time_eq;

assert!(constant_time_eq(b"secret", b"secret"));
assert!(!constant_time_eq(b"secret", b"secreT"));
assert!(!constant_time_eq(b"secret", b"secre"));

Source

src/bytes/constant_time_eq.rs