Crate libcrux_hkdf 

HKDF

This crate implements HKDF (RFC 5869) on SHA2-256, SHA2-384, and SHA2-512. The implementation is based on code extracted from verified crypto code from the HACL* project.

Examples

Using the typed SHA2-256 API

use libcrux_hkdf::{Hkdf, Sha2_256};
use libcrux_secrets::{U8, Classify, ClassifyRef, DeclassifyRef};

// Input key material and salt
let ikm = &[0x0b; 22].classify(); // 22 bytes of 0x0b
let salt = b"salt".classify_ref();

// Extract phase: derive pseudorandom key
let mut prk = [0u8; 32].classify(); // SHA2-256 output length
Hkdf::<Sha2_256>::extract(&mut prk, salt, ikm).unwrap();

// Expand phase: derive keys for different purposes
let mut encrypt_key = [0u8; 16].classify();
let mut mac_key = [0u8; 16].classify();

Hkdf::<Sha2_256>::expand(&mut encrypt_key, &prk, b"encrypt").unwrap();
Hkdf::<Sha2_256>::expand(&mut mac_key, &prk, b"mac").unwrap();

Using the dynamic API

use libcrux_hkdf::{extract, expand, Algorithm};
use libcrux_secrets::{U8, Classify, ClassifyRef, DeclassifyRef};

// Input key material and salt
let ikm = &[0x0b; 22].classify();
let salt = b"salt".classify_ref();

// Extract phase using SHA2-512
let mut prk = [0u8; 64].classify(); // SHA2-512 output length
extract(Algorithm::Sha512, &mut prk, salt, ikm).unwrap();

// Expand phase: derive keys for different purposes
let mut encrypt_key = [0u8; 32].classify();
let mut mac_key = [0u8; 32].classify();

expand(Algorithm::Sha512, &mut encrypt_key, &prk, b"encrypt").unwrap();
expand(Algorithm::Sha512, &mut mac_key, &prk, b"mac").unwrap();

Modules

hacl

This module contains generated hacl code.

sha2_256

HKDF implementation for SHA2-256.

sha2_384

HKDF implementation for SHA2-384.

sha2_512

HKDF implementation for SHA2-512.

Structs

Hkdf

HKDF implementation with compile-time algorithm selection.

Sha2_256

Type marker for SHA2-256 hash algorithm.

Sha2_384

Type marker for SHA2-384 hash algorithm.

Sha2_512

Type marker for SHA2-512 hash algorithm.

Enums

Algorithm

The HKDF algorithm defining the used hash function. Only needed for the functions with dynamic algorithm selection.

ArrayReferenceExpandError

ArrayReferenceExtractError

ExpandError

ExtractError

Functions

expand

HKDF expand. The argument names match the specification. The result is written to okm. The algo argument is used for dynamic algorithm selection.

extract

HKDF extract using the salt and the input key material ikm. The result is written to prk. The algo argument is used for dynamic algorithm selection.

hkdf

Full HKDF, i.e. both extract and expand, using the salt and the input key material ikm. The argument names match the specification. The result is written to okm. The algo argument is used for dynamic algorithm selection.