Struct HKDF 

pub struct HKDF;

HMAC-based Key Derivation Function (HKDF) implementation using SHA-512.

HKDF is a key derivation function based on HMAC, standardized in RFC 5869. It derives cryptographically strong keys from input keying material.

The HKDF process consists of two stages:

1. Extract: Takes input keying material and an optional salt, produces a pseudorandom key (PRK)
2. Expand: Takes the PRK and optional context info, generates output keying material

Examples

let prk = hmac_sha512::HKDF::extract(b"salt value", b"input key material");

let mut okm = [0u8; 128];
hmac_sha512::HKDF::expand(&mut okm, prk, b"application info");

Implementations

impl HKDF

pub fn extract(salt: impl AsRef<[u8]>, ikm: impl AsRef<[u8]>) -> [u8; 64]

Performs the HKDF-Extract function.

Extracts a pseudorandom key from the input keying material using the optional salt.

Arguments

• salt - Optional salt value (a non-secret random value)
• ikm - Input keying material (the secret input)

Returns

A 64-byte pseudorandom key

pub fn expand(out: &mut [u8], prk: impl AsRef<[u8]>, info: impl AsRef<[u8]>)

Performs the HKDF-Expand function.

Expands the pseudorandom key into output keying material of the desired length.

Arguments

• out - Buffer to receive the output keying material
• prk - Pseudorandom key (from the extract step)
• info - Optional context and application specific information

Panics

Panics if the requested output length is greater than 255 * 64 bytes (16320 bytes).