Struct Hash

pub struct Hash { /* private fields */ }

SHA-256 hash implementation.

This struct provides both streaming and one-shot APIs for computing SHA-256 hashes.

Examples

One-shot hashing:

let hash = hmac_sha256::Hash::hash(b"hello world");

Incremental hashing:

let mut hasher = hmac_sha256::Hash::new();
hasher.update(b"hello ");
hasher.update(b"world");
let hash = hasher.finalize();

Implementations

impl Hash

pub fn new() -> Hash

Creates a new SHA-256 hasher.

pub fn update(&mut self, input: impl AsRef<[u8]>)

Absorbs content into the hasher state.

This method can be called multiple times to incrementally add data to be hashed.

Example

let mut hasher = hmac_sha256::Hash::new();
hasher.update(b"first chunk");
hasher.update(b"second chunk");
let hash = hasher.finalize();

pub fn finalize(self) -> [u8; 32]

Computes the SHA-256 hash of all previously absorbed content.

This method consumes the hasher and returns the computed 32-byte digest.

Example

let mut hasher = hmac_sha256::Hash::new();
hasher.update(b"data to hash");
let hash: [u8; 32] = hasher.finalize();

pub fn finalize_verify(self, expected: &[u8; 32]) -> bool

Verifies that the hash of absorbed content matches the expected digest.

This provides constant-time comparison to prevent timing attacks.

Example

let expected = hmac_sha256::Hash::hash(b"original data");

let mut hasher = hmac_sha256::Hash::new();
hasher.update(b"original data");
assert!(hasher.finalize_verify(&expected));

let mut hasher = hmac_sha256::Hash::new();
hasher.update(b"modified data");
assert!(!hasher.finalize_verify(&expected));

pub fn verify(input: impl AsRef<[u8]>, expected: &[u8; 32]) -> bool

Hashes the provided input and verifies it against the expected digest in a single operation.

This is a convenience method that combines hashing and verification in a single call. It provides constant-time comparison to prevent timing attacks.

Example

let expected = hmac_sha256::Hash::hash(b"original data");

// Verify in one shot
assert!(hmac_sha256::Hash::verify(b"original data", &expected));
assert!(!hmac_sha256::Hash::verify(b"modified data", &expected));

pub fn verify_with_ref(self, expected: &[u8]) -> bool

Verifies that the hash of absorbed content matches the expected digest using a reference.

This method accepts a reference to a slice of bytes and verifies against it using constant-time comparison to prevent timing attacks. Unlike finalize_verify, this method does not require the expected value to be exactly 32 bytes, but will return false if the length is not 32 bytes.

Arguments

• expected - The expected hash value to compare against

Returns

true if the computed hash matches the expected value, false otherwise

Example

let expected = hmac_sha256::Hash::hash(b"original data");

let mut hasher = hmac_sha256::Hash::new();
hasher.update(b"original data");
assert!(hasher.verify_with_ref(&expected));

// Can also verify with a slice
let expected_slice = &expected[..];
let mut hasher2 = hmac_sha256::Hash::new();
hasher2.update(b"original data");
assert!(hasher2.verify_with_ref(expected_slice));

// Or use the one-shot verification
assert!(hmac_sha256::Hash::verify(b"original data", &expected));

pub fn hash(input: &[u8]) -> [u8; 32]

Computes the SHA-256 hash of the provided input in a single operation.

This is a convenience method for simple hashing operations.

Example

let hash = hmac_sha256::Hash::hash(b"data to hash");

Trait Implementations

impl Clone for Hash

fn clone(&self) -> Hash

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Default for Hash

fn default() -> Self

Returns the “default value” for a type.

impl Copy for Hash