Implementation of the SHA-256 hashing function. More...

Detailed Description

Implementation of the SHA-256 hashing function.

Files
file	sha256.h
	Header definitions for the SHA256 hash function.

Data Structures
struct	hmac_context_t
	Context for HMAC operations based on sha256. More...

struct	sha256_chain_idx_elm_t
	sha256-chain indexed element More...

Macros
#define	SHA256_DIGEST_LENGTH 32
	Length of SHA256 digests in bytes.

#define	SHA256_INTERNAL_BLOCK_SIZE (64)
	512 Bit (64 Byte) internally used block size for sha256

Typedefs
typedef sha2xx_context_t	sha256_context_t
	Context for cipher operations based on sha256.

Functions
void	sha256_init (sha256_context_t *ctx)
	SHA-256 initialization.

static void	sha256_update (sha256_context_t ctx, const void data, size_t len)
	Add bytes into the hash.

static void	sha256_final (sha256_context_t ctx, void digest)
	SHA-256 finalization.

void	sha256 (const void data, size_t len, void digest)
	A wrapper function to simplify the generation of a hash, this is useful for generating sha256 for one buffer.

void	hmac_sha256_init (hmac_context_t ctx, const void key, size_t key_length)
	hmac_sha256_init HMAC SHA-256 calculation.

void	hmac_sha256_update (hmac_context_t ctx, const void data, size_t len)
	hmac_sha256_update Add data bytes for HMAC calculation

void	hmac_sha256_final (hmac_context_t ctx, void digest)
	hmac_sha256_final HMAC SHA-256 finalization.

void	hmac_sha256 (const void key, size_t key_length, const void data, size_t len, void *digest)
	function to compute a hmac-sha256 from a given message

void *	sha256_chain (const void seed, size_t seed_length, size_t elements, void tail_element)
	function to produce a hash chain starting with a given seed element.

void *	sha256_chain_with_waypoints (const void seed, size_t seed_length, size_t elements, void tail_element, sha256_chain_idx_elm_t waypoints, size_t waypoints_length)
	function to produce a hash chain starting with a given seed element.

int	sha256_chain_verify_element (void element, size_t element_index, void tail_element, size_t chain_length)
	function to verify if a given chain element is part of the chain.

Macro Definition Documentation

◆ SHA256_DIGEST_LENGTH

#define SHA256_DIGEST_LENGTH 32

Length of SHA256 digests in bytes.

Definition at line 62 of file sha256.h.

◆ SHA256_INTERNAL_BLOCK_SIZE

#define SHA256_INTERNAL_BLOCK_SIZE (64)

512 Bit (64 Byte) internally used block size for sha256

Definition at line 67 of file sha256.h.

Typedef Documentation

◆ sha256_context_t

typedef sha2xx_context_t sha256_context_t

Context for cipher operations based on sha256.

Definition at line 72 of file sha256.h.

Function Documentation

◆ hmac_sha256()

void hmac_sha256	(	const void *	key,
		size_t	key_length,
		const void *	data,
		size_t	len,
		void *	digest
	)

function to compute a hmac-sha256 from a given message

Parameters

[in]	key	key used in the hmac-sha256 computation
[in]	key_length	the size in bytes of the key
[in]	data	pointer to the buffer to generate the hmac-sha256
[in]	len	the length of the message in bytes
[out]	digest	the computed hmac-sha256, length MUST be SHA256_DIGEST_LENGTH

◆ hmac_sha256_final()

void hmac_sha256_final	(	hmac_context_t *	ctx,
		void *	digest
	)

hmac_sha256_final HMAC SHA-256 finalization.

Finish HMAC calculation and export the value

Parameters

[in]	ctx	hmac_context_t handle to use
[out]	digest	the computed hmac-sha256, length MUST be SHA256_DIGEST_LENGTH

◆ hmac_sha256_init()

void hmac_sha256_init	(	hmac_context_t *	ctx,
		const void *	key,
		size_t	key_length
	)

hmac_sha256_init HMAC SHA-256 calculation.

Initiate calculation of a HMAC

Parameters

[in]	ctx	hmac_context_t handle to use
[in]	key	key used in the hmac-sha256 computation
[in]	key_length	the size in bytes of the key

◆ hmac_sha256_update()

void hmac_sha256_update	(	hmac_context_t *	ctx,
		const void *	data,
		size_t	len
	)

hmac_sha256_update Add data bytes for HMAC calculation

Parameters

[in]	ctx	hmac_context_t handle to use
[in]	data	pointer to the buffer to generate hash from
[in]	len	length of the buffer

◆ sha256()

void sha256	(	const void *	data,
		size_t	len,
		void *	digest
	)

A wrapper function to simplify the generation of a hash, this is useful for generating sha256 for one buffer.

Parameters

[in]	data	pointer to the buffer to generate hash from
[in]	len	length of the buffer
[out]	digest	Pointer to an array for the result, length must be SHA256_DIGEST_LENGTH

◆ sha256_chain()

void * sha256_chain	(	const void *	seed,
		size_t	seed_length,
		size_t	elements,
		void *	tail_element
	)

function to produce a hash chain starting with a given seed element.

The chain is computed by taking the sha256 from the seed, hash the resulting sha256 and continuing taking sha256 from each result consecutively.

Parameters

[in]	seed	the seed of the sha256-chain, i.e. the first element
[in]	seed_length	the size of seed in bytes
[in]	elements	the number of chained elements, i.e. the index of the last element is (elements-1)
[out]	tail_element	the final element of the sha256-chain

Returns: pointer to tail_element

◆ sha256_chain_verify_element()

int sha256_chain_verify_element	(	void *	element,
		size_t	element_index,
		void *	tail_element,
		size_t	chain_length
	)

function to verify if a given chain element is part of the chain.

Parameters

[in]	element	the chain element to be verified
[in]	element_index	the position in the chain
[in]	tail_element	the last element of the sha256-chain
[in]	chain_length	the number of elements in the chain

Returns: 0 if element is verified to be part of the chain at element_index 1 if the element cannot be verified as part of the chain

◆ sha256_chain_with_waypoints()

void * sha256_chain_with_waypoints	(	const void *	seed,
		size_t	seed_length,
		size_t	elements,
		void *	tail_element,
		sha256_chain_idx_elm_t *	waypoints,
		size_t *	waypoints_length
	)

function to produce a hash chain starting with a given seed element.

The chain is computed the same way as done with sha256_chain(). Additionally intermediate elements are saved while computing the chain. This slows down computation, but provides the caller with indexed "waypoint"-elements. They are supposed to shortcut computing verification elements, this comes in handy when using long chains, e.g. a chain with 2³² elements.

Parameters

[in]	seed	the seed of the sha256-chain, i.e. the first element
[in]	seed_length	the size of seed in bytes
[in]	elements	the number of chained elements, i.e. the index of the last element is (elements-1)
[out]	tail_element	the final element of the sha256-chain
[out]	waypoints	intermediate elements are stored there.
[in,out]	waypoints_length	the size of the waypoints array. If the given size is equal or greater elements, the complete chain will be stored. Otherwise every n-th element is stored where: n = floor(elements / waypoints_length); floor is implicitly used since we perform unsigned integer division. The last used waypoint index is stored in the variable after call. That is (elements - 1) if the complete chain is stored, and (*waypoints_length - 1) if we only store some waypoints.

Returns: pointer to tail_element

◆ sha256_final()

static void sha256_final	(	sha256_context_t *	ctx,
		void *	digest
	)

inlinestatic

SHA-256 finalization.

Pads the input data, exports the hash value, and clears the context state.

Parameters

ctx	sha256_context_t handle to use
digest	resulting digest, this is the hash of all the bytes

Definition at line 120 of file sha256.h.

◆ sha256_init()

void sha256_init ( sha256_context_t * ctx )

SHA-256 initialization.

Begins a SHA-256 operation.

Parameters

ctx	sha256_context_t handle to init

◆ sha256_update()

static void sha256_update	(	sha256_context_t *	ctx,
		const void *	data,
		size_t	len
	)

inlinestatic

Add bytes into the hash.

Parameters

	ctx	sha256_context_t handle to use
[in]	data	Input data
[in]	len	Length of `data`

Definition at line 108 of file sha256.h.

Detailed Description

Files

Data Structures

Macros

Typedefs

Functions

Macro Definition Documentation

◆ SHA256_DIGEST_LENGTH

◆ SHA256_INTERNAL_BLOCK_SIZE

Typedef Documentation

◆ sha256_context_t

Function Documentation

◆ hmac_sha256()

◆ hmac_sha256_final()

◆ hmac_sha256_init()

◆ hmac_sha256_update()

◆ sha256()

◆ sha256_chain()

◆ sha256_chain_verify_element()

◆ sha256_chain_with_waypoints()

◆ sha256_final()

◆ sha256_init()

◆ sha256_update()