sha256.c File Reference

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

Macros
#define	__DEBUG_HEADER__   "[SHA256]"
	Change header.
#define	__DEBUG_LEVEL__   LOGLEVEL_NOTICE
	Set log level.
#define	ROTLEFT(a, b)   (((a) << (b)) | ((a) >> (32 - (b))))
	Rotate left operation on a 32-bit unsigned integer. More...
#define	ROTRIGHT(a, b)   (((a) >> (b)) | ((a) << (32 - (b))))
	Rotate right operation on a 32-bit unsigned integer. More...
#define	CH(x, y, z)   (((x) & (y)) ^ (~(x) & (z)))
	Chooses bits from y if x is set, otherwise from z. More...
#define	MAJ(x, y, z)   (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
	Majority function used in SHA-256. More...
#define	EP0(x)   (ROTRIGHT(x, 2) ^ ROTRIGHT(x, 13) ^ ROTRIGHT(x, 22))
	First expansion function for the working variables. More...
#define	EP1(x)   (ROTRIGHT(x, 6) ^ ROTRIGHT(x, 11) ^ ROTRIGHT(x, 25))
	Second expansion function for the working variables. More...
#define	SIG0(x)   (ROTRIGHT(x, 7) ^ ROTRIGHT(x, 18) ^ ((x) >> 3))
	First Sigma function for message scheduling. More...
#define	SIG1(x)   (ROTRIGHT(x, 17) ^ ROTRIGHT(x, 19) ^ ((x) >> 10))
	Second Sigma function for message scheduling. More...
#define	SHA256_MAX_DATA_LENGTH   (SHA256_BLOCK_SIZE * 2)
	Max data length for message scheduling expansion.

Functions
static void	__sha256_transform (SHA256_ctx_t *ctx, const uint8_t data[])
	Transforms the state of the SHA-256 context based on a block of input data. More...
void	sha256_bytes_to_hex (uint8_t *src, size_t src_length, char *out, size_t out_length)
	Converts a byte array into its hexadecimal string representation. More...
void	sha256_init (SHA256_ctx_t *ctx)
	Initializes the SHA-256 context. More...
void	sha256_update (SHA256_ctx_t *ctx, const uint8_t data[], size_t len)
	Adds data to the SHA-256 context for hashing. More...
void	sha256_final (SHA256_ctx_t *ctx, uint8_t hash[])
	Finalizes the hashing and produces the final SHA-256 digest. More...

Variables
static const uint32_t	k [SHA256_MAX_DATA_LENGTH]
	The constants used in the SHA-256 algorithm, as defined by the specification. These are the first 32 bits of the fractional parts of the cube roots of the first 64 primes (2..311). More...

Detailed Description

Implementation of the SHA-256 hashing algorithm.

The original code was written by Brad Conte, and is available at: https://github.com/B-Con/crypto-algorithms

SHA-256 is one of the three algorithms in the SHA2 specification. The others, SHA-384 and SHA-512, are not offered in this implementation. Algorithm specification can be found here: http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf This implementation uses little endian byte order.

Macro Definition Documentation

CH

#define CH	(		x,
			y,
			z
	)		(((x) & (y)) ^ (~(x) & (z)))

Chooses bits from y if x is set, otherwise from z.

Parameters

x,y,z

Input values.

Returns

Result of CH function.

EP0

#define EP0

(

x

)

(ROTRIGHT(x, 2) ^ ROTRIGHT(x, 13) ^ ROTRIGHT(x, 22))

First expansion function for the working variables.

Parameters

x	Input value.

Returns

Result of EP0.

EP1

#define EP1

(

x

)

(ROTRIGHT(x, 6) ^ ROTRIGHT(x, 11) ^ ROTRIGHT(x, 25))

Second expansion function for the working variables.

Parameters

x	Input value.

Returns

Result of EP1.

MAJ

#define MAJ	(		x,
			y,
			z
	)		(((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))

Majority function used in SHA-256.

Parameters

x,y,z

Input values.

Returns

Result of the majority function.

ROTLEFT

#define ROTLEFT	(		a,
			b
	)		(((a) << (b)) | ((a) >> (32 - (b))))

Rotate left operation on a 32-bit unsigned integer.

Parameters

a	The value to rotate.
b	The number of positions to rotate.

Returns

The rotated value.

ROTRIGHT

#define ROTRIGHT	(		a,
			b
	)		(((a) >> (b)) | ((a) << (32 - (b))))

Rotate right operation on a 32-bit unsigned integer.

Parameters

a	The value to rotate.
b	The number of positions to rotate.

Returns

The rotated value.

SIG0

#define SIG0

(

x

)

(ROTRIGHT(x, 7) ^ ROTRIGHT(x, 18) ^ ((x) >> 3))

First Sigma function for message scheduling.

Parameters

x	Input value.

Returns

Result of SIG0.

SIG1

#define SIG1

(

x

)

(ROTRIGHT(x, 17) ^ ROTRIGHT(x, 19) ^ ((x) >> 10))

Second Sigma function for message scheduling.

Parameters

x	Input value.

Returns

Result of SIG1.

Function Documentation

__sha256_transform()

static void __sha256_transform ( SHA256_ctx_t *  ctx, const uint8_t  data[]  )

inlinestatic

Transforms the state of the SHA-256 context based on a block of input data.

Parameters

ctx	Pointer to the SHA-256 context. Must not be NULL.
data	Input data block to process (64 bytes). Must not be NULL.

sha256_bytes_to_hex()

void sha256_bytes_to_hex	(	uint8_t *	src,
		size_t	src_length,
		char *	out,
		size_t	out_length
	)

Converts a byte array into its hexadecimal string representation.

Converts a byte array to its hexadecimal string representation.

Parameters

src	Pointer to the source byte array.
src_length	Length of the source byte array.
out	Pointer to the output buffer for the hexadecimal string.
out_length	Length of the output buffer (must be at least 2 * src_length + 1).

The output string will be null-terminated if the buffer is large enough.

sha256_final()

void sha256_final	(	SHA256_ctx_t *	ctx,
		uint8_t	hash[]
	)

Finalizes the hashing and produces the final SHA-256 digest.

Parameters

ctx	Pointer to the SHA-256 context.
hash	Pointer to a buffer where the final hash will be stored (must be at least 32 bytes long).

sha256_init()

void sha256_init

(

SHA256_ctx_t *

ctx

)

Initializes the SHA-256 context.

Parameters

ctx	Pointer to the SHA-256 context to initialize.

sha256_update()

void sha256_update	(	SHA256_ctx_t *	ctx,
		const uint8_t	data[],
		size_t	len
	)

Adds data to the SHA-256 context for hashing.

Parameters

ctx	Pointer to the SHA-256 context.
data	Pointer to the data to be hashed.
len	Length of the data to hash, in bytes.

Variable Documentation

k

const uint32_t k[SHA256_MAX_DATA_LENGTH]

static

Initial value:

= {
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
    0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
    0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
    0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
    0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
    0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
}

The constants used in the SHA-256 algorithm, as defined by the specification. These are the first 32 bits of the fractional parts of the cube roots of the first 64 primes (2..311).