internal-ghash.h File Reference

GHASH algorithm for supporting GCM mode. More...

#include "internal-util.h"
#include <stddef.h>

Go to the source code of this file.

Data Structures
struct	gf128_value_t
	Representation of a value in the GF(2^128) field. More...
struct	ghash_state_t
	State information for GHASH. More...

Macros
#define	GHASH_SHOUP_4BIT   1
	Define to 1 to use Shoup's 4-bit method for GF(2^128) multiplications, or define to 0 to use a simpler but slower bit-by-bit method.

Functions
void	ghash_init (ghash_state_t *state, const unsigned char *key)
	Initializes the GHASH state. More...
void	ghash_update (ghash_state_t *state, const unsigned char *data, size_t size)
	Updates a GHASH state with more data. More...
void	ghash_pad (ghash_state_t *state)
	Pads a GHASH state with zeroes to the next block boundary. More...
void	ghash_finalize (ghash_state_t *state, unsigned char *hash)
	Finalizes a GHASH state. More...

Detailed Description

GHASH algorithm for supporting GCM mode.

Note: This implementation is not constant cache. Internally it uses lookup tables for multiplication in the GF(2^128) field. This means that it has similar behaviour to other fast but memory-efficient software implementations of GHASH but is not suitable for use where memory cache attacks are a concern.

Function Documentation

void ghash_finalize	(	ghash_state_t *	state,
		unsigned char *	hash
	)

Finalizes a GHASH state.

Parameters

state	GHASH state to be finalized.
hash	Points to the output hash value, which is 16 bytes in length.

void ghash_init	(	ghash_state_t *	state,
		const unsigned char *	key
	)

Initializes the GHASH state.

Parameters

state	GHASH state to be initialized.
key	128-bit key.

void ghash_pad

(

ghash_state_t *

state

)

Pads a GHASH state with zeroes to the next block boundary.

Parameters

state

GHASH state to be padded.

void ghash_update	(	ghash_state_t *	state,
		const unsigned char *	data,
		size_t	size
	)

Updates a GHASH state with more data.

Parameters

state	GHASH state to be updated.
data	Points to the input data.
size	Number of bytes of input data.