aes-internal-dec.c File Reference

AES (Rijndael) cipher - decrypt. More...

#include "includes.h"
#include "common.h"
#include "crypto.h"
#include "aes_i.h"

Macros
#define	ROUND(i, d, s)

Functions
void *	aes_decrypt_init (const u8 *key, size_t len)
	Initialize AES for decryption. More...
void	aes_decrypt (void *ctx, const u8 *crypt, u8 *plain)
	Decrypt one AES block. More...
void	aes_decrypt_deinit (void *ctx)
	Deinitialize AES decryption. More...

Detailed Description

AES (Rijndael) cipher - decrypt.

Modifications to public domain implementation:

• cleanup
• use C pre-processor to make it easier to change S table access
• added option (AES_SMALL_TABLES) for reducing code size by about 8 kB at cost of reduced throughput (quite small difference on Pentium 4, 10-25% when using -O1 or -O2 optimization)

Macro Definition Documentation

#define ROUND	(		i,
			d,
			s
	)

Value:

d##0 = TD0(s##0) ^ TD1(s##3) ^ TD2(s##2) ^ TD3(s##1) ^ rk[4 * i]; \
d##1 = TD0(s##1) ^ TD1(s##0) ^ TD2(s##3) ^ TD3(s##2) ^ rk[4 * i + 1]; \
d##2 = TD0(s##2) ^ TD1(s##1) ^ TD2(s##0) ^ TD3(s##3) ^ rk[4 * i + 2]; \
d##3 = TD0(s##3) ^ TD1(s##2) ^ TD2(s##1) ^ TD3(s##0) ^ rk[4 * i + 3]

Function Documentation

void aes_decrypt	(	void *	ctx,
		const u8 *	crypt,
		u8 *	plain
	)

Decrypt one AES block.

Parameters

ctx	Context pointer from aes_encrypt_init()
crypt	Encrypted data (16 bytes)
plain	Buffer for the decrypted data (16 bytes)

void aes_decrypt_deinit

(

void *

ctx

)

Deinitialize AES decryption.

Parameters

ctx	Context pointer from aes_encrypt_init()

void* aes_decrypt_init	(	const u8 *	key,
		size_t	len
	)

Initialize AES for decryption.

Parameters

key	Decryption key
len	Key length in bytes (usually 16, i.e., 128 bits)

Returns

Pointer to context data or NULL on failure