tc_aes_decrypt.c File Reference

#include "tc_aes.h"
#include "tc_constants.h"
#include "tc_utils.h"

Macros
#define	mult8(a)   (_double_byte(_double_byte(_double_byte(a))))
#define	mult9(a)   (mult8(a)^(a))
#define	multb(a)   (mult8(a)^_double_byte(a)^(a))
#define	multd(a)   (mult8(a)^_double_byte(_double_byte(a))^(a))
#define	multe(a)   (mult8(a)^_double_byte(_double_byte(a))^_double_byte(a))

Functions
int	tc_aes128_set_decrypt_key (TCAesKeySched_t s, const uint8_t *k)
	Set the AES-128 decryption key Uses key k to initialize s. More...
static void	mult_row_column (uint8_t *out, const uint8_t *in)
static void	inv_mix_columns (uint8_t *s)
static void	add_round_key (uint8_t *s, const unsigned int *k)
static void	inv_sub_bytes (uint8_t *s)
static void	inv_shift_rows (uint8_t *s)
int	tc_aes_decrypt (uint8_t *out, const uint8_t *in, const TCAesKeySched_t s)
	AES-128 Encryption procedure Decrypts in buffer into out buffer under key schedule s. More...

Variables
static const uint8_t	inv_sbox [256]

Macro Definition Documentation

mult8

#define mult8

(

a

)

(_double_byte(_double_byte(_double_byte(a))))

mult9

#define mult9

(

a

)

(mult8(a)^(a))

multb

#define multb

(

a

)

(mult8(a)^_double_byte(a)^(a))

multd

#define multd

(

a

)

(mult8(a)^_double_byte(_double_byte(a))^(a))

multe

#define multe

(

a

)

(mult8(a)^_double_byte(_double_byte(a))^_double_byte(a))

Function Documentation

add_round_key()

static void add_round_key ( uint8_t *  s, const unsigned int *  k  )

inlinestatic

inv_mix_columns()

static void inv_mix_columns ( uint8_t *  s )

inlinestatic

inv_shift_rows()

static void inv_shift_rows ( uint8_t *  s )

inlinestatic

inv_sub_bytes()

static void inv_sub_bytes ( uint8_t *  s )

inlinestatic

mult_row_column()

static void mult_row_column ( uint8_t *  out, const uint8_t *  in  )

inlinestatic

tc_aes128_set_decrypt_key()

int tc_aes128_set_decrypt_key	(	TCAesKeySched_t	s,
		const uint8_t *	k
	)

Set the AES-128 decryption key Uses key k to initialize s.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: s == NULL or k == NULL

Note

This is the implementation of the straightforward inverse cipher using the cipher documented in FIPS-197 figure 12, not the equivalent inverse cipher presented in Figure 15

Warning

This routine skips the additional steps required for keys larger than 128, and must not be used for AES-192 or AES-256 key schedule – see FIPS 197 for details

Parameters

s	IN/OUT – initialized struct tc_aes_key_sched_struct
k	IN – points to the AES key

tc_aes_decrypt()

int tc_aes_decrypt	(	uint8_t *	out,
		const uint8_t *	in,
		const TCAesKeySched_t	s
	)

AES-128 Encryption procedure Decrypts in buffer into out buffer under key schedule s.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: out is NULL or in is NULL or s is NULL

Note

Assumes s was initialized by aes_set_encrypt_key out and in point to 16 byte buffers

Parameters

out	IN/OUT – buffer to receive ciphertext block
in	IN – a plaintext block to encrypt
s	IN – initialized AES key schedule

Variable Documentation

inv_sbox

const uint8_t inv_sbox[256]

static

Initial value:

= {
  0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e,
  0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
  0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32,
  0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49,
  0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
  0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50,
  0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
  0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05,
  0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
  0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41,
  0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
  0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8,
  0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
  0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b,
  0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
  0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59,
  0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
  0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d,
  0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
  0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63,
  0x55, 0x21, 0x0c, 0x7d
}