Šifra Rijndael (dnes zvaná AES) je vítězem soutěže pro nový kryptografický standard (Advanced Encryption Standard) z roku 2000, který nahradil standard (a stejnojmennou šifru) DES. Její předností je vysoká bezpečnost, nevýhoda šifry je vysoká komplexnost (např. v porovnání se srovnatelně bezpečnou šifrou RC6). Pracuje se vstupním blokem velikosti 128 bitů. Počet rund a délka klíče určuje bezpečnost šifry, nejnižší délka klíče je 128 bitů (a 10 rund), střední je 192 bitů (12 rund) a nejbezpečnější je 256 bitů (a 14 rund).
Probíhá pomocí následujících čtyř funkcí, níže je popsáno pořadí, tj. struktura jednotlivých rund.
KeyExpansions vypočte jednotlivé 128 bitové klíče pro každou šifrovací rundu.
AddRoundKey je funkce, která udělá XOR vstupu s příslušným klíčem příslušejícím dané rundě.
SubBytes je funkce provádějící substituci vstupních bajtů dle předpisu určeného tabulkou (substituce je nelineární).
ShiftRows je permutace posledních tří řádků vstupu (vstup se uvažuje ve tvaru matice).
MixColumn představuje vynásobení každého sloupečku vstupní matice vhodnou maticí. Tato transformace je lineární (má inverzi).
Data určená k šifrování je vhodné reprezentovat maticí velikosti 4x4. Kde se jednotlivé šifrované bajty zapisují po sloupcích.
KeyExpansions)Proběhne inicializační runda, složená pouze z kroku AddRoundKey
Proběhne požadovaný počet rund, složených z následujících kroků:
SubBytesShiftRowsMixColumnAddRoundKeyProběhne finální runda složená z těchto kroků:
SubBytesShiftRowsAddRoundKeyJednotlivé kroky algoritmu jsou představeny v kódu jazyka C++ níže (zdroj ZDE).
#include <stdint.h>
#include <string.h> // CBC mode, for memset
#include "aes.h"
/*****************************************************************************/
/* Defines: */
/*****************************************************************************/
// The number of columns comprising a state in AES. This is a constant in AES. Value=4
#define Nb 4
// The number of 32 bit words in a key.
#define Nk 4
// Key length in bytes [128 bit]
#define KEYLEN 16
// The number of rounds in AES Cipher.
#define Nr 10
// jcallan@github points out that declaring Multiply as a function
// reduces code size considerably with the Keil ARM compiler.
// See this link for more information: https://github.com/kokke/tiny-AES128-C/pull/3
#ifndef MULTIPLY_AS_A_FUNCTION
#define MULTIPLY_AS_A_FUNCTION 0
#endif
/*****************************************************************************/
/* Private variables: */
/*****************************************************************************/
// state - array holding the intermediate results during decryption.
typedef uint8_t state_t[4][4];
static state_t* state;
// The array that stores the round keys.
static uint8_t RoundKey[176];
// The Key input to the AES Program
static const uint8_t* Key;
#if defined(CBC) && CBC
// Initial Vector used only for CBC mode
static uint8_t* Iv;
#endif
// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM -
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
static const uint8_t sbox[256] = {
//0 1 2 3 4 5 6 7 8 9 A B C D E F
0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 };
static const uint8_t rsbox[256] =
{ 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 };
// The round constant word array, Rcon[i], contains the values given by
// x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
// Note that i starts at 1, not 0).
static const uint8_t Rcon[255] = {
0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb };
/*****************************************************************************/
/* Private functions: */
/*****************************************************************************/
static uint8_t getSBoxValue(uint8_t num)
{
return sbox[num];
}
static uint8_t getSBoxInvert(uint8_t num)
{
return rsbox[num];
}
// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
static void KeyExpansion(void)
{
uint32_t i, j, k;
uint8_t tempa[4]; // Used for the column/row operations
// The first round key is the key itself.
for(i = 0; i < Nk; ++i)
{
RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
}
// All other round keys are found from the previous round keys.
for(; (i < (Nb * (Nr + 1))); ++i)
{
for(j = 0; j < 4; ++j)
{
tempa[j]=RoundKey[(i-1) * 4 + j];
}
if (i % Nk == 0)
{
// This function rotates the 4 bytes in a word to the left once.
// [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
// Function RotWord()
{
k = tempa[0];
tempa[0] = tempa[1];
tempa[1] = tempa[2];
tempa[2] = tempa[3];
tempa[3] = k;
}
// SubWord() is a function that takes a four-byte input word and
// applies the S-box to each of the four bytes to produce an output word.
// Function Subword()
{
tempa[0] = getSBoxValue(tempa[0]);
tempa[1] = getSBoxValue(tempa[1]);
tempa[2] = getSBoxValue(tempa[2]);
tempa[3] = getSBoxValue(tempa[3]);
}
tempa[0] = tempa[0] ^ Rcon[i/Nk];
}
else if (Nk > 6 && i % Nk == 4)
{
// Function Subword()
{
tempa[0] = getSBoxValue(tempa[0]);
tempa[1] = getSBoxValue(tempa[1]);
tempa[2] = getSBoxValue(tempa[2]);
tempa[3] = getSBoxValue(tempa[3]);
}
}
RoundKey[i * 4 + 0] = RoundKey[(i - Nk) * 4 + 0] ^ tempa[0];
RoundKey[i * 4 + 1] = RoundKey[(i - Nk) * 4 + 1] ^ tempa[1];
RoundKey[i * 4 + 2] = RoundKey[(i - Nk) * 4 + 2] ^ tempa[2];
RoundKey[i * 4 + 3] = RoundKey[(i - Nk) * 4 + 3] ^ tempa[3];
}
}
// This function adds the round key to state.
// The round key is added to the state by an XOR function.
static void AddRoundKey(uint8_t round)
{
uint8_t i,j;
for(i=0;i<4;++i)
{
for(j = 0; j < 4; ++j)
{
(*state)[i][j] ^= RoundKey[round * Nb * 4 + i * Nb + j];
}
}
}
// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void SubBytes(void)
{
uint8_t i, j;
for(i = 0; i < 4; ++i)
{
for(j = 0; j < 4; ++j)
{
(*state)[j][i] = getSBoxValue((*state)[j][i]);
}
}
}
// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
static void ShiftRows(void)
{
uint8_t temp;
// Rotate first row 1 columns to left
temp = (*state)[0][1];
(*state)[0][1] = (*state)[1][1];
(*state)[1][1] = (*state)[2][1];
(*state)[2][1] = (*state)[3][1];
(*state)[3][1] = temp;
// Rotate second row 2 columns to left
temp = (*state)[0][2];
(*state)[0][2] = (*state)[2][2];
(*state)[2][2] = temp;
temp = (*state)[1][2];
(*state)[1][2] = (*state)[3][2];
(*state)[3][2] = temp;
// Rotate third row 3 columns to left
temp = (*state)[0][3];
(*state)[0][3] = (*state)[3][3];
(*state)[3][3] = (*state)[2][3];
(*state)[2][3] = (*state)[1][3];
(*state)[1][3] = temp;
}
static uint8_t xtime(uint8_t x)
{
return ((x<<1) ^ (((x>>7) & 1) * 0x1b));
}
// MixColumns function mixes the columns of the state matrix
static void MixColumns(void)
{
uint8_t i;
uint8_t Tmp,Tm,t;
for(i = 0; i < 4; ++i)
{
t = (*state)[i][0];
Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3] ;
Tm = (*state)[i][0] ^ (*state)[i][1] ; Tm = xtime(Tm); (*state)[i][0] ^= Tm ^ Tmp ;
Tm = (*state)[i][1] ^ (*state)[i][2] ; Tm = xtime(Tm); (*state)[i][1] ^= Tm ^ Tmp ;
Tm = (*state)[i][2] ^ (*state)[i][3] ; Tm = xtime(Tm); (*state)[i][2] ^= Tm ^ Tmp ;
Tm = (*state)[i][3] ^ t ; Tm = xtime(Tm); (*state)[i][3] ^= Tm ^ Tmp ;
}
}
// Multiply is used to multiply numbers in the field GF(2^8)
#if MULTIPLY_AS_A_FUNCTION
static uint8_t Multiply(uint8_t x, uint8_t y)
{
return (((y & 1) * x) ^
((y>>1 & 1) * xtime(x)) ^
((y>>2 & 1) * xtime(xtime(x))) ^
((y>>3 & 1) * xtime(xtime(xtime(x)))) ^
((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))));
}
#else
#define Multiply(x, y) \
( ((y & 1) * x) ^ \
((y>>1 & 1) * xtime(x)) ^ \
((y>>2 & 1) * xtime(xtime(x))) ^ \
((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ \
((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))) \
#endif
// MixColumns function mixes the columns of the state matrix.
// The method used to multiply may be difficult to understand for the inexperienced.
// Please use the references to gain more information.
static void InvMixColumns(void)
{
int i;
uint8_t a,b,c,d;
for(i=0;i<4;++i)
{
a = (*state)[i][0];
b = (*state)[i][1];
c = (*state)[i][2];
d = (*state)[i][3];
(*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
(*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
(*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
(*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
}
}
// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void InvSubBytes(void)
{
uint8_t i,j;
for(i=0;i<4;++i)
{
for(j=0;j<4;++j)
{
(*state)[j][i] = getSBoxInvert((*state)[j][i]);
}
}
}
static void InvShiftRows(void)
{
uint8_t temp;
// Rotate first row 1 columns to right
temp=(*state)[3][1];
(*state)[3][1]=(*state)[2][1];
(*state)[2][1]=(*state)[1][1];
(*state)[1][1]=(*state)[0][1];
(*state)[0][1]=temp;
// Rotate second row 2 columns to right
temp=(*state)[0][2];
(*state)[0][2]=(*state)[2][2];
(*state)[2][2]=temp;
temp=(*state)[1][2];
(*state)[1][2]=(*state)[3][2];
(*state)[3][2]=temp;
// Rotate third row 3 columns to right
temp=(*state)[0][3];
(*state)[0][3]=(*state)[1][3];
(*state)[1][3]=(*state)[2][3];
(*state)[2][3]=(*state)[3][3];
(*state)[3][3]=temp;
}
// Cipher is the main function that encrypts the PlainText.
static void Cipher(void)
{
uint8_t round = 0;
// Add the First round key to the state before starting the rounds.
AddRoundKey(0);
// There will be Nr rounds.
// The first Nr-1 rounds are identical.
// These Nr-1 rounds are executed in the loop below.
for(round = 1; round < Nr; ++round)
{
SubBytes();
ShiftRows();
MixColumns();
AddRoundKey(round);
}
// The last round is given below.
// The MixColumns function is not here in the last round.
SubBytes();
ShiftRows();
AddRoundKey(Nr);
}
static void InvCipher(void)
{
uint8_t round=0;
// Add the First round key to the state before starting the rounds.
AddRoundKey(Nr);
// There will be Nr rounds.
// The first Nr-1 rounds are identical.
// These Nr-1 rounds are executed in the loop below.
for(round=Nr-1;round>0;round--)
{
InvShiftRows();
InvSubBytes();
AddRoundKey(round);
InvMixColumns();
}
// The last round is given below.
// The MixColumns function is not here in the last round.
InvShiftRows();
InvSubBytes();
AddRoundKey(0);
}
static void BlockCopy(uint8_t* output, uint8_t* input)
{
uint8_t i;
for (i=0;i<KEYLEN;++i)
{
output[i] = input[i];
}
}
/*****************************************************************************/
/* Public functions: */
/*****************************************************************************/
#if defined(ECB) && ECB
void AES128_ECB_encrypt(uint8_t* input, const uint8_t* key, uint8_t* output)
{
// Copy input to output, and work in-memory on output
BlockCopy(output, input);
state = (state_t*)output;
Key = key;
KeyExpansion();
// The next function call encrypts the PlainText with the Key using AES algorithm.
Cipher();
}
void AES128_ECB_decrypt(uint8_t* input, const uint8_t* key, uint8_t *output)
{
// Copy input to output, and work in-memory on output
BlockCopy(output, input);
state = (state_t*)output;
// The KeyExpansion routine must be called before encryption.
Key = key;
KeyExpansion();
InvCipher();
}
#endif // #if defined(ECB) && ECB
#if defined(CBC) && CBC
static void XorWithIv(uint8_t* buf)
{
uint8_t i;
for(i = 0; i < KEYLEN; ++i)
{
buf[i] ^= Iv[i];
}
}
void AES128_CBC_encrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, const uint8_t* key, const uint8_t* iv)
{
uintptr_t i;
uint8_t remainders = length % KEYLEN; /* Remaining bytes in the last non-full block */
BlockCopy(output, input);
state = (state_t*)output;
// Skip the key expansion if key is passed as 0
if(0 != key)
{
Key = key;
KeyExpansion();
}
if(iv != 0)
{
Iv = (uint8_t*)iv;
}
for(i = 0; i < length; i += KEYLEN)
{
XorWithIv(input);
BlockCopy(output, input);
state = (state_t*)output;
Cipher();
Iv = output;
input += KEYLEN;
output += KEYLEN;
}
if(remainders)
{
BlockCopy(output, input);
memset(output + remainders, 0, KEYLEN - remainders); /* add 0-padding */
state = (state_t*)output;
Cipher();
}
}
void AES128_CBC_decrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, const uint8_t* key, const uint8_t* iv)
{
uintptr_t i;
uint8_t remainders = length % KEYLEN; /* Remaining bytes in the last non-full block */
BlockCopy(output, input);
state = (state_t*)output;
// Skip the key expansion if key is passed as 0
if(0 != key)
{
Key = key;
KeyExpansion();
}
// If iv is passed as 0, we continue to encrypt without re-setting the Iv
if(iv != 0)
{
Iv = (uint8_t*)iv;
}
for(i = 0; i < length; i += KEYLEN)
{
BlockCopy(output, input);
state = (state_t*)output;
InvCipher();
XorWithIv(output);
Iv = input;
input += KEYLEN;
output += KEYLEN;
}
if(remainders)
{
BlockCopy(output, input);
memset(output+remainders, 0, KEYLEN - remainders); /* add 0-padding */
state = (state_t*)output;
InvCipher();
}
}
#endif // #if defined(CBC) && CBC