Diff: aes/aes128cbc.c

Revision:

19:f22327e8be7b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/aes/aes128cbc.c	Tue Oct 15 07:26:15 2019 +0000
@@ -0,0 +1,449 @@
+/*
+This is an implementation of the AES algorithm, specifically ECB, CTR and CBC mode.
+Block size can be chosen in aes.h - available choices are AES128, AES192, AES256.
+The implementation is verified against the test vectors in:
+  National Institute of Standards and Technology Special Publication 800-38A 2001 ED
+ECB-AES128
+----------
+  plain-text:
+    6bc1bee22e409f96e93d7e117393172a
+    ae2d8a571e03ac9c9eb76fac45af8e51
+    30c81c46a35ce411e5fbc1191a0a52ef
+    f69f2445df4f9b17ad2b417be66c3710
+  key:
+    2b7e151628aed2a6abf7158809cf4f3c
+  resulting cipher
+    3ad77bb40d7a3660a89ecaf32466ef97 
+    f5d3d58503b9699de785895a96fdbaaf 
+    43b1cd7f598ece23881b00e3ed030688 
+    7b0c785e27e8ad3f8223207104725dd4 
+NOTE:   String length must be evenly divisible by 16byte (str_len % 16 == 0)
+        You should pad the end of the string with zeros if this is not the case.
+        For AES192/256 the key size is proportionally larger.
+*/
+
+
+/*****************************************************************************/
+/* Includes:                                                                 */
+/*****************************************************************************/
+#include <stdint.h>
+#include <string.h> // CBC mode, for memset
+#include "aes128cbc.h"
+
+/*****************************************************************************/
+/* Defines:                                                                  */
+/*****************************************************************************/
+// The number of columns comprising a state in AES. This is a constant in AES. Value=4
+#define Nb 4
+
+#define Nk 4        // The number of 32 bit words in a key.
+#define Nr 10       // The number of rounds in AES Cipher.
+
+
+struct Aes128CbcState
+{
+  uint8_t RoundKey[176];
+  uint8_t Iv[AES128CBC_BLOCK_SIZE];
+};
+
+/*****************************************************************************/
+/* Private variables:                                                        */
+/*****************************************************************************/
+// state - array holding the intermediate results during decryption.
+typedef uint8_t state_t[4][4];
+
+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 the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
+static const uint8_t Rcon[11] = { 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };
+
+/*
+ * Jordan Goulder points out in PR #12 (https://github.com/kokke/tiny-AES-C/pull/12),
+ * that you can remove most of the elements in the Rcon array, because they are unused.
+ *
+ * From Wikipedia's article on the Rijndael key schedule @ https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
+ * 
+ * "Only the first some of these constants are actually used – up to rcon[10] for AES-128 (as 11 round keys are needed), 
+ *  up to rcon[8] for AES-192, up to rcon[7] for AES-256. rcon[0] is not used in AES algorithm."
+ */
+
+
+/*****************************************************************************/
+/* Private functions:                                                        */
+/*****************************************************************************/
+/*
+static uint8_t getSBoxValue(uint8_t num)
+{
+  return sbox[num];
+}
+*/
+#define getSBoxValue(num) (sbox[(num)])
+/*
+static uint8_t getSBoxInvert(uint8_t num)
+{
+  return rsbox[num];
+}
+*/
+#define getSBoxInvert(num) (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(uint8_t* RoundKey, const uint8_t* Key)
+{
+  unsigned 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 = Nk; i < Nb * (Nr + 1); ++i)
+  {
+    {
+      k = (i - 1) * 4;
+      tempa[0]=RoundKey[k + 0];
+      tempa[1]=RoundKey[k + 1];
+      tempa[2]=RoundKey[k + 2];
+      tempa[3]=RoundKey[k + 3];
+
+    }
+
+    if (i % Nk == 0)
+    {
+      // This function shifts the 4 bytes in a word to the left once.
+      // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
+
+      // Function RotWord()
+      {
+        const uint8_t u8tmp = tempa[0];
+        tempa[0] = tempa[1];
+        tempa[1] = tempa[2];
+        tempa[2] = tempa[3];
+        tempa[3] = u8tmp;
+      }
+
+      // 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];
+    }
+    j = i * 4; k=(i - Nk) * 4;
+    RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
+    RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
+    RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
+    RoundKey[j + 3] = RoundKey[k + 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, state_t* state, const uint8_t* RoundKey)
+{
+  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(state_t* state)
+{
+  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(state_t* state)
+{
+  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(state_t* state)
+{
+  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 ;
+  }
+}
+
+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)))))); /* this last call to xtime() can be omitted */
+  }
+
+// 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(state_t* state)
+{
+  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(state_t* state)
+{
+  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(state_t* state)
+{
+  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(state_t* state, const uint8_t* RoundKey)
+{
+  uint8_t round = 0;
+
+  // Add the First round key to the state before starting the rounds.
+  AddRoundKey(0, state, RoundKey); 
+  
+  // 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(state);
+    ShiftRows(state);
+    MixColumns(state);
+    AddRoundKey(round, state, RoundKey);
+  }
+  
+  // The last round is given below.
+  // The MixColumns function is not here in the last round.
+  SubBytes(state);
+  ShiftRows(state);
+  AddRoundKey(Nr, state, RoundKey);
+}
+
+static void InvCipher(state_t* state, const uint8_t* RoundKey)
+{
+  uint8_t round = 0;
+
+  // Add the First round key to the state before starting the rounds.
+  AddRoundKey(Nr, state, RoundKey); 
+
+  // 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(state);
+    InvSubBytes(state);
+    AddRoundKey(round, state, RoundKey);
+    InvMixColumns(state);
+  }
+  
+  // The last round is given below.
+  // The MixColumns function is not here in the last round.
+  InvShiftRows(state);
+  InvSubBytes(state);
+  AddRoundKey(0, state, RoundKey);
+}
+
+/*****************************************************************************/
+/* Public functions:                                                         */
+/*****************************************************************************/
+
+static void XorWithIv(uint8_t* buf, const uint8_t* Iv)
+{
+  uint8_t i;
+  for (i = 0; i < AES128CBC_BLOCK_SIZE; ++i) // The block in AES is always 128bit no matter the key size
+  {
+    buf[i] ^= Iv[i];
+  }
+}
+
+static void init(struct Aes128CbcState* ctx, const uint8_t* key, const uint8_t* iv)
+{
+  KeyExpansion(ctx->RoundKey, key);
+  memcpy (ctx->Iv, iv, AES128CBC_BLOCK_SIZE);
+}
+
+static void encrypt(struct Aes128CbcState *ctx, uint8_t* buf, uint32_t length)
+{
+  uintptr_t i;
+  uint8_t *Iv = ctx->Iv;
+  for (i = 0; i < length; i += AES128CBC_BLOCK_SIZE)
+  {
+    XorWithIv(buf, Iv);
+    Cipher((state_t*)buf, ctx->RoundKey);
+    Iv = buf;
+    buf += AES128CBC_BLOCK_SIZE;
+  }
+  memcpy(ctx->Iv, Iv, AES128CBC_BLOCK_SIZE);
+}
+
+static void decrypt(struct Aes128CbcState* ctx, uint8_t* buf,  uint32_t length)
+{
+  uintptr_t i;
+  uint8_t storeNextIv[AES128CBC_BLOCK_SIZE];
+  for (i = 0; i < length; i += AES128CBC_BLOCK_SIZE)
+  {
+    memcpy(storeNextIv, buf, AES128CBC_BLOCK_SIZE);
+    InvCipher((state_t*)buf, ctx->RoundKey);
+    XorWithIv(buf, ctx->Iv);
+    memcpy(ctx->Iv, storeNextIv, AES128CBC_BLOCK_SIZE);
+    buf += AES128CBC_BLOCK_SIZE;
+  }
+}
+
+void Aes128CbcEncrypt(const uint8_t* key, const uint8_t* iv, uint8_t* buf, uint32_t length)
+{
+    struct Aes128CbcState ctx;
+    init(&ctx, key, iv);
+    encrypt(&ctx, buf, length);
+}
+void Aes128CbcDecrypt(const uint8_t* key, const uint8_t* iv, uint8_t* buf, uint32_t length)
+{
+    struct Aes128CbcState ctx;
+    init(&ctx, key, iv);
+    decrypt(&ctx, buf, length);
+}