Andrew Boyson
A simple library to support serving https.
Dependents: oldheating gps motorhome heating
Diff: aes-cbc/aes128cbc.c
- Revision:
- 20:197c3e6e8b8d
- Parent:
- 19:f22327e8be7b
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/aes-cbc/aes128cbc.c Wed Oct 16 11:11:03 2019 +0000
@@ -0,0 +1,383 @@
+/*
+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.
+*/
+
+#include <stdint.h>
+#include <string.h> // CBC mode, for memset
+#include "aes128cbc.h"
+
+#define NB 4 // The number of columns comprising a state in AES. This is a constant in AES. Value=4
+#define NK 4 // The number of 32 bit words in a key.
+#define NR 10 // The number of rounds in AES Cipher.
+
+/*
+union state_u
+{
+ uint8_t d1[16];
+ uint8_t d2[4][4];
+};
+typedef union state_u state_t; // state - array holding the intermediate results during decryption.
+*/
+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 };
+
+// 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] = sbox[tempa[0]];
+ tempa[1] = sbox[tempa[1]];
+ tempa[2] = sbox[tempa[2]];
+ tempa[3] = sbox[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, uint8_t* state, const uint8_t* roundKey)
+{
+ uint8_t i,j;
+ for (i = 0; i < 4; ++i)
+ {
+ for (j = 0; j < 4; ++j)
+ {
+ *(state + i*4 + 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(uint8_t* state)
+{
+ uint8_t i, j;
+ for (i = 0; i < 4; ++i)
+ {
+ for (j = 0; j < 4; ++j)
+ {
+ *(state + j*4 + i) = sbox[*(state + j*4 + 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(uint8_t* state)
+{
+ uint8_t temp;
+
+ // Rotate first row 1 columns to left
+ temp = *(state + 4*0 + 1);
+ *(state + 4*0 + 1) = *(state + 4*1 + 1);
+ *(state + 4*1 + 1) = *(state + 4*2 + 1);
+ *(state + 4*2 + 1) = *(state + 4*3 + 1);
+ *(state + 4*3 + 1) = temp;
+
+ // Rotate second row 2 columns to left
+ temp = *(state + 4*0 + 2);
+ *(state + 4*0 + 2) = *(state + 4*2 + 2);
+ *(state + 4*2 + 2) = temp;
+
+ temp = *(state + 4*1 + 2);
+ *(state + 4*1 + 2) = *(state + 4*3 + 2);
+ *(state + 4*3 + 2) = temp;
+
+ // Rotate third row 3 columns to left
+ temp = *(state + 4*0 + 3);
+ *(state + 4*0 + 3) = *(state + 4*3 + 3);
+ *(state + 4*3 + 3) = *(state + 4*2 + 3);
+ *(state + 4*2 + 3) = *(state + 4*1 + 3);
+ *(state + 4*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(uint8_t* state)
+{
+ uint8_t i;
+ uint8_t tmp, tm, t;
+ for (i = 0; i < 4; ++i)
+ {
+ t = *(state + 4*i + 0);
+ tmp = *(state + 4*i + 0) ^ *(state + 4*i + 1) ^ *(state + 4*i + 2) ^ *(state + 4*i + 3);
+ tm = *(state + 4*i + 0) ^ *(state + 4*i + 1) ; tm = xtime(tm); *(state + 4*i + 0) ^= tm ^ tmp ;
+ tm = *(state + 4*i + 1) ^ *(state + 4*i + 2) ; tm = xtime(tm); *(state + 4*i + 1) ^= tm ^ tmp ;
+ tm = *(state + 4*i + 2) ^ *(state + 4*i + 3) ; tm = xtime(tm); *(state + 4*i + 2) ^= tm ^ tmp ;
+ tm = *(state + 4*i + 3) ^ t ; tm = xtime(tm); *(state + 4*i + 3) ^= tm ^ tmp ;
+ }
+}
+
+static uint8_t multiply(uint8_t x, uint8_t y)
+{
+ return (((y>>0 & 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(uint8_t* state)
+{
+ int i;
+ uint8_t a, b, c, d;
+ for (i = 0; i < 4; ++i)
+ {
+ a = *(state + 4*i + 0);
+ b = *(state + 4*i + 1);
+ c = *(state + 4*i + 2);
+ d = *(state + 4*i + 3);
+
+ *(state + 4*i + 0) = multiply(a, 0x0e) ^ multiply(b, 0x0b) ^ multiply(c, 0x0d) ^ multiply(d, 0x09);
+ *(state + 4*i + 1) = multiply(a, 0x09) ^ multiply(b, 0x0e) ^ multiply(c, 0x0b) ^ multiply(d, 0x0d);
+ *(state + 4*i + 2) = multiply(a, 0x0d) ^ multiply(b, 0x09) ^ multiply(c, 0x0e) ^ multiply(d, 0x0b);
+ *(state + 4*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(uint8_t* state)
+{
+ uint8_t i, j;
+ for (i = 0; i < 4; ++i)
+ {
+ for (j = 0; j < 4; ++j)
+ {
+ *(state + 4*j + i) = rsbox[*(state + 4*j + i)];
+ }
+ }
+}
+
+static void invShiftRows(uint8_t* state)
+{
+ uint8_t temp;
+
+ // Rotate first row 1 columns to right
+ temp = *(state + 4*3 + 1);
+ *(state + 4*3 + 1) = *(state + 4*2 + 1);
+ *(state + 4*2 + 1) = *(state + 4*1 + 1);
+ *(state + 4*1 + 1) = *(state + 4*0 + 1);
+ *(state + 4*0 + 1) = temp;
+
+ // Rotate second row 2 columns to right
+ temp = *(state + 4*0 + 2);
+ *(state + 4*0 + 2) = *(state + 4*2 + 2);
+ *(state + 4*2 + 2) = temp;
+
+ temp = *(state + 4*1 + 2);
+ *(state + 4*1 + 2) = *(state + 4*3 + 2);
+ *(state + 4*3 + 2) = temp;
+
+ // Rotate third row 3 columns to right
+ temp = *(state + 4*0 + 3);
+ *(state + 4*0 + 3) = *(state + 4*1 + 3);
+ *(state + 4*1 + 3) = *(state + 4*2 + 3);
+ *(state + 4*2 + 3) = *(state + 4*3 + 3);
+ *(state + 4*3 + 3) = temp;
+}
+
+// Cipher is the main function that encrypts the PlainText.
+static void cipher(uint8_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(uint8_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: */
+/*****************************************************************************/
+
+void Aes128CbcEncrypt(const uint8_t* key, const uint8_t* iv, uint8_t* buf, uint32_t length)
+{
+ uint8_t ctxRoundKey[176];
+ keyExpansion(ctxRoundKey, key);
+
+ const uint8_t* prevIv = iv;
+ for (int i = 0; i < length; i += AES128CBC_BLOCK_SIZE)
+ {
+ for (int j = 0; j < AES128CBC_BLOCK_SIZE; ++j) buf[j] ^= prevIv[j];
+ cipher(buf, ctxRoundKey);
+ prevIv = buf;
+ buf += AES128CBC_BLOCK_SIZE;
+ }
+}
+void Aes128CbcDecrypt(const uint8_t* key, const uint8_t* iv, uint8_t* buf, uint32_t length)
+{
+ uint8_t ctxRoundKey[176];
+ keyExpansion(ctxRoundKey, key);
+
+ uint8_t ctxIv[AES128CBC_BLOCK_SIZE];
+ memcpy (ctxIv, iv, AES128CBC_BLOCK_SIZE);
+
+ uint8_t storeNextIv[AES128CBC_BLOCK_SIZE];
+ for (int i = 0; i < length; i += AES128CBC_BLOCK_SIZE)
+ {
+ memcpy(storeNextIv, buf, AES128CBC_BLOCK_SIZE);
+ invCipher(buf, ctxRoundKey);
+ for (int j = 0; j < AES128CBC_BLOCK_SIZE; ++j) buf[j] ^= ctxIv[j];
+ memcpy(ctxIv, storeNextIv, AES128CBC_BLOCK_SIZE);
+ buf += AES128CBC_BLOCK_SIZE;
+ }
+}