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aes_keyschedule.c
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aes_keyschedule.c
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/* ===================================================================== */
/* This file is a little helper to compute AES key scheduling */
/* from any round key */
/* Original author: Philippe Teuwen <phil@teuwen.org> 2016 */
/* */
/* Usage: */
/* aes_keyschedule AES_key_in_hex */
/* aes_keyschedule Round_key_in_hex Round_key_number_between_0_and_10 */
/* */
/* Examples: */
/* aes_keyschedule 11223344556677881122334455667788 */
/* aes_keyschedule 23D7F7B876B180306793B37432F5C4FC 1 */
/* aes_keyschedule 43EDA420DD033E7627347DC2CC6E0B4E 9 */
/* aes_keyschedule EAC68B6B37C5B51D10F1C8DFDC9FC391 10 */
/* */
/* Based on the Tiny AES128 in C https://github.com/kokke/tiny-AES128-C */
/* and released under the same licensing terms: */
/* */
/* This is free and unencumbered software released into the public domain*/
/* */
/* Anyone is free to copy, modify, publish, use, compile, sell, or */
/* distribute this software, either in source code form or as a compiled */
/* binary, for any purpose, commercial or non-commercial, and by any */
/* means. */
/* */
/* In jurisdictions that recognize copyright laws, the author or authors */
/* of this software dedicate any and all copyright interest in the */
/* software to the public domain. We make this dedication for the benefit*/
/* of the public at large and to the detriment of our heirs and */
/* successors. We intend this dedication to be an overt act of */
/* relinquishment in perpetuity of all present and future rights to this */
/* software under copyright law. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
/* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR */
/* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, */
/* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR */
/* OTHER DEALINGS IN THE SOFTWARE. */
/* */
/* For more information, please refer to <http://unlicense.org/> */
/* ===================================================================== */
/*****************************************************************************/
/* Includes: */
/*****************************************************************************/
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*****************************************************************************/
/* Defines: */
/*****************************************************************************/
// The number of columns comprising a state in AES. This is a constant in AES. Value=4
#define Nb 4
/*****************************************************************************/
/* Private variables: */
/*****************************************************************************/
// state - array holding the intermediate results during decryption.
// The array that stores the round keys.
static uint8_t RoundKey[240];
// The Key input to the AES Program
static uint8_t Key[32];
// 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 };
// 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[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.
void KeyExpansion(uint8_t start, uint16_t AesSize)
{
uint32_t i, j, k;
uint8_t tempa[4]; // Used for the column/row operations
uint8_t Nk = AesSize / 32;
// Nr: The number of rounds in AES Cipher: 10, 12 or 14
uint8_t Nr = Nk+6;
start *=4;
// The first round key is the key itself.
for(i = start; i < (Nk+start); ++i)
{
RoundKey[(i * 4) + 0] = Key[((i-start) * 4) + 0];
RoundKey[(i * 4) + 1] = Key[((i-start) * 4) + 1];
RoundKey[(i * 4) + 2] = Key[((i-start) * 4) + 2];
RoundKey[(i * 4) + 3] = Key[((i-start) * 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] = 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];
}
else if (Nk > 6 && i % Nk == 4)
{
// Function Subword()
{
tempa[0] = sbox[tempa[0]];
tempa[1] = sbox[tempa[1]];
tempa[2] = sbox[tempa[2]];
tempa[3] = sbox[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];
}
for(i=(Nk+start-1); i>(Nk-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] = 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];
}
else if (Nk > 6 && i % Nk == 4)
{
// Function Subword()
{
tempa[0] = sbox[tempa[0]];
tempa[1] = sbox[tempa[1]];
tempa[2] = sbox[tempa[2]];
tempa[3] = sbox[tempa[3]];
}
}
RoundKey[(i - Nk) * 4 + 0] = RoundKey[i * 4 + 0] ^ tempa[0];
RoundKey[(i - Nk) * 4 + 1] = RoundKey[i * 4 + 1] ^ tempa[1];
RoundKey[(i - Nk) * 4 + 2] = RoundKey[i * 4 + 2] ^ tempa[2];
RoundKey[(i - Nk) * 4 + 3] = RoundKey[i * 4 + 3] ^ tempa[3];
}
for(j = 0; j < 16*(Nr+1); ++j)
{
if (j%16==0)
printf("K%02i: ", j/16);
printf("%02X", RoundKey[j]);
if (j%16==15)
printf("\n");
}
}
unsigned char is_hex_char(char c)
{
return (
(c >= '0' && c <= '9') ||
(c >= 'a' && c <= 'f') ||
(c >= 'A' && c <= 'F')
);
}
int main(int argc, char *argv[])
{
uint8_t i;
uint8_t round=0;
if (argc<2) {
printf("Usage: \n%s AES_key_in_hex\n", argv[0]);
printf("%s Round_key(s)_in_hex Initial_round_key_number_between_0_and_10#11#13\n", argv[0]);
printf("Examples:\n");
printf("- AES-128: (provide 1 round key)\n");
printf(" %s B1BA2737C83233FE7F7A7DF0FBB01D4A\n", argv[0]);
printf(" %s 97F926D5677B324AC439D77C8B03FDF8 5\n", argv[0]);
printf(" %s FAEF63792F9A97A1FB78C88C4CA7048F 10\n", argv[0]);
printf("- AES-192: (provide 1.5 round keys)\n");
printf(" %s B1BA2737C83233FE7F7A7DF0FBB01D4A7835FA62BE9726A1\n", argv[0]);
printf(" %s D42AAFEB1510F368D8AA1354A707697696D6CC20F7737995 5\n", argv[0]);
printf(" %s 504B601C4EEB5C33B3D208B8E4966BA37B07118538961350 11\n", argv[0]);
printf(" Tip: check if the second half round key is the same as yours. If not => AES-256\n");
printf("- AES-256: (provide 2 round keys)\n");
printf(" %s B1BA2737C83233FE7F7A7DF0FBB01D4A7835FA62BE9726A1BB39F261BAC4729C\n", argv[0]);
printf(" %s F2E96B6FD53C1BBB49D0990E6FF86927DF8F909C21310695C43D2751C133AC12 5\n", argv[0]);
printf(" %s 4D69A4975189FCA00DB0AC8F686EE58C033BE6307A3C13C226DF38591EEAC857 13\n", argv[0]);
return EXIT_FAILURE;
}
uint32_t arglen = strlen(argv[1]);
if( (arglen != 32) && (arglen != 48) && (arglen != 64)) {
printf("Error: AES_key must be 16, 24 or 32-byte long\n");
return EXIT_FAILURE;
}
uint16_t AesSize = arglen * 4;
for(i = 0; i < arglen; i += 2)
{
if(is_hex_char(argv[1][i]) == 0 || is_hex_char(argv[1][i + 1]) == 0)
return EXIT_FAILURE;
unsigned char str_bytes[3] = {
argv[1][i],
argv[1][i + 1],
0
};
Key[ i / 2] = strtoul((const char*)str_bytes, NULL, 16);
}
if (argc > 2)
round = atoi(argv[2]);
KeyExpansion(round, AesSize);
}