Last active
December 23, 2015 18:19
-
-
Save joostrijneveld/6675202 to your computer and use it in GitHub Desktop.
Computing the T-boxes that enable fast computation of AES through lookup.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#include <stdint.h> | |
#include <stdio.h> | |
using namespace std; | |
unsigned char s[256] = | |
{ | |
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 | |
}; | |
uint8_t gmul(uint8_t a, uint8_t b) { | |
//source: http://en.wikipedia.org/wiki/Finite_field_arithmetic#C_programming_example | |
uint8_t p = 0; | |
uint8_t counter; | |
uint8_t carry; | |
for (counter = 0; counter < 8; counter++) { | |
if (b & 1) | |
p ^= a; | |
carry = (a & 0x80); | |
a <<= 1; | |
if (carry) | |
a ^= 0x001B; /* what x^8 is modulo x^8 + x^4 + x^3 + x^2 + 1 */ | |
b >>= 1; | |
} | |
return p; | |
} | |
int main() { | |
//T0 | |
for (int i = 0; i < 256; i++) { | |
uint8_t a = i; | |
printf("(%02x, %02x, %02x, %02x), ", gmul(s[a], 0x02), s[a], s[a], gmul(s[a], 0x03)); | |
} | |
printf("%s", "\n\n"); | |
//T1 | |
for (int i = 0; i < 256; i++) { | |
uint8_t a = i; | |
printf("(%02x, %02x, %02x, %02x), ", gmul(s[a], 0x03), gmul(s[a], 0x02), s[a], s[a]); | |
} | |
printf("%s", "\n\n"); | |
//T2 | |
for (int i = 0; i < 256; i++) { | |
uint8_t a = i; | |
printf("(%02x, %02x, %02x, %02x), ", s[a], gmul(s[a], 0x03), gmul(s[a], 0x02), s[a]); | |
} | |
printf("%s", "\n\n"); | |
//T3 | |
for (int i = 0; i < 256; i++) { | |
uint8_t a = i; | |
printf("(%02x, %02x, %02x, %02x), ", s[a], s[a], gmul(s[a], 0x03), gmul(s[a], 0x02)); | |
} | |
return 0; | |
} | |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment