Protecting Against Eavesdroppers with Symmetric Cryptography - Implementing SSL/TLS Using Cryptography and PKI - page 76

Listing 2-40: “aes.c” inversion routines
static void inv_shift_rows( unsigned char state[ ][ 4 ] )
{
int tmp;
tmp = state[ 1 ][ 2 ];
state[ 1 ][ 2 ] = state[ 1 ][ 1 ];
state[ 1 ][ 1 ] = state[ 1 ][ 0 ];
state[ 1 ][ 0 ] = state[ 1 ][ 3 ];
state[ 1 ][ 3 ] = tmp;
tmp = state[ 2 ][ 0 ];
state[ 2 ][ 0 ] = state[ 2 ][ 2 ];
state[ 2 ][ 2 ] = tmp;
tmp = state[ 2 ][ 1 ];
state[ 2 ][ 1 ] = state[ 2 ][ 3 ];
state[ 2 ][ 3 ] = tmp;
tmp = state[ 3 ][ 0 ];
state[ 3 ][ 0 ] = state[ 3 ][ 1 ];
state[ 3 ][ 1 ] = state[ 3 ][ 2 ];
state[ 3 ][ 2 ] = state[ 3 ][ 3 ];
state[ 3 ][ 3 ] = tmp;
}
static unsigned char inv_sbox[ 16 ][ 16 ] = {
{ 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,