# AES Decrypt

The Advanced Encryption Standard (AES) also known as Rijndael is a specification for the encryption of electronic data.

For AES Encrypt algorithm click here.

` ````
private static byte[,] aes_sbox = {
{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}
};
private static byte[,] aes_invsbox = {
{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}
};
private static byte[,] gf_mul = {
{0x00,0x00,0x00,0x00,0x00,0x00},{0x02,0x03,0x09,0x0b,0x0d,0x0e},
{0x04,0x06,0x12,0x16,0x1a,0x1c},{0x06,0x05,0x1b,0x1d,0x17,0x12},
{0x08,0x0c,0x24,0x2c,0x34,0x38},{0x0a,0x0f,0x2d,0x27,0x39,0x36},
{0x0c,0x0a,0x36,0x3a,0x2e,0x24},{0x0e,0x09,0x3f,0x31,0x23,0x2a},
{0x10,0x18,0x48,0x58,0x68,0x70},{0x12,0x1b,0x41,0x53,0x65,0x7e},
{0x14,0x1e,0x5a,0x4e,0x72,0x6c},{0x16,0x1d,0x53,0x45,0x7f,0x62},
{0x18,0x14,0x6c,0x74,0x5c,0x48},{0x1a,0x17,0x65,0x7f,0x51,0x46},
{0x1c,0x12,0x7e,0x62,0x46,0x54},{0x1e,0x11,0x77,0x69,0x4b,0x5a},
{0x20,0x30,0x90,0xb0,0xd0,0xe0},{0x22,0x33,0x99,0xbb,0xdd,0xee},
{0x24,0x36,0x82,0xa6,0xca,0xfc},{0x26,0x35,0x8b,0xad,0xc7,0xf2},
{0x28,0x3c,0xb4,0x9c,0xe4,0xd8},{0x2a,0x3f,0xbd,0x97,0xe9,0xd6},
{0x2c,0x3a,0xa6,0x8a,0xfe,0xc4},{0x2e,0x39,0xaf,0x81,0xf3,0xca},
{0x30,0x28,0xd8,0xe8,0xb8,0x90},{0x32,0x2b,0xd1,0xe3,0xb5,0x9e},
{0x34,0x2e,0xca,0xfe,0xa2,0x8c},{0x36,0x2d,0xc3,0xf5,0xaf,0x82},
{0x38,0x24,0xfc,0xc4,0x8c,0xa8},{0x3a,0x27,0xf5,0xcf,0x81,0xa6},
{0x3c,0x22,0xee,0xd2,0x96,0xb4},{0x3e,0x21,0xe7,0xd9,0x9b,0xba},
{0x40,0x60,0x3b,0x7b,0xbb,0xdb},{0x42,0x63,0x32,0x70,0xb6,0xd5},
{0x44,0x66,0x29,0x6d,0xa1,0xc7},{0x46,0x65,0x20,0x66,0xac,0xc9},
{0x48,0x6c,0x1f,0x57,0x8f,0xe3},{0x4a,0x6f,0x16,0x5c,0x82,0xed},
{0x4c,0x6a,0x0d,0x41,0x95,0xff},{0x4e,0x69,0x04,0x4a,0x98,0xf1},
{0x50,0x78,0x73,0x23,0xd3,0xab},{0x52,0x7b,0x7a,0x28,0xde,0xa5},
{0x54,0x7e,0x61,0x35,0xc9,0xb7},{0x56,0x7d,0x68,0x3e,0xc4,0xb9},
{0x58,0x74,0x57,0x0f,0xe7,0x93},{0x5a,0x77,0x5e,0x04,0xea,0x9d},
{0x5c,0x72,0x45,0x19,0xfd,0x8f},{0x5e,0x71,0x4c,0x12,0xf0,0x81},
{0x60,0x50,0xab,0xcb,0x6b,0x3b},{0x62,0x53,0xa2,0xc0,0x66,0x35},
{0x64,0x56,0xb9,0xdd,0x71,0x27},{0x66,0x55,0xb0,0xd6,0x7c,0x29},
{0x68,0x5c,0x8f,0xe7,0x5f,0x03},{0x6a,0x5f,0x86,0xec,0x52,0x0d},
{0x6c,0x5a,0x9d,0xf1,0x45,0x1f},{0x6e,0x59,0x94,0xfa,0x48,0x11},
{0x70,0x48,0xe3,0x93,0x03,0x4b},{0x72,0x4b,0xea,0x98,0x0e,0x45},
{0x74,0x4e,0xf1,0x85,0x19,0x57},{0x76,0x4d,0xf8,0x8e,0x14,0x59},
{0x78,0x44,0xc7,0xbf,0x37,0x73},{0x7a,0x47,0xce,0xb4,0x3a,0x7d},
{0x7c,0x42,0xd5,0xa9,0x2d,0x6f},{0x7e,0x41,0xdc,0xa2,0x20,0x61},
{0x80,0xc0,0x76,0xf6,0x6d,0xad},{0x82,0xc3,0x7f,0xfd,0x60,0xa3},
{0x84,0xc6,0x64,0xe0,0x77,0xb1},{0x86,0xc5,0x6d,0xeb,0x7a,0xbf},
{0x88,0xcc,0x52,0xda,0x59,0x95},{0x8a,0xcf,0x5b,0xd1,0x54,0x9b},
{0x8c,0xca,0x40,0xcc,0x43,0x89},{0x8e,0xc9,0x49,0xc7,0x4e,0x87},
{0x90,0xd8,0x3e,0xae,0x05,0xdd},{0x92,0xdb,0x37,0xa5,0x08,0xd3},
{0x94,0xde,0x2c,0xb8,0x1f,0xc1},{0x96,0xdd,0x25,0xb3,0x12,0xcf},
{0x98,0xd4,0x1a,0x82,0x31,0xe5},{0x9a,0xd7,0x13,0x89,0x3c,0xeb},
{0x9c,0xd2,0x08,0x94,0x2b,0xf9},{0x9e,0xd1,0x01,0x9f,0x26,0xf7},
{0xa0,0xf0,0xe6,0x46,0xbd,0x4d},{0xa2,0xf3,0xef,0x4d,0xb0,0x43},
{0xa4,0xf6,0xf4,0x50,0xa7,0x51},{0xa6,0xf5,0xfd,0x5b,0xaa,0x5f},
{0xa8,0xfc,0xc2,0x6a,0x89,0x75},{0xaa,0xff,0xcb,0x61,0x84,0x7b},
{0xac,0xfa,0xd0,0x7c,0x93,0x69},{0xae,0xf9,0xd9,0x77,0x9e,0x67},
{0xb0,0xe8,0xae,0x1e,0xd5,0x3d},{0xb2,0xeb,0xa7,0x15,0xd8,0x33},
{0xb4,0xee,0xbc,0x08,0xcf,0x21},{0xb6,0xed,0xb5,0x03,0xc2,0x2f},
{0xb8,0xe4,0x8a,0x32,0xe1,0x05},{0xba,0xe7,0x83,0x39,0xec,0x0b},
{0xbc,0xe2,0x98,0x24,0xfb,0x19},{0xbe,0xe1,0x91,0x2f,0xf6,0x17},
{0xc0,0xa0,0x4d,0x8d,0xd6,0x76},{0xc2,0xa3,0x44,0x86,0xdb,0x78},
{0xc4,0xa6,0x5f,0x9b,0xcc,0x6a},{0xc6,0xa5,0x56,0x90,0xc1,0x64},
{0xc8,0xac,0x69,0xa1,0xe2,0x4e},{0xca,0xaf,0x60,0xaa,0xef,0x40},
{0xcc,0xaa,0x7b,0xb7,0xf8,0x52},{0xce,0xa9,0x72,0xbc,0xf5,0x5c},
{0xd0,0xb8,0x05,0xd5,0xbe,0x06},{0xd2,0xbb,0x0c,0xde,0xb3,0x08},
{0xd4,0xbe,0x17,0xc3,0xa4,0x1a},{0xd6,0xbd,0x1e,0xc8,0xa9,0x14},
{0xd8,0xb4,0x21,0xf9,0x8a,0x3e},{0xda,0xb7,0x28,0xf2,0x87,0x30},
{0xdc,0xb2,0x33,0xef,0x90,0x22},{0xde,0xb1,0x3a,0xe4,0x9d,0x2c},
{0xe0,0x90,0xdd,0x3d,0x06,0x96},{0xe2,0x93,0xd4,0x36,0x0b,0x98},
{0xe4,0x96,0xcf,0x2b,0x1c,0x8a},{0xe6,0x95,0xc6,0x20,0x11,0x84},
{0xe8,0x9c,0xf9,0x11,0x32,0xae},{0xea,0x9f,0xf0,0x1a,0x3f,0xa0},
{0xec,0x9a,0xeb,0x07,0x28,0xb2},{0xee,0x99,0xe2,0x0c,0x25,0xbc},
{0xf0,0x88,0x95,0x65,0x6e,0xe6},{0xf2,0x8b,0x9c,0x6e,0x63,0xe8},
{0xf4,0x8e,0x87,0x73,0x74,0xfa},{0xf6,0x8d,0x8e,0x78,0x79,0xf4},
{0xf8,0x84,0xb1,0x49,0x5a,0xde},{0xfa,0x87,0xb8,0x42,0x57,0xd0},
{0xfc,0x82,0xa3,0x5f,0x40,0xc2},{0xfe,0x81,0xaa,0x54,0x4d,0xcc},
{0x1b,0x9b,0xec,0xf7,0xda,0x41},{0x19,0x98,0xe5,0xfc,0xd7,0x4f},
{0x1f,0x9d,0xfe,0xe1,0xc0,0x5d},{0x1d,0x9e,0xf7,0xea,0xcd,0x53},
{0x13,0x97,0xc8,0xdb,0xee,0x79},{0x11,0x94,0xc1,0xd0,0xe3,0x77},
{0x17,0x91,0xda,0xcd,0xf4,0x65},{0x15,0x92,0xd3,0xc6,0xf9,0x6b},
{0x0b,0x83,0xa4,0xaf,0xb2,0x31},{0x09,0x80,0xad,0xa4,0xbf,0x3f},
{0x0f,0x85,0xb6,0xb9,0xa8,0x2d},{0x0d,0x86,0xbf,0xb2,0xa5,0x23},
{0x03,0x8f,0x80,0x83,0x86,0x09},{0x01,0x8c,0x89,0x88,0x8b,0x07},
{0x07,0x89,0x92,0x95,0x9c,0x15},{0x05,0x8a,0x9b,0x9e,0x91,0x1b},
{0x3b,0xab,0x7c,0x47,0x0a,0xa1},{0x39,0xa8,0x75,0x4c,0x07,0xaf},
{0x3f,0xad,0x6e,0x51,0x10,0xbd},{0x3d,0xae,0x67,0x5a,0x1d,0xb3},
{0x33,0xa7,0x58,0x6b,0x3e,0x99},{0x31,0xa4,0x51,0x60,0x33,0x97},
{0x37,0xa1,0x4a,0x7d,0x24,0x85},{0x35,0xa2,0x43,0x76,0x29,0x8b},
{0x2b,0xb3,0x34,0x1f,0x62,0xd1},{0x29,0xb0,0x3d,0x14,0x6f,0xdf},
{0x2f,0xb5,0x26,0x09,0x78,0xcd},{0x2d,0xb6,0x2f,0x02,0x75,0xc3},
{0x23,0xbf,0x10,0x33,0x56,0xe9},{0x21,0xbc,0x19,0x38,0x5b,0xe7},
{0x27,0xb9,0x02,0x25,0x4c,0xf5},{0x25,0xba,0x0b,0x2e,0x41,0xfb},
{0x5b,0xfb,0xd7,0x8c,0x61,0x9a},{0x59,0xf8,0xde,0x87,0x6c,0x94},
{0x5f,0xfd,0xc5,0x9a,0x7b,0x86},{0x5d,0xfe,0xcc,0x91,0x76,0x88},
{0x53,0xf7,0xf3,0xa0,0x55,0xa2},{0x51,0xf4,0xfa,0xab,0x58,0xac},
{0x57,0xf1,0xe1,0xb6,0x4f,0xbe},{0x55,0xf2,0xe8,0xbd,0x42,0xb0},
{0x4b,0xe3,0x9f,0xd4,0x09,0xea},{0x49,0xe0,0x96,0xdf,0x04,0xe4},
{0x4f,0xe5,0x8d,0xc2,0x13,0xf6},{0x4d,0xe6,0x84,0xc9,0x1e,0xf8},
{0x43,0xef,0xbb,0xf8,0x3d,0xd2},{0x41,0xec,0xb2,0xf3,0x30,0xdc},
{0x47,0xe9,0xa9,0xee,0x27,0xce},{0x45,0xea,0xa0,0xe5,0x2a,0xc0},
{0x7b,0xcb,0x47,0x3c,0xb1,0x7a},{0x79,0xc8,0x4e,0x37,0xbc,0x74},
{0x7f,0xcd,0x55,0x2a,0xab,0x66},{0x7d,0xce,0x5c,0x21,0xa6,0x68},
{0x73,0xc7,0x63,0x10,0x85,0x42},{0x71,0xc4,0x6a,0x1b,0x88,0x4c},
{0x77,0xc1,0x71,0x06,0x9f,0x5e},{0x75,0xc2,0x78,0x0d,0x92,0x50},
{0x6b,0xd3,0x0f,0x64,0xd9,0x0a},{0x69,0xd0,0x06,0x6f,0xd4,0x04},
{0x6f,0xd5,0x1d,0x72,0xc3,0x16},{0x6d,0xd6,0x14,0x79,0xce,0x18},
{0x63,0xdf,0x2b,0x48,0xed,0x32},{0x61,0xdc,0x22,0x43,0xe0,0x3c},
{0x67,0xd9,0x39,0x5e,0xf7,0x2e},{0x65,0xda,0x30,0x55,0xfa,0x20},
{0x9b,0x5b,0x9a,0x01,0xb7,0xec},{0x99,0x58,0x93,0x0a,0xba,0xe2},
{0x9f,0x5d,0x88,0x17,0xad,0xf0},{0x9d,0x5e,0x81,0x1c,0xa0,0xfe},
{0x93,0x57,0xbe,0x2d,0x83,0xd4},{0x91,0x54,0xb7,0x26,0x8e,0xda},
{0x97,0x51,0xac,0x3b,0x99,0xc8},{0x95,0x52,0xa5,0x30,0x94,0xc6},
{0x8b,0x43,0xd2,0x59,0xdf,0x9c},{0x89,0x40,0xdb,0x52,0xd2,0x92},
{0x8f,0x45,0xc0,0x4f,0xc5,0x80},{0x8d,0x46,0xc9,0x44,0xc8,0x8e},
{0x83,0x4f,0xf6,0x75,0xeb,0xa4},{0x81,0x4c,0xff,0x7e,0xe6,0xaa},
{0x87,0x49,0xe4,0x63,0xf1,0xb8},{0x85,0x4a,0xed,0x68,0xfc,0xb6},
{0xbb,0x6b,0x0a,0xb1,0x67,0x0c},{0xb9,0x68,0x03,0xba,0x6a,0x02},
{0xbf,0x6d,0x18,0xa7,0x7d,0x10},{0xbd,0x6e,0x11,0xac,0x70,0x1e},
{0xb3,0x67,0x2e,0x9d,0x53,0x34},{0xb1,0x64,0x27,0x96,0x5e,0x3a},
{0xb7,0x61,0x3c,0x8b,0x49,0x28},{0xb5,0x62,0x35,0x80,0x44,0x26},
{0xab,0x73,0x42,0xe9,0x0f,0x7c},{0xa9,0x70,0x4b,0xe2,0x02,0x72},
{0xaf,0x75,0x50,0xff,0x15,0x60},{0xad,0x76,0x59,0xf4,0x18,0x6e},
{0xa3,0x7f,0x66,0xc5,0x3b,0x44},{0xa1,0x7c,0x6f,0xce,0x36,0x4a},
{0xa7,0x79,0x74,0xd3,0x21,0x58},{0xa5,0x7a,0x7d,0xd8,0x2c,0x56},
{0xdb,0x3b,0xa1,0x7a,0x0c,0x37},{0xd9,0x38,0xa8,0x71,0x01,0x39},
{0xdf,0x3d,0xb3,0x6c,0x16,0x2b},{0xdd,0x3e,0xba,0x67,0x1b,0x25},
{0xd3,0x37,0x85,0x56,0x38,0x0f},{0xd1,0x34,0x8c,0x5d,0x35,0x01},
{0xd7,0x31,0x97,0x40,0x22,0x13},{0xd5,0x32,0x9e,0x4b,0x2f,0x1d},
{0xcb,0x23,0xe9,0x22,0x64,0x47},{0xc9,0x20,0xe0,0x29,0x69,0x49},
{0xcf,0x25,0xfb,0x34,0x7e,0x5b},{0xcd,0x26,0xf2,0x3f,0x73,0x55},
{0xc3,0x2f,0xcd,0x0e,0x50,0x7f},{0xc1,0x2c,0xc4,0x05,0x5d,0x71},
{0xc7,0x29,0xdf,0x18,0x4a,0x63},{0xc5,0x2a,0xd6,0x13,0x47,0x6d},
{0xfb,0x0b,0x31,0xca,0xdc,0xd7},{0xf9,0x08,0x38,0xc1,0xd1,0xd9},
{0xff,0x0d,0x23,0xdc,0xc6,0xcb},{0xfd,0x0e,0x2a,0xd7,0xcb,0xc5},
{0xf3,0x07,0x15,0xe6,0xe8,0xef},{0xf1,0x04,0x1c,0xed,0xe5,0xe1},
{0xf7,0x01,0x07,0xf0,0xf2,0xf3},{0xf5,0x02,0x0e,0xfb,0xff,0xfd},
{0xeb,0x13,0x79,0x92,0xb4,0xa7},{0xe9,0x10,0x70,0x99,0xb9,0xa9},
{0xef,0x15,0x6b,0x84,0xae,0xbb},{0xed,0x16,0x62,0x8f,0xa3,0xb5},
{0xe3,0x1f,0x5d,0xbe,0x80,0x9f},{0xe1,0x1c,0x54,0xb5,0x8d,0x91},
{0xe7,0x19,0x4f,0xa8,0x9a,0x83},{0xe5,0x1a,0x46,0xa3,0x97,0x8d}
};
private static T[] SubArray<T>(T[] data, int index, int length = -1)
{
if (length == -1)
length = data.Length - index;
T[] result = new T[length];
Array.Copy(data, index, result, 0, length);
return result;
}
private static void AddRoundKey(byte[,] state, uint[] w)
{
byte[] subkey = new byte[4];
subkey[0] = (byte)(w[0] >> 24);
subkey[1] = (byte)(w[0] >> 16);
subkey[2] = (byte)(w[0] >> 8);
subkey[3] = (byte)(w[0]);
state[0, 0] ^= subkey[0];
state[1, 0] ^= subkey[1];
state[2, 0] ^= subkey[2];
state[3, 0] ^= subkey[3];
subkey[0] = (byte)(w[1] >> 24);
subkey[1] = (byte)(w[1] >> 16);
subkey[2] = (byte)(w[1] >> 8);
subkey[3] = (byte)(w[1]);
state[0, 1] ^= subkey[0];
state[1, 1] ^= subkey[1];
state[2, 1] ^= subkey[2];
state[3, 1] ^= subkey[3];
subkey[0] = (byte)(w[2] >> 24);
subkey[1] = (byte)(w[2] >> 16);
subkey[2] = (byte)(w[2] >> 8);
subkey[3] = (byte)(w[2]);
state[0, 2] ^= subkey[0];
state[1, 2] ^= subkey[1];
state[2, 2] ^= subkey[2];
state[3, 2] ^= subkey[3];
subkey[0] = (byte)(w[3] >> 24);
subkey[1] = (byte)(w[3] >> 16);
subkey[2] = (byte)(w[3] >> 8);
subkey[3] = (byte)(w[3]);
state[0, 3] ^= subkey[0];
state[1, 3] ^= subkey[1];
state[2, 3] ^= subkey[2];
state[3, 3] ^= subkey[3];
}
private static void InvShiftRows(byte[,] state)
{
byte t;
t = state[1, 3];
state[1, 3] = state[1, 2];
state[1, 2] = state[1, 1];
state[1, 1] = state[1, 0];
state[1, 0] = t;
t = state[2, 3];
state[2, 3] = state[2, 1];
state[2, 1] = t;
t = state[2, 2];
state[2, 2] = state[2, 0];
state[2, 0] = t;
t = state[3, 3];
state[3, 3] = state[3, 0];
state[3, 0] = state[3, 1];
state[3, 1] = state[3, 2];
state[3, 2] = t;
}
private static void InvSubBytes(byte[,] state)
{
state[0, 0] = aes_invsbox[state[0, 0] >> 4, state[0, 0] & 0x0F];
state[0, 1] = aes_invsbox[state[0, 1] >> 4, state[0, 1] & 0x0F];
state[0, 2] = aes_invsbox[state[0, 2] >> 4, state[0, 2] & 0x0F];
state[0, 3] = aes_invsbox[state[0, 3] >> 4, state[0, 3] & 0x0F];
state[1, 0] = aes_invsbox[state[1, 0] >> 4, state[1, 0] & 0x0F];
state[1, 1] = aes_invsbox[state[1, 1] >> 4, state[1, 1] & 0x0F];
state[1, 2] = aes_invsbox[state[1, 2] >> 4, state[1, 2] & 0x0F];
state[1, 3] = aes_invsbox[state[1, 3] >> 4, state[1, 3] & 0x0F];
state[2, 0] = aes_invsbox[state[2, 0] >> 4, state[2, 0] & 0x0F];
state[2, 1] = aes_invsbox[state[2, 1] >> 4, state[2, 1] & 0x0F];
state[2, 2] = aes_invsbox[state[2, 2] >> 4, state[2, 2] & 0x0F];
state[2, 3] = aes_invsbox[state[2, 3] >> 4, state[2, 3] & 0x0F];
state[3, 0] = aes_invsbox[state[3, 0] >> 4, state[3, 0] & 0x0F];
state[3, 1] = aes_invsbox[state[3, 1] >> 4, state[3, 1] & 0x0F];
state[3, 2] = aes_invsbox[state[3, 2] >> 4, state[3, 2] & 0x0F];
state[3, 3] = aes_invsbox[state[3, 3] >> 4, state[3, 3] & 0x0F];
}
private static void InvMixColumns(byte[,] state)
{
byte[] col = new byte[4];
col[0] = state[0, 0];
col[1] = state[1, 0];
col[2] = state[2, 0];
col[3] = state[3, 0];
state[0, 0] = gf_mul[col[0], 5];
state[0, 0] ^= gf_mul[col[1], 3];
state[0, 0] ^= gf_mul[col[2], 4];
state[0, 0] ^= gf_mul[col[3], 2];
state[1, 0] = gf_mul[col[0], 2];
state[1, 0] ^= gf_mul[col[1], 5];
state[1, 0] ^= gf_mul[col[2], 3];
state[1, 0] ^= gf_mul[col[3], 4];
state[2, 0] = gf_mul[col[0], 4];
state[2, 0] ^= gf_mul[col[1], 2];
state[2, 0] ^= gf_mul[col[2], 5];
state[2, 0] ^= gf_mul[col[3], 3];
state[3, 0] = gf_mul[col[0], 3];
state[3, 0] ^= gf_mul[col[1], 4];
state[3, 0] ^= gf_mul[col[2], 2];
state[3, 0] ^= gf_mul[col[3], 5];
col[0] = state[0, 1];
col[1] = state[1, 1];
col[2] = state[2, 1];
col[3] = state[3, 1];
state[0, 1] = gf_mul[col[0], 5];
state[0, 1] ^= gf_mul[col[1], 3];
state[0, 1] ^= gf_mul[col[2], 4];
state[0, 1] ^= gf_mul[col[3], 2];
state[1, 1] = gf_mul[col[0], 2];
state[1, 1] ^= gf_mul[col[1], 5];
state[1, 1] ^= gf_mul[col[2], 3];
state[1, 1] ^= gf_mul[col[3], 4];
state[2, 1] = gf_mul[col[0], 4];
state[2, 1] ^= gf_mul[col[1], 2];
state[2, 1] ^= gf_mul[col[2], 5];
state[2, 1] ^= gf_mul[col[3], 3];
state[3, 1] = gf_mul[col[0], 3];
state[3, 1] ^= gf_mul[col[1], 4];
state[3, 1] ^= gf_mul[col[2], 2];
state[3, 1] ^= gf_mul[col[3], 5];
col[0] = state[0, 2];
col[1] = state[1, 2];
col[2] = state[2, 2];
col[3] = state[3, 2];
state[0, 2] = gf_mul[col[0], 5];
state[0, 2] ^= gf_mul[col[1], 3];
state[0, 2] ^= gf_mul[col[2], 4];
state[0, 2] ^= gf_mul[col[3], 2];
state[1, 2] = gf_mul[col[0], 2];
state[1, 2] ^= gf_mul[col[1], 5];
state[1, 2] ^= gf_mul[col[2], 3];
state[1, 2] ^= gf_mul[col[3], 4];
state[2, 2] = gf_mul[col[0], 4];
state[2, 2] ^= gf_mul[col[1], 2];
state[2, 2] ^= gf_mul[col[2], 5];
state[2, 2] ^= gf_mul[col[3], 3];
state[3, 2] = gf_mul[col[0], 3];
state[3, 2] ^= gf_mul[col[1], 4];
state[3, 2] ^= gf_mul[col[2], 2];
state[3, 2] ^= gf_mul[col[3], 5];
col[0] = state[0, 3];
col[1] = state[1, 3];
col[2] = state[2, 3];
col[3] = state[3, 3];
state[0, 3] = gf_mul[col[0], 5];
state[0, 3] ^= gf_mul[col[1], 3];
state[0, 3] ^= gf_mul[col[2], 4];
state[0, 3] ^= gf_mul[col[3], 2];
state[1, 3] = gf_mul[col[0], 2];
state[1, 3] ^= gf_mul[col[1], 5];
state[1, 3] ^= gf_mul[col[2], 3];
state[1, 3] ^= gf_mul[col[3], 4];
state[2, 3] = gf_mul[col[0], 4];
state[2, 3] ^= gf_mul[col[1], 2];
state[2, 3] ^= gf_mul[col[2], 5];
state[2, 3] ^= gf_mul[col[3], 3];
state[3, 3] = gf_mul[col[0], 3];
state[3, 3] ^= gf_mul[col[1], 4];
state[3, 3] ^= gf_mul[col[2], 2];
state[3, 3] ^= gf_mul[col[3], 5];
}
private static uint SubWord(uint word)
{
uint result;
result = aes_sbox[(word >> 4) & 0x0000000F, word & 0x0000000F];
result += (uint)aes_sbox[(word >> 12) & 0x0000000F, (word >> 8) & 0x0000000F] << 8;
result += (uint)aes_sbox[(word >> 20) & 0x0000000F, (word >> 16) & 0x0000000F] << 16;
result += (uint)aes_sbox[(word >> 28) & 0x0000000F, (word >> 24) & 0x0000000F] << 24;
return (result);
}
private static uint KE_ROTWORD(uint x)
{
return (((x) << 8) | ((x) >> 24));
}
public static void KeyExpansion(byte[] key, uint[] w, int keysize)
{
int Nb = 4, Nr, Nk, idx;
uint temp;
uint[] Rcon = { 0x01000000,0x02000000,0x04000000,0x08000000,0x10000000,0x20000000,
0x40000000,0x80000000,0x1b000000,0x36000000,0x6c000000,0xd8000000,
0xab000000,0x4d000000,0x9a000000 };
switch (keysize)
{
case 128: Nr = 10; Nk = 4; break;
case 192: Nr = 12; Nk = 6; break;
case 256: Nr = 14; Nk = 8; break;
default: return;
}
for (idx = 0; idx < Nk; ++idx)
{
w[idx] = (uint)(((key[4 * idx]) << 24) | ((key[4 * idx + 1]) << 16) |
((key[4 * idx + 2]) << 8) | ((key[4 * idx + 3])));
}
for (idx = Nk; idx < Nb * (Nr + 1); ++idx)
{
temp = w[idx - 1];
if ((idx % Nk) == 0)
temp = SubWord(KE_ROTWORD(temp)) ^ Rcon[(idx - 1) / Nk];
else if (Nk > 6 && (idx % Nk) == 4)
temp = SubWord(temp);
w[idx] = w[idx - Nk] ^ temp;
}
}
public static void Decrypt(byte[] input, byte[] output, uint[] key, int keysize)
{
byte[,] state = new byte[4, 4];
state[0, 0] = input[0];
state[1, 0] = input[1];
state[2, 0] = input[2];
state[3, 0] = input[3];
state[0, 1] = input[4];
state[1, 1] = input[5];
state[2, 1] = input[6];
state[3, 1] = input[7];
state[0, 2] = input[8];
state[1, 2] = input[9];
state[2, 2] = input[10];
state[3, 2] = input[11];
state[0, 3] = input[12];
state[1, 3] = input[13];
state[2, 3] = input[14];
state[3, 3] = input[15];
if (keysize > 128)
{
if (keysize > 192)
{
AddRoundKey(state, SubArray(key, 56));
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 52)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 48)); InvMixColumns(state);
}
else
{
AddRoundKey(state, SubArray(key, 48));
}
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 44)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 40)); InvMixColumns(state);
}
else
{
AddRoundKey(state, SubArray(key, 40));
}
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 36)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 32)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 28)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 24)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 20)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 16)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 12)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 8)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 4)); InvMixColumns(state);
InvShiftRows(state); InvSubBytes(state); AddRoundKey(state, SubArray(key, 0));
output[0] = state[0, 0];
output[1] = state[1, 0];
output[2] = state[2, 0];
output[3] = state[3, 0];
output[4] = state[0, 1];
output[5] = state[1, 1];
output[6] = state[2, 1];
output[7] = state[3, 1];
output[8] = state[0, 2];
output[9] = state[1, 2];
output[10] = state[2, 2];
output[11] = state[3, 2];
output[12] = state[0, 3];
output[13] = state[1, 3];
output[14] = state[2, 3];
output[15] = state[3, 3];
}
```

### Example

` ````
byte[] ciphertext = { 0x8e,0xa2,0xb7,0xca,0x51,0x67,0x45,0xbf,
0xea,0xfc,0x49,0x90,0x4b,0x49,0x60,0x89 };
byte[] key = { 0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,
0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f,0x10,0x11,
0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0x1a,
0x1b,0x1c,0x1d,0x1e,0x1f };
byte[] plaintext = new byte[16];
uint[] key_schedule = new uint[60];
KeyExpansion(key, key_schedule, 256);
Decrypt(ciphertext, plaintext, key_schedule, 256);
for (int idx = 0; idx < 16; idx++)
Console.Write("{0:x2}", plaintext[idx]);
```

### Output

` ``00112233445566778899aabbccddeeff`