GIFT_64-128.c

#define ROUNDS 28

typedef unsigned char u8;
typedef unsigned int u32;

//Sbox
const u8 GIFT_S[16] = { 1,10, 4,12, 6,15, 3, 9, 2,13,11, 7, 5, 0, 8,14};
const u8 GIFT_S_inv[16] = {13, 0, 8, 6, 2,12, 4,11,14, 7, 1,10, 3, 9,15, 5};


//bit permutation
const u8 GIFT_P[] = {
/* Block size = 64 */
  0, 17, 34, 51, 48,  1, 18, 35, 32, 49,  2, 19, 16, 33, 50,  3,
  4, 21, 38, 55, 52,  5, 22, 39, 36, 53,  6, 23, 20, 37, 54,  7,
  8, 25, 42, 59, 56,  9, 26, 43, 40, 57, 10, 27, 24, 41, 58, 11,
 12, 29, 46, 63, 60, 13, 30, 47, 44, 61, 14, 31, 28, 45, 62, 15
};

const u8 GIFT_P_inv[] = {
/* Block size = 64 */
  0,  5, 10, 15, 16, 21, 26, 31, 32, 37, 42, 47, 48, 53, 58, 63,
 12,  1,  6, 11, 28, 17, 22, 27, 44, 33, 38, 43, 60, 49, 54, 59,
  8, 13,  2,  7, 24, 29, 18, 23, 40, 45, 34, 39, 56, 61, 50, 55,
  4,  9, 14,  3, 20, 25, 30, 19, 36, 41, 46, 35, 52, 57, 62, 51
};


// round constants
const u8 GIFT_RC[62] = {
    0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3E, 0x3D, 0x3B, 0x37, 0x2F,
    0x1E, 0x3C, 0x39, 0x33, 0x27, 0x0E, 0x1D, 0x3A, 0x35, 0x2B,
    0x16, 0x2C, 0x18, 0x30, 0x21, 0x02, 0x05, 0x0B, 0x17, 0x2E,
    0x1C, 0x38, 0x31, 0x23, 0x06, 0x0D, 0x1B, 0x36, 0x2D, 0x1A,
    0x34, 0x29, 0x12, 0x24, 0x08, 0x11, 0x22, 0x04, 0x09, 0x13,
    0x26, 0x0c, 0x19, 0x32, 0x25, 0x0a, 0x15, 0x2a, 0x14, 0x28,
    0x10, 0x20
};



void blockcipher_encrypt(u8 *ct, const u8 *pt, const u8 *masterkey){

	//convert input data from bytes to halfbytes
    u8 key[32];
    for(u8 i=0; i<16; i++){
        key[2*i] = masterkey[i]&0xF;
        key[2*i+1] = (masterkey[i]&0xF0)>>4;
    }
	
	u8 input[16];
    for(u8 i=0; i<8; i++){
        input[2*i] = pt[i]&0xF;
        input[2*i+1] = (pt[i]&0xF0)>>4;
    }
	
    //input = MSB [15][14]...[1][0] LSB
    //key = MSB [31][30]...[1][0] LSB


	u8 bits[64];
	u8 perm_bits[64];
	u8 key_bits[128];
	u8 temp_key[32];
	
	for(u8 r=0; r<ROUNDS; r++){

		//SubCells
		for(u8 i=0; i<16; i++){
			input[i] = GIFT_S[input[i]];
		}		

		
		//PermBits
		//input to bits
		for(u8 i=0; i<16; i++){
			for(u8 j=0; j<4; j++){
				bits[4*i+j] = (input[i] >> j) & 0x1;
			}
		}
		
		//permute the bits
		for(u8 i=0; i<64; i++){
			perm_bits[GIFT_P[i]] = bits[i];
		}
		
		//perm_bits to input
		for(u8 i=0; i<16; i++){
			input[i]=0;
			for(u8 j=0; j<4; j++){
				 input[i] ^= perm_bits[4*i+j] << j;
			}
		}

		
		//AddRoundKey
		//input to bits
		for(u8 i=0; i<16; i++){
			for(u8 j=0; j<4; j++){
				bits[4*i+j] = (input[i] >> j) & 0x1;
			}
		}
		
		//key to key_bits
		for(u8 i=0; i<32; i++){
			for(u8 j=0; j<4; j++){
				key_bits[4*i+j] = (key[i] >> j) & 0x1;
			}
		}

		//add round key
		u8 kbc=0;  //key_bit_counter
		for(u8 i=0; i<16; i++){
			bits[4*i] ^= key_bits[kbc];
			bits[4*i+1] ^= key_bits[kbc+16];
			kbc++;
		}

		//add constant
		bits[3] ^= GIFT_RC[r] & 0x1;
		bits[7] ^= (GIFT_RC[r]>>1) & 0x1;
		bits[11] ^= (GIFT_RC[r]>>2) & 0x1;
		bits[15] ^= (GIFT_RC[r]>>3) & 0x1;
		bits[19] ^= (GIFT_RC[r]>>4) & 0x1;
		bits[23] ^= (GIFT_RC[r]>>5) & 0x1;
		bits[63] ^= 1;

		//bits to input
		for(u8 i=0; i<16; i++){
			input[i]=0;
			for(u8 j=0; j<4; j++){
				 input[i] ^= bits[4*i+j] << j;
			}
		}
		
		
		//key update
		//entire key>>32
		for(u8 i=0; i<32; i++){
			temp_key[i] = key[(i+8)%32];
		}
		for(u8 i=0; i<24; i++){
			key[i] = temp_key[i];
		}
		
		//k0>>12
		key[24] = temp_key[27];
		key[25] = temp_key[24];
		key[26] = temp_key[25];
		key[27] = temp_key[26];
		
		//k1>>2
		key[28] = ((temp_key[28]&0xc)>>2) ^ ((temp_key[29]&0x3)<<2);
		key[29] = ((temp_key[29]&0xc)>>2) ^ ((temp_key[30]&0x3)<<2);
		key[30] = ((temp_key[30]&0xc)>>2) ^ ((temp_key[31]&0x3)<<2);
		key[31] = ((temp_key[31]&0xc)>>2) ^ ((temp_key[28]&0x3)<<2);
	}
	
	//convert back from half-bytes
	for(u8 i=0; i<8; i++){
		ct[i] = input[2*i+1]<<4 | input[2*i];
	}
	return;
}