text: /* 20170201 NaJiwoong */
  /* 2020 April 23 */
  
  /*	Reference	
   *
   *	Open source code from
   *	<openluopworld>
   *	-"https://github.com/openluopworld/aes_128"
   */
  
  
  #include <stdint.h>
  #include <stdio.h>
  
  #include "aes-128.h"
  
  /*
   * round constants
   */
  static uint8_t RC[] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};
  
  /*
   * Sbox
   */
  static uint8_t SBOX[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};
  
  /*
   * Inverse Sboxs
   */
  static uint8_t INV_SBOX[256] = {
  	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};
  
  /**
   * https://en.wikipedia.org/wiki/Finite_field_arithmetic
   * Multiply two numbers in the GF(2^8) finite field defined
   * by the polynomial x^8 + x^4 + x^3 + x + 1 = 0
   * We do use mul2(int8_t a) but not mul(uint8_t a, uint8_t b)
   * just in order to get a higher speed.
   */
  static inline uint8_t mul2(uint8_t a) {
  	return (a&0x80) ? ((a<<1)^0x1b) : (a<<1);
  }
  
  /**
   * @purpose:    ShiftRows
   * @descrption:
   *  Row0: s0  s4  s8  s12   <<< 0 byte
   *  Row1: s1  s5  s9  s13   <<< 1 byte
   *  Row2: s2  s6  s10 s14   <<< 2 bytes
   *  Row3: s3  s7  s11 s15   <<< 3 bytes
   */
  static void shift_rows(uint8_t *state) {
  	uint8_t temp;
  	// row1
  	temp        = *(state+1);
  	*(state+1)  = *(state+5);
  	*(state+5)  = *(state+9);
  	*(state+9)  = *(state+13);
  	*(state+13) = temp;
  	// row2
  	temp        = *(state+2);
  	*(state+2)  = *(state+10);
  	*(state+10) = temp;
  	temp        = *(state+6);
  	*(state+6)  = *(state+14);
  	*(state+14) = temp;
  	// row3
  	temp        = *(state+15);
  	*(state+15) = *(state+11);
  	*(state+11) = *(state+7);
  	*(state+7)  = *(state+3);
  	*(state+3)  = temp;
  }
  
  /**
   * @purpose:    Inverse ShiftRows
   * @description
   *  Row0: s0  s4  s8  s12   >>> 0 byte
   *  Row1: s1  s5  s9  s13   >>> 1 byte
   *  Row2: s2  s6  s10 s14   >>> 2 bytes
   *  Row3: s3  s7  s11 s15   >>> 3 bytes
   */
  static void inv_shift_rows(uint8_t *state) {
  	uint8_t temp;
  	// row1
  	temp        = *(state+13);
  	*(state+13) = *(state+9);
  	*(state+9)  = *(state+5);
  	*(state+5)  = *(state+1);
  	*(state+1)  = temp;
  	// row2
  	temp        = *(state+14);
  	*(state+14) = *(state+6);
  	*(state+6)  = temp;
  	temp        = *(state+10);
  	*(state+10) = *(state+2);
  	*(state+2)  = temp;
  	// row3
  	temp        = *(state+3);
  	*(state+3)  = *(state+7);
  	*(state+7)  = *(state+11);
  	*(state+11) = *(state+15);
  	*(state+15) = temp;
  }
  
  void aes_key_schedule_128(const uint8_t *key, uint8_t *roundkeys) {
  
  	uint8_t temp[4];
  	uint8_t *last4bytes; // point to the last 4 bytes of one round
  	uint8_t *lastround;
  	uint8_t i;
  
  	for (i = 0; i < 16; ++i) {
  		*roundkeys++ = *key++;
  	}
  
  	last4bytes = roundkeys-4;
  	for (i = 0; i < AES_ROUNDS; ++i) {
  		// k0-k3 for next round
  		temp[3] = SBOX[*last4bytes++];
  		temp[0] = SBOX[*last4bytes++];
  		temp[1] = SBOX[*last4bytes++];
  		temp[2] = SBOX[*last4bytes++];
  		temp[0] ^= RC[i];
  		lastround = roundkeys-16;
  		*roundkeys++ = temp[0] ^ *lastround++;
  		*roundkeys++ = temp[1] ^ *lastround++;
  		*roundkeys++ = temp[2] ^ *lastround++;
  		*roundkeys++ = temp[3] ^ *lastround++;
  		// k4-k7 for next round        
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		// k8-k11 for next round
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		// k12-k15 for next round
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  		*roundkeys++ = *last4bytes++ ^ *lastround++;
  	}
  }
  
  void aes_encrypt_128(const uint8_t *roundkeys, const uint8_t *plaintext, uint8_t *ciphertext
  		, int flag, uint8_t **roundcipher) {
  
  	uint8_t tmp[16], t;
  	uint8_t i, j;
  
  	// first AddRoundKey
  	for ( i = 0; i < AES_BLOCK_SIZE; ++i ) {
  		*(ciphertext+i) = *(plaintext+i) ^ *roundkeys++;
  	}
  
  	// 9 rounds
  	for (j = 1; j < AES_ROUNDS; ++j) {
  		
  		// SubBytes
  		for (i = 0; i < AES_BLOCK_SIZE; ++i) {
  			*(tmp+i) = SBOX[*(ciphertext+i)];
  		}
  		shift_rows(tmp);
  		/*
  		 * MixColumns 
  		 * [02 03 01 01]   [s0  s4  s8  s12]
  		 * [01 02 03 01] . [s1  s5  s9  s13]
  		 * [01 01 02 03]   [s2  s6  s10 s14]
  		 * [03 01 01 02]   [s3  s7  s11 s15]
  		 */
  		for (i = 0; i < AES_BLOCK_SIZE; i+=4)  {
  			t = tmp[i] ^ tmp[i+1] ^ tmp[i+2] ^ tmp[i+3];
  			ciphertext[i]   = mul2(tmp[i]   ^ tmp[i+1]) ^ tmp[i]   ^ t;
  			ciphertext[i+1] = mul2(tmp[i+1] ^ tmp[i+2]) ^ tmp[i+1] ^ t;
  			ciphertext[i+2] = mul2(tmp[i+2] ^ tmp[i+3]) ^ tmp[i+2] ^ t;
  			ciphertext[i+3] = mul2(tmp[i+3] ^ tmp[i]  ) ^ tmp[i+3] ^ t;
  		}
  
  		// AddRoundKey
  		for ( i = 0; i < AES_BLOCK_SIZE; ++i ) {
  			*(ciphertext+i) ^= *roundkeys++;
  		}
  		
  		// Store round ciphered text
  		for (i = 0; i < AES_BLOCK_SIZE; i++){
  			roundcipher[j-1][i] = ciphertext[i];
  		}
  
  	}
  
  	// last round
  	for (i = 0; i < AES_BLOCK_SIZE; ++i) {
  		*(ciphertext+i) = SBOX[*(ciphertext+i)];
  	}
  	shift_rows(ciphertext);
  	for ( i = 0; i < AES_BLOCK_SIZE; ++i ) {
  		*(ciphertext+i) ^= *roundkeys++;
  	}
  
  }
  
  void aes_decrypt_128(const uint8_t *roundkeys, const uint8_t *ciphertext, uint8_t *plaintext) {
  
  	uint8_t tmp[16];
  	uint8_t t, u, v;
  	uint8_t i, j;
  
  	roundkeys += 160;
  
  	// first round
  	for ( i = 0; i < AES_BLOCK_SIZE; ++i ) {
  		*(plaintext+i) = *(ciphertext+i) ^ *(roundkeys+i);
  	}
  	roundkeys -= 16;
  	inv_shift_rows(plaintext);
  	for (i = 0; i < AES_BLOCK_SIZE; ++i) {
  		*(plaintext+i) = INV_SBOX[*(plaintext+i)];
  	}
  
  	for (j = 1; j < AES_ROUNDS; ++j) {
  
  		// Inverse AddRoundKey
  		for ( i = 0; i < AES_BLOCK_SIZE; ++i ) {
  			*(tmp+i) = *(plaintext+i) ^ *(roundkeys+i);
  		}
  
  		/*
  		 * Inverse MixColumns
  		 * [0e 0b 0d 09]   [s0  s4  s8  s12]
  		 * [09 0e 0b 0d] . [s1  s5  s9  s13]
  		 * [0d 09 0e 0b]   [s2  s6  s10 s14]
  		 * [0b 0d 09 0e]   [s3  s7  s11 s15]
  		 */
  		for (i = 0; i < AES_BLOCK_SIZE; i+=4) {
  			t = tmp[i] ^ tmp[i+1] ^ tmp[i+2] ^ tmp[i+3];
  			plaintext[i]   = t ^ tmp[i]   ^ mul2(tmp[i]   ^ tmp[i+1]);
  			plaintext[i+1] = t ^ tmp[i+1] ^ mul2(tmp[i+1] ^ tmp[i+2]);
  			plaintext[i+2] = t ^ tmp[i+2] ^ mul2(tmp[i+2] ^ tmp[i+3]);
  			plaintext[i+3] = t ^ tmp[i+3] ^ mul2(tmp[i+3] ^ tmp[i]);
  			u = mul2(mul2(tmp[i]   ^ tmp[i+2]));
  			v = mul2(mul2(tmp[i+1] ^ tmp[i+3]));
  			t = mul2(u ^ v);
  			plaintext[i]   ^= t ^ u;
  			plaintext[i+1] ^= t ^ v;
  			plaintext[i+2] ^= t ^ u;
  			plaintext[i+3] ^= t ^ v;
  		}
  
  		// Inverse ShiftRows
  		inv_shift_rows(plaintext);
  
  		// Inverse SubBytes
  		for (i = 0; i < AES_BLOCK_SIZE; ++i) {
  			*(plaintext+i) = INV_SBOX[*(plaintext+i)];
  		}
  
  		roundkeys -= 16;
  
  	}
  
  	// last AddRoundKey
  	for ( i = 0; i < AES_BLOCK_SIZE; ++i ) {
  		*(plaintext+i) ^= *(roundkeys+i);
  	}
  
  }
  