MD5 hash function - C Code Bank

                
/* reduce typing */
typedef unsigned int INT ;


/* results of a sinus function, this is constant in every md5 hash process */
unsigned int t[] = {
0xd76aa478L, /* 1 */
0xe8c7b756L, /* 2 */
0x242070dbL, /* 3 */
0xc1bdceeeL, /* 4 */
0xf57c0fafL, /* 5 */
0x4787c62aL, /* 6 */
0xa8304613L, /* 7 */
0xfd469501L, /* 8 */
0x698098d8L, /* 9 */
0x8b44f7afL, /* 10 */
0xffff5bb1L, /* 11 */
0x895cd7beL, /* 12 */
0x6b901122L, /* 13 */
0xfd987193L, /* 14 */
0xa679438eL, /* 15 */
0x49b40821L, /* 16 */
0xf61e2562L, /* 17 */
0xc040b340L, /* 18 */
0x265e5a51L, /* 19 */
0xe9b6c7aaL, /* 20 */
0xd62f105dL, /* 21 */
0x02441453L, /* 22 */
0xd8a1e681L, /* 23 */
0xe7d3fbc8L, /* 24 */
0x21e1cde6L, /* 25 */
0xc33707d6L, /* 26 */
0xf4d50d87L, /* 27 */
0x455a14edL, /* 28 */
0xa9e3e905L, /* 29 */
0xfcefa3f8L, /* 30 */
0x676f02d9L, /* 31 */
0x8d2a4c8aL, /* 32 */
0xfffa3942L, /* 33 */
0x8771f681L, /* 34 */
0x6d9d6122L, /* 35 */
0xfde5380cL, /* 36 */
0xa4beea44L, /* 37 */
0x4bdecfa9L, /* 38 */
0xf6bb4b60L, /* 39 */
0xbebfbc70L, /* 40 */
0x289b7ec6L, /* 41 */
0xeaa127faL, /* 42 */
0xd4ef3085L, /* 43 */
0x04881d05L, /* 44 */
0xd9d4d039L, /* 45 */
0xe6db99e5L, /* 46 */
0x1fa27cf8L, /* 47 */
0xc4ac5665L, /* 48 */
0xf4292244L, /* 49 */
0x432aff97L, /* 50 */
0xab9423a7L, /* 51 */
0xfc93a039L, /* 52 */
0x655b59c3L, /* 53 */
0x8f0ccc92L, /* 54 */
0xffeff47dL, /* 55 */
0x85845dd1L, /* 56 */
0x6fa87e4fL, /* 57 */
0xfe2ce6e0L, /* 58 */
0xa3014314L, /* 59 */
0x4e0811a1L, /* 60 */
0xf7537e82L, /* 61 */
0xbd3af235L, /* 62 */
0x2ad7d2bbL, /* 63 */
0xeb86d391L  /* 64 */
};
/* another constant thing in md5 hash algoritham */
unsigned int r[] = 	{   7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,  
			    5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,   
			    4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,   
			    6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21   
			};


unsigned int leftrotate(INT x,INT c){

	return (x << c) | (x >> (32-c));
}

void md5(unsigned char *input){

	/* md5 works with block of 512 bits or 64 bytes so if a message is 150 bytes the algorithm should break it into 64+64+22 block and append at the
	last block a bite with value 1 and the length of the message in bites in this case 150*8 */

	/* this algorithm assumes that the input wont be bigger then  55 bytes, so in the end we will have only one block of 64 bytes (after appending 
		all the data(bite 1 and the length))*/ 

	unsigned char output[16],buff[64];

	INT len=strlen((char *)input),w[16],stat[4],f,a,b,c,d,g,i,j,temp;

	bzero((char *)buff,sizeof(buff));

	for(i=0;i<len && i<55;i++){

		buff[i]=input[i];
	}

	/* appending a bite with value of 1 and length of the string at the and of the block */

	if(len<55){ buff[len]=0x80;  len*=8;}
	else { buff[55]=0x80; len=55*8; }

	for(i=0;i<4;i++){

		buff[i+56]=len >> (i*8);
	}

	/* dividing 512 block into 16x4 byte blocks e.g. int */ 

	for(i=0,j=0;i<16;i++,j+=4){
		

		w[i]=0;
		w[i]=(((INT)buff[j]) | ((INT)buff[j+1]<<8) | ((INT)buff[j+2] << 16) | ((INT)buff[j+3]<<24));

	}

	/* another static value in md5 */

	stat[0]=0x67452301;
	stat[1]=0xefcdab89;
	stat[2]=0x98badcfe;
	stat[3]=0x10325476;

	a=stat[0];
	b=stat[1];
	c=stat[2];
	d=stat[3];

	/* md5 hash functions */

	for(i=0;i<64;i++){

		if (0 <= i && i<= 15 ){
			f = (b & c) | ((~ b) & d);
			g = i;
		}else if (16 <= i && i<= 31){
			f = (d & b) | ((~ d) & c);
			g = (5*i + 1) % 16;
		}else if (32 <= i && i<= 47){
			f = b ^ c ^ d;
			g = (3*i + 5) % 16;
		}else if (48 <= i && i<= 63){
			f = c ^ (b | (~ d));
			g = (7*i) % 16;
		}

		temp = d;
		   d = c;
		   c = b;
		   b = b + leftrotate((a + f + t[i] + w[g]) , r[i]);
		   a = temp;

	}

	stat[0]=a + stat[0];
	stat[1]=b + stat[1];
	stat[2]=c + stat[2];
	stat[3]=d + stat[3];

	/* appending the result into one string */

	for(i=0,j=0;j<16;i++,j+=4){

		output[j]=(unsigned char)( stat[i]);
		output[j+1]=(unsigned char)( stat[i]>>8);
		output[j+2]=(unsigned char)( stat[i]>>16);
		output[j+3]=(unsigned char)(stat[i]>>24);
	}
	/* printing hex value of the result */
	for(j=0;j<16;j++){
		printf("%02x",output[j]);
	}

return ;
}