I'm in the process of writing an app using MD5, and rather than using a library I decided to write my own function to really understand what's going on.
Anyway, my main reference is Wikipedia, I have taken certain parts from other source code, specifically values for k and r.
Using the input "" the expected hash is d41d8cd98f00b204e9800998ecf8427e however I'm getting 5de5ae832d1f479f89adb8bdfa2a0655, obviously due to the nature of the hash it's extremely difficult to trace the issue back so I'm hoping someone might be able to notice my mistake and let me know so I can get on and fix it!
Anyway, my main reference is Wikipedia, I have taken certain parts from other source code, specifically values for k and r.
Code:
// generated by using floor(fabs(sin(loop + 1))) * 2^32 where 0 <= loop < 64
unsigned int k[] =
{
3614090360u, 3905402710u, 606105819u, 3250441966u, 4118548399u, 1200080426u, 2821735955u, 4249261313u,
1770035416u, 2336552879u, 4294925233u, 2304563134u, 1804603682u, 4254626195u, 2792965006u, 1236535329u,
4129170786u, 3225465664u, 643717713u, 3921069994u, 3593408605u, 38016083u, 3634488961u, 3889429448u,
568446438u, 3275163606u, 4107603335u, 1163531501u, 2850285829u, 4243563512u, 1735328473u, 2368359562u,
4294588738u, 2272392833u, 1839030562u, 4259657740u, 2763975236u, 1272893353u, 4139469664u, 3200236656u,
681279174u, 3936430074u, 3572445317u, 76029189u, 3654602809u, 3873151461u, 530742520u, 3299628645u,
4096336452u, 1126891415u, 2878612391u, 4237533241u, 1700485571u, 2399980690u, 4293915773u, 2240044497u,
1873313359u, 4264355552u, 2734768916u, 1309151649u, 4149444226u, 3174756917u, 718787259u, 3951481745u
};
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
};
inline unsigned int left_rotate(unsigned int x, unsigned int c)
{
return (x << c) | (x >> (32 - c));
}
void c_md5::md5(const char *input, unsigned int length)
{
unsigned int h0 = 0x67452301;
unsigned int h1 = 0xEFCDAB89;
unsigned int h2 = 0x98BADCFE;
unsigned int h3 = 0x10325476;
char *buffer;
int bufLen;
// get the original input length
bufLen = length;
if(((bufLen % 64) > 0) || (bufLen == 0))
{
if(64 - bufLen < 8)
{
bufLen += 64;
}
int tempVal;
tempVal = bufLen % 64;
bufLen += 64 - tempVal;
}
if(debug)
{
printf("Checking if buffer length is divisible by 512... ");
if(bufLen % 64 == 0)
{
printf("done!\n");
}
else
{
printf("failed!\n");
return;
}
}
// create our new buffer
buffer = new char [bufLen];
if(debug)
{
printf("Checking if buffer is created... ");
if(buffer)
{
printf("done!\n");
}
else
{
printf("failed\n");
return;
}
}
// copy content over
for(int loop = 0; loop < length; loop++)
{
buffer[loop] = input[loop];
}
// blank the padding
for(int loop = length; loop < bufLen; loop++)
{
buffer[loop] = 0x00u;
}
// set the first bit of the padding
buffer[length] = 0x80u;
// fill in the length of the original stream into the padding
{
int tempLength = length * 8;
int tempVal;
tempVal = tempLength;
// use some bitwise shifting to access the length correctly
buffer[bufLen - 1] = (unsigned char)tempVal;
tempVal = tempLength >> 8;
buffer[bufLen - 2] = (unsigned char)tempVal;
//tempVal = tempLength >> 8;
tempVal = tempLength >> 16;
buffer[bufLen - 3] = (unsigned char)tempVal;
//tempVal = tempLength >> 8;
tempVal = tempLength >> 24;
buffer[bufLen - 4] = (unsigned char)tempVal;
}
if(debug)
{
printf("Checking reported length = stream length... ");
if((unsigned char)buffer[bufLen - 4] * 256 * 256 * 256 + (unsigned char)buffer[bufLen - 3] * 256 * 256 + (unsigned char)buffer[bufLen - 2] * 256 + (unsigned char)buffer[bufLen - 1] == length * 8)
{
printf("done!\n");
}
else
{
printf("failed!\n");
printf("length (in bits) : %u\n", length * 8);
printf("padding(in bits) : %u\n", (unsigned char)buffer[bufLen - 4] * 256 * 256 * 256 + (unsigned char)buffer[bufLen - 3] * 256 * 256 + (unsigned char)buffer[bufLen - 2] * 256 + (unsigned char)buffer[bufLen - 1]);
return;
}
}
///
/// !Error likely introduced somewhere below!
///
// below based on psuedo code from Wikipedia
for(int MD5_loop = 0; MD5_loop < bufLen / 64; MD5_loop++)
{
unsigned int a, b, c, d;
a = h0;
b = h1;
c = h2;
d = h3;
unsigned int word[16];
for(int loop = 0; loop < 16; loop++)
{
int tempVal;
tempVal = 0;
tempVal |= (unsigned char)buffer[MD5_loop * 64 + loop * 4];
tempVal <<= 8;
tempVal |= (unsigned char)buffer[MD5_loop * 64 + loop * 4 + 1];
tempVal <<= 8;
tempVal |= (unsigned char)buffer[MD5_loop * 64 + loop * 4 + 2];
tempVal <<= 8;
tempVal |= (unsigned char)buffer[MD5_loop * 64 + loop * 4 + 3];
if(debug)
{
printf("%08x\n", tempVal);
}
word[loop] = tempVal;
}
unsigned int f, g, tempVal;
for(int loop = 0; loop < 64; loop++)
{
if(loop < 16)
{
// (b and c) or (not b and d)
f = ((b & c) | ((!b) & d));
g = loop;
}
else if(loop < 32)
{
// (d and b) or (not d and c)
f = ((d & b) | ((!d) & c));
g = (5 * loop + 1) % 16;
}
else if(loop < 48)
{
// b xor c xor d
f = (b ^ c ^ d);
g = (3 * loop + 5) % 16;
}
else if(loop < 64)
{
// c xor (b or not d)
f = (c ^ (b | (!d)));
g = (7 * loop) % 16;
}
tempVal = d;
d = c;
c = b;
b = (unsigned int)b + (unsigned int)left_rotate(a + f + k[loop] + word[g], r[loop]);
a = tempVal;
}
h0 += (unsigned int)a;
h1 += (unsigned int)b;
h2 += (unsigned int)c;
h3 += (unsigned int)d;
}
if(debug)
{
printf("Stream content:\n");
for(int loop = 0; loop < bufLen; loop++)
{
printf("0x%02X ", (unsigned char)buffer[loop]);
}
}
printf("%08x%08x%08x%08x\n", h0, h1, h2, h3);
}Using the input "" the expected hash is d41d8cd98f00b204e9800998ecf8427e however I'm getting 5de5ae832d1f479f89adb8bdfa2a0655, obviously due to the nature of the hash it's extremely difficult to trace the issue back so I'm hoping someone might be able to notice my mistake and let me know so I can get on and fix it!
