proper conversion of unsigned char [16] -> unsigned long [4] [modified]

saiyuk6 7

I am stuck actually, im trying to write a md5 / blowfish function im not sure if i am correctly converting the MD5[16] buffer into a unsigned long[4] this doesnt really make too much sense too me

typedef struct _tag2Long {
unsigned long _1;
unsigned long _2;
unsigned long _3;
unsigned long _4;
} _2LONG;

void SignBuffer(unsigned char *pbzKey, unsigned char *pbzBuffer,
unsigned int iSize, unsigned long pSignature[4])
{
MD5_CTX md5;
BLOWFISH_CTX bf;

MD5Init(&md5);
MD5Update(&md5, pbzBuffer, iSize);
MD5Final(&md5);

_2LONG *tl = (_2LONG*) md5.digest;

printf("BLE 1\t\t %x %x %x %x\n", tl->_1, tl->_2, tl->_3, tl->_4);

Blowfish_Init(&bf, pbzKey, 16);
Blowfish_Encrypt(&bf, &tl->_1, &tl->_2);
Blowfish_Encrypt(&bf, &tl->_3, &tl->_4);

pSignature[0] = tl->_1;
pSignature[1] = tl->_2;
pSignature[2] = tl->_3;
pSignature[3] = tl->_4;

printf("BLE 2\t\t %x %x %x %x\n", pSignature[0], pSignature[1],
pSignature[2], pSignature[3]);
}

bool VerifyBuffer(unsigned char *pbzKey, unsigned char *pSignature,
unsigned int iSize, unsigned long pBuffer[4])
{
BLOWFISH_CTX bf;
MD5_CTX md5;
bool bResult = false;

printf("BLD 1\t\t %x %x %x %x\n", pBuffer[0], pBuffer[1],
pBuffer[2], pBuffer[3]);

Blowfish_Init(&bf, pbzKey, 16);
Blowfish_Decrypt(&bf, &pBuffer[0], &pBuffer[1]);
Blowfish_Decrypt(&bf, &pBuffer[2], &pBuffer[3]);

printf("BLD 2\t\t %x %x %x %x\n", pBuffer[0], pBuffer[1],
pBuffer[2], pBuffer[3]);

MD5Init(&md5);
MD5Update(&md5, pSignature, iSize);
MD5Final(&md5);

_2LONG *tl = (_2LONG*) md5.digest;
// printf("BLD 3\t\t %x %x %x %x\n", tl->_1, tl->_2, tl->_3, tl->_4);

if (tl->_1 == pBuffer[0] && tl->_2 == pBuffer[1] &&
tl->_3 == pBuffer[2] && tl->_4 == pBuffer[4])
bResult = true;

return bResult;
}

void main(void)
{
unsigned char bszBuffer[2] = {'A', 'B'};
unsigned long ulSig[4];
SignBuffer((unsigned char*)"key", bszBuffer, 2, ulSig);
printf("\n");
if (VerifyBuffer((unsigned char*)"key", bszBuffer, 2, ulSig))
printf("\nok");
else printf("\nerr");
}

and this is the output of them

BLE 1 b0c66fb8 733df651 4c2d26de a9a0e334
BLE 2 f12b0ed9 782fae18

Chris Losinger

the conversion looks fine. but doesn't Blowfish use 64-bit (8-byte) blocks ? so this Blowfish_Encrypt(&bf, &tl->_1, &tl->_2); will encrypt the 8 bytes starting at tl->_1 ? since _1 is only four bytes, it's going to run over into _2. so, you're doing BF(_1 + _2) -> _2 + _3. or maybe not. i don't know what Blowfish_Encrypt looks like.

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Code o mat

Hello! It might only be me but it is not obvious (to me) where you are trying to do this conversion you are talking about, you should at least highlight the part of interest in your code so people who want to help don't have to study your whole program trying to grasp the way you think.

> The problem with computers is that they do what you tell them to do and not what you want them to do. < > "It doesn't work, fix it" does not qualify as a bug report. < > Amazing what new features none of the programmers working on the project ever heard of you can learn about when reading what the marketing guys wrote about it. <

saiyuk6 7

well it would be total 8 blocks for both _1 and _2, because a unsigned long is 4 bytes i am using Paul Kocher Blowfish Algorithm http://www.schneier.com/code/bfsh-koc.zip[^]

saiyuk6 7

BLE 2 f12b0ed9 782fae18 a87960ac f37b342e

is passed into VerifyBuffer, but when it is decrypted it doesnt match BLE 1 b0c66fb8 733df651 4c2d26de a9a0e334 when i pass a MD5 comparision from unsigned char *pSignature hope that makes sense? it seems to lose data some how, not sure

Chris Losinger

ah, ok. it's expecting 2 32-bit parts. i thought the params were input and output.

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saiyuk6 7

do you happen to know how i can fix it? i am lost

Chris Losinger

you're doing this, right: Sign: Sig = BFE(MD5(data)) Verify: X = BFD(Sig) Sig2 = MD5(Sig) Compare: X == Sig2 ? but shouldn't that bold line be Sig2 = MD5(data) ? the MD5 of the signature doesn't get you anything.

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saiyuk6 7

i fixed it, thank you very much for your help, i noticed

if (tl->_1 == pBuffer[0] && tl->_2 == pBuffer[1] &&
tl->_3 == pBuffer[2] && tl->_4 == pBuffer[4])
bResult = true;

pBuffer[4] should of been pBuffer[3] i was going out of range of the array which didnt exist here is the updated code

int _ustrlen(unsigned char *pbz)
{
const unsigned char *ptr;
for (ptr = pbz; *ptr; ++ptr);
return (ptr - pbz);
}

void SignBuffer(unsigned char *pbzKey, unsigned char *pbzBuffer,
unsigned int iSize, unsigned long *pSignature)
{
MD5_CTX md5, md5key;
BLOWFISH_CTX bf;

MD5Init(&md5);
MD5Update(&md5, pbzBuffer, iSize);
MD5Final(&md5);

_2LONG *tl = (_2LONG*) md5.digest;

printf("BLE 1\t\t %x %x %x %x\n", tl->_1, tl->_2, tl->_3, tl->_4);

MD5Init(&md5key);
MD5Update(&md5key, pbzKey, _ustrlen(pbzKey));
MD5Final(&md5key);

Blowfish_Init(&bf, md5key.digest, 16);
Blowfish_Encrypt(&bf, &tl->_1, &tl->_2);
Blowfish_Encrypt(&bf, &tl->_3, &tl->_4);

pSignature[0] = tl->_1;
pSignature[1] = tl->_2;
pSignature[2] = tl->_3;
pSignature[3] = tl->_4;

printf("BLE 2\t\t %x %x %x %x\n", pSignature[0], pSignature[1],
pSignature[2], pSignature[3]);
}

bool VerifyBuffer(unsigned char *pbzKey, unsigned char *pSignature,
unsigned int iSize, unsigned long *pBuffer)
{
BLOWFISH_CTX bf;
MD5_CTX md5, md5key;
bool bResult = false;

printf("BLD 1\t\t %x %x %x %x\n", pBuffer[0], pBuffer[1],
pBuffer[2], pBuffer[3]);

MD5Init(&md5key);
MD5Update(&md5key, pbzKey, _ustrlen(pbzKey));
MD5Final(&md5key);

Blowfish_Init(&bf, md5key.digest, 16);
Blowfish_Decrypt(&bf, &pBuffer[0], &pBuffer[1]);
Blowfish_Decrypt(&bf, &pBuffer[2], &pBuffer[3]);

printf("BLD 2\t\t %x %x %x %x\n", pBuffer[0], pBuffer[1],
pBuffer[2], pBuffer[3]);

MD5Init(&md5);
MD5Update(&md5, pSignature, iSize);
MD5Final(&md5);

_2LONG *tl = (_2LONG*) md5.digest;
printf("BLD 3\t\t %x %x %x %x\n", tl->_1, tl->_2, tl->_3, tl->_4);

if (tl->_1 == pBuffer[0] && tl->_2 == pBuffer[1] &&
tl->_3 == pBuffer[2] && tl->_4 == pBuffer[3])
bResult = true;

return bResult;