Re: CryptDeriveKey seems to create different keys with the same initial values?
From: Rauno Uusitalo (rauno.uusitalo_at_no_spam.fi)
Date: 09/18/03
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Date: Thu, 18 Sep 2003 13:48:00 +0300
Stupid me! Just forget to copy the data to be encrypted into it's place.
if (CryptEncrypt(hKey, NULL, TRUE, 0, NULL, pBufSize, 0))
CryptEncrypt(hKey, NULL, TRUE, 0, reinterpret_cast<BYTE*>(malloc(*pBufSize)), pBufSize, *pBufSize);
should be
if (CryptEncrypt(hKey, NULL, TRUE, 0, NULL, pBufSize, 0))
{
*ppBuf = malloc(*pBufSize);
CopyMemory(*ppBuf, szString, size);
CryptEncrypt(hKey, NULL, TRUE, 0, reinterpret_cast<BYTE*>(*ppBuf), pBufSize, *pBufSize);
}
Sorry about the trouble,
Rauno
"Rauno Uusitalo" <rauno.uusitalo@no_spam.fi> wrote in message news:OyPGARcfDHA.392@TK2MSFTNGP12.phx.gbl...
Hi there!
Hope somebody could point out what am I doing wrong. Purpose is to create functions to encrypt and decrypt strings by a given password. To me it seems like the CryptDeriveKey-calls are generating different keys with the same passwords resulting unability to decrypt the string. Please help!
Best Regards,
Rauno Uusitalo
#include <wincrypt.h>
#include <malloc.h>
#include <stdio.h>
void EncryptStr(LPCTSTR szString,
LPCTSTR szPassword,
LPVOID* ppBuf,
DWORD* pBufSize)
{
HCRYPTPROV hProv = NULL;
HCRYPTHASH hHash = NULL;
HCRYPTKEY hKey = NULL;
LPTSTR szEncrypted = NULL;
*ppBuf = NULL;
*pBufSize = 0;
if (!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, CRYPT_SILENT))
CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, CRYPT_NEWKEYSET | CRYPT_SILENT);
if (NULL != hProv)
{
if (CryptCreateHash(hProv, CALG_MD5, 0, 0, &hHash))
{
if (CryptHashData(hHash, reinterpret_cast<BYTE*>(const_cast<LPTSTR>(szPassword)), lstrlen(szPassword) * sizeof *szPassword, 0))
if (CryptDeriveKey(hProv, CALG_RC4, hHash, 0, &hKey))
{
DWORD size = (lstrlen(szString) + 1) * sizeof *szString;
*pBufSize = size;
if (CryptEncrypt(hKey, NULL, TRUE, 0, NULL, pBufSize, 0))
CryptEncrypt(hKey, NULL, TRUE, 0, reinterpret_cast<BYTE*>(malloc(*pBufSize)), pBufSize, *pBufSize);
CryptDestroyKey(hKey);
}
CryptDestroyHash(hHash);
}
CryptReleaseContext(hProv, 0);
}
}
LPTSTR DecryptStr(LPVOID pBuf,
DWORD bufSize,
LPCTSTR szPassword)
{
HCRYPTPROV hProv = NULL;
HCRYPTHASH hHash = NULL;
HCRYPTKEY hKey = NULL;
BYTE* pDecrypted = NULL;
if (!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, CRYPT_SILENT))
CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_FULL, CRYPT_NEWKEYSET | CRYPT_SILENT);
if (NULL != hProv)
{
if (CryptCreateHash(hProv, CALG_MD5, 0, 0, &hHash))
{
if (CryptHashData(hHash, reinterpret_cast<BYTE*>(const_cast<LPTSTR>(szPassword)), lstrlen(szPassword) * sizeof *szPassword, 0))
if (CryptDeriveKey(hProv, CALG_RC4, hHash, 0, &hKey))
{
pDecrypted = reinterpret_cast<BYTE*>(malloc(bufSize));
CryptDecrypt(hKey, NULL, TRUE, 0, pDecrypted, &bufSize);
CryptDestroyKey(hKey);
}
CryptDestroyHash(hHash);
}
CryptReleaseContext(hProv, 0);
}
return reinterpret_cast<LPTSTR>(pDecrypted);
}
int _tmain(int argc, _TCHAR* argv[])
{
LPCTSTR szPlainText = _T("ABC");
LPCTSTR szPassword = _T("Password");
LPVOID pBuf = NULL;
DWORD bufSize = 0;
EncryptStr(szPlainText, szPassword, &pBuf, &bufSize);
LPTSTR szDecrypt = DecryptStr(pBuf, bufSize, szPassword);
_tprintf(_T("%s\n"), szDecrypt);
free(szDecrypt);
free(pBuf);
}
- Next message: Michel Gallant: "Re: CAPICOM and key container"
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- In reply to: Rauno Uusitalo: "CryptDeriveKey seems to create different keys with the same initial values?"
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