| BOOL WINAPI AesDecryptString( |
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LPCTSTR lpszPassword, |
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LPCTSTR lpszInputString, |
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LPCTSTR lpszOutputString, |
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LONG nMaxLength |
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The AesDecryptString function decrypts the contents of a
string.
Parameters
- lpszPassword
- A pointer to a null terminated string of characters that will be
used to generate the decryption key. This parameter may be NULL or a
zero-length string, in which case a default internal hash value is
used to decrypt the data. Password strings that exceed 215 characters will be truncated.
- lpszInputString
- A pointer to a null terminated string which contains the data to
be decrypted. The encrypted input data must be base64 encoded and
identical to the encrypted string returned by the
AesEncryptString function. If this parameter is NULL or
points to an empty string the function will fail.
- lpszOutputString
- A pointer to the buffer which will contain the decrypted string
data. This parameter
cannot be NULL.
- nMaxLength
- The maximum number of characters that can be copied to the
output string buffer. The output buffer must be large enough to
store the complete decrypted string
and is terminated with a null character. This value must be greater
than zero. If the output string buffer is not large enough, the
function will fail.
Return Value
A non-zero value is returned if the string was successfully
encrypted. A zero value indicates that the string could not be
decrypted. To get extended error information, call GetLastError.
Remarks
The AesDecryptString function will decrypt a
string using a 256-bit AES (Advanced Encryption Standard) algorithm and returns
a copy of the decrypted string o the caller. The password (or
passphrase) provided by the caller is used to generate a SHA-256 hash
value which is used as part of the decryption process. The
lpszPassword value
must be identical to the value used to encrypt the data using the
AesEncryptString function.
Due to how the SHA-256 hash is generated, this function cannot be
used to decrypt strings that were encrypted using another third-party
library. It can only be used to decrypt strings that were previously
encrypted using AesEncryptString.
If you wish to decrypt the contents of a file, use the
AesDecryptFile function.
This function uses the Microsoft CryptoAPI and the RSA AES
cryptographic provider. This provider may not be available in some
languages, countries or regions. The availability of this provider may
also be constrained by cryptography export restrictions imposed by the
United States or other countries. If the required cryptographic
provider is not available, the function will fail.
Example
BOOL bIsDecrypted = FALSE;
LPCTSTR lpszPassword = _T("NFr-E{Ki3_1w0iV+LI@z");
TCHAR szDecryptedText[MAX_STRING_LENGTH];
bIsDecrypted = AesDecryptString(lpszPassword,
szEncryptedText,
szDecryptedText,
MAX_STRING_LENGTH);
if (bIsDecrypted)
{
_tprintf(_T("The decrypted string is \"%s\"\n"), szDecryptedText);
}
Requirements
Minimum Desktop Platform: Windows 7 Service Pack 1
Minimum Server Platform: Windows Server 2008 R2 Service Pack 1
Header File: cstools11.h
Import Library: csncdv11.lib
Unicode: Implemented as Unicode and ANSI versions
See Also
AesDecryptBuffer,
AesDecryptFile,
AesEncryptString
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