The CryptCreateHash function is used to initiate the hashing of a stream of data. It returns to the caller a handle to a CSP hash object. This handle can also be used in subsequent calls to CryptHashData and CryptHashSessionKey in order to hash streams of data and session keys.
BOOL CRYPTFUNC CryptCreateHash(
HCRYPTPROV hProv, | |
ALG_ID Algid, | |
HCRYPTKEY hKey, | |
DWORD dwFlags, | |
HCRYPTHASH *phHash | |
); |
The valid values for this parameter will vary, depending on the CSP that is
used. See the “Remarks” section for the list of default algorithms.
The key must be to a block cipher, such as RC2, with a cipher mode of CBC.
The Microsoft RSA Base Provider defines the following hashing algorithms:
Constant |
Description |
CALG_MAC |
Message Authentication Code |
CALG_MD2 |
MD2 |
CALG_MD5 |
MD5 |
CALG_SHA |
US DSA Secure Hash Algorithm |
The computation of the actual hash is done with the CryptHashData and CryptHashSessionKey functions. These require a handle to the hash object. Once all the data has been added to the hash object, exactly one of the following operations can be performed:
Once one of the functions from this list has been called, the only hashing function that can be used with the same hash handle is CryptDestroyHash.
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To retrieve extended error information, use the GetLastError function.
The following table lists the error codes most commonly returned by the GetLastError function. The error codes prefaced by “NTE” are generated by the particular CSP you are using.
Error |
Description |
ERROR_INVALID_HANDLE |
One of the parameters specifies an invalid handle. |
ERROR_INVALID_PARAMETER |
One of the parameters contains an invalid value. This is most often an illegal pointer. |
ERROR_NOT_ENOUGH_MEMORY |
The operating system ran out of memory during the operation. |
NTE_BAD_ALGID |
The Algid parameter specifies an algorithm that this CSP does not support. |
NTE_BAD_FLAGS |
The dwFlags parameter is nonzero. |
NTE_BAD_KEY |
A keyed hash algorithm (such as CALG_MAC) is specified by Algid and the hKey parameter is either zero or it specifies an invalid key handle. This error code will also be returned if the key is to a stream cipher, or if the cipher mode is anything other than CBC. |
NTE_NO_MEMORY |
The CSP ran out of memory during the operation. |
See the “Example” section in the CryptSignHash function.
CryptAcquireContext, CryptDeriveKey, CryptDestroyHash, CryptGetHashParam, CryptHashData, CryptHashSessionKey, CryptSignHash, CryptVerifySignature
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