CryptCreateHash info  Overview  Group

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(

Parameters

hProv

[in] A handle to the CSP to use. An application obtains this handle using the CryptAcquireContext function.

Algid

[in] An algorithm identifier of the hash algorithm to use.

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.

hKey

[in] If the type of hash algorithm is a keyed hash, such as a MAC algorithm, the key for the hash should be passed in this parameter. For nonkeyed algorithms, this parameter should be set to zero.

The key must be to a block cipher, such as RC2, with a cipher mode of CBC.

dwFlags

[in] The flag values. This parameter is reserved for future use and should always be zero.

phHash

[out] The address to which the function copies a handle to the new hash object.

Remarks

The Microsoft RSA Base Provider defines the following hashing algorithms:

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:

• The hash value can be retrieved using CryptGetHashParam.

• A session key can be derived using CryptDeriveKey.

• The hash can be signed using CryptSignHash.

• A signature can be verified using CryptVerifySignature.

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.

Return Values

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.

Example

See the “Example” section in the CryptSignHash function.

See Also

CryptAcquireContext, CryptDeriveKey, CryptDestroyHash, CryptGetHashParam, CryptHashData, CryptHashSessionKey, CryptSignHash, CryptVerifySignature