CryptHashData

[New - Windows NT]

[New - Windows 95, OEM Service Release 2]

The CryptHashData function is used to compute the cryptographic hash on a stream of data. This function and CryptHashSessionKey can be called multiple times to compute the hash on long streams or on discontinuous streams.

Before calling this function, the CryptCreateHash function must be called to get a handle to a hash object.

BOOL CRYPTFUNC CryptHashData(

HCRYPTHASH hHash,
BYTE *pbData,
DWORD dwDataLen,
DWORD dwFlags
);

Parameters

hHash

[in] A handle to the hash object. An application obtains this handle using the CryptCreateHash function.

pbData

[in] The address of the data to be hashed.

dwDataLen

[in] The number of bytes of data to be hashed. This must be zero if the CRYPT_USERDATA flag is set.

dwFlags

[in] The flag values. The following values are currently defined:

• CRYPT_USERDATA

When this flag is set, the CSP will prompt the user to input some data directly. This is then added to the hash. The application is not allowed access to the data. For example, this flag can be used to allow the user to enter a PIN into the system.

The Microsoft RSA Base Provider ignores this parameter.

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.

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.
NTE_BAD_ALGID	The hHash handle specifies an algorithm that this CSP does not support.
NTE_BAD_FLAGS	The dwFlags parameter contains an invalid value.
NTE_BAD_HASH	The hash object specified by the hHash parameter is invalid.
NTE_BAD_HASH_STATE	An attempt was made to add data to a hash object that is already marked "finished."
NTE_BAD_KEY	A keyed hash algorithm is being used, but the session key is no longer valid. This error will be generated if the session key is destroyed before the hashing operating is complete.
NTE_BAD_LEN	The CRYPT_USERDATA flag is set and the dwDataLen parameter has a nonzero value.
NTE_BAD_UID	The CSP context that was specified when the hash object was created cannot be found.
NTE_FAIL	The function failed in some unexpected way.
NTE_NO_MEMORY	The CSP ran out of memory during the operation.

Example

See the "Example" section in the CryptSignHash function.

See Also

CryptCreateHash, CryptHashSessionKey, CryptSignHash

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