CryptSetHashParam

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This function customizes the operations of a hash object. Currently, only a single parameter is defined for this function.

Syntax

BOOL WINAPI CryptSetHashParam( 
  HCRYPTHASH hHash,
  DWORD dwParam, 
  BYTE* pbData, 
  DWORD dwFlags
);

Parameters

• hHash
  [in] HCRYPTHASH handle to the hash object on which to set parameters.

• dwParam
  [in] Specifies the parameter value.

  The following table shows the possible values.

  Value	Description
  HP_HASHVAL	Byte array containing a hash value to place directly into the hash object. Before setting this value, the size of the hash value must be determined by reading the HP_HASHSIZE value with the CryptGetHashParam function. Some CSPs do not support this capability.
  HP_HMAC_INFO	HMAC_INFO structure that specifies the underlying hash algorithm and any optional parameters.

  Some cryptographic service provider (CSP) types can add additional values that can be set with this function.

• pbData
  [in] Pointer to a parameter data buffer. Place the parameter data in this buffer before calling the CryptSetHashParam function. The form of this data varies depending on the parameter number.

• dwFlags
  [in] Reserved for future use and must be set to zero.

Return Value

TRUE indicates success. FALSE indicates failure. To get extended error information, call the GetLastError function.

The following table shows the common values for the GetLastError function. The error values prefaced by NTE are generated by the particular CSP you are using.

Remarks

Occasionally, a hash value that has been generated elsewhere must be signed. The following sequence of operations accomplishes the task:

1. Create a hash object with CryptCreateHash.
2. Set the dwParam parameter to HP_HASHVAL.
3. Sign the hash value by using CryptSignHash, thereby obtaining a digital signature block.
4. Destroy the hash object by using CryptDestroyHash.

Example Code

// EXAMPLE CODE FOR USING CryptSetHashParam
// Set up the variables.
HCRYPTHASH   hHash; // A handle to the hash object on which to set
 // parameters
DWORD dwParam; // dwParam- paramater # can be HP_HMAC_INFO-
 // initialized elsewhere
BYTE pbData[16]; // The parameter data buffer
DWORD dwFlags = 0;// set to zero
BOOL Return;
Return = CryptSetHashParam(hHash, dwParam, pbData, dwFlags);
if (Return) {
 cout<< "function succeeds"<< endl;
}
else {
 cout<< "retrieve error"<< endl;
}

Requirements

See Also

Reference

CryptCreateHash
CryptDestroyHash
CryptGetHashParam
CryptSetKeyParam
CryptSignHash
HMAC_INFO