CPDuplicateHash

The CPDuplicateHash function makes an exact copy of a hash and its state.

BOOL CPDuplicateHash(
  HCRYPTPROV hUID,          // in
  HCRYPTHASH hHash,         // in
  DWORD *pdwReserved,       // in
  DWORD dwFlags,            // in
  HCRYPTHASH *phHash        // out
);

Parameters

hUID

Handle to a particular key container within the CSP. This handle is obtained by a call to CPAcquireContext.

hHash

The handle to the hash to be duplicated.

pdwReserved

This parameter is reserved for future use and must be NULL.

dwFlags

This parameter is reserved for future use and must be zero.

phHash

The address of the handle to the duplicated hash. Must be the address of a buffer with enough memory allocated to hold the duplicated hash.

Return Values

If the function succeeds, the return value is TRUE.

If the function fails, the return value is FALSE, and the appropriate error code from the following table must be set using SetLastError.

Remarks

CPDuplicateHash makes a copy of a hash including its exact state. To generate two different hashes starting with some common hashed data,

1. create a single hash object
2. hash the common data to that object
3. duplicate the object the CPDuplicateHash function.
4. hash different data to the original hash object and the newly create object

CPDestroyHash must be called to destroy any hashes created with CPDuplicateHash. Destroying the original hash does not cause the duplicate hash to be destroyed. Once a duplicate hash is made, it is separate from the original hash. There is no shared state between the two hashes.

Requirements

  Windows NT/2000: Requires Windows NT 4.0 or later.
  Windows 95/98: Requires Windows 95 OSR2 or later (or Windows 95 with Internet Explorer 3.02 or later).
  Header: Declared in Wincrypt.h.

See Also

CPDestroyHash, CryptDuplicateHash