The OffloadModExpo function offloads modular exponentiation from a CSP to a hardware accelerator.

Syntax

BOOL WINAPI OffloadModExpo(
  __in   BYTE *pbBase,
  __in   BYTE *pbExpo,
  __in   DWORD cbExpo,
  __in   BYTE *pbMod,
  __in   DWORD cbMod,
  __out  BYTE *pbResult,
  __in   void *pReserved,
  __in   DWORD dwFlags
);

Parameters

pbBase [in]

A pointer to the base value to be raised by the exponent. The value is in little-endian form and the length (number of bytes in the value) must be the length passed in cbMod. The value must be padded with 0x00 bytes if the most significant byte does not have a bit set. This value must be less than the value passed in the pbMod parameter.

pbExpo [in]

A pointer to the exponent the base value is to be raised to. The value is in little-endian form and the length (number of bytes in the value) must be the length passed in cbMod. The value must be padded with 0x00 bytes if the most significant byte does not have a bit set. This value must be less than the value passed in the pbMod parameter.

cbExpo [in]

DWORD value representing the length of the exponent in bytes.

pbMod [in]

A pointer to the modulus. The value is in little-endian form and the length (number of bytes in the value) must be the length passed in cbMod. The most significant byte of the modulus value must not be a 0x00 byte.

cbMod [in]

DWORD value representing the length of the modulus in bytes.

pbResult [out]

A pointer to the calculated result.

pReserved [in]

This parameter is reserved for future use and is set to NULL.

dwFlags [in]

This parameter is reserved for future use and is set to NULL.

Return Value

If the function succeeds, the return value is TRUE.

If the function fails, the return value is FALSE. To retrieve extended error information, call GetLastError.

Remarks

A CSP will check in the registry for the value HKLM\Software\Microsoft\Cryptography\Offload\ExpoOffload that can be the name of a DLL. The CSP uses LoadLibrary to load that DLL and calls GetProcAddress to get the OffloadModExpo entry point. The CSP uses the entry point to perform all modular exponentiations for both public and private key operations.

Requirements

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Build date: 10/2/2009