CryptDecryptMessage (Compact 2013)

3/28/2014

This function decodes and decrypts a message.

Syntax

BOOL WINAPI CryptDecryptMessage(
    __in PCRYPT_DECRYPT_MESSAGE_PARA pDecryptPara,
    __in const BYTE* pbEncryptedBlob,
      __in DWORD cbEncryptedBlob,
      __out_opt BYTE* pbDecrypted,
      __inout_opt DWORD* pcbDecrypted,
      __out_opt PCCERT_CONTEXT* ppXchgCert
);

Parameters

• pDecryptPara
  [in] Pointer to a CRYPT_DECRYPT_MESSAGE_PARA structure that contains decryption parameters.

• pbEncryptedBlob
  [in] Pointer to a buffer that contains the encoded and encrypted message to be decrypted.

• cbEncryptedBlob
  [in] Size, in bytes, of the encoded and encrypted message.

• pbDecrypted
  [out, optional] Pointer to a buffer that receives the decrypted message.
  To set the size of this information for memory allocation purposes, this parameter can be NULL. A decrypted message will not be returned if this parameter is NULL. For more information, see Retrieving Data of Unknown Length.

• pcbDecrypted
  [in, out, optional] Pointer to a DWORD that specifies the size, in bytes, of the buffer to which the pbDecrypted parameter points. When the function returns, this variable contains the size, in bytes, of the decrypted message copied to pbDecrypted.

  Note

  When processing the data returned in the pbDecrypted buffer, applications must use the actual size of the data returned. The actual size can be slightly smaller than the size of the buffer specified in pcbDecrypted on input. On input, buffer sizes are usually specified large enough to ensure that the largest possible output data will fit in the buffer. On output, the DWORD is updated to the actual size of the data copied to the buffer.

• ppXchgCert
  [out, optional] Pointer to a CERT_CONTEXT structure of a certificate that corresponds to the private exchange key needed to decrypt the message. To indicate that the function should not return the certificate context used to decrypt, set this parameter to NULL.

Return Value

Returns true if function succeeds; otherwise, false. To retrieve extended error information, call GetLastError.

The following error codes are most commonly returned by the GetLastError function.

If the function fails, GetLastError may return an Abstract Syntax Notation One (ASN.1) encoding/decoding error. For information about these errors, see ASN.1 Encoding/Decoding Return Values.

Remarks

When NULL is passed for pbDecrypted, and pcbDecrypted is not NULL, NULL is returned for the address passed in ppXchgCert; otherwise, a pointer to a CERT_CONTEXT is returned. For a successfully decrypted message, this pointer to a CERT_CONTEXT points to the certificate context used to decrypt the message. It must be freed by calling CertFreeCertificateContext. If the function fails, the value at ppXchgCert is set to NULL.

Requirements

See Also

Reference

Certificates Functions