In asymmetric decryption, the key ID of the intended recipient's key is contained in the encrypted stream, so GnuPG automatically chooses that key for the decryption. dvf5907's question, though, is how do you pass the key passphrase to GnuPG since the only parameter to GPG_Decrypt_Asym is the encrypted datastream?

From your code, I can only assume that your private key is not itself encrypted with a passphrase, otherwise, GnuPG would require that passphrase to decrypt the key to decrypt the data.

--isotope
http://www.skylab.org/~isotope/