This property is available in EFT Server 5.2 and later.
Use the ICIPgpActionParams interface SignKeyID property to retrieve the OpenPGP key ID for the signing key (for Encrypt operation only). You can also use the property to change the key used to sign.
HRESULT SignKeyID([out, retval] BSTR *pVal);
HRESULT SignKeyID([in] BSTR newVal);
pgpParams.SignKeyID = "0x071894C0"