Processes PGP-message from file.
This method processes data from ASourceFile. TElPGPReader reads portion of data and tries to decrypt and/or verify it. If all these operations were successful it fires OnRequestOutputFile event. File for output data has to be created in this event handler. Name of this file is specified by OutputFile property. Then TElPGPReader will read rest of input data and store clear processed data in the created output file.
If there's signed data in ASourceFile, then Verify() fires OnSigned and OnSignatures events. OnSigned lets you know the IDs of the keys, used for verification. Verification results are passed via OnSignatures event.