This method processes data from ASourceStream TElPGPReader reads portion of data and tries to decrypt and/or verify it. If all these operations were successful it fires OnCreateOutputStream event. Stream for output data (e.g. file) has to be created in this event handler. This stream is specified by OutputStream property. Then TElPGPReader will read rest of input data and return clear processed data to the created output stream.
If there's signed data in SourceStream, 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.
Note, in Delphi versions older than 7, works only with streams of sizes smaller than 2GB (because of TStream limitation). Use DecryptAndVerifyFile instead.