I've just read the RFC 4880 specs and there is nothing about OAEP; only PKCS#1 v1.5. If it is true that the OpenPGP-standard only supports the PKCS#1 v1.5 padding-scheme, is this a security issue?
Usually it's said that you should not use PKCS#1 v1.5 anymore or just for legacy reasons because it allows padding-oracle-attacks. However, OpenPGP/GnuPG is considered secure. So, are the padding-oracle-attacks feasible?
(I think they shouldn't be possible, because the recipient doesn't send any information back to the sender; but I'm not an expert, so I'm asking here)
Some second thoughts: Padding-oracle-attacks should not be possible if you verify the signature of the sender and only decrypt the message if the sender is valid or am I wrong here?