How can I encrypt a message with GnuPG so that PGP is able to decrypt it?
It depends on the PGP version. • PGP 2.x You can’t do that because PGP 2.x normally uses IDEA which is not supported by GnuPG as it is patented (see 3.3), but if you have a modified version of PGP you can try this: $ gpg –rfc1991 –cipher-algo 3des … Please don’t pipe the data to encrypt to gpg but provide it using a filename; otherwise, PGP 2 will not be able to handle it. As for conventional encryption, you can’t do this for PGP 2. • PGP 5.x and higher You need to provide two additional options: –compress-algo 1 –cipher-algo cast5 You may also use “3des” instead of “cast5”, and “blowfish” does not work with all versions of PGP 5. You may also want to put: compress-algo 1 into your ~/.gnupg/options file – this does not affect normal GnuPG operation. This applies to conventional encryption as well.
It depends on the PGP version. • PGP 2.x You can’t do that because PGP 2.x normally uses IDEA which is not supported by GnuPG as it is patented (see 3.3), but if you have a modified version of PGP you can try this: gpg –rfc1991 –cipher-algo 3des … Please don’t pipe the data to encrypt to gpg but provide it using a filename; otherwise, PGP 2 will not be able to handle it. As for conventional encryption, you can’t do this for PGP 2. • PGP 5.x and higher You need to provide two additional options: –compress-algo 1 –cipher-algo cast5 You may also use “3des” instead of “cast5”, “blowfish” does not work with all versions of pgp5. You may also want to put compress-algo 1 into your ~/.gnupg/options file – this does not affect normal gnupg operation. This applies to conventional encryption as well.
