if you encrypt a message with OpenPGP and then "ACSII armor" the result, i.e. encode it in Base64, then this encoding enlarges the data by 34%: 3 bytes become 4 characters (plus the odd newline). Compression with DEFLATE will be effective at cancelling this enlargement (thanks to Huffman codes). That's a case of usefulness of compression after encryption -- but, really, that's more compression over Base64, rather than compression over encryption.
http://security.stackexchange.com/questions/19969/encryption-and-compression-of-data
1. https://users.cs.jmu.edu/buchhofp/forensics/formats/pkzip.html
2. http://ricardo.ecn.wfu.edu/~cottrell/pkzip.html
encode
creates archive in the UUEncode format
note: PKZIP will create two files when the encode option is invoked; a .ZIP archive (e.g. save.zip) as well as UUEncoded version of the .ZIP file (e.g. save.uue) are created
