This was originally posted by Otto42 in this thread -
Hopefully this will help some people, and avoid posts to the forum about encrypted theme files. Use these tools to decode them yourself.
Better yet, avoid encrypted themes entirely. They're always malicious in some fashion. There is no legitimate reason for a theme author to encrypt a theme file.
This page will let you decode the encryption that seems most commonplace, the one that looks like $o=whatever:
http://ottodestruct.com/decoder.php
Otto based the interface for it off of this one, which will decode the type of encryption that starts with $_F=__FILE__:
http://www.tareeinternet.com/scripts/byterun.php
Otto also created this one, for encoded files that start with $OOO0O0O00=__FILE__;$O00O00O00=__LINE__;:
http://ottodestruct.com/decoder2.php
Another one is here, for those that look like eval(gzinflate(base64_decode('...')));:
http://www.tareeinternet.com/scripts/decrypt.php
These sites support a whole lot of different decoding methods. All you have to do is upload the encoded file and it spits out the decoded one:
http://base64-encoder-online.waraxe.us/
(Yes, I know they're not really "encrypted", they're obfuscated. Semantics.)
Please, before adding to this thread asking for someone to decode an encrypted theme, actually try it out yourself first through the methods above.