This tool can be used to encode and decode messages using a Atbash cipher, which reverses the alphabet. Want to encode or decode a message? Just copy the plaintext into the message box and hit translate.
The atbash cipher is a simple substitution cipher from Biblical times; it reverses the alphabet such that each letter is mapped to the letter in the same position in the reverse of the alphabet (A -> Z, B -> Y). The original implementation (ca. 500 BC) was for the Hebrew alphabet and there are Old Testament references to it. The Atbash cipher has also been associated with various forms of mysticism. In modern times, it is referred to as a reverse alphabet code (see these cubscout materials). The atbash cipher is trivial to crack, once you realize that you're dealing with a substitution cipher, and is highly vulnerable to letter frequency analysis. It's primary modern application is puzzles and games. This atbash translater (including both atbash encoder and atbash decoder) can help you decode these cipher messages.
This tool is an atbash decoder; it is also an atbash encoder, since the two are exactly identical. To use the atbash translator to translate a message (atbash encoder setting), paste your message into the text box and hit translate message. The result will appear below. To decipher the atbash cipher message, copy the text from the results box into the text box (which serves as the atbash encoder) and hit translate message. You should be looking at your original text.
For a low-tech cipher, the atbash cipher is surprisingly effective. While it relies completely upon suprise (hint: don't use it to encode truly secret messages), most decoders mentally try the caesar cipher (fixed letter shift), which fails, and assume a mixed alphabet cipher. This is a much more complicated cipher to attack, even with a computer. So don't laugh at the atbash encoder and atbash decoder - they may be rustic, but they are certainly enough to confuse most of the people some of the time. Granted the task of an atbash decoder was harder before computer automation.