Cyphers & Encryption - Rot13 Cypher

Introduction:

This page allows you to encode and decode text that has been encrypted with the 'Rot 13' cypher. In modern times this does not provide the security of cod systems like RSA or DES, but was commonly used in ancient times, and is still fun today.
Click on any of the links at the top of the page to reveal (or hide) more information about this calculator.

Caveats:

If you are reading this paragraph, then you probably don't have JavaScript installed/enabled on your computer.
At this point in time the calculators on this site are entirely dependant on JavaScript. Given enough time and money it is hoped to develop a version in the future which will be able to operate independantly. Since JavaScript runs on your own computer, rather than on this server, it has been possible to set up this site much more quickly than if a server-side language was used, and it is possible to serve far more pages with the available bandwidth.
If you think that you can assist with this project in any way, then please visit the Support section and leave a message.

Definitions:

Offset

The difference in position between each encrypted and un-encrypted character.

Rot

Short for 'Rotation'; referring to the fact that in the classical implementation of this cypher, the alphabet can be written in a circle, and larger numbers that would otherwise be beyond the end of the alphabet move round to the start of the alphabet.

Formulae:

The Rot13 Cypher works in the same manner as Caesar's Cypher, but uses a fixed offset of 13. The cypher works by converting each character into a corresponding number, like so: a=1, b=2 etc. Once this conversion is complete, the 'offset' is added to each number, then converted back to a character. This is the same mechanism as Caesar's Cypher, except that the offset is always the same. When used with the English alphabet, this has an important advantage: exactly the same mechanism is used to decrypt a message as is used to encrypt. This is because two 'rotations' by thirteen positions adds up to a single rotation by twenty-six positions, ie straight back to the original letter. Unfortunatly, the whole basis of the Rot13 cypher is dependant on a single alphabet of 26 letters, so any punctuation or numbers in the input will remain un-encrypted.

Instructions

1. Type, or Copy-and-Paste the text to be encrypted / decrypted where indicated.
2. Click the 'Encrypt/Decrypt' button below the input field.
3. The encrypted text will be displayed below.
   
4. To do further encryptions / decryptions simply change the text in the input field, and then click the 'Encrypt/Decrypt' button again.