This is a standard Caesarian Shift cipher encoder, also known as a rot-N encoder and is also a style of substitution cipher. This way, you can add one, two, or any number up to 25 to your string and see how it changes. This is an offshoot of the rot13 encoder on this web site. To perform this shift by hand, you could just write the alphabet on two strips of paper. Line them up so the top strip's A matches the bottom strip's D (or something) and then you can encode. A simple test to see how this works would be to insert the alphabet into the encoder and then change the values of N.

This sort of cipher can also be known as a wheel cipher. This is where an inner wheel has the alphabet around the outside, and that is placed upon an outer wheel, also with the alphabet going around it. You can rotate the wheels so that ABC lines up with ABC, or ABC may line up with QRS.

To encode something, just pick an N and type in your message. To decode something, subtract the encryption N from 26 and it should be decoded for you.

This is your encoded or decoded text: