25 Years of Programming
An open source source for C, C++, OWL, BASIC, MDB, XLS, DOT, and more...
Create and solve substitution ciphers
On this page you can create and solve simple substitution ciphers. In a substitution cipher, each letter of the alphabet is replaced with a different letter.
A Caesar cipher is the simplest type of substitution cipher. Each letter of the alphabet is shifted by a fixed number of places. For example, with a shift of 1, every occurrence of the letter A becomes a B, every B becomes a C, and so on. The sequence "wraps around", so Z gets shifted to A. The reason this cipher is so simple is that in English there are only 25 possible ways to shift the alphabet, so it takes a maximum of 25 decoding attempts to find the original text.
For example, using a Caesar cipher with a shift of 1, HELLO becomes IFMMP. With a shift of 2, it's JGNNQ.
An alphabet reversal cipher is another special case of a substitution cipher, where A becomes Z, B becomes Y, C becomes X, and so on. The encoding/decoding key looks like this:
Other substitution ciphers are more complicated and harder to decode. Every letter A-Z is replaced uniquely by some other letter A-Z, but it is done randomly, not by a simple shifting of the alphabet. You have to decode one letter at a time.
However, substitution ciphers, and Caesar ciphers in particular, don't provide any real security. They are very easy to break and are best viewed only as fun puzzles.
Create a cipher
Enter your plain text here:
Read your ciphered text here:
Decode a cipher
Enter your enciphered text here:
Letter frequencies in the ciphered text:
Decoded text, color coded to show locked letters, but in one long paragraph:
Decoded plain text, formatted same as the input:
Command Line. Enter the letters to change and click an action button below:
Ciphers to solve. Random difficulty. Copy and paste above. One of them is a Caesar cipher.
Copyright ©2012 Steven Whitney. Last modified Sun 07/29/2012 11:28:52 -0700.