The need to communicate with each other secretly has been a constant feature of human existence, from ancient civilisations sending tentative messages to each other, proposing an alliance, to present day users of the Internet passing their credit card details to online sellers.
The battle between those trying to keep their secret messages secure and those trying to intercept and unravel them is much like the never-ending arms race between predator and prey in the wild. As the prey animal species evolves to develop a better disguise and to run faster, so the predator evolves to develop better eyesight and the capacity to run faster, forcing the prey to evolve again to survive. Similarly, a new cipher is created and may initially survive attempts to crack it, but, once vulnerabilities in it are discovered, so the code-makers try to develop more sophisticated ciphers to guarantee the security of their messages.
This website looks at some of the most important ciphers developed during this continual struggle between those creating ciphers and those trying to crack them. As well as giving some information about those ciphers, it allows you to create secret messages using these ciphers and it will also try to automatically crack messages for you.
Follow the links or buttons to the Crack ciphers page and then copy your message into the top box. You need to then select the cipher from the options just under the box. If, for example, you think that the message has been encoded using a Caesar cipher, then select 'Crack Caesar cipher' before pressing the black 'Crack code' button.
|Affine cipher||Amsco cipher|
|Beaufort cipher||Bifid Cipher|
|Caesar cipher||Hill cipher|
|Playfair cipher||Polybius cipher|
|Porta cipher||Rail Fence cipher|
|Substitution cipher||Transposition cipher|