The Caesar cipher is a basic substitution cipher. It is also known as a shift cipher or Caesar shift. In this cipher, each letter is replaced by another letter some fixed number of positions down the alphabet. For example with a right shift of 3, the letter A would be replaced by D. The cipher is named after Julius Caesar, who used it in his private communications. A Caesar cipher with a shift of 13 is the same as a ROT13 cipher.
Decode Caesar cipher
Note that you can type in either the ciphertext or plaintext area.
- The Caesar cipher is a simple form of monoalphabetic substitution cipher.
- Other names for the same cipher include Caesar's cipher, shift cipher, Caesar's code and Caesar shift.
- ROT13 encryption is widely used on Usenet and forums to obfuscate text. It is equivalent to a Caesar cipher with a shift of 13.
- To increase obfuscation, spaces can be removed or replaced with a character, such as X, in the plaintext before encryption.
- A Caesar cipher can very easily be broken, since there are only a very limited number of keys.
- The alphabet shift is usually to the right.
Caesar cipher, and variants of it, are often used in easy geocaching mystery caches, and easy logic puzzles. It can easily be detected using letter frequency analysis of the ciphertext, but it's usually easiest and quickest to just try every shift manually ("brute force attack").
V PNZR, V FNJ, V PBADHRERQ.
The ciphertext above represents "I CAME, I SAW, I CONQUERED." encrypted using a shift of 13.