A C++ implementation of the Vigenère cipher as described at Wikipedia
"...each letter of the plaintext is encoded with a different Caesar cipher, whose increment is determined by the corresponding letter of another text, the key."
This is a text encoder/decoder that is capable of encrypting and decrypting plaintext with a supplied key using Vigenère's cipher, which is based upon the Caesar cipher method of shifting/rotating letters. This implementation is NOT case-sensitive, and spaces are not counted in the provided key.
The program itself is a simple commandline tool. Compile the cpp code and run it, or find a pre-built .exe file in the releases tab.
Verify results against University of Denver's Vigenère encoder/decoder (Note: In each of these cases, the Key is used to encrypt as well as decrypt. Whitespaces and upper/lowercase are filtered out and ignored by this program.)
| Plaintext | Key | Ciphertext |
|---|---|---|
| attacking tonight | OCULORHINOLARINGOLOGY | ovnlqbpvt hznzouz |
| Humpty Dumpty sat on a wall | egg | lastze hastze wgz st g agrp |
| Humpty Dumpty sat on a wall | The egg fell | abqtze iyxamf wez us e hles |
| abcdefg | 1 | bcdefgh |
| abcdefg | 10 | bbddffh |
In the example where keytext is "1", inputting a key of just one produces a caesar cipher by shifting each letter of the plaintext forward by that amount. A keytext of "10" DOES NOT result in a shift of 10, as the Vigenère algorithm considers each digit to be its own thing.