Vigenèrecipher
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Vigenère cipher
One of the most well known cipher methods. Each letter of the message is shifted by a corresponding character of the key, running out of characters in the key will loop back to the beginning. For example: Hello encrypted with a key of World would shift like:
H → W → D
e → o → s
l → r → c
l → l → w
o → d → r
- for the next letters, the key would loop back and start from the W in World again. There is more information available on the Vigenère cipher Wikipedia page.