The *Vignère Cipher* is a [[Symmetric Encryption|symmetric encryption]], named after Blaise de Vignère, and an extension of the [[Ceasar Cipher|Ceasar cipher]]. In the case of the [[Ceasar Cipher|Caesar ]] each letter is shifted by the same amount. In cryptographic terms, the key has length one. Since there are only 25 valid keys for the [[Ceasar Cipher]], it is rather easy to break. The idea of the *Vignère cipher* is to shift each letter by a specific amount specified by a key. If the letter of the key is $B$, then the original message letter is shifted by 1, 2 for a $C$, 3 for a $D$, etc. A message encrypted with this scheme is still easy to decrypt if the message is long in relation to the key, since a statistical analysis of the message is easily feasible. ![[vignere_cipher.exaclidraw.light.svg]] The *Vignère cipher* becomes cryptographically secure if the key is as long as the message. Then, it is equivalent to a [[One-Time Pad|one-time pad]]. >[!read]- Further Reading >- [[Encryption]] >- [[Symmetric Encryption]] >[!ref]- References