An Early Polyalphabetic Substitution Cyper named after Blaise de Vignère, although first described by Giovan Battista Bellaso in 1553.
It uses a Key Stream (a repeated key phrase) to select a different alphabet shift per letter during encryption, making it hard to break.
Instructions: Enter a Key Phrase and type into either the Plain Text or Cypher Text boxes to see the encryption in action.