For many years, cryptographers attempted to hide the telltale frequencies by using several different substitutions for common letters, but this technique was unable to fully hide patterns in the substitutions for plaintext letters.
I mange år forsøgte kryptograferne at skjule frekvenserne ved at bruge flere forskellige substitutioner for de almindelige bogstaver, men denne metode er ude af stand til helt at skjule mønstre i substitutioner for almindelige bogstaver.