Aone-timepadsystemistheonlysystemknownthatcannotbecrackedbyothers.ThissystemisalsocalledtheVernam-cipherorperfectcipher.Amessageusingthissystemcannotbebrokenbecausetheencryptionkeyisarandomnumberandbecausethekeyisusedonlyonce.Whenintelligenceagencieswanttosendmissioncriticalme