Shannon's definition of perfect Secrecy The One-Time Pad Ek(m=mok ciphertext C One-Time ad k bits of random key K use random key sequence only once and then discard it 1001101010 1101000111Shannon‘s Definition of Perfect Secrecy m ciphertext C One-Time Pad k bits of random key K 1 0 0 1 1 0 1 0 1 0 0 1 1 1 0 1 1 0 1 1 1 1 0 1 0 0 0 1 1 1 use random key sequence only once and then discard it ! The One-Time Pad Ek (m) = m  k k