●●●●● ●●●● ●●0 Monoalphabetic Cipher ●●● ●●●● e Rather than just shifting the alphabet, we could shuffle the letters arbitrarily each plaintext letter maps to a different random ciphertext letter o key is now 26 letters long, so there are 26!or greater than 4x1026 possible keys e Seems to be secure enough but Plain: abcdefghijklmnopqrstuvwxyz Key Cipher: DKVQFIBJWPESCXHTMYAUOLRGZN Plaintext: ifwewishtoreplaceletters Ciphertext: WIRFRWAJUHYFTSDVESFUUFYA COMP4690. HKBUCOMP4690, HKBU 13 Monoalphabetic Cipher ⚫ Rather than just shifting the alphabet, we could shuffle the letters arbitrarily ⚫ each plaintext letter maps to a different random ciphertext letter ⚫ key is now 26 letters long, so there are 26! or greater than 4x1026 possible keys. ⚫ Seems to be secure enough, but … Plain: abcdefghijklmnopqrstuvwxyz Cipher: DKVQFIBJWPESCXHTMYAUOLRGZN Plaintext: ifwewishtoreplaceletters Ciphertext: WIRFRWAJUHYFTSDVFSFUUFYA Key