●●●●● ●●●● ●●0 Requirements ●●● ●●●● o two requirements for secure use of symmetric encryption a strong encryption algorithm: the opponent should be unable to decrypt ciphertext or discover the key even if he has a number of ciphextexts together with the plaintext that produced each ciphertext o sender and recipient must have the secret key in a secure fashion and must keep the key secure o assume encryption algorithm is known assume a secure channel to distribute the key COMP4690. HKBUCOMP4690, HKBU 6 Requirements ⚫ two requirements for secure use of symmetric encryption: ⚫ a strong encryption algorithm: the opponent should be unable to decrypt ciphertext or discover the key even if he has a number of ciphextexts together with the plaintext that produced each ciphertext ⚫ sender and recipient must have the secret key in a secure fashion, and must keep the key secure ⚫ assume encryption algorithm is known ⚫ assume a secure channel to distribute the key