Traditional cryptography

Outline Cryptography Traditional cryptography Statistical attacks Secret-key encryption Public-key encryption encrypt ciphertext plaintext 6/8/2002 2:08 PM Cryptography 1 6/8/2002 2:08 PM Cryptography 2 Encryption Scenario: wants to send a message (plaintext p) to Bob. The communication channel is insecure and can be eavesdropped If Alice and Bob have previously agreed on an encryption scheme (cipher), the message can be sent encrypted (ciphertext c) Alice Traditional Cryptography Ciphers were already studied in ancient times Caesars cipher: replace replace replace a with d b with e z with c Issues: is a good encryption scheme? What is the complexity of encrypting/decrypting?

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