ITM 301 Lecture Notes - Symmetric-Key Algorithm, Block Cipher, X.509
6 Jan 2023
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Document Summary
Symmetric key cryptographic algorithms use a secret: called a key . Key space large enough to protect against exhaustive search. Two major types: stream ciphers, block ciphers. Block cipher: encrypts blocks of 64 bits using a 64-bit key, outputs 64 bits of cipher-text. Product cipher: basic unit is the bit, performs both substitution and transposition (permutation) on the bits. Private key: known only to owner (individual, website, etc. ) Confidentiality: only the owner of the private key knows it, so text enciphered with public key cannot be read by anyone except the owner of the private key. Authentication: only the owner of the private key knows it, so text enciphered with private key must have been generated by the owner. Alice needs to generate a random public key p and a corresponding private key q. Bob sends a confidential message to alice. Alice sends a message to bob, bob authenticates alice.
