# Definitions These are definitions found in course material (mostly exercises) which may prove useful for the exam || Confidentiality || preventing unauthorised disclosure of information || || Integrity || preventing unauthorised (accidental or deliberate) modification or destruction of information || || Availability || ensuring resources are accessible when required by an authorised user || || Entity authentication || provides confirmation of the claimed identity of an entity || || Data origin authentication || provides confirmation of the claimed source (origin) of a data unit (message) || || Non-repudiation || Placeholder || || Cipher || See own section || || Kerckhoffs’ principle || the cryptanalyst has complete knowledge of the cipher, i.e. only unknown thing is the decryption key || || Transposition || the characters in the plaintext are mixed up with each other (permuted) ||

TODO: Scrape definitions from all exercises (currently they are just from exercise 1) # Ciphers ## Symmetric cipher (secret key cipher) encryption and decryption keys known only to sender and receiver. (DES) ## Asymmetric cipher (public key cipher) each participant has a public key and a private key, may allow both encryption and signatures. (RSA) ## Attacks ### Ciphertext only attack the cryptanalyst has available only the intercepted cipher text. ### Known plaintext attack the cryptanalyst knows a small amount of plaintext and its cipher text equivalent ### Chosen plaintext attack The cryptanalyst can obtain the cipher text equivalent of some plaintext which can be selected by the attacker, i.e the attacker has an "inside encryptor” available ### Chosen cipher text attack The cryptanalyst can obtain the plaintext equivalent of some cipher text which can be selected by the attacker, i.e. the attacker has an “inside decryptor” available. ## Block ciphers ### Block cipher modes ## Stream ciphers ## Historical ciphers - Caesar - Substitution - Vigenère. Caesar, but also uses a key in order to choose how many steps to shift the alphabet for each letter ### DES ### AES ### RSA ## Cipher attacks ciphertext only attack, known plaintext attack, chosen plaintext attack, and chosen ciphertext attack