Cryptography Flashcards
What is a cipher?
an algorithm performing encryption and decryption
What is a key?
specifies the transformation of data for encryption / decryption
What is a Substitution cipher?
Every character is substituted with another one. ex. Caesar Cipher
What is a Polyalphabetic cipher?
Based on substitution, Uses multiple substitution alphabets. ex. Vigenère cipher
What is a Transposition cipher?
Plain text is repositioned (shifted) to create a ciphertext. Also called a zigzag cipher
ex. Rail fence cipher (ancient Greeks)
Define computationally infeasible
A computation which although computable would take far too many resources to actually compute.
What is a Block cipher?
Fixed-size blocks are split up into blocks and fed into the cipher using a symmetric key
What is a Stream cipher?
Combines One bit at a time using a symmetric key with a pseudorandom cipher digit stream (keystream)
What is a XOR cipher?
If the inputs match, the output is a 0; otherwise, it is a 1.
What layer of OSI stack does PPP encryption happen?
Data link layer
What layer of OSI stack does IPSec encryption happen?
Internet layer
What layer of OSI stack does TCP encryption happen?
Transport layer
What layer of OSI stack does SSL / TLSencryption happen?
Application layer
