[MA101] - Midterm Exam Guide - Everything you need to know! (17 pages long)
Document Summary
Need for cryptography in military and government areas. Today there is an increased need for secure communications. In its most elemental form, the objective of any secret communication scheme is to allow two parties, Alice and bob, to communicate over an insecure channel so that an adversary (oscar) cannot understand what is being communicated. The information that alice communicates is called the message/plaintext. The active transforming of the plaintext into cipher text is called enciphering/encryption. The rules for enciphering are called an algorithm, which uses a key, which is an input into the algorithm. The active transforming of cipher text into plaintext using the key is called deciphering, or decryption. In a substitution cipher, one letter of the alphabet used in the cipher text replaces one letter of the alphabet used in the plaintext. Suppose the message sender was cautious and removed all spaces, or randomly inserted spaces.
