25-04 Cryptography

Last updated Aug 17, 2023 Edit Source

The practice and study of techniques for secure communication in the presence of third parties called adversaries

The process of encoding (scrabbling) information using a key and a cypher to store sensitive data in an unintelligible format as a means of protection. An encryption takes in plaintext and produces ciphertext.

The enigma machine was used during WW2. A different key for each day was used to set the position of the rotors. It relied on simple cypher substitution.

A cipher (also spelled “cypher”) is a cryptographic technique that encrypts information to ensure its confidentiality and integrity. It scrambles data, making it unreadable without the correct decryption key or algorithm.

• Ciphertext is the encrypted form of a message or data resulting from applying encryption to plaintext.
• A codebook is a type of document used for gathering and storing cryptography codes

A key is a variable used in conjunction with an encryption algorithm in order to encrypt or decrypt data.

The same key is used for encoding and decoding. eg Advanced Encryption Standard (AES)

Two keys are used. One to encode and one to decode eg. Rivest–Shamir–Adleman (RSA)