Symmetric-Key Cryptography Flashcards

Flashcards covering key vocabulary and concepts from a lecture on Symmetric-Key Cryptography.

Symmetric Encryption Algorithms

Encryption algorithms that use the same key for both encryption and decryption.

Plaintext

The unencrypted message or data.

Ciphertext

The encrypted message or data, appearing as gibberish.

Key

A secret number used by cryptographic algorithms to encrypt and decrypt data.

Decryption

The process of converting ciphertext back into its original plaintext form.

Lock

An encryption algorithm used to protect the contents of files on a computer.

Cryptanalysis

The study of methods to defeat cryptographic techniques.

Random Values

Values that pass statistical tests of randomness and are unrepeatable.

Random Number Generator (RNG) / True Random Number Generator (TRNG)

A device or hardware that gathers numbers from unpredictable inputs to generate random numbers.

Pseudo-Random Number Generators (PRNGs)

Algorithms that produce numbers that pass statistical tests but are repeatable.

Seed

Value used to change the output of a Pseudo-Random Number Generator.

Entropy

Describes the measure of chaos or randomness in a system. The greater the value, the greater the chaos.

Ciphertext-only attack

An attack where an attacker only has collection of ciphertexts

Known-plaintext attack

An attack where the attacker knows some pairs of ciphertext and corresponding plaintext

Chosen-plaintext attack

An attack where the attacker can choose a number of messages and obtain the ciphertexts

Chosen-ciphertext attack

An attack where the adversary can choose a number of ciphertexts and obtain the plaintexts.

Brute-Force Attack

An exhaustive search that tries all possible keys to decrypt a ciphertext.

Key Table

A pseudo-random array of a particular size and in a particular format.

Key Setup

The process of building a key table, or initialisation.

Confusion

Technique used to obscure the relationship between the key and the ciphertext.

Diffusion

Encryption operation where the influence of one plaintext symbol is spread over many ciphertext symbols.

Block Cipher

Cipher that divides plaintext into fixed-size blocks, encrypting each block independently.

Padding

Adding extra bytes to an incomplete block to make it complete for encryption.

Triple DES (3DES)

Nested application of DES with three different keys.

Advanced Encryption Standard (AES)

Symmetric encryption algorithm selected by NIST in 2001 with 128-bit blocks and variable key lengths.

Feedback Modes

Avoid copies in ciphertext utilizing feedback modes.

Cipher Block Chaining (CBC)

A feedback mode in which you XOR the current block of plaintext with the preceding block of ciphertext

Initialization Vector (IV)

A random block separately transmitted encrypted

One-Time Pad (OTP)

Encryption algorithm where the plaintext is combined with a random key, or "pad," that is as long as the plaintext and used only once.

Stream Cipher

Generates a pad based on the key where the pad can be as big as it needs to be. The algorithm will XOR the plaintext with the pad

Key Stream

In cryptography circles, the "pad" is called this.