Cryptography midterm2

ElGamal

asymmetric encryption; encrypt with a public key and decrypt with a private key, based on the Diffie-Hellman key exchange. depends on a prime and primitive root; key is (p,alpha,beta)

Diffusion

ensures the influence of one plaintext bit is spread over many ciphertext bits, enhancing security. (like RSA, not affine ciphers)

Confusion

hides the relationship between the plaintext and ciphertext, making it difficult to deduce the original message from the encrypted data. (Like RSA and shift ciphers)

Block Ciphers

symmetric key algorithms that encrypt data in fixed-size blocks, providing confidentiality and security.

Hill Ciphers

a type of block cipher that uses linear algebra to encrypt blocks of text, enhancing security through matrix operations. gcd(det(M),26)=1

the Electronic Codebook (ECB)

method of encrypting data where each block of plaintext is encrypted independently with the same key, making it susceptible to known cipher text attacks.

Cipher Block Chaining (CBC)

a mode of operation for block ciphers that combines each plaintext block with the previous ciphertext block before encryption, enhancing security by ensuring that identical plaintext blocks produce different ciphertexts. Makes it harder to see patterns in encrypted data

Stream Ciphers

a type of cipher that encrypts data one bit or byte at a time, allowing for continuous data streams to be encrypted without the need for fixed block sizes. High speed and low cost computationally

Pseudorandom bit generators

algorithms that generate a sequence of numbers that approximates the properties of random numbers.

linear feedback shift register sequences (LFSR)

A type of pseudorandom bit generator that uses linear feedback to produce sequences of bits. Generated using a shift register and feedback taps, providing efficient and fast random bit generation. easily implemented in hardware, have long periods

the Data Encryption Standard

a symmetric-key algorithm for encrypting digital data, using a fixed 56-bit key to transform data into a secure format. It was widely used for securing sensitive information until being superseded by more advanced encryption standards. Operates as a block cipherthat processes data in 64-bit blocks and employs a series of permutations and substitutions to enhance security.

Multiple encryption

a technique that applies encryption algorithms multiple times to enhance security, often involving different keys or algorithms for each round of encryption.

meet-in-the-middle attack

A cryptographic attack that attempts to defeat a cipher by dividing the encryption process into two halves and searching for a match between the two, significantly reducing the computational effort required compared to brute-force methods. This method is particularly effective against encryption schemes that use multiple keys or rounds, as it allows an attacker to find the key more efficiently.

Diffie-Hellman Key Exchange

A method for securely exchanging cryptographic keys over a public channel. It enables two parties to generate a shared secret key used for encrypted communication without transmitting the key itself.