Match correctly the cryptographic algorithm with their corresponding key-length.1. DES a. 128-256 bits 2. Rj indeal b. 1-448 bits 3. RC4 c. 56 bits 4. Blowfish d. 1-2048 bits
Matching Cryptographic Algorithms with Key Lengths
This question requires matching specific cryptographic algorithms with their typical key lengths. Let's break down each algorithm and its associated key size.
Algorithm-Key Length Matching
| Algorithm | Label | Key Length |
|---|---|---|
| 1. DES | c | 56 bits |
| 2. Rijndael | a | 128-256 bits |
| 3. RC4 | d | 1-2048 bits |
| 4. Blowfish | b | 1-448 bits |
Detailed Explanation of Matches
1. DES (Data Encryption Standard) - 56 bits
DES is a symmetric-key block cipher. It operates on 64-bit blocks of data. The original DES algorithm uses a key size of 64 bits, but only 56 bits are actually used for encryption, with the other 8 bits acting as parity bits. Therefore, its effective key length is 56 bits.
2. Rijndael - 128-256 bits
Rijndael is the algorithm that was selected as the Advanced Encryption Standard (AES). It is a symmetric-key block cipher. Rijndael supports three different key lengths: 128 bits, 192 bits, and 256 bits. The choice of key length affects the number of transformation rounds.
3. RC4 - 1-2048 bits
RC4 is a stream cipher known for its simplicity and speed. It uses a variable key length, typically ranging from 40 bits up to 2048 bits. While flexible, RC4 has known security vulnerabilities, especially with shorter key lengths or specific implementation practices.
4. Blowfish - 1-448 bits
Blowfish is another symmetric-key block cipher, designed as a fast, free alternative to DES. It operates on 64-bit blocks. Blowfish supports variable key lengths, ranging from 32 bits up to 448 bits. The key is used to initialize a key-dependent S-box.
Final Matching Summary
Based on the standard key lengths for these algorithms, the correct matches are:
- DES corresponds to 56 bits.
- Rijndael corresponds to 128-256 bits.
- RC4 corresponds to 1-2048 bits.
- Blowfish corresponds to 1-448 bits.
This corresponds to the pairing: 1-c, 2-a, 3-d, 4-b.
Important Questions from Cryptography - Teaching
- In symmetric key cryptography, if every person in a group of 12 people needs to communicate with every other person in the group, how many secret keys are required?
- Decryption of the ciphertext "Z" with the key pair (7, 2) in modulus 26 is
In the RSA public key cryptosystem, the private and public keys are $(e, n)$ and $(d, n)$ respectively, where $n = p \times q$ and $p$ and $q$ are large primes. Besides, $n$ is public and $p$ and $q$ are private. Let M be an integer such that $0 <M< n$ and $\phi(n) = (p-1)(q - 1)$. now consider the following equations.
I. M’ =\( M^e\) mod n M =\( (M')^d\) mod nII. ed ≡1 mod n
III. ed ≡1 mod f(n)
IV. M’ = \(M^e \)mod f(n)
M = \( (M')^d\) mod
Which of the above equations correctly represent RSA cryptosystem?- Let M be a message consisting of 50 AES blocks. Alice encrypts using CBC mode and transmits the resulting ciphertext to Bob. Due to a network error, ciphertext block number 45 is corrupted during transmission. All other ciphertext blocks are transmitted and received correctly. Once Bob decrypts the received ciphertext, number of plaintext blocks corrupted is
- Match the type of attack and its prevention mechanism:
1. Brute-Force Attack a. Change of keys 2. Statistical Attack b. Number of possible keys are large 3. Pattern Attack c. Hide the characteristics of the
language4. Known - Plain Text Attack d. Ciphertext is as random as
possible
