5 Questions
What is the size of the input (plaintext) block in Simplified DES?
8-bits
How many rounds are there in Simplified DES?
2
Which permutation is used for the initial key generation in S-DES?
P10
How many bits does the key consist of in Simplified DES?
10-bits
What is the size of the output (ciphertext) block in Simplified DES?
8
Study Notes
- The lesson is about Symmetric Encryption, specifically Stream Ciphers and the Simplified DES algorithm.
- Stream Ciphers and Block Ciphers are two main types of encryption, Stream Ciphers encrypt bits individually, and Block Ciphers encrypt full blocks of bits.
- Stream Ciphers have simple encryption and decryption functions, which consist of additions modulo 2(XOR).
- Security for Stream Ciphers depends entirely on the key stream si, and it must be reproducible by both sender and receiver.
- Two main types of Stream Ciphers are Synchronous and Asynchronous. Synchronous Stream Cipher has a random key stream, while Asynchronous Stream Cipher depends on the ciphertext.
- Simplified DES is a symmetric encryption algorithm, with an 8-bit input(plaintext), 8-bit output(ciphertext), and a 10-bit key.
- Simplified DES has two rounds, and each round uses permutations and left shifts to generate round keys.
- The S-Box is a significant component of DES, used for substitutions. It functions as a matrix, and its output depends on the input's first and last bits.
- Simplified DES key generation uses specific permutations (P10 and P8) and the First and Final Permutations to encrypt and decrypt the data.
- The first permutation, Initial Permutation, mixes up the input's 8 bits.
- Simplified DES encryption includes the Initial Permutation, Round Function, and Switch Halves.
- Simplified DES decryption is similar to encryption, except it uses round keys in the opposite order.
Test your knowledge on symmetric encryption methods with this quiz. Topics covered include Stream Cipher vs. Block Cipher, encryption and decryption processes with Stream Ciphers, and S-DES cipher.
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