What is a Feistel cipher?
Q: What is a Feistel cipher?
A: A Feistel cipher is a symmetric structure used in the construction of block ciphers, named after the German IBM cryptographer Horst Feistel. It is also commonly known as a Feistel network.
Q: What are some advantages of using a Feistel structure?
A: The main advantage of using a Feistel structure is that encryption and decryption operations are very similar, even identical in some cases, requiring only a reversal of the key schedule. This reduces the size of code or circuitry required to implement such a cipher by nearly half. Additionally, it's iterative nature makes implementing the cryptosystem in hardware easier.
Q: How does Claude Shannon describe "confusion and diffusion"?
A: Claude Shannon described "confusion and diffusion" as having large amounts of both elements present in order to make it difficult for an attacker to decipher an encrypted message.
Q: What techniques are used to create confusion and diffusion?
A: Confusion and diffusion are created through bit shuffling (often called permutation boxes or P-boxes) and simple non-linear functions (often called substitution boxes or S-boxes), as well as linear mixing (in the sense of modular algebra) using XOR. Bit shuffling creates the diffusion effect, while substitution is used for confusion.
Q: What type of cipher is a Feistel network?
A: A Feistel network is a type of product cipher which combines multiple rounds of repeated operations in order to encrypt data securely.
Q: Who developed this type of cryptography?
A: The Feistel structure was developed by German IBM cryptographer Horst Feistel.
Q: Is Data Encryption Standard based on this type of cryptography?
A: Yes, Data Encryption Standard uses this type of cryptography which utilizes the same principles outlined above for creating confusion and diffusion within an encrypted message.
