Reference no: EM133236632

Instructions:

Block cipher: n-bit block cipher takes n-plaintext and produces n-bit ciphertext.

Assuming that the encryption algorithm uses a symmetric key and is reversible (each plain text block produces unique ciphertext block), please answer the following questions:

1. Show possible different plaintext blocks for a 2-bit block cipher?
2. Show all possible transformations for a 2-bit block cipher? (for all possible different plaintext blocks)
3. What is the chance to have exactly one output the same as input considering all possible transformations for a 2-bit block cipher?
4. How many possible different plaintext blocks are there for n-bit block cipher?
5. What is the total number of transformations for n-bit block cipher? (no. of possible keys)?
6. What is the chance to have exactly one output the same as input considering all possible transformations for a n-bit block cipher? Show your calculations.
7. Explain the relation of key length and the brute force attack to break the chipper?