Type of cryptanalytic attacks on encrypted messages

1. What are the essential ingredients of a symmetric encryption scheme?

2. What is cryptanalysis? Summarize the various types of cryptanalytic attacks on encrypted messages.

3. List the parameters of a symmetric block cipher for greater security.

4. What is a block cipher? Name the important symmetric block ciphers.

1. Describe the data encryption algorithm for 64-bit length plaintext and 56-bit length key.

2. Why is the middle portion of triple DES a decryption rather than an encryption?

3. What are the advantages and disadvantages of triple DES?

4. Why is it not desirable to reuse a key in encryption using a stream cipher?