Express Learning: Cryptography and Network Security

3

Symmetric-key Ciphers

1. Define a symmetric-key cipher.

Ans.: A cipher (a combination of encryption and decryption algorithms) that uses the same key for both encryption and decryption is referred to as a symmetric-key cipher.

2. Explain the symmetric cipher model.             Or             Explain the conventional encryption model.

Ans.: A symmetric cipher model (also referred to as a conventional encryption model) consists of various components (see Figure 3.1), which are described as follows:

Figure 3.1 Symmetric Cipher Model

(a) Plaintext: This refers to the original message that the sender wishes to send securely. It is an input to ...