Information Security: Principles and Practices 2nd Edition by Jim Breithaupt, Mark S. Merkow

Exercise 17

Which of the following statements related to a private key cryp- tosystem is false?

A. The encryption key should be secure.

B. Data Encryption Standard (DES) is a typical private key eryptosystem.

C. The key used for decryption is known to the sender.

D. Two different keys are used for the encryption and decryption.

Step 1 of 2

Private Key Cryptosystem

Cryptosystems are of two types: public key and private key cryptosystems. The former is also known as asymmetric key cryptosystem and the latter is also known as symmetric key cryptosystem.

The private key cryptosystem uses a single key which is shared between both the sender and the receiver. The same key is used to encrypt and decrypt the message.

Thus, the statement about private key cryptosystem that is false is that two keys are used for encryption and decryption.

Therefore, the correct false option is,

D. Two different keys are used for the encryption and decryption.