Chapter 2

Question 1

is the process of converting plain text, which can be seen by anyone, into an incomprehensible form of ciphertext. is the process of converting ciphertext back into plaintext, so that it can be understood.

Answer 1

Encryption

Question 2

The mathematical function used in these conversion process is called

Answer 2

cryptographic algorithm

Question 3

is the process of converting ciphertext back into plaintext, so that it can be understood.

Answer 3

Decryption

Question 4

It can be divided into the symmetric key cryptosystem, in which encryption key and the decryption key are the same, and public key cryptosystem, in which the encryption key and the decryption key are different, depending on whether the encryption key and the decryption are the same.

Answer 4

Cryptographic techniques

Question 5

It refers to the protocols that use cryptographic techniques. As a protocol means a series of finite phases in which is more than 2 persons participate to achieve a certain purpose, the cryptographic protocol should prevent repudiation by a participant, or a third party, to ensure a certain purpose of the concerned cryptographic protocol (authentication, confidentiality, integrity, and non-repudiation, etc.) as well as the meaning of each message.

Answer 5

Cryptographic protocols

Question 6

All the elements that are needed for a series of encryption and decryption processes are called

Answer 6

Cryptosystem

Question 7

The secret key encryption algorithm has the advantage that the encryption key used for encryption and the decryption key used for decryption are the same. And that the length od the key may be short, and the speed of encryption and decryption operations is fast.

Answer 7

Private key cryptographic algorithm

Question 8

It performs the encryption and decryption process, using cryptographic algorithm that transforms fixed size input blocks into fixed size output blocks using a secret key. The block cipher algorithm includes Feistel Network, Data Encryption Standard(DES), Advanced Encryption Standard (AES), International Data Encryption Algorithm (IDEA), SEED, and ARIA.

Answer 8

Block Cipher Algorithm

Question 9

A stream cipher is a method developed mainly in Europe. Ciphertext is created by bitwise XOR operation of the plaintext bit string, and bit string of the key. RC$ is representative stream cipher, and there are other algorithm, such as A5/1 and A5/2.

Answer 9

Stream Cipher Algorithm

Question 10

A mathematical function that outputs a short hash value (hash code) with a fixed length from random data of various.

Answer 10

Hash Function