4
Encryption technology
Reference
“Encryption” is the process of converting plaintext (source text) into different data. Decryption is the process of returning the encrypted data to
plaintext. A key is required for both encryption and decryption.
Approaches for encryption include “common key cryptography” and
“public key cryptography,” which are distinguished by their respective
use of keys.
The sender sends the ciphertext that was encrypted using the common key.
Plaintext
Test
Replace with next
character in alphabet
Encryption
Ciphertext
Uftu
Replace with preceding
character in alphabet
Encryption
Plaintext
Test
Reference
DES
Abbreviation for “Data Encryption
Standard.”
Technology element
Sender generates a common key, and confidentially transmits the common
key to the recipient.
Encryption by “replacing each character
with the next character” in the alphabet.
Chapter 9
(1)Common key cryptography (Secret key cryptography)
“Common key cryptography” is an approach that uses the same key
(common key) for encryption and decryption. The common key must be
confidentially shared since it is not possible to prevent interception or falsification if the key becomes known to a third party.
For this reason, common key cryptography is also called “secret key
cryptography” and “shared key cryptography.” The “DES (Data Encryption Standard)” is a commonly used method of common key cryptography.
The framework and characteristics of communications using common key
cryptography are summarized below.
Encryption example
The recipient decrypts the ciphertext using the common key.
●Characteristics
• Fast encryption and decryption s