Lab 4 - Cryptography Extended

Cryptography Extended

In this lab we learn that cryptography algorithm can be classified into two categories, symmetric and asymmetric. Symmetric is using same key to encrypted and decrypted the plain text whereas asymmetric using different key to encrypted and decrypted plain text.

Symmetric can divide to:

1. Substitute encryption

· In substitute encryption, character in plain text being substitute with another character. Each character can be substitute with one character or multiple characters. Caesar cipher is example of substitute with one character and Vigenere cipher is example of substitute with multiple characters. Caesar cipher is easy to break by using brute force attack; an attacker can easily try every combinations of character to break the code as the numbers of possibility is 26. Vigenere cipher is an improvement from Caesar cipher.

2. Transposition encryption

· This method is change the location of characters or reordering the character in plain text. The first character in plain text might be placed on fifth position and fifth character might be placed in another location in plain text.

Asymmetric encryption involves two key in encryption and decryption. The encryption key is called public key and decryption key called private or secret key. These algorithms allow the public key to be publicized, which means people with the public key can encrypt the plain text and the proper recipient with the private key can decrypt the plain text. To produce this to key used RSA algorithm. RSA is founded by Rivest, Shamir and Adleman of MIT in 1977.