Cryptography

• Plaintext Clear text that is readable.
• Ciphertext Data that is scrambled and unreadable.
• Cryptographic key A key is a piece of information that controls how the cryptographic algorithm functions. It can be used to control the transformation of plaintext to ciphertext or ciphertext to plaintext. As an example, the Caesar cipher uses a key that moves forward three characters to encrypt and back by three characters to decrypt.
• Substitution cipher A simple method of encryption in which units of plaintext are substituted with ciphertext according to a regular system. This could be by advancing one or more letters in the alphabet. The receiver deciphers the text by performing an inverse substitution.

Table FF.14. Encryption Advantages and Disadvantages

Type of Encryption	Advantage	Disadvantage
Symmetric	Faster than asymmetric	Key Distribution
		Only provides confidentiality
Asymmetric	Easy key exchange	Slower than symmetric
	Can provide confidentiality and authentication

• Digital certificates are used to prove your identity when performing electronic transactions.

Penetration Testing