Security

Encryption fundamentals

• Encryption can be used as a routine procedure when storing data within a
  computing system. However, the focus in this chapter is on the use of encryption when transmitting data over a network.
  

• There are three issues that will be considered in this chapter:
  • is the encryption algorithm sufficiently robust to prevent the encrypted data being decrypted by some unauthorized third-party?
  • how is it possible to ensure that a secret key remains secret?
  • how can the receiver of a communication be sure who sent the communication?

Plaintext:

data before encryption

Ciphertext:

the result of applying an encryption algorithm to plaintext, also known as encrypted or encoded information

Key:

a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data.
Encryption:

• the process of encoding data or message so that it can not be understood by others

Security concerns

• There are a number of security concerns relating to a transmission.
  Confidentiality: Only the intended recipient should be able to decrypt the ciphertext.
  
  • Authenticity: The receiver must be certain who sent the ciphertext.
  • Integrity: The ciphertext must not be modified during transmission.
  • Non-repudiation: Neither sender nor receiver should be able to deny involvement in the transmission.
  • Availability: Nothing should happen to prevent the receiver from receiving the transmission.

• This chapter will consider only confidentiality, authenticity and integrity.
  • The confidentiality concern arises because a message could be intercepted during transmission and the contents read by an unauthorized person.
  • The concern about integrity reflects the fact that the transmission might be interfered with deliberately but also that there might be accidental corruption of the data during transmission.