Cryptography

A systematic method of encrypting and decrypting messages or data. It is used in Computer Security by protecting Data Communications and Computer Networking.

Fully integrates CIA Triad, that must be achieved at all cost:

  • Confidentiality

  • Integrity

  • Availability

Cryptography is not limited to encrypting messages where Plain Text is converted into Cipher Text, but instead a broader concept that involves other processes necessary for securing messages such as Encryption, Hashing, and Authentication.

History

Paper Era

A "pen and ink" period. Codes in this era is relatively simple because messages had to be decoded by hand. Not very secure compared to modern standards.

Because of common cipher types Substitution Cipher and Transposition Cipher.

Mechanical Era

  • Enigma machine

Modern Era

Heavy reliance on mathematics and electronic computers.

  • One-Time Pad

  • Data Encryption Standard by National Institute for Standards in Technology

Confidentiality, Integrity, and Authenticity

Confidentiality

The goal is to prevent everyone except the intended entity from reading or tampering a message, known as Plain Text, by transforming the message into an encrypted message, known as a Cipher Text.

If the message is confidential, then the attacker does not know its contents.

Integrity

If the message has integrity, then the attacker cannot change its contents without being detected.

Authenticity

If the message has authenticity, then it’s guaranteed that the message was written by the entity who claims to have written it.

For implementations of techniques, see Cryptographic Systems.