# Cryptography and Network Security

--Originally published at Blog | Cesar Arturo Gonzalez

What is Cryptography? Crypto == “hidden or secret” Graphy == “study of writing” So with this breakdown of words we can conclude that cryptography is the study of writing something hidden or secret. Cryptography has been around for centuries with the creation of the Caesars cipher created by Julius Caesar. Before modern times cryptography was used …

# Cryptography – Goals and Methods

--Originally published at TC2027 – Titel der Website

Cryptography is a word from the oldgreek language. „κρυπτός kryptós“ means hidden or secret and „γράφεινgráphein“ means writing.

Cryptography is originally the science of encryption of information. In simple we can say that cryptography is the encryption of data or messages of any kind.

### Goals

Modern cryptography has four main objects for protecting data, messages and / or transmission channels:

1. Confidentiality: It is to ensure that only the person who receives the message can read and read it.
2. Integrity: The receiver should be able to determine whether the data or the message was changed after its creation.
3. Authenticity: sender or originator of data or messages shall be identifiable or the recipient shall be able to verify who is the author.
4. Liability: The author shall not be able to deny that he is also the author of the data / message.

It should be noted, that that cryptographic methods do not necessarily always fulfill all four objectives. It always depends on the method, which target is followed. So, you have to estimate which method is implemented.

### Methods of Cryptography

Cryptography is divided into classical and modern procedures.

The classical procedures:

As long as no electronic computers were used for cryptography, encryption was always replaced by complete letters or groups of letters. Such procedures are now obsolete and unsafe.

• Transposition: The letters of the message are simply arranged differently. Example: Garden fence method or Skytale.
• Substitution: The letters of the message are replaced by a different letter or symbol. Monoalphabetic substitution and Polyalphabetic substitution. Examples include Caesar encryption and Vigenère encryption.

The modern procedures: