# Cryptography

**Cryptography** (from Ancient Greek *κρυπτός* "hidden" + *γράφω* "I write") is the science of methods that allow you to provide:

- privacy (inability to get access to the information);
- data integrity (inability to bring changes to the data stored);
- authentication (authentication of authorship or other properties of an object);
- encryption (data encoding).

## History

Texts started to be encrypted back in the third millennium BC. Both in the Roman Empire and in the Middle Ages, important messages and military orders were encrypted.

For example, Julius Caesar used a very simple form of cryptography for his messages, known as a "shift cipher". Each letter in his text was replaced by the third letter in the alphabet. So instead of A, he wrote D. The recipient had to know the cipher code to read the right words.

During the Second World War, special devices were already used to encrypt messages — cryptography became more complicated. It took the military several years to unravel the keys and read the messages of other countries.

Today, cryptography is able to guarantee the security of information much more reliably, and the ciphers that Caesar once used can now be solved in a couple of seconds.

## Symmetric and asymmetric encryption

In modern cryptography, symmetric and asymmetric encryption are distinguished.

**Symmetric encryption** means that both parties involved in data exchange have exactly the same keys for encrypting and decrypting data.

In symmetric encryption, senders and recipients use the same key — as in Caesar's encrypted letters. For this, the key must be known to both parties, respectively, one transmits it to the other in unencrypted form.

**Asymmetric encryption** involves using two different keys in a pair — public and secret (private). In this method, the keys work in pairs: if the data is encrypted with a public key, then they can only be decrypted with the corresponding secret key, and vice versa — if the data is encrypted with a secret key, then they can only be decrypted with the corresponding public key. It is impossible to use a public key from one pair and a secret key from another, since each pair of asymmetric keys is connected by mathematical dependencies.

**Cryptography proposes many different methods of data encryption. Many of them are based on complex mathematical structures such as elliptic curves, rings, and finite bodies.**

## Cryptanarchism

**Cryptanarchism** is a philosophy that calls for the use of cryptography to protect privacy and personal freedom.

The term first appeared in 1993 in an article by Steven Levy, in which he talked about the brewing movement of cipher banks and the concentration of data in the hands of large corporations.

Cryptanarchists create virtual communities where each participant remains anonymous until he wants to reveal himself.

## Cipherpunks

Cipherpunks are an informal group of people interested in cryptography and interested in maintaining anonymity. Initially, cipherpunks communicated through a network of anonymous remailers, and the goal of this group was to achieve anonymity and security through the active use of cryptography.

The term "cipherpunk" was first used by Jude Milhon as a pun on a group of cryptanarchists.