# What is encryption

#encryption

• What does encryption mean

• Why encryption

• Cryptography and arithmetic

• How coding is done

• What are the functions of encryption

• Cryptoanalysis or hacking

• What methods of cryptanalysis

## What does encryption mean

The word cryptography is a generic term that designates the set of techniques that allow code that is, make them unintelligible without specific action. The verb encrypt it is sometimes used, but we prefer to use the verb codify.

## Why encryption

Man has always felt the need to conceal information, even before the appearance of the first computers and calculating machines.

Since its creation, the Internet has evolved so much that it has become an essential communication tool. However, this communication increasingly puts at stake strategic problems linked to the activity of companies on the Web. Transactions made over the network can be intercepted, even more so since the laws have difficulty imposing themselves on the Internet. In this way, it is necessary to guarantee the security of this information, and it is the encryption that takes care of that.

## Cryptography and arithmetic

Cryptography is essentially based on arithmetic. In the case of a text, it is a question of transforming the letters that make up the message into a succession of numbers (in the form of bits, in the case of information technology, since the functioning of the PCs is based on the binary code) and then make calculations with these numbers to change them so that they are incomprehensible.

The result of this change (the coded message) is called cryptogram as opposed to the initial message, called normal. On the other hand, it is also necessary to ensure that the recipient of the message understands its content when he receives it. Encoding a message in a way that makes it secret is called codification and the opposite method, which is to find the original message, decoding:

## How coding is done

In general, coding is done with the help of a encryption keyand, in turn, decoding requires a decryption key. We distinguish, then, two types of keys, the symmetric keys, also called secret key encodings, which are used for both encryption and decryption and asymmetric keys, used in cases of asymmetric encryption (also called public key encryption). In this case, we use different keys for encryption and decryption.

## What are the functions of encryption

Encryption is traditionally used to conceal messages from certain users. Today, this use is of even greater interest, as communications via the Internet circulate in infrastructures where reliability and confidentiality cannot be guaranteed. Today, encryption serves not only to preserve the confidentiality of data, but also to guarantee its integrity and authenticity.

## Cryptoanalysis or hacking

We call cryptanalysis the reconstruction of a message encoded in its original format, with the help of mathematical methods. Thus, any cryptosystem must necessarily be resistant to cryptanalysis methods. When a cryptanalysis method allows decrypting an encrypted message with the help of a cryptosystem, the encryption algorithm is said to have ‘been broken’.

Decrypting is the attempt to illegitimately decrypt a message (whether the decryption key is known to the hacker or not). When the decryption key is known to the hacker, there is talk of cryptanalysis

Cryptology it is science that studies the scientific aspects of these techniques, that is, it encompasses cryptography and cryptanalysis.

## What methods of cryptanalysis

Typically, we distinguish four methods of cryptanalysis: one attack on encoded text only, which consists of finding the decryption key for one or more encrypted messages; one known plaintext attack, which consists of finding the decryption key using one or more encrypted messages, knowing the corresponding normal text; one attack on the chosen normal text, which consists of finding the decryption key from one or more encrypted texts, the hacker being able to generate them from normal texts; one attack on the chosen encoded text, which consists of finding the decryption key from one or more encrypted texts, with the hacker being able to generate them from normal texts.