The subject classification of cryptography, what are the main categories of modern cryptography?

Cryptography is divided into two categories: cryptographic coding and cryptanalysis.

The main division of coding is the confidentiality system and the authentication system, which are divided into symmetric cryptography and asymmetric cryptography (also known as public key cryptography) from the strategy of using keys.

The design and use of cryptosystems in cryptanalysis must be based on: Kirkhoff's criterion. The algorithm must be exposed to protect the key.

The development of cryptography can be divided into three stages: classical cryptography, modern cryptography and modern cryptography.

Cryptography is an important means of confidentiality for the two parties to carry out special transformation of information according to the agreed rules. According to these rules, changing plaintext into ciphertext is called cryptographic transformation; Ciphertext is plaintext, which is called decryption transformation. In the early days, passwords only added and decrypted text or numbers, but with the development of communication technology, they can be added and declassified for voice, first companion images, data, etc.

Cryptography has been gradually developed in the practice of the struggle between coding and decipherment, and with the application of advanced science and technology, it has become a comprehensive cutting-edge technical science. It has extensive and close ties with linguistics, mathematics, electronics, acoustics, information theory, computer science, etc. Its real-world research results, especially the current methods of cipher compilation and decipherment used by various countries, are highly confidential.

Advances in computer technology have made data more accessible, and while this may provide huge advantages, it also has drawbacks. There are many threats to data, including theft and corruption. Cryptography (or cryptography) is a solution that can protect information from the risks associated with data storage and distribution.

This is not to say that the concept of encrypting data is new. Even before the digital age, people have been blocking messages to prevent unintentional audiences from reading them. But the increased use of computing devices has taken cryptoscience to a whole new level.

In short, cryptography is the science of hiding information. More specifically, modern cryptography uses mathematical theories and calculations to encrypt and decrypt data or guarantee the integrity and authenticity of information.

In the basic process of text encryption, plaintext (data that can be clearly understood) goes through an encryption process that turns it into ciphertext (unreadable). By doing so, it is guaranteed that the information sent can only be read by the person who has the specific decryption key.

By using specific encryption techniques, people can send sensitive data even over unsecured networks. The level of encryption will depend on the level of protection required for the data. For example, the type of security used for regular personal files, such as contacts, is different from the type of security used for cryptocurrency networks.

Understanding how cryptography works is essential to understanding its importance in the cryptocurrency system. Most blockchain systems, such as Bitcoin, use a specific set of cryptography that enables them to act as a decentralized public ledger through which digital transactions can be carried out in a very secure manner.

Modern cryptography encompasses a variety of fields of study, but some of the most relevant are those that deal with symmetric encryption, asymmetric encryption, hash functions, and digital signatures.

The Bitcoin protocol utilizes cryptographic proofs to secure the network and ensure the validity of every transaction. The digital signature guarantees that each user can only use the funds in their own wallet, and these funds cannot be used more than once. For example, if Alice sends 2 bitcoins to Bob, she creates a transaction, essentially a message confirming the addition of 2 bitcoins to Bob's wallet while taking the coins from Alice's wallet.

However, she can only do this by providing a digital signature.

Another important element of the Bitcoin protocol is the hashcash function, which defines the proof-of-work consensus mechanism and mining process (responsible for securing the network, validating transactions, and generating new coins). Hashcash uses a cryptographic function called SHA-256.

Cryptography is an important part of blockchain technology, so it is essential for any cryptocurrency. Cryptographic proofs applied to distributed networks have the ability to create trustless economic systems that have given rise to Bitcoin and other decentralized digital currencies.