Cryptography, the study of compiling and breaking codes, the purpose of which is to hide information and transmit it, originated in the war.

History of cryptography

  • Classical cryptography: Before 1949 cryptography was an art form
  • Modern cryptography: cryptography became a science in 1949 ~ 1975
  • Modern cryptography: the new direction of cryptography after 1976 — key cryptography and public key cryptography developed together

What passwords do

  • * Confidentiality – * confirm the confidentiality of information, not to be stolen (classical and modern passwords)

  • ** Integrity – ** Ensure that the message you receive has not been tampered with (classical, modern passwords)

  • ** Repudiation resistance — ** Evidence to ensure that the transaction is not repudiated (Hyundai)

  • ** Identification and authorization — ** Confirms the identity of the other party and ensures that it does not exceed its authority (Hyundai)

Classical encryption

art

In the early stage, the spread of the password came from painting, stamping and other artistic products.

Substitution method

In the substitution method, characters in plain text are replaced with other characters. If a single table is used to replace each character during the whole encryption process, the password is replaced with a single table. Similarly, if different tables are used to replace each character during the whole encryption process, the password is replaced with multiple tables.

Shifting method

In addition to substitution, the shift method is also popular. According to the password rules in the figure above, each character of “authing” needs to be moved 12 Spaces to the right, namely: mgFtuzs.

Caesar password

A cipher used by Julius Caesar, an ancient Roman general, juxtaposed two lines of text and then substituted. For example, in the following table, OHARA can be replaced with LEXOX.

Modern encryption

Enig code machine

Essence: shift, replace.

Engima, which means enigma in German, and we have this word in English now, meaning enigma and something mysterious.

The Enig code machine is the product of the application of cryptography, which directly contributed to the beginning of information computing civilization. It is no exaggeration to say that if there were no Enig code machine, it would still be in the era of personal computer or pre-Internet. Then the Internet and BAT opportunities are also for the next generation.

Modern encryption

MD5

A widely used cryptographic hash function that produces a 128-bit hash value to ensure complete and consistent transmission of information.

Symmetric encryption

Symmetric encryption uses the encryption method of a single-key cryptosystem. The same key can be used to encrypt and decrypt information at the same time. This encryption method is called symmetric encryption, also known as single-key encryption.

Asymmetric encryption

Unlike symmetric encryption algorithms, asymmetric encryption algorithms require two keys: a public key and a private key. The public key and private key are a pair. If the public key is used to encrypt data, only the corresponding private key can be used to decrypt data.

Symmetric encryption and asymmetric encryption have their own advantages and disadvantages:

  • Symmetric encryption algorithm: fast encryption/decryption, but serious key distribution problems

  • Asymmetric cryptography: slow encryption/decryption, but no key distribution problem one

Passwords: the cornerstone of security

Nowadays, passwords have become the core technology and basic support to ensure network security. It has become a social consensus to use password technology to protect network and information security, build a network security and trust system based on passwords, and maintain a new order of network security.