# QTS_Unit 3_Question 2

Here are some other examples of message encryption and decryption:

**Classical Coding**

Classical coding works on an alphabetical basis, done either by hand or by some simple mechanical machine. Classical encryption is vulnerable to ciphertext attacks, or without knowing the specifics of the encryption system using frequency analysis tools.

**One-Way Encryption****(HASH)**

This method is used to encode things that do not need to be translated into the original. For example, when you log into a Website, the password you enter is converted into a long string of characters by something called a hash function.

Currently, the two most commonly used hash function algorithms are MD5 and SHA.

**Symmetrical Coding (SYMMETRIC KEY ENCRYPTION)**

Symmetric encryption is a key-based security method. The key is the key so that the algorithm can look at it and know the way to encrypt and decrypt data. In symmetric encryption, the key for encryption and decryption is the same, so it is called symmetric. According to some documents, symmetric encryption is the most commonly used solution today.

**Asymmetrical coding (PUBLIC KEY ENCRYPTION)**

If above, the encryption key and the decryption key are the same, then with the asymmetric method, the two keys are completely different. To distinguish between the two, the encryption key is called the public key, and the decryption key is the private key.

Public, as the name suggests, is “public” and can be used to encrypt data by anyone. However, only the person in the possession of the private key can decrypt the data for viewing.

The disadvantage of asymmetric encryption is that the decoding speed is slower than symmetric encryption, which means we have to spend more CPU processing power, have to wait longer, leading to high “cost”. than. How much longer depends on the encryption algorithm, encryption method and key.

That’s why at present, few people encrypt a file with an asymmetric method. Instead, they use an asymmetric method to encrypt the same key used in symmetric encryption (or generate that key by combining the sender and receiver’s public and private keys).

**TRANSFORM CODE**– adjacent characters are swapped.**EXPAND CODE**– additional characters are added between data characters.**COMPRESSION ENCODING**– characters in the data are deleted and stored elsewhere.

Refer at: https://viblo.asia/p/tim-hieu-ma-hoa-giai-ma-cac-thuat-toan-ma-hoa-phan-1-YWOZrjMpZQ0

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