Lesson 1: Welcome to the world of encrypted blockchain.

What is encryption anyway?

Encryption refers to the overall mechanism used to exchange information that you do not want a third party to know.

Encryption has become commonplace with the spread of the Internet, but it was used in various situations even before the advent of the Internet.

For example, in the exchange of letters, encryption can be used to convert letters into characters that can only be understood by the parties concerned, or to send special signals.

Decryption is the process of restoring the original text (plain text) from an encrypted exchange.

In the digital world, it is also possible to encrypt image files other than text.

Let's get to know some of the cryptographic techniques

As computers have evolved and the Internet has become more widespread, the demand for cryptography has increased dramatically.

Let's touch on some of the cryptographic techniques in detail here.

Enigma Cryptography

Enigma refers to a cryptographic machine developed by Nazi Germany during World War II.

When you input plain text into Enigma, the cipher text is output.

Conversely, when ciphertext is input into Enigma, plaintext is output.

Encryption and decryption with Enigma uses a combination pattern of multiple rotors, the order in which the rotors are installed, the initial settings of the scales, and the plugboard wiring.

If even one of these settings differs, different results will be output even if the same plaintext or ciphertext is input, so that only people who know the rotor settings can obtain information from each other.

Common key cryptography

Along with public-key cryptography, symmetric-key cryptography is a typical example of modern cryptography.

Public key cryptography uses different keys for encryption and decryption, while symmetric key cryptography uses the same key for encryption and decryption.

Imagine a front door or a locked drawer. (You use the same key to close and open the door, right?)

Since common-key cryptography is faster to process than public-key cryptography, it is increasingly being used in Internet communication situations such as SSL/TLS.

Let's use Alice and Bob

When learning about blockchain and cryptography, not only PoL, people like "Alice" and "Bob" often appear.

In fact, when explaining cryptography, it is customary to use names like "Alice" and "Bob" as hypothetical characters.