Block Chain Cryptography (i): Cryptography Basics and concepts

First, the concept

This paper mainly introduces some concepts of asymmetric encryption.

Public key, private key: can be encrypted or decrypted, paired. Generally speaking, the private key used for decryption and signature, is for their own use. The public key is made public and used to encrypt and verify the signature, which is for others.
Signature: Content->hash->digest-> private key encryption-> signature
Verification: Use the public key to decrypt the signature to get a summary, and then the original file through the hash to get a summary, and the decryption of the summary to compare.
Certificate: A digital certificate is a certificate certification authority (CA) after the authenticity of the certificate applicant authentication, a digital file is formed by using the root certificate of the CA to sign some basic information about the applicant and the applicant's public key (equivalent to the official seal of the issuing authority, that is, the CA's private key is encrypted). Ii. Illustrative examples

Assuming that a writes a letter to B, the letter will contain three parts as follows:
1, the content of the letter itself
2, A's digital signature
3, A's digital certificate

Then B receives this letter, B would like to know that this is a sent from a. Has the letter been tampered with in the course of the transmission or is it complete? It is only when B confirms clearly that the content of the letter is reliable.
b then use the public key provided by the CA to unlock the digital certificate, according to get: such as a personal information, determine is a sent over, get a public key and so on.

Then, using a's public key to unlock A's digital signature can get a summary of the contents of the letter itself. The contents of the letter are then hashed and a summary is compared to two summaries, if the contents of the same description letter are not tampered with.