RSA encryption colloquial explanation

1. The problem of prime factorization of large numbers

RSA The encryption algorithm adopts the problem of large number prime factor decomposition , So as to prevent the leakage of secrets . Prime factorization of large numbers refers to , Give you a big number （ The number of thousands is even greater ）, You need to decompose this number into the product of two prime numbers .

We can easily multiply the product of two prime numbers to obtain large numbers , But it is difficult to decompose the product of two prime numbers from large numbers .

such as ：

Here is a big number for you , It's hard for you to decompose it into the product of two prime numbers .

2.RSA The algorithm is an asymmetric encryption algorithm

Asymmetric encryption algorithm

It means that different keys are used for encryption and decryption , Encryption uses the public key , Decryption with private key .

Symmetric encryption algorithm

It means that the same key is used for encryption and decryption .

3.RSA Illustration of encryption and decryption process

A Need to send file to B, It can be divided into 5 A process ：
（1）B Combine a set of public and private keys in some way （ Public keys are similar to large numbers , Private keys are similar to prime factors of large numbers ）
（2）B Send the public key to A
（3）A Encrypt the file with the public key
（4）A Send the encrypted file to B
（5）B Decrypt the encrypted file with the private key , Get the original document .

In the process , The thief can only get the public key and the encrypted file , It is difficult for the secret thief to decompose the private key from the public key , So it is very difficult for the secret stealer to get the original document .