RSA asymmetric encryption

Password and encryption

Traditional cryptographic: 
    encryption algorithm is a secret 
modern cryptography: encryption algorithm is disclosed; secret keys (secret key is used for encryption) 
    symmetric encryption: encryption and decryption using a secret key 
    asymmetric cryptography: Use two secret keys, one for encryption and one for decryption

RSA encryption is used for information transmission, hash map database stored with the password, md5 or sha

Asymmetric encryption

Using two keys, a public key and private key, public key encryption to decrypt the private key, private key encryption or public key to decrypt. 
For example RSA encryption algorithm used: https protocol, Linux remote login without a password. 
    Public Key: used to encrypt, are public 
    private key: used to decrypt, it is private