信息安全

What are the roles of Public and Private Key?

A user's private key is kept private and known only to the user. The user's public key is made available to others to use. The private key can be used to encrypt a signature that can be verified by anyone with the public key. Or the public key can be used to encrypt information that can only be decrypted by the possessor of the private key

What are three broad categories of applications of public-key cryptosystems?(公钥密码系统的三大类应用是什么？)

Encryption/decryption, Digital signature and Key exchange