Cryptology can be divided into three types: stream cipher, symmetrical cipher (block cipher) and asymmetrical cipher (public-key cipher) and it is the key technology of information security.

• 密码算法是信息安全技术的核心，大概可以分为三类：序列密码，对称密码（分组密码），以及非对称密码（公钥制密码）。