X.509

　　X.509 describes two levels of Authentication, simple authentication, based on use of a password to verify user identity, and strong authentication, using credentials created by cryptographic methods. The standard recommends that only strong authentication should be used as the basis of providing secure services. Public-Key Cryptography is used for strong authentication, but X.509 is not dependent on the use of a particular cryptographic Algorithm, though two users wishing to authenticate must support the same Algorithm.

　　

　　X.509描述了两个级别的认证，简单认证和强认证，简单认证基于使用一个密码验证用户身份，强认证使用加密方法创建的数字证书。标准建议只有强认证能够作为提供安全服务的基础。强认证使用公钥加密方式，但是X.509并不依赖于使用特殊加密算法，尽管两个用户希望认证必须支持同一算法。