目前企业面临的计算环境和过去有很大的变化，许多数据资源能够依靠网络来远程存取，而且越来越多的通讯依赖于公共网络公共网络（如 Internet），而这些环境并不保证实体间的安全通信，数据在传输过程可能被其它人读取或篡改。-currently facing the enterprise computing environment and past a great change, many data resources to be able to rely on remote network acce

恺撒密码是据传过去是恺撒大帝用来保护军情的加密系统。属于一种置换密码。-Caesar cipher is the Caesar is said in the past is the encryption used to protect military systems. Is a replacement password.