SHA1会产生一个160位的消息摘要。该算法经过加密专家多年来的发展和改进已日益完善，并被广泛使用。该算法的思想是接收一段明文，然后以一种不可逆的方式将它转换成一段（通常更小）密文，也可以简单的理解为取一串输入码（称为预映射或信息），并把它们转化为长度较短、位数固定的输出序列即散列值（也称为信息摘要或信息认证代码）的过程。(SHA1 generates a 160 bit message digest. The algorithm has been developed and improved by encryption experts for many years, and has been widely used. The idea of the algorithm is to receive a plaintext, then in an irreversible manner to convert it into a (usually smaller) ciphertext, also can be simply understood as taking a string of input code (called pre mapping or information), and put them into a short, fixed length digit output sequence the hash value (also known as the information or message authentication code) process)