主要适用于数字签名标准（Digital Signature Standard DSS）里面定义的数字签名算法（Digital Signature Algorithm DSA）。对于长度小于2^64位的消息，SHA1会产生一个160位的消息摘要。当接收到消息的时候，这个消息摘要可以用来验证数据的完整性。-The main standard for digital signatures (Digital Signature Standard DSS) which defines the Digital Signature Algorithm (Digital Signature Algorithm DSA). The length is less than 2 ^ 64 bits of information, SHA1 produces a 160-bit message digest. When the received message when the message digest can be used to verify data integrity.