It by proverbially used encrypt magnitude document and e-mail,in order to assure they security transmission in network ,or for document as figure underwrite ,according to prevent tamper and forge.

• 它被广泛地用来加密重要文件和电子邮件，以保证它们在网络上的安全传输，或为文件作数字签名，以防止篡改和伪造。