Because a digital certificate (digital certificate: Attachment for a file, macro project, or e-mail message that vouches for authenticity, provides secure encryption, or supplies a verifiable signature.

• 由于自己创建的数字证书(数字证书:文件、宏项目或电子邮件的附件,它证明上述各项的真实性、提供安全的加密或提供可验证的签名。