Because a signature alone does not guarantee that the sender is who they say they are, the message transmission is vulnerable to techniques such as replay attacks by some malicious third party.

因为仅仅有数字签名并无法保证发送方就是他们自己所声称的人，消息的传输很容易遭受恶意第三方诸如再现攻击等技术的袭击。