When you apply a digital signature to a document, a kind of checksum is computed from the document's content plus your personal key. The checksum and your public key are stored together with the document.
在对某文档应用数字签名时，会从该文档的内容和您的个人密钥计算出一种校验和。该校验和与您的公钥随该文档一起存储。