Simply put, it is some data attached to the data unit, or the cryptographic transformation of the data unit. After making these changes, the data receiver can confirm the integrity of the data.

The realization of this technology is digital signature.

In order to ensure that the signature on the electronic document can be confirmed as the true will of the parties and prevent it from being stolen or tampered with, certain technical means are needed, usually using the technology in the field of public key encryption.