Legally speaking, a signature has two main proving functions: identifying the identity of the signer and indicating the signer's approval of the contents of the document. In addition, with the development of forensic technology, based on the fading principle, we can identify the time when the document was made and the time when the seal handwriting was formed, and know the approximate signing time of the document. At the same time, changes to written documents will leave traces and be easily noticed. The above is the evidence function that a written signing document can play.

Handwritten signature has two main proving functions and one additional proving function. If electronic signature technology is to replace handwritten signature, it must have the following three functions:

1. Identify the signer;

2. After the electronic signature of the relevant data message, the data message must have the function of preventing others from tampering with the file, regardless of whether the file is stored in the memory or transmitted in the network;

3. It can prove the signing time of electronic signature. As long as the proof function of handwritten signature can be replaced by technical means, electronic signature technology can be applied to the signing of data messages, and its evidential effect can be recognized by law.

Electronic signature is an electronic technical means, which can identify the true identities of both parties in electronic documents, ensure the security, authenticity and non-repudiation of transactions, and play the same role as handwritten signature or seal.