Digital signature can solve the problem that the signer denies the signature or others forge the signature in handwritten signature. Digital signature has the following functions:

The receiver can confirm the signature of the sender, but it cannot forge it;

After the sender sends the signature information, it can no longer deny it;

The receiver cannot deny the received signature information;

Once there is a dispute between the sender and the receiver, the arbitrator can have sufficient evidence to make a judgment.

Digital signature includes digital signature based on public key cryptosystem and digital signature based on private key cryptosystem.