A. According to the different encrypted information, digital signatures can be divided into three forms. B the necessary functions of digital signature include: no one else can copy the signature, and the signer cannot deny his signature. If there is a dispute between the two parties, an impartial third party is needed to confirm the authenticity of the signature. C methods to realize digital signature include user name/password, IC card authentication, dynamic password, biometric authentication, mobile digital certificate authentication, etc. D. Digital signature can guarantee the accuracy of information.

Digital signature (also known as public key digital signature) is a digital string that can only be generated by the sender of information, and others cannot forge it. This number string is also an effective proof of the authenticity of the information sent by the information sender.

It is a method to authenticate digital information, which is similar to the ordinary physical signature written on paper, but it is realized by using the technology in the field of public key encryption. A set of digital signatures usually defines two complementary operations, one for signing and the other for verification. Digital signature is the application of asymmetric key encryption technology and digital digest technology.

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The main functions of digital signature:

1, anti-counterfeiting (forgery). Only the signer knows the private key, so it is impossible for others to construct it correctly.

2, can identify the identity. Because the traditional manual signature is usually a direct meeting between the two parties, the identity can be clear. In the network environment, the receiver must be able to identify the identity claimed by the sender.

3. Tampering (preventing the integrity of information from being destroyed). For the traditional manual signature, if you want to sign a 200-page contract, do you just sign at the end of the contract? Or sign every page? If you only sign at the end of the contract, won't the other party steal a few pages? For digital signature, the signature and the original file have formed a mixed whole data, which can not be tampered with, thus ensuring the integrity of the data.

4. Anti-replay. For example, in daily life, A borrows money from B and writes an IOU to B. When A pays back the money, he must ask B for the IOU he wrote and tear it up. Otherwise, I'm afraid he'll have to ask A for money again with an iou.