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.
5. Anti-negation. As mentioned above, the digital signature can identify the identity, and it is impossible to pretend to be forged. Then, as long as the signed message is retained, it is like retaining the handwritten contract text, that is, retaining the evidence, and the signer cannot deny it.
6. Confidentiality (confidentiality). With confidentiality guarantee, interception attack is invalid. Handwritten documents (like text) are not confidential, and once the document is lost, the information in it is likely to be leaked.