Digital certificate adopts public key system, that is, a pair of matching keys are used for encryption and decryption. Each user sets a specific private key that only belongs to himself, and uses it to decrypt and sign; At the same time, a public key is set to be made public by myself and enjoyed by a group of users for encryption and signature verification. When sending confidential documents, the sender uses the public key of the receiver to encrypt the data, and the receiver uses its own private key to decrypt the data, so that the information can reach the destination safely and correctly.
And through digital means to ensure that the encryption process is an irreversible process, that is, only the private key can be used to decrypt. If others want to crack it, it will take at least thousands of years according to the current level of computer technology.
Therefore, in a sense, electronic documents signed with electronic signatures are much safer than written documents signed and sealed.