Public key cryptography can not only achieve digital signature, but also be safe and convenient. Compared with traditional cryptography, it is easier to achieve written signature, so public key cryptography is very popular!

Because there are many forms of digital signature, such as universal digital signature, arbitration digital signature, undeniable signature, blind signature, group signature, threshold signature and so on. Here I use the general method of digital signature to answer!

(1) Party A and Party B publicly register their own public key Ke and store it in the public key database PKDB of the management center, which will be used as one of the data for the other party and the arbitrator to verify their signatures.

(2)A signs plaintext data M with its own secret decryption key Kda to get a signature S, then A queries PKDB to find B's public encryption key Kea, and uses Kea to re-encrypt S to get ciphertext C..

(3) Finally, A sends C to B, leaving S and C as the bottom.