What is a digital signature? (1)

1.

Bob has two keys: one is the public key and the other is the private key.

2.

Bob sent the public key to his friends, who are Parti, Doug, and Susan.

3.

Susan wants to write a confidential letter to Bob. After writing it, She encrypted it with Bob's public key to achieve the effect of confidentiality.

4.

After Bob received the email, He decrypted it with the private key and saw the content of the email. It should be emphasized that, as long as Bob's private key is not disclosed, this letter is safe and cannot be decrypted even if it falls into the hands of others.

5.

Bob replied to Susan and decided to adopt "Digital Signature ". He uses the Hash function to generate the digest of the letter ).