Describe the steps for a user named Mike to send a digitally signed message to a user named Sophie.

What will be an ideal response?

The steps for Mike to send a digitally signed message to Sophie are:

1. After creating a memo, Mike generates a digest on it.

2. Mike then encrypts the digest with his private key. This encrypted digest is the digital signature for the memo.

3. Mike sends both the memo and the digital signature to Sophie.

4. When Sophie receives them, she decrypts the digital signature using Mike's public key, revealing the digest. If she cannot decrypt the digital signature, then she knows that it did not come from Mike (because only Mike's public key is able to decrypt the digest generated with his private key).

5. Sophie then hashes the memo with the same hash algorithm Mike used and compares the result to the digest she received from Mike. If they are equal, Sophie can be confident that the message has not changed since he signed it. If the digests are not equal, Sophie will know the message has changed since it was signed.