Suppose that Alice signs the message M I love you and then

Suppose that Alice signs the message M = \"I love you\" and then encrypts it with Bob\'s public key before sending it to Bob. As discussed in the text, Bob can decrypt this to obtain the signed message and then encrypt the signed message with, say, Charlie\'s public key and forward the resulting cipher text to Charlie. Could Alice prevent this \"attack\" by using symmetric key cryptography?

Solution

If Bob can read the data, he can do whatever he likes to do with that piece of information and no one can do anything about it. Alice can not do anything to prevent this.