9.5 Summary
In this chapter, we learned how public key cryptography can be used to generate digital signatures, an extremely important cryptographic mechanism providing message authenticity and non-repudiation. We covered both RSA-based signatures and signatures based on discrete logarithms. Finally, we looked into digital signature algorithms used in TLS 1.3 in more detail.
In the next chapter, we will learn how digital certificates and certification authorities are used to ensure the authenticity of Alice’s public key that Bob uses to securely communicate with Alice and verify her signatures. Without authenticity, attacker Eve could trick Bob into believing that her public key is that of Alice. As a result, Eve would be able to read any message Bob encrypts for Alice using the fake public key and generate a valid digital signature for any message apparently sent by Alice.