ABSTRACT
We have observed that public-key cryptosystems have the advantage over secretkey cryptosystems that a secure channel is not needed to exchange a key. But, unfortunately, most public-key cryptosystems (e.g., RSA) are much slower than secret-key systems (e.g., AES). So, in practice, secret-key systems are usually used to encrypt “long” messages. But then we come back to the problem of key establishment, the topic of this and the next chapter.
