ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 88)

A message to be sent can be signed using various techniques. One of them uses

public-key algorithms but hash functions are mostly used.

Use of Public Keys

In addition to confidentiality, public-key cryptography has the advantage of allow-

ing message sender authentications. The electronic signature is the second use for

public keys.

For authentication purposes, the sender uses his or her private key to sign a mes-

sage. The receiver uses the public key of the sender to make sure that the message

has been signed. In this way, the receiver can check that the data has not been modi-

fied and that it has been sent by the sender.

Figure 4.7 illustrates how public-key authentication operates.

Although messages can actually be signed using this technique, confidentiality

is not guaranteed, as the encrypted message and the public key may be intercepted

and the data contents could be accessed.

The Hash Function

The hash function provides an alternative to the use of signatures using public and

private keys.

The purpose of the hash function is to create a kind of digital digest of the mes-

sage that must be sent. The size of this digest is very small compared with that of the

message. Another characteristic of this technique is that it is very difficult, or even

impossible, to find the original message again from its digest. This ensures the

authenticity and integrity of the message sent.

Overview of Network Security Issues 69

Figure 4.7 Public-key authentication

1 2 ... 83 84 85 86 87 88 89 90 91 92 93 ... 348 349

Sin comentarios

ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 88