Resumen
This article focuses on the need for more secure emails. Secure messaging means the ability to provide data confidentiality and non-repudiation of origin services for email. It informs that the technologies to provide these services are cryptography in general, and data encryption, digital envelope and digital signature mechanisms in particular. It is felt that Web-based messaging has made the problem of how to securely store and use private keys more challenging. Consequently, the deployment of secure messaging has turned out to be slower than expected. It is agreed that no implementation will be free of bugs, and sooner or later some of these bugs will be found and exploited. Certified mail schemes based on trusted systems, which look fine in theory, have been questioned because their usefulness and security are often overestimated. The technologies and solutions that can be used to provide certified mail services on the Internet have been discussed in detail and among these approaches, the use of online trusted third party (TTPs) is found most appropriate.

Resumen
This article discusses firewall technology and the security protocols that have been proposed for the Internet, transport and application layer. A firewall builds a blockade between an internal network that is assumed to be secure and trusted, and another network, usually an external (inter)network, such as the Internet, that is not assumed to be secure and trusted. The general reasoning behind firewall usage is that without a firewall, a network's systems are more exposed to inherently insecure Internet protocols and corresponding services, such as probes and attacks from hosts elsewhere on the Internet. A firewall system usually consists of screening routers and proxy servers. A screening router is a multiported IP router that applies a set of rules to each incoming IP packet and decides whether it is to be forwarded on or not. A proxy server is a server process running on a firewall system to perform a specific TCP/IP function as a proxy on behalf of the network users. Firewall advocates consider firewalls as important additional safeguards because they aggregate security functions in a single point, simplifying installation, configuration and management.