RAS: Remote Access Service: Microsoft's utility for connecting computers over dial-up lines or for connecting laptops.

RC4: A cipher designed by RSA Data Security, Inc., which can accept keys of arbitrary length, and is essentially a pseudo random number generator with the output of the generator being XORed with the data stream to produce the encrypted data. For this reason, it is very important that the same RC4 key never be used to encrypt two different data streams. The algorithm is very fast, its security is unknown, but breaking it does not seem trivial either.

Registry: The database in which configuration information is registered. This database takes the place of most configuration and initialization files for the system and new applications.

Registration Authority: An entity which registers Applicants for Keys and Certificates. RAs may have other functions or obligations specified in the relevant CP. The contact details for each RA (including physical address, postal address, email and facsimile) will be published in the Repository.

Remote Access: The hookup of a remote computing device via communication lines such as ordinary phone lines or wide area networks to access network applications and information.

Remote Presentation Services Protocol: A protocol is a set of rules and procedures for exchanging data between computers on a network. A remote presentation services protocol transfers user interface, keystrokes, and mouse movements between a server and client.

Replicator: Any program that acts to produce copies of itself -- examples include, a worm, a fork bomb or virus. It is even claimed by some that UNIX and C are the symbiotic halves of an extremely successful replicator.

Resident Extension: In PC-DOS, programs can install a part of themselves in memory, and this part can remain active after the program has ended. This memory resident part is called a resident extension, since it is effectively an extension to the operating system. Many viruses install themselves as resident extensions, which will then look for files to infect when those files are accessed or executed later.

Revocation: For several reasons a certificate may need to be revoked, i.e. need to be declared invalid prior to the expiration of the validity period. Circumstances which might cause a certificate revocation could be, e.g., if the holder's name changes, if association between subject and CA changes, if the secret key is compromised or is suspected to be compromised, or if the holder misuses his certificate.

Risk Analysis: The analysis of an organization's information resources, existing controls and computer system vulnerabilities. It establishes a potential level of monetary damage and/or other assets.

Rogue Program: Any program intended to damage programs or data. Encompasses malicious Trojan horses.

Root Authority: (Also: Root CA) Certification authority that is not certified by any other CA. Its certificate is signed by its own private key. See also 'Root Certificate'.

Root Certificate: Certificate of the highest certification authority of a hierarchy (root authority). It is the basis of all trust in a hierarchical PKI. A PSE with certificate is tightly bound to the certification hierarchy and the root certificate. The tight binding allows trustworthy communications with other partners, even when they have been certified by subordinate certification authorities.

Rootkit: A hacker security tool that captures passwords and message traffic to and from a computer. A collection of tools that allows a hacker to provide a backdoor into a system, collect information on other systems on the network, mask the fact that the system is compromised, and much more. Rootkit is a classic example of Trojan horse software.

Router: This is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its final destination. The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any juncture networks or gatway, including each Internet point of presence. A router is often included as part of a network switch.

RSA: A public key cryptosystem named by its inventors, Rivest, Shamir and Adelman, who hold the patent.