With the explosive growth of the Internet and the increased use of wireless technology, many folks have been thinking of the security of there networks. In a recent seminar I got a question about encryption that many folks wanted an answer to. The question was, "If I am logging onto a network with a wireless link, how do I avoid having someone discover my password by eavesdropping on the wireless link?" After asking a few more questions I discovered that the link was based on spread spectrum technology and that no encryption was used. So the answer was, "Someone could eavesdrop, if they were close enough and had the right equipment, so change your password often." This brought out a barrage of questions on security and encryption. There are three important considerations in dealing with the security of any computer system. 1) The question of physical site-based security; 2) The question of backup security; snd 3) The question of data security and encryption as it passes over networks out of your control. Physical Site Security Do you have a good lock and key on every room that has a network linked to your file server? Is the file server in a place that is secure, and that includes good UPS (standby power) and surge suppression on both power and data lines? Is each person that has a key on a master list and is a key control policy in place that has employee keys picked up after they no longer need them? If the answer to any of these questions is no you have a big hole in your security. Each network computer system represents a huge investment in the company and often holds some of your most important secrets. If someone stole the file server, would your secrets be let out to the world for your competitors to see? Site security also includes a backup plan in case your site is incapacitated. The World Trade Center and Oklahoma bombings proved that having an alternate site at which to run your system can be crucial to business recovery. Check with your equipment vendors to find out who else has equipment like yours and try to make an agreement that you could run an emergency backup into their system to get out crucial work if there was a problem. Don't wait until your building is on fire to try to negotiate these kinds of deals. Backup Security All computer consultants and industry professionals insist on backups, but from a security standpoint there are two problems: 1) Despite these recommendations, many times backups are not made (a desperately dangerous situation); 2) If they are made and an off-site copy is kept (as most professional recommend), they are often not password-protected and in a common format so anyone could read them. One manager had the off-site backup in his briefcase that was stolen during a flight, and when he got home he discovered the competition had just outbid him by fractions of a percent. This might have been a coincidence, but the thief was later caught and had a steal-to-order confession come out as part of his plea bargain. The $3.2 million contract was voided and rebid, the manager barely kept his position, so it all worked out. But it leads to a call for caution. Almost all backups can have a password attached and that is a minimum step to avoid these kinds of problems. Be sure to change your passwords any time an employee leaves or situations and affiliations in the company change. Passwords should include both numbers and letters, to prevent an attacker from throwing the dictionary at it. Change your passwords often and make them long as you can. Pass phrases are a good tool to both protect systems and be easy to remember. An example would be: GetBack2me. This is a ten digit pass phrase that includes both numbers and letters, and for Unix systems also includes both lower and upper case letters that must be patterned the same way. By the way, please don't use this one. It is now compromised. You and a few thousand of my close friends now know it! Protecting Networks With Encryption In the old days important messages were sent in code. Encryption serves to provide a code that can be unlocked with the appropriate key. Most people know about encryption as a code, but here is a simple example: Just rotate the letters of the alphabet by 13 and you have a simple way for the computer to cloud the meaning of what we normally call "plain" text. This simple code is enough to stop the casual thief, and Unix systems have it built in so it is a lot better than nothing. To do a better job of encryption, I can scramble my plain text a lot more by using a more sophisticated algorithm to do the job. However I do it, I still have another problem, and that is the security of the key that unlocks the message. With all messages there is a sender and potentially many receivers of that message. They somehow have to be able to unlock the message, preferably without the locking key (having it would pose a huge security risk). The solution is to use a technique that involves two keys. It was not always possible to use the two-key approach. The change came about in 1976 when a new form of cryptography called asymmetric, or public key, was first publicly proposed. This technique, despite the efforts of the governments of the world to not let it escape, has revolutionized the technology of keeping secrets. Prior to that time, all cryptographic techniques were symmetric--sender and receiver had to have the same key. In 1976 two researchers (Diffie and Hellman) proposed the first asymmetric key encryption algorithm. Many programs have since developed based on the theories of these two men. Today the field is dominated by RSA Data Security in Redwood City, CA (415) 595-8782 and its RSA Public Key Algorithm. What all this means in practical terms is that using the RSA program, anyone can openly publish a public key, which anyone they send it to can use to lock the message which then can only be opened by the private key. The public key just LOCKS! Only the private key can unlock the message. Since anyone can know your public key, from which the private key or the message cannot be guessed. The security of the final unlocking key is never lost by the technique itself. Messages so treated are protected from being cracked as long as the key length is sufficient, say 112 to 1024 bytes. By extending these techniques it is also possible to sign the document in question proving authentication and time. I prefer not to go into exactly how this is done, as the technique would take several pages to explain, but it is straight forward to do. By applying the RSA technique to the transmission of network packets, wireless or not, the integrity of the network can be maintained. Many network integrators can help you with setting up these more secure network tools, and we can also help you protect US-based networks. The U.S. Government has an antiquated policy on the export of encryption so for international work we have to work harder, but your secrets and passwords or anything else can be protected. By the way, it isn't that these systems can't be cracked, just that the cost and complexity of doing so would tax even the resources of governments, and in the case of the best systems, the universe would suffer heat death before the algorithms could be cracked. You can have Pretty Good Privacy. In fact one program is called exactly that. We also have other common questions answered in our FAQ athttp://www.ctcwi.com.
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