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The purpose of this article is to describe the various means by which security is sought and compromised, the differing kinds of security possible, and the current means and their degree of security readily available. With many communications taking place over long distance and mediated by technology, and increasing awareness of the importance of interception issues, technology and its compromise are at the heart of this debate. For this reason, this article focusses on communications mediated or intercepted by technology. Also see '' Trusted Computing '', an approach under present development that achieves security in general at the potential cost of compelling obligatory trust in corporate and governmental bodies. USERS AND NEEDS Many forms of everyday communication are "reasonably" secure, thus, we do not assume telephone calls are intercepted when we use them. However in some areas such as online intellectual property rights, legal, criminal, political and commercial communications, this assumption is inadequate. HISTORY One of the most famous forms of secure communication was the Green Hornet. During WWII, Winston Churchill had to make vital calls to the President of the United States, Franklin D. Roosevelt. These calls talked about such things as shipping and troop movements. At first, the calls where made using a radio phone as this was thought to be secure. Unfortunately, due to the Nazis having a listening station in Holland they where able to hear every last word. As soon as it was realised they stopped using the radio phone and started work on a whole new system, the Green Hornet. It worked by playing a copy of white noise over the conversation and then an identical copy was subtracted on the other end of the line. This meant that anyone listening in would just hear white noise but as the only two identical copies where held with the Prime Minister and the President the conversation was clear to them. As secrecy was paramount, the location of the Green Hornet was only known by the people who built it and Winston Churchill, and if anyone did see him entering the room it was kept in, all they would see was the Prime Minister entering a closet labeled 'Broom Cupboard.' It is the said that because of the way the Green Hornet works it is not able to be beaten, even today. NATURE AND LIMITATIONS OF SECURE COMMUNICATION Types of security Security can be broadly categorised under the following headings, with examples:
Each of the three is important, and depending on the circumstances any of these may be critical. For example, if a communication is not readily identifiable, then it is unlikely to attract attention for identification of parties, and the mere fact a communication has taken place (regardless of content) is often enough by itself to establish an evidential link in legal prosecutions. It is also important with computers, to be sure where the security is applied, and what is covered. BORDERLINE CASES A further category, which touches upon secure communication, is software intended to take advantage of security openings at the end-points. This software category includes Trojan Horse s, Keylogger s and other Spyware . These types of activity are usually addressed with everyday mainstream security methods, such as Antivirus software, Firewall s, programs that identify or neutralize Adware and Spyware , as well as web filtering programs such as Proxomitron and Privoxy which check all web pages being read and identify and remove common nuisances contained. As a rule they fall under Computer Security rather than secure communications. TOOLS USED TO OBTAIN SECURITY Encryption See Also: Encryption Encryption is where data is rendered hard to read by an unauthorised party. Since encryption can be made extremely hard to break, many communication methods either use deliberately weaker encryption than possible, or have Backdoor s inserted to permit rapid decryption. In some cases government authorities have required backdoors be installed in secret. Many methods of encryption are also subject to "man in the middle" attack whereby a third party who can 'see' the establishment of the secure communication is made privy to the encryption method, this would apply for example to interception of computer use at an ISP. Provided it is correctly programmed, sufficiently powerful, and the keys not intercepted, encryption would usually be considered secure. The article on Key Size examines the key requirements for certain degrees of encryption security. The encryption can be implemented in way to require the use of encryption, i.e. if encrypted communication is impossible then no traffic is sent, or opportunisticly. Opportunistic Encryption is a lower security method to generally increase the percentage of generic traffic which is encrypted. This is analogous to beginning every conversation with "Do you speak Navajo ?" If the response is affirmative, then the conversation proceedes in Navajo, otherwise it uses the common language of the two speakers. This method does not generally provide Authentication or Anonymity but it does protect the content of the conversation from Eavesdropping . Steganography )'' Anonymized networks Recently, anonymous networking has been used to secure communications. In principle, a large number of users running the same system, can have communications routed between them in such a way that it is very hard to detect what any complete message is, which user sent it, and where it is ultimately going from or to. Examples are Crowds , Tor , I2P , Mixminion , various Anonymous P2P networks, and others. Anonymous communication devices In theory, an unknown device would not be noticed, since so many other devices are in use. This is not altogether the case in reality, due to the presence of systems such as Carnivore and Echelon which can monitor communications over entire networks, and the fact that the far end may be monitored as before. Examples include Payphone s, Internet Cafe , etc. METHODS USED TO "BREAK" SECURITY Bugging See Also: Covert listening device The placing covertly of monitoring and/or transmission devices either within the communication device, or in the premises concerned. Computers (general) See Also: Computer security Any security obtained from a computer is limited by the many ways it can be compromised - by hacking, Keystroke Logging , Backdoor s, or even in extreme cases by monitoring the tiny electrical signals given off by keyboard or monitors to reconstruct what is typed or seen ( TEMPEST , which is quite complex). Laser reading of windows See Also: Laser microphone In certain cases individuals have had private spoken communications intercepted by means of laser. This usually involves a sensitive laser directed at a window, capable of picking up the tiny glass movements caused by sounds, and conversion back to speech. SYSTEMS OFFERING A DEGREE OF SECURE COMMUNICATION Anonymous cellphones Cellphones can easily be obtained, but are also easily traced and "tapped". There is no (or only limited) encryption, the phones are traceable - often even when switched off - since the phone and SIM card broadcast their International Mobile Subscriber Identity ( was assassinated after he was located by using his cellphone signal. Landlines Landline requires authority to tap, but offers no other security. Cordless phones may possibly be intercepted by scanning and decryption. Anonymous internet See Also: Anonymity Using a third party system of any kind (payphone, internet cafe) is often quite secure, however if that system is used to access known locations (a known email account or 3rd party) then it may be tapped at the far end, or noted, and this will remove any security benefit obtained. Some countries also impose mandatory registration of internet cafe users. Anomymous Proxies are another common type of protection, which allow one to access the net via a third party (often in a different country) and make tracing difficult. Note that there is seldom any guarantee that the Plaintext is not tappable, nor that the proxy does not keep its own records of users or entire dialogs. As a result anonymous proxies are a generally useful tool but may not be as secure as other systems whose security can be better assured. Their most common use is to prevent a record of the originating IP , or address, being left on the target site's own records. Typical anonymous proxies are found at both regular websites such as Anonymizer.com and spynot.com, as well as on proxy sites which maintain up to date lists of large numbers of temporary proxies in operation. Programs offering more secure communications
SEE ALSO General background Software selections and comparisons Other
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