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SkypeSkype (pronounced to rhyme with ripe) is a peer-to-peer internet telephony (VoIP) network, founded by Niklas Zennstrm and Janus Friis, the creators of Kazaa. The network is provided by all combined users of the free desktop software application. Skype users can speak to other Skype users for free, call traditional telephone numbers for a fee (SkypeOut), receive calls from traditional phones (SkypeIn), and receive voicemail messages. Features The basic computer-to-computer service allows users of the Skype software to send voice or text messages to one another from their computers via the Internet at no cost. Conferences of up to five users are supported. SkypeOut allows Skype users to dial regular telephones. Calls (including tax) cost 0.020 Euro (US$0.026) per minute to many countries (including the U.S., Canada, Chile, Western Europe, Australia and New Zealand), with calls calls to mobile or cell phones often costing more. Rates rise to over 1.00 Euro per minute for calls to certain isolated islands (the country of the originating is not a factor in determing cost). Almost any telephone can be dialed from Skype. SkypeIn allows Skype users to receive calls on their computers dialed by regular phone subscribers to regular phone numbers. Beta released March 10, 2005, SkypeIn permits users to subscribe to numbers in UK, USA, France and Hong Kong. Cost is 30 Euro for a 12-month subscription, or 10 Euro for a three month subscription. Also released on March 10, the VoiceMail service allows callers to leave voice-mail messages for Skype users who are not online, or on another call. This is also on a subscription basis, although much less expensive than SkypeIn. Version 1.2 for Windows was released in March 23, 2005. Its most significant new feature is the provision of centrally-stored contact lists so that a user's contact information is available from any computer that is connected to Skype (in other previous versions, contact information is stored on the local computer). Versions now exist for Microsoft Windows (Windows 2000, Windows XP and Windows CE (Pocket PC)), Mac OS X and GNU/Linux. Technology Each Skype user must have the Skype software running on his computer. This software is free and can be downloaded from the company website. The Skype code and protocol remain closed and proprietary. The main difference between Skype and other VoIP clients is that it operates on a peer-to-peer model rather than on the more traditional server-client model. The Skype user directory is entirely decentralized and distributed among the nodes in the network, which means the network can scale very easily to large sizes (currently in the tens of millions of users) without a complex and costly centralized infrastructure. Skype also routes calls through other peers on the network, which allows it to traverse NATs and firewalls, unlike most other VoIP programs (notably those based on the SIP protocol, see article). This, however, puts extra burden on those who connect to the Internet without NAT, as their computers and network bandwidth may be used to route the calls of other users. The selection of intermediary computers is fully automatic, with individual users having no option to disable such use of their resources. This fact is not clearly communicated, however; in fact, it seems to contradict the license agreement which would limit Skypes utilization of the users processor and bandwidth the purpose of facilitating the communication between user and other Skype Software users (section 4.1). Security As Skype communication may get routed via peers other than the recipient of the call, 256-bit AES encryption is used in order to actively encrypt the data in each Skype call or instant message. Skype uses 1536 to 2048 bit RSA to negotiate symmetric AES keys. The Skype server certifies users' public keys when they log in. Security problems As the Skype source code is not public, the security of the software cannot be readily established. It is known to open several ports on the users computer and to directly manipulate Windows XPs built-in firewall. In addition, it provides a feature-rich API that could potentially enable a virus to initiate calls, either to people on the users contact list, causing them discomfort, or the attackers premium rate telephone number, if the user has subscribed to the SkypeOut service. Unlike instant messaging or email skype executable acts as both a client and a server, so there are no safeguards you might otherwise have. It would take any small weakness in the code for a virus to fully control more than 2 million machines within a few minutes. Another weakness comes from peer-to-peer nature of the network too: the backbone (supernodes) is formed from the most connected and least protected regular skype clients. At any given time there might be a few thousand machines that form the backbone, and none of them are protected by a firewall. A dedicated attacker can build up a list of current supernodes and by launching a ddos attack against them can bring the whole network down. History - April 23 2003 Skype.com and Skype.net domain names registered
- August 29 2003 First public beta version released
- July 27 2004 Release of Version 1.0 for Windows
- October 20 2004 First time 1 million Skype users are online at once
- February 14 2005 First reached 2 million online
- March 10 2005 SkypeIn Public Beta starts
- March 11 2005 Skype press release reports 1 million Skype-out users and 29 million registered users
- March 11 2005 Software has been downloaded 84 million times and 5.98 billion talk minutes served
Skype has established partnerships with online web properties including Tom.com, PcHomeOnline, Daum and Livedoor as well as hardware manufacturers including Plantronics, Logitech, Motorola, VTech, RTX and Siemens. Another boost to the distribution of Skype came in November 2004 when Kazaa bundled Skype with version 3.0 of its software. Graphs See also External links
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