Skype

Skype

Skype /ˈskaɪp/ is a freemium voice-over-IP service and instant messaging client, developed by the Microsoft Skype Division. The name was derived from "sky" and "peer". Skype was first released in August 2003. It was written by developers Ahti Heinla, Priit Kasesalu, and Jaan Tallinn (Estonia), Janus Friis (Denmark) and Niklas Zennström (Sweden) who had also originally developed Kazaa.[20] Skype had 663 million registered users as of the end of 2010.[21] It was bought by Microsoft in 2011 for $8.5 billion. Microsoft's Skype division headquarters is in Luxembourg, but most of the development team and 44% of the overall employees of the division are still situated in Tallinn and Tartu, Estonia. The service allows users to communicate with peers by voice using a microphone, video by using a webcam, and instant messaging over the Internet. Phone calls may be placed to recipients on the traditional telephone networks. Calls to other users within the Skype service are free of charge, while calls to landline telephones and mobile phones are charged via a debit-based user account system. Skype has also become popular for its additional features, including file transfer, and videoconferencing. Competitors include SIP and H.323-based services, such as Linphone and Google Hangouts. Unlike most other VoIP services, Skype is a hybrid peer-to-peer and client–server system. It makes use of background processing on computers running Skype software, and this is reflected in Skype's original proposed name of Sky Peer-to-Peer. Some network administrators have banned Skype on corporate, government, home and education networks, citing reasons such as inappropriate usage of resources, excessive bandwidth usage, and security concerns.

Features

Registered users of Skype are identified by a unique Skype Name, and may be listed in the Skype directory.[36] Skype allows these registered users to communicate through both instant messaging and voice chat. Voice chat allows telephone calls between pairs of users and conference calling, and uses a proprietary audio codec. Skype's text chat client allows group chats, emoticons, storing chat history and editing of previous messages. Offline messages were implemented in a beta of version 5, but removed after a few weeks without notification. The usual features familiar to instant messaging users — user profiles, online status indicators, and so on — are also included. The Online Number, a.k.a. SkypeIn, service allows Skype users to receive calls on their computers dialed by conventional phone subscribers to a local Skype phone number; local numbers are available for Australia, Belgium, Brazil, Chile, Colombia, Denmark, the Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Hungary, Ireland, Japan, Mexico, Nepal, New Zealand, Poland, Romania, South Africa, South Korea, Sweden, Switzerland, Turkey, the Netherlands, the United Kingdom, and the United States.[37][38] A Skype user can have local numbers in any of these countries, with calls to the number charged at the same rate as calls to fixed lines in the country. The countries on this growing list are referred to collectively as the SkypeIn Countries. Skype supports conference calls up to 25 people at a time. Skype also supports video chat between two people for free. Screen sharing and group video calling is available for Premium subscribers between a maximum of 10 people.[39] Skype does not provide the ability to call emergency numbers such as 112 in Europe, 911 in North America, 000 in Australia, 100 Call Police in India and Nepal[40] The U.S. Federal Communications Commission (FCC) has ruled that, for the purposes of section 255 of the Telecommunications Act, Skype is not an "interconnected VoIP provider".[41] As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.[42] On 14 July 2011, Skype partnered with Comcast to bring its video chat service to Comcast subscribers via their HDTV sets.[43] On 17 June 2013, Skype released a free video messaging service which can be operated on Windows and Mac OS, iOS, Android and BlackBerry.[44] On 12 August 2013, Skype released the 4.10 update to the app for Apple iPhone and iPad that allows HD quality video for iPhone 5 and fourth generation iPads.

Security and privacy:

Skype is claimed initially to be a secure communication, with one of its early web pages stating "highly secure with end-to-end encryption".[104] Security services were invisible to the user, and encryption cannot be disabled. Skype reportedly uses publicly documented, widely trusted encryption techniques: RSA for key negotiation and the Advanced Encryption Standard to encrypt conversations.[105] However, it is impossible to verify that these algorithms are used correctly, completely and at all times as there is no public review possible without a protocol specification and/or the program source code. Skype provides an uncontrolled registration system for users with no proof of identity. Instead, a free choice of nicknames permits users to use the system without revealing their identity to other users. It is trivial to set up an account using any name; the displayed caller's name is no guarantee of authenticity. A third party paper analyzing the security and methodology of Skype was presented at Black Hat Europe 2006. It analyzed Skype and found a number of security issues with the current security model.[106] Skype incorporates some features, which tend to hide its traffic, but it is not specifically designed to thwart traffic analysis and therefore does not provide anonymous communication. Some researchers have been able to watermark the traffic so that it is identifiable even after passing through an anonymizing network.