First released in August 2003, Skype was created by Dane Janus Friis and Swede Niklas Zennström in cooperation with Estonians Ahti Heinla, Priit Kasesalu, and Jaan Tallinn, who developed the backend which was also used in music-sharing application Kazaa. In September 2005, eBay acquired Skype for $2.6 billion. In September 2009, Silver Lake, Andreessen Horowitz and the Canada Pension Plan Investment Board announced the acquisition of 65% of Skype for $1.9 billion from eBay, valuing the business at $2.75 billion. Skype was later acquired by Microsoft in May 2011 for $8.5 billion. Microsoft's Skype division headquarters are 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.
Skype allows users to communicate by voice using a microphone, video by using a webcam, and instant messaging over the Internet. Skype-to-Skype calls to other users are free of charge, while calls to landline telephones and mobile phones (over traditional telephone networks) are charged via a debit-based user account system called Skype Credit.
Skype originally featured a hybrid peer-to-peer and client–server system, however since May 2012 Skype is entirely powered by Microsoft-operated supernodeThe 2013 mass surveillance disclosures revealed that Microsoft has granted intelligence agencies unfettered access to supernodes and Skype communication content.
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.
History
Main article: Skype Technologies
Skype was founded in 2003 by Janus Friis from Denmark and Niklas Zennström from Sweden. The Skype software was created by Estonians Ahti Heinla, Priit Kasesalu, and Jaan Tallinn The first public beta version was released on 29 August 2003.
In June 2005, Skype entered into an agreement with the Polish web portal Onet.pl. On 12 September 2005, eBay Inc. agreed to acquire Luxembourg-based Skype Technologies SA for approximately US$2.5 billion in up-front cash and eBay stock, plus potential performance-based consideration.
On 1 September 2009, it was announced that eBay was selling 65% of Skype to Silver Lake, Andreessen Horowitz and the Canada Pension Plan Investment Board for US$1.9 billion, valuing Skype at US$2.75 billion.
Microsoft acquisition
On 10 May 2011, Microsoft Corporation acquired Skype Communications, S.à r.l for US$8.5 billion.The company was incorporated as a division of Microsoft, and Microsoft acquired all of the company's technologies with the purchase. This was completed on 13 October 2011.
Microsoft phased out its long-standing Windows Live Messenger instant messaging service in favour of Skype, although Messenger continues in mainland China.Microsoft began this transition on 8 April 2013, and completed the move by 30 April of the same year.
Features
Main article: Features of Skype
Registered users of Skype are identified by a unique Skype Name, and may be listed in the Skype 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. 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, video chats and screen sharing between 25 people at a time for free.
Skype does not provide the ability to call emergency numbers such as 112 in Europe, 911 in North America, 100 Call Police in India and Nepal. However, as of December 2012 there is limited support for emergency calls in the United Kingdom, Australia, Denmark and Finland. 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". As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.
On 14 July 2011, Skype partnered with Comcast to bring its video chat service to Comcast subscribers via their HDTV sets.
On 17 June 2013, Skype released a free video messaging service which can be operated on Windows and Mac OS, iOS, Android and BlackBerry.
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.
On 20 November 2014, Microsoft Office's team announced that a new chat powered by Skype is going to be implemented in their software, giving tools to be able to chat with co-workers in the same document.
Client applications and devices
Skype runs on a number of platforms including Microsoft Windows (XP, Vista, 7, 8), OS X (10.6 or newer), Linux (Ubuntu and others), Android, BlackBerry 10, iOS, and Windows Phone 8.
On 29 October 2007, Skype launched its own mobile phone under the brand name 3 Skypephone, which runs a BREW OS
Skype also offers a Skype Wi-Fi Phone, which is a wireless mobile phone that allows users to make Skype calls, using a wireless Internet connection. The Skype Wi-Fi Phone has an on-screen menu that lets Skype users see who is online and available to talk, similar to what is seen on a PC. It can also be used to talk with non-Skype users. SkypeOut minutes can be used to call any phone for a low price and no monthly fee. The Skype Wi-Fi phone does not contain a web browser and so can not access hotspots that require web-based login or authentication.
Other platforms officially supported include:
The Nokia N800, N810 and N900 Internet Tablets, which run Maemo
The Nokia N9, which runs MeeGo, comes with Skype voice calling and text messaging integrated however lacks video-calling.
Both the Sony mylo COM-1 and COM-2 models
The PlayStation Portable Slim and Lite series, though the user needs to purchase a specially designed microphone peripheral. The PSP-3000 has a built in microphone, which allows communication without the Skype peripheral.[78] The PSP Go has the ability to use Bluetooth connections with the Skype application, in addition to its built-in microphone.Skype for PlayStation Vita may be downloaded via the PlayStation Network in the U.S. It includes the capability to receive incoming calls with the application running in the background.
Samsung Smart TV has a Skype app which can be downloaded for free.It uses the built in camera and microphone for the newer models. Alternatively a separate mountable Skype camera with built in speakers and microphones is available to purchase for older models.
Some devices are made to work with Skype by talking to a desktop Skype client or by embedding Skype software into the device. These are usually either tethered to a PC, or have a built-in Wi-Fi client to allow calling from Wi-Fi hotspots like the Netgear SPH101 Skype Wi-Fi Phone, the SMC WSKP100 Skype Wi-Fi Phone, the Belkin F1PP000GN-SK Wi-Fi Skype Phone, the Panasonic KX-WP1050 Wi-Fi Phone for Skype Executive Travel Set, the IPEVO So-20 Wi-Fi Phone for Skype and the Linksys CIT200 Wi-Fi Phone.
Third-party developers, such as Truphone, Nimbuzz and Fring, previously allowed Skype to run in parallel with several other competing VoIP/IM networks (Truphone and Nimbuzz provide TruphoneOut and NimbuzzOut as a competing paid service) in any Symbian or Java environment. Nimbuzz made Skype available to BlackBerry users and Fring provided mobile video calling over Skype as well as support for the Android platform. Skype disabled Fring users from accessing Skype in July 2010. Nimbuzz discontinued support on request of Skype in October 2010.
Before and during the Microsoft acquisition, Skype withdrew licensing from several third parties producing software and hardware compatible with Skype. The Skype for Asterisk product from Digium was withdrawn as "no longer available for sale". The Senao SN358+ long-range (10–15 km) cordless phone were discontinued due to loss of licenses to participate in the Skype network as peers. In combination these two products made it possible to create roaming cordless mesh networks with robust handoff.
Protocol
Main article: Skype protocol
Skype uses a proprietary Internet telephony (VoIP) network called the Skype protocol. The protocol has not been made publicly available by Skype and official applications using the protocol are closed-source. Part of the Skype technology relies on the Global Index P2P protocol belonging to the Joltid Ltd. corporation. The main difference between Skype and standard VoIP clients is that Skype operates on a peer-to-peer model (originally based on the Kazaa softwar), rather than the more usual client–server model (note that the very popular Session Initiation Protocol (SIP) model of VoIP is also peer-to-peer, but implementation generally requires registration with a server, as does Skype).
As far as networking stack support is concerned, Skype only supports the IPv4 protocol. It lacks support for the next generation Internet protocol, IPv6.
Protocol detection and control
Many networking and security companies claim to detect and control Skype's protocol for enterprise and carrier applications. While the specific detection methods used by these companies are often private, Pearson's chi-squared test and naive Bayes classification are two approaches that were published in 2008. Combining statistical measurements of payload properties (such as byte frequencies and initial byte sequences) as well as flow properties (like packet sizes and packet directions) has also shown to be an effective method for identifying Skype's TCP- and UDP-based protocols.
Audio codecs
G.729 and SVOPC. Skype added a Skype-created codec called SILK to Skype 4.0 for Windows and other Skype clients. SILK is intended to be "lightweight and embeddable". Additionally, Skype has released Opus, and an open source codec which integrates the SILK codec principles for voice transmission with the CELT codec principles for higher quality audio transmissions such as live music performances. Opus was submitted to the Internet Engineering Task Force (IETF) in September 2010. Since then it has been standardized as RFC 6716
Video codecs
VP7 is used for versions prior to Skype 5.5
As of version 5.7 VP8 is used for both group and one on one standard definition video chat and H.264 is used for 720p and 1080p high definition group and one on one video chat
Security and privacy
Main article: Skype security
Skype is claimed initially to be a secure communication, with one of its early web pages stating "highly secure with end-to-end encryption".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.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
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.
In an interview Kurt Sauer, the Chief Security Officer of Skype, said, "We provide a safe communication option. I will not tell you whether we can listen or not."This does not deny the fact that NSA monitors Skype conversations. Skype's client uses an undocumented and proprietary protocol. The Free Software Foundation (FSF) is concerned by user privacy issues arising from using proprietary software and protocols and has made a replacement for Skype one of their high priority projects. Security researchers Biondi and Desclaux have speculated that Skype may have a back door, since Skype sends traffic even when it is turned off and because Skype has taken extreme measures to obfuscate their traffic and functioning of their program.[106] Several media sources reported that at a meeting about the "Lawful interception of IP based services" held on 25 June 2008, high-ranking unnamed officials at the Austrian interior ministry said that they could listen in on Skype conversations without problems. Austrian public broadcasting service ORF, citing minutes from the meeting, reported that "the Austrian police are able to listen in on Skype connections". Skype declined to comment on the reports. One easily demonstrated method of monitoring is to set up two computers with the same Skype user ID and password. When a message is typed or a call is received on one computer, the second computer duplicates the audio and text. This requires knowledge of the user ID and password.
The United States Federal Communications Commission (FCC) has interpreted the Communications Assistance for Law Enforcement Act (CALEA) as requiring digital phone networks to allow wiretapping if authorized by an FBI warrant, in the same way as other phone services. In February 2009 Skype said that, not being a telephone company owning phone lines, it is exempt from CALEA and similar laws, which regulate US phone companies, and in fact it is not clear whether Skype could support wiretapping even if it wanted to. According to the ACLU, the Act is inconsistent with the original intent of the Fourth Amendment to the U.S. Constitution; more recently, the ACLU has expressed the concern that the FCC interpretation of the Act is incorrect. It has been suggested that Microsoft made changes to Skype's infrastructure to ease various wiretapping requirements however, Skype denies the claims.
Some time before Skype was sold in 2009, the company had started its own program, called Project Chess, to explore legal and technical ways to easily share calls with intelligence agencies and law enforcement.
On 20 February 2009 the European Union's Eurojust agency announced that the Italian Desk at Eurojust would "play a key role in the coordination and cooperation of the investigations on the use of internet telephony systems (VoIP), such as 'Skype'. ... The purpose of Eurojust’s coordination role is to overcome the technical and judicial obstacles to the intereption of internet telephony systems, taking into account the various data protection rules and civil rights"
In November 2010, a flaw was disclosed to Skype that showed how hackers could secretly track any user's IP address As of 2013, this has still not been fixed.
In 2012, Skype introduced automatic updates to better protect users from security risks, but received some challenge from users of the Mac product, as the updates cannot be disabled from version 5.6 on, both on Mac OS and Windows versions, although in the latter, and only from version 5.9 on, automatic updating can be turned off in certain cases.
According to a 2012 Washington Post article, Skype "has expanded its cooperation with law enforcement authorities to make online chats and other user information available to police"; the article additionally mentions Skype made changes to allow authorities access to addresses and credit card numbers.
In November 2012, Skype was reported to have handed over user data of a pro-Wikileaks activist to Dallas, Texas-based private security company iSIGHT Partners without a warrant or court order. The allegation was an apparent breach of Skype's privacy policy. Skype responded with a statement that it launched an internal investigation to probe the breach of user data privacy.
13 November 2012, a Russian user published a flaw in Skype's security, which allowed any person to take over a Skype account knowing only the victim's email by following 7 steps.This vulnerability was claimed to exist for months, and existed for more than 12 hours since published widely.
14 May 2013, it was documented that a URL sent via a Skype instant messaging session was usurped by the Skype service and subsequently used in a HTTP HEAD query originating from an IP address registered to Microsoft in Redmond (the IP address used was 65.52.100.214). The Microsoft query used the full URL supplied in the IM conversation, and was generated by a previously undocumented security service. Security experts speculate the action was triggered by a technology similar to Microsoft's SmartScreen Filter used in its browsers.
The 2013 mass surveillance disclosures revealed that agencies such as the NSA and the FBI have the ability to eavesdrop on Skype, including the monitoring and storage of text and video calls and file transfers. The PRISM surveillance program, which requires FISA court authorization, reportedly has allowed the NSA unfettered access to its data center supernodes. According to the leaked documents, integration work began in November 2010, but it was not until February 2011 that the company was served with a directive to comply signed by the attorney general, with NSA documents showing that collection began on 31 March 2011.
On November 4, 2014, Skype scored 2 out of 7 points on the Electronic Frontier Foundation's secure messaging scorecard. It lost points because users can't verify contacts' identities, past messages are not secure if the encryption keys are stolen, the code is not open to independent review, the security design is not properly documented, and there has not been a recent independent code audit. On November 10, 2014, Skype lost yet another point because communications are not encrypted with a key the provider doesn't have access to.
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