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Skype |
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| Developed by | Skype Limited |
|---|---|
| Initial release | August 2003 |
| Stable release | 3.8.0.180 (Windows), 2.7.0.330 (Mac OS X), 2.0.0.72 (Linux x86), 2.2.0.45 (Windows Mobile Professional (Pocket PC)), 2.2.0.44 (Windows Mobile Standard (Smartphone)) (August 14, 2008 (Windows), May 14, 2008 (Mac OS X), March 27, 2008 (Linux), July 31, 2008 (Windows Mobile Professional (Pocket PC)), May 9, 2008 (Windows Mobile Standard (Smartphone)) ) +/− |
| Preview release | 4.0.0.169 (Windows) (30 October 2008) +/− |
| OS | Cross-platform |
| Available in | multilingual |
| Type | voice over IP / instant messaging/ videoconferencing |
| License | Freeware (with some paid features) |
| Website | http://www.skype.com/ |
Skype (IPA: [skaɪp]) is software that allows users to make telephone calls over the Internet. Calls to other users of the service and to free-of-charge numbers are free, while calls to other landlines and mobile phones can be made for a fee. Additional features include instant messaging, file transfer and video conferencing.
It was created by entrepreneurs Niklas Zennström, Janus Friis, and a team of software developers based in Tallinn, Estonia.1 The Skype Group has its headquarters in Luxembourg, with offices in London, Tallinn, Tartu, Stockholm, Prague,2 and San Jose.
Skype has experienced rapid growth in popular usage since the launch of its services. It was acquired by eBay in September 2005 for $2.6 billion.3
Contents |
SkypeIn allows Skype users to receive calls on their computers dialed by regular phone subscribers to a local Skype phone number; local numbers are available for Australia, Brazil, Chile,4 Denmark, the Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Ireland, Japan, Mexico, New Zealand,4 Poland, Romania, South Korea, Sweden, Switzerland, 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. Some jurisdictions, including France and Germany, forbid the registration of their telephone numbers to anyone without a physical presence or citizenship in the countrycitation needed.
Videoconferencing was introduced in January 2006 for the Windows and Mac OS X platform clients. Skype 2.0 for Linux, which was released on March 13, 2008, also features support for videoconferencing.5 Skype for Windows, starting with version 3.6.0.216, supports “High Quality Video" with quality and features (e.g. full-screen and screen-in-screen modes) similar to that of mid-range videoconferencing systems.6
Skypecasting is a portmanteau of 'Skype' and 'podcasting'. Its original usage referred to recording Skype voice over IP voice calls and teleconferences. The recordings would be used as podcasts, which allow audio or video content to be syndicated over the Internet.
Skype launched a "Skypecasts Beta" service in 2006 where it remained in beta until its end in September 2008. Skypecasts hosted public conference calls, up to 100 people at a time. Unlike ordinary Skype p2p conference calls, Skypecasts support moderation features suitable for panel discussions, lectures, and town hall forums. Skype operates a directory of public Skypecasts. On August 26, 2008, Skype announced that Skypecasts would be discontinued beginning September 1, 2008.[1] 01 September 2008 at 12:00 GMT, Skypecasts were shutdown without any concrete explanation.
On April 24, 2008, Skype announced that they offer Skype on around 50 mobile phones.7 On October 29, 2007, Skype launched its own mobile phone under the brand name 3 Skypephone, which runs a BREW OS.8
Skype is available for the N800 and N810 Internet Tablets, which use the Linux Maemo environment. Skype is available on both the Sony Mylo COM-1 and newer COM-2 models.
Skype is available for the PSP (PlayStation Portable) Slim and Lite with firmware version 3.90 or higher, but the user needs to purchase one of three microphone input peripherals. The new PSP-3000 has a built in microphone which allows communication without the Skype peripheral 9
Skype is available on mobile devices running Windows Mobile.10 The official Symbian version is currently under development.11 Official Skype support is available on Symbian and Java as part of X-Series together with mobile operator 3.
Other companies produce dedicated Skype phones which connect via WiFi. Third party developers, such as Nimbuzz and Fring, have allowed Skype to run in parallel with several other competing VoIP/IM networks in any Symbian or Java environment. Nimbuzz has made Skype available to BlackBerry users.
In the United States, the FCC has interpreted the Communications Assistance for Law Enforcement Act as requiring digital phone networks to allow wiretapping in the presence of an FBI warrant, in the same way as traditional phone service. Skype is not yet compliant with the act and has, so far, stated that it does not plan to comply.17
It has been reported that German authorities have been wiretapping Skype conversations using a trojan horse.18 A number of individuals involved in publicly disclosing this information have been placed under investigation.18
In 2008 it was discovered that messages sent by customers of Tom-Skype, a joint venture between a Chinese wireless operator and Skype, were being monitored by China's system of internet censorship.19 Niklas Zennström, chief executive to Skype, told reporters that its joint venture partner in China is operating in compliance with domestic law. "TOM Online had implemented a text filter, which is what everyone else in that market is doing," said Zennström. "Those are the regulations," he said. "I may like or not like the laws and regulations to operate businesses in the UK or Germany or the US, but if I do business there I choose to comply with those laws and regulations. I can try to lobby to change them, but I need to comply with them. China in that way is not different."20
Since late September, users in China trying to download the Skype software are redirected to the TOM site from which a modified Chinese version can be downloaded. Activists in China have stated that TOM's versions may have more trojan capability.21
Chinese authorities are monitoring both the text messages of Skype users inside of China as well text messages exchanged with users outside the country. It is a well known fact however, that communications going in and out of China have been monitored by the Chinese government for a number of years now.22
The Wall Street Journal and the New York Times reported on October 2, 2008 that China has been monitoring Skype text messages for political content using automated systems, and saving the full message contents on Chinese government-owned servers. The saved messages contain personally identifiable information about the messages' senders. Ronald J. Deibert, associate professor of political science at the University of Toronto told the New York Times, "This is the worst nightmares of the conspiracy theorists around surveillance coming true." The restricted content includes words related to Falun Gong, Taiwan independence, Chinese Communist Party, milk powder, earthquake, and democracy. When such words are found, both the messages and the information pertaining to them are recorded in a log, which is, or was until recently, open to the public. Citizen Lab observed log files containing IP addresses, usernames (as well as land line phone numbers) used to send or receive TOM-Skype calls, and the entire content of filtered messages, including the time and date of each message. The personal information of Skype users interacting with TOM-Skype users was also obtained.232425
| Date | Total user accounts (in millions)373839 |
Skype to Skype minutes (in billions) |
SkypeOut minutes (in billions) |
Net revenue USD (in millions) |
|---|---|---|---|---|
| Q4 2005 | 74.7 | N/A | N/A | N/A |
| Q1 2006 | 94.6 | 6.9 | 0.7 | 35 |
| Q2 2006 | 113.1 | 7.1 | 0.8 | 44 |
| Q3 2006 | 135.9 | 6.6 | 1.1 | 50 |
| Q4 2006 | 171.2 | 7.6 | 1.5 | 66 |
| Q1 2007 | 195.5 | 7.7 | 1.3 | 79 |
| Q2 2007 | 219.6 | 7.1 | 1.3 | 90 |
| Q3 2007 | 245.7 | 6.1 | 1.4 | 98 |
| Q4 2007 | 276.3 | N/A | N/A | 115 |
| Q1 2008 | 309.3 | 14.2 | 1.7 | 126 |
As of December 31, 2007 Skype had 276 million user accounts. Users may have more than one account, and it is not possible to identify users with multiple accounts.
It was reported that 14,011,745 concurrent Skype users were online as of October 20, 2008.40
| Date | Users 41 | Days |
|---|---|---|
| 2008-10-20 | 14,000,000 | 35 |
| 2008-09-15 | 13,000,000 | 209 |
| 2008-02-18 | 12,000,000 | 42 |
| 2008-01-07 | 11,000,000 | 84 |
| 2007-10-15 | 10,000,000 | 259 |
| 2007-01-29 | 9,000,000 | 82 |
| 2006-11-08 | 8,000,000 | 71 |
| 2006-08-29 | 7,000,000 | 155 |
| 2006-03-27 | 6,000,000 | 66 |
| 2006-01-20 | 5,000,000 | 92 |
| 2005-10-20 | 4,000,000 | 155 |
| 2005-05-18 | 3,000,000 | 93 |
| 2005-02-14 | 2,000,000 | 117 |
| 2004-10-20 | 1,000,000 | 418 |
| 2003-08-29 | 0 | - |
The volume of international traffic routed via Skype is significant, though small compared to total global switched and VoIP traffic. Computer-to-computer traffic between Skype users in 2005 was 2.9% of international carrier traffic in 2005 and about 4.4% of the total international traffic of 264 billion minutes in 2006.42
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 network43.
Skype uses a proprietary Internet telephony (VoIP) network. The protocol has not been made publicly available by Skype and official applications using the protocol are proprietary and closed-source. The main difference between Skype and standard VoIP clients is that Skype operates on a peer-to-peer model (originally based on the Kazaa software44) rather than the more usual client-server model. The Skype user directory is entirely decentralized and distributed among the nodes of the network—i.e., users' computers—which allows the network to scale very easily to large sizes (currently about 240 million users)45 without a complex centralized infrastructure costly to the Skype Group.
Skype Protocol Detection
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 proprietary, Pearson's Chi-Square Test and stochastic characterization with Naive Bayesian Classifiers are two approaches that were publicly published in 2007.46
Secure communication is a feature of Skype; encryption cannot be disabled, and is invisible to the user. Skype reportedly uses non-proprietary, widely trusted encryption techniques: RSA for key negotiation and the Advanced Encryption Standard to encrypt conversations.47 Skype provides an uncontrolled registration system for users with absolutely no proof of identity. This permits users to use the system without revealing their identity to other users. It is trivial, of course, for anybody 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 48.
Versions now exist for Linux (32-bit x86 only), Linux-based Maemo, Mac OS X (Intel and PPC), Microsoft Windows (2000, XP, Vista and Windows Mobile).
 Skype 1.4, running on a Linux desktop. |
 Skype 2.7, running on Mac OS X. |
 Skype 2.2, running on a Windows Mobile 6 device. |
 Skype 4.0 Beta running in Windows XP. |
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