Skype

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Skype
Screenshot
Developed by Skype Limited
Initial release August 2003
Stable release 3.8.0.139 (Windows),
2.7.0.330 (Mac OS X),
2.0.0.68 (Linux x86),
2.2.0.37 (Windows Mobile)
  (April 29, 2008 (Windows),
May 14, 2008 (Mac OS X),
April 3, 2008 (Linux),
May 9, 2008 (Windows Mobile)) [+/−]
Preview release [1]  () [+/−]
OS Cross-platform
Available in multilingual
Genre voice over IP / instant messaging/ videoconferencing
License Freeware (with some paid features)
Website http://www.skype.com/

Skype (IPA: [skaɪp]) is a software program that allows users to make telephone calls over the Internet. Calls to other users of the service are free of charge, while calls to landlines and cell 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, Prague,[2] and San Jose, California.

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.

Contents

[edit] Features

Main article: Features of Skype
A typical early version of Skype 1.0, running on a Windows XP desktop.
A typical early version of Skype 1.0, running on a Windows XP desktop.
Skype 3.6 Beta running in Windows Vista.
Skype 3.6 Beta running in Windows Vista.
Skype 1.4, running on a Linux desktop.
Skype 1.4, running on a Linux desktop.
Skype 2.2, running on a Windows Mobile 6 device.
Skype 2.2, running on a Windows Mobile 6 device.

[edit] SkypeOut

SkypeOut allows Skype users to call traditional telephone numbers, including mobile telephones, for a fee which varies depending on location.

[edit] SkypeIn

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,[3] Denmark, the Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Ireland, Japan, Mexico, New Zealand,[3] Poland, Romania, South Korea, Sweden, Switzerland, UK, and the United States. A Skype user anywhere 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 Norway, forbid the registration of their telephone numbers to anyone without a physical presence or citizenship in the country.

[edit] Videoconferencing

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.[4]

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.[5]

[edit] Skype on mobile devices

On April 24, 2008, Skype announced that they offer Skype on around 50 mobile phones.[6] On October 29, 2007, Skype launched its own mobile phone under the brand name 3 Skypephone, which runs a BREW OS.[7]

Skype is available for the N800 and N810 Internet Tablets.

Skype is available for the PSP (PlayStation Portable) Slim and Lite when you download the 3.90 firmware update, but you need a microphone that connects to the PSP 2000 headphones.[8]

Skype is available on mobile devices running Windows Mobile.[9] The official Symbian version is currently under development.[10] 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 have made Skype available to BlackBerry users.

[edit] Security features

Main article: Skype security

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.[11] 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 trivially easy, of course, for anybody to set up an account using any name; the displayed caller's name is no guarantee of authenticity.

One major problem with Skype is that its source code is not open source, and therefore cannot be inspected by most people - including most security specialists - for back doors that can be exploited by hackers or government agents. Security specialist Bruce Schneier said in one of his monthly Crypto-Gram newsletters,[12] that "In the cryptography world, we consider open source necessary for good security; we have for decades." [13]

[edit] Issues

[edit] Security concerns

A third party paper analyzing the security and methodology of Skype was presented at Black Hat Europe 2006.[14] It analyzed Skype and made these observations:

  • Skype keeps chatting on the network, even when idle (even for non-supernodes. May be used for NAT traversal)
  • Assumes a 'blind trust' of anything else speaking Skype
  • Ability to build a parallel Skype network
  • Lack of privacy (Skype has the keys to decrypt calls or sessions)
  • 'Heap overflow' in Skype
  • Skype makes it hard to enforce a (corporate) security policy
  • No way to know if there is or will be a 'backdoor'
  • Skype has been found to access BIOS data[15] to identify individual computers and provide DRM protection for plug-ins.[16][17]
  • There is no assurance that Skype calls are not being intercepted.
  • Skype is owned by eBay, whose privacy policy is perhaps the least protective of customers of any large corporation. eBay claims it goes above and beyond what it is required to do by law, seeking out and giving police all the information it stores about users excluding some financial data, for which they require a subpoena.[18]

[edit] Skype service issues

  • There have been complaints about Skype's poor customer support.[19] As of June 2007, Skype did not provide a way to contact customer support, offering indirect assistance through its web portal only. There have also been criticisms of Skype blocking and disabling customer accounts from using the SkypeOut service.[20]
  • While available for Windows, Mac OS X and Linux (i386 platform) operating systems, there is no Skype version for the Palm OS, used in mobile devices like the Treo 700p smartphone.
  • Skype has been criticized for bugs and delays in its Linux version.[21]
  • Users of Skype on Mac OS X report poor audio quality when connecting to Mac/Mobile clients, with newer audio engines showing more and more problems.[citation needed] Audio quality when connecting from Mac to Windows seem to be acceptable.
  • Skype cannot be used with VOIP analogue telephone adapters (ATAs). Consequently, Skype users are limited to either using software phones or expensive Skype only hardware. However, there are applications that enable Skype users to connect to SIP providers.[22]
  • SkypeOut has been criticized because it does not support caller ID in the United States, where people frequently reject calls from unrecognized numbers.[23] The recipient sees "+0000123456" instead of a real phone number. By contrast, the Gizmo service shows the user's call-in number on caller ID.[24] On June 6, 2008, Skype extended its outgoing caller ID support to include USA online numbers, as well as verified cellular numbers from various countries.[25]
  • SkypeOut does not support storing or (automatically) calling numbers with extensions.[26] Instead, a user must call the number (without the extension), wait for the call to connect and then manually enter the extension. This means that many business customers in practice need a separate contact list that includes extensions, causing the built-in contact list to be of little use. This is by many customers considered a fairly basic feature, and other phone services typically support it by allowing numbers to contain a symbol to represent a pause, as in "1-800-123-4567 x54321" or "1-800-123-4567,,,54321" where 54321 is the extension.

[edit] Compliance with the Communications Assistance for Law Enforcement Act

In May 2006, the FCC successfully applied the Communications Assistance for Law Enforcement Act to allow wiretapping on digital phone networks. Skype is not yet compliant with the act, and has so far stated that it does not plan to comply.[27]

[edit] Censorship in China

Skype is one of many companies (others include AOL, Google, Microsoft, Yahoo, Cisco) which has cooperated with the Chinese government in implementing a system of Internet censorship in the People's Republic of China. 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."[28]

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 are warning about the possibility that TOM's versions have or will have more trojan capability.[29]

[edit] Company timeline of events

2002
2003
  • April 2003: Skype.com and Skype.net domain names registered.
  • August 2003: First public beta version released.
2005
2006
  • April 2006: Number of registered users reaches 100 million.
  • October 2006: Skype 2.0 for Mac is released, the first full release of Skype with video for Macintosh.
  • December 2006: Skype announces a new pricing structure as of January 18, 2007, with connection fees for all SkypeOut calls.[33] Skype 3.0 for Windows is released.[34]
2007
  • March 2007: Skype 3.1 is released, adding some new features, including Skype Find and Skype Prime. Skype also released a 3.2 beta with a new feature called Send Money which allows users to send money via PayPal from one Skype user to another.
  • August 2007: Skype 3.5 for Windows released with additions such as video in mood, inclusion of video content in chat, call transfer to another person or a group, auto-redial.
  • August 15, 2007: Skype 2.7.0.49 (beta) for Mac OS X released adding availability of contacts in the Mac Address Book to the Skype contact list, auto redial, contact groups, public chat creation, and an in-window volume slider to the call window.
  • August 16 / August 17, 2007: Skype users unable to connect to full Skype network in many countries.[35][36] Skype reports the system-wide crash was the result of exceptional number of logins after a Windows patch reboot ("Patch Tuesday").[37]
  • November 2007: Skype users are set to lose their 020 7 numbers after 20 December 2007.[38]
2008

[edit] Usage and traffic

Date Total user accounts
(in millions)[39][40][41]		 Skype to Skype minutes
(in billions)		 Skype Out 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 12,547,006 concurrent Skype users were online as of April 16, 2008.[42]

Date Users [43] Days
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.[44]

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[45].

[edit] System and software

Versions now exist for Microsoft Windows (2000, XP, Vista and Windows Mobile), Mac OS X (Intel and PPC) and Linux (32-bit x86 only). Under Windows Skype can be run from a USB stick without being installed on the target computer.[46] The Linux version runs on FreeBSD through its Linux binary compatibility layer. Skype can also run in Solaris branded zones.

[edit] Detailed changelogs

[edit] Skype protocol

Main article: Skype Protocol

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 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)[47] without a complex centralized infrastructure costly to the Skype Group.

[edit] See also

[edit] References

  1. ^ Skype - A Baltic Success Story. credit-suisse.com. Retrieved on 2008-02-24.
  2. ^ Jaanus Kase. Skype is expanding engineering to Prague. Skype Blogs. Retrieved on 2006-12-05.
  3. ^ a b Villu Arak. Four new SkypeIn countries. Skype Blogs. Retrieved on 2007-08-13.
  4. ^ Skype 2.0 Beta for Linux, the Great Revolution (November 7, 2007). Retrieved on 2008-02-19.
  5. ^ Skype User Guide Using Skype for Desk-top Video-Conferences.
  6. ^ Skype: Skype Tests Software for Mass-Market Mobile Phones, April 24, 2008
  7. ^ Skype: 3 Skypephone Delivers Free Skype to Skype Mobile Calls and Instant Messages at the Touch of a Button, October 29, 2007
  8. ^ Skype: Skype Expands Mobile Strategy at 2008 International CES, January 7, 2008
  9. ^ Skype on your mobile device
  10. ^ Skype for Symbian Coming
  11. ^ Skype Privacy FAQ. Skype. Retrieved on 2006-12-05.
  12. ^ http://www.Schneier.com/crypto-gram.html
  13. ^ September 15, 1999 - http://www.schneier.com/crypto-gram-9909.html#OpenSourceandSecurity
  14. ^ Philippe BIONDI and Fabrice DESCLAUX. Silver Needle in the Skype. blackhat. Retrieved on 2006-03-02.
  15. ^ pagetable.com » Blog Archive » Skype Reads Your BIOS and Motherboard Serial Number
  16. ^ Skype Security Blog - Skype Extras plug-in manager
  17. ^ The Register » Skype snoop agent reads mobo serial numbers
  18. ^ Skype security and privacy concerns, Scott Granneman, 2005-09-22, SecurityFocus.com
  19. ^ Ben Charny. Skype callers: 'Customer service, please?'.
  20. ^ SKYPE Account Blocked - Skype Forums
  21. ^ Skype Forums: Linux Users are fed up.
  22. ^ Uplink Skype to SIP Adapter Software - Connect SIP to the Skype Network
  23. ^ (SDS-208) Skype losing SkypeOut Customers due to lack of caller id in the US. Skype Developer Zone.
  24. ^ Does my Caller-ID show when I call a regular phone? Gizmo Project FAQ
  25. ^ Finally -- Skype CallerID for North Americans Skype Journal
  26. ^ Skype Forums Support for 'pauses' in SkypeOut numbers.
  27. ^ Can Skype Keep Its Secrets?
  28. ^ "Skype says texts are censored by China", FT.com, Financial Times, April 18, 2006. 
  29. ^ Dynamic Internet Technology Inc. Alleges Skype Redirects Users in China to Censorware Version - Ten Days After Users Are Able To Download Freegate Software Through Skype, TMCnet, September 24, 2007
  30. ^ Jack McCarthy. China bans Skype. InfoWorld. Retrieved on 2006-06-17.
  31. ^ eBay Completes Acquisition of Skype. eBay. Retrieved on 2006-06-17.
  32. ^ Skype Launches Next Generation Free Internet and Video Calling for Everyone. Skype. Retrieved on 2006-06-17.
  33. ^ Skype to Announce Disruptive Pricing Strategy for SkypeOut Retrieved: December 19, 2006
  34. ^ What is Skype?
  35. ^ http://www.chron.com/disp/story.mpl/ap/fn/5059323.html
  36. ^ Error in Skype’s Software Shuts Down Phone Service. NY Times. Retrieved on 2007-08-17.
  37. ^ "Skype blames outage on user reboot". 
  38. ^ "Skype Bombshell: 0207 SkypeIn Numbers Must Change", 2007-11-21. Retrieved on 2007-11-29. 
  39. ^ eBay Inc. reports third quarter 2006 results.
  40. ^ eBay Inc. reports first quarter 2007 results.
  41. ^ eBay Inc. reports first quarter 2008 results.
  42. ^ All-Time peak of concurrent real users.
  43. ^ 12 million in record time!. skypenumerology. Retrieved on 2008-03-12.
  44. ^ International carriers' traffic grows despite Skype popularity. TeleGeography Report and Database. Retrieved on 2006-12-07.
  45. ^ http://ise.gmu.edu/~xwangc/Publications/CCS05-VoIPTracking.pdf
  46. ^ Skype VoIP User Guide, FAQ, Hints and Resources How to run Skype from a USB stick.
  47. ^ 1 million Joost users prepare for year-end launch

[edit] External links

v • d • e
Instant messaging clients (and comparison of clients and protocols)
Proprietary and/or
single protocol
Multi-protocol:
Adium  · aMSN  · Ayttm  · Digsby  · Empathy  · IBM Lotus Sametime  · Instantbird  · Kopete  · meebo  · Miranda IM  · Pidgin  · Qnext  · QIP Infium  · SIM  · Trillian
Jabber/XMPP:
ICQ: