Skype:

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]

Features

SkypeIn

Videoconferencing

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]

Skype on mobile devices

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 PSP (PlayStation Portable) Slim and Lite with firmware version 3.90 or higher, but you need to purchase one of three microphone input peripherals. The first is the Skype headset kit, which comes with a headset with a boom microphone and the PSP remote, but in the colour black instead of the standard silver. The other two which plug in to the proprietary USB accessory connector at the top being the dedicated microphone peripheral or the PSP camera which also has a built in microphone.The Upcoming 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 have made Skype available to BlackBerry users.

Security features

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.^[12] 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.

Skype's source code is not open source, and therefore cannot be inspected by the general public - including many 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,^[13] that "In the cryptography world, we consider open source necessary for good security; we have for decades." ^[14]

Issues

Security concerns

A third party paper analyzing the security and methodology of Skype was presented at Black Hat Europe 2006.^[15] It analysed Skype and made these observations:

Skype service issues

Compliance with the Communications Assistance for Law Enforcement Act

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.^[24]

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."^[25]

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 warned about the possibility that TOM's versions have or will have more trojan capability.^[26]

Company timeline of events

Usage and traffic

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.^[40]

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 network^[43].

System and software

Detailed changelogs

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)^[44] without a complex centralized infrastructure costly to the Skype Group.

Ports

Skype

Contents