Voice over IP-protocol and Skype

“Skype and Skype cordless phones and other gadgets” – it is not only a convenient service that allows people to communicate in the most natural way – voice, moreover, for little money. Skype – is a whole world with its technological innovations, gadgets like skype cordless phones, scandals, achievements and losses. And that happens in the “Skype”-the world, regularly tells our blog. Stay in touch, use the services of IP-telephony with Skype!

With the increase in the rate of high-speed Internet access, a growing number of companies and private users are beginning to use iternet as a tool for phone calls by skype cordless phones. This technology is called “Voice over IP-protocol» (VoIP). All phone system in the world using a microphone for converting sound waves into electrical, and a speaker to convert electrical signals back into sound at the other end. But the technology used to connect a microphone and speaker, has improved significantly over the past 125 years. Earlier system connected the microphone directly to the speaker through a copper wire. In 1970, AT & T used the first system that could transmit many phone calls on a single wire, converting each call into a stream of digital data. VoIP systems have continued this evolution by taking independent digital data, compressing them, breaking the flow of data packets and sending those packets over the Internet. Naturally, getting this process going in the opposite direction. For VoIP system two people can talk to each other using headsets and microphones connected to their computers. As an alternative, can be used VoIP-adapter to convert voice signals to standard analog phone internet packages. VoIP gateways connect internet system with public telephone networks (PSTN). As a rule the use of these gateways – are paid. Companies such as, for example, Vonage sell customers a package that includes VoIP-adapter and use the company’s VoIP gateway that allows customers, Vonage illusion of a conventional phone, with the only difference is that the Vonage adapter to connect to a cable modem or home network, rather than to a pair wires to a central office telephone company.
There are many different, generally incompatible technologies for sending voice over the Internet. Standard H.225 of International Telecommunication Association provides a voice and video teleconferencing; Problem With Design Internet (IETF) is an incompatible system called Session Initiation Protocol (SIP). Cisco has developed a proprietary system, called the Skinny Client Control Protocol (SCCP). Skype is a proprietary system of VoIP, which was developed by Skype Technologies SA – Corporation, registered in Luxembourg. This company was founded by Janus Friis (Janus Friis) and Niklas Zeenstromom (Niklas Zennstrom), the same entrepreneurs that have developed a popular system for sharing files – KaZaA. Just like KaZaA, Skype uses technology Peer-peer (peers) using peer-to-peer, rather
 than pass all calls through a central server, as does Vonage, Skype-client and seek and find other Skype-client then from these bonds is building a network that can be used to find other users and send them messages. But unlike the program KaZaA, which gets its revenue from advertising, Skype currently svobodet from additional and spyware (adware and spyware). Instead, the system Skype earns revenue due to the fact that he takes charge users for the use of terminal gateways that connect the network of Skype software from public telephone networks.

Program Skype in comparison to other VoIP-systems

Skype differs from other VoIP-systems for several major factors:
Skype is very popular. During the first week in August 2003, the year more than 60 thousand people have downloaded a Skype-client. Today, Skype is available for the following operating systems: MS Windows, MacOS, PocketPC and Linux. In October 2004 the creators of Skype sad that their programs are already more than a million people. Using the software and the Skype network for free , and there are only nominal prices for calls made using the functions «Skype Out» and «SkypeIn», which allow you to make calls from Skype to the telephone networks use with skype cordless phones it’s a easily way to do it.
Program Skype is much easier to use than any other VoIP-system. Skype-client fairly easy to install. In addition to selecting a user name, no other configuration is required. And in contrast to SIP-system used by Vonage, Skype-clients to easily work through firewalls (firewalls / firewalls) and network address translation systems (NAT).
Skype offers superior sound quality compressor, which is often superior to the traditional phone system, provided if the Skype user a high-speed Internet access. In addition to voice telephony Skype supports instant messaging, search and file transfer. Skype uses encryption. Unlike traditional telephone service and other VoIP-systems, Skype claims that the transfer of all information is encrypted using 128-bit or higher encryption codes, which they claim makes it almost impossible to intercept Skype passive dialects, and the ability to decipher and to hear their contents.

Program Skype in comparison with ISDN

ISDN is another type of digital telephone systems, which is popular in Europe and Asia. The system is similar to ISDN VoIP so that the sound is digitized and sent over the network, and also the fact that the telephone line ISDN, in order to use them, require special equipment. Voice calls made using Skype, differ from the calls, make phone ISDN, in the following respect: While Skype uses the Internet, ISDN uses a conventional telephone lines.
While Skype is encrypted, ISDN phone calls usually do not shifruyutsya, except when using special encoding ISDN-phones or faxes. (Such equipment exists, but is represented in limited quantities). While Skype is a free program, very rare to find a free phone calls of ISDN. Skype does not support video conferencing, while this feature is present in many systems, and ISDN-up Apple’s iChat. In Overall, Skype gives the impression of the program extremely useful for private users and organizations that require voice communication quality, and have access to broadband Internet.

Program Skype in comparison with other peers Peer-to-Peer Systems

While Skype uses an ad hoc communications such as peer-to-peer in order to determine the location of other Skype users and send voice messages, there are many aspects on which Skype is different from other “pure» peer-to-peer systems: Skype relies on a central server ID, which identifies the user and distributes software. According to observers program Skype, and user authentication and distribution of software is using a private key RSA digital signatures. The matching RSA public key included in each module loaded Skype. Some sites have the Skype status of special units, so-called “backbones”. When Skype runs on a computer that has a public IP-address and is not behind a firewall, he becomes the “backbones” These computers are used as a rendezvous point, so that computers behind firewalls, can communicate with other users of Skype. Although the company Skype refuses to explain the details of his protocol is likely that computers behind firewalls, scan the Internet for their backbones, then form and maintain a lasting connection with those other computers.Then backbones are designated points for communication with the points that are behind firewalls and connection with that complicated. When using the functions SkypeIn or SkypeOut, all information must pass through the server, Skype, which are in different countries and areas dialing.

Program Skype in comparison with KaZaA

KaZaA is a popular program for sharing files. While sharing some files with this program going, with the consent of copyright owners, however it seems that the main use of KaZaA – this is an illegal pirated copies of music sharing and movie files. KaZaA and Skype seem to be companies that have something in common. Both were founded by the same people, the technical staff in both companies are almost identical, and most of the technology used by Skype, were originally developed for the program KaZaA. Version 3.0 software KaZaA also includes Skype-client; KaZaA 3.0 can send voice messages via Skype. Are distributed two versions of the program KaZaA. The free version is supported by advertising, while the fee, which costs about 25-ty dollars, do not contain advertising. Advertising free version of KaZaA-s are placed there with the help of software developed by GAIN. Such software is often called «spyware», because it scans the Web sites visited by users and therefore places where advertisements. The company KaZaA questioned the statement that GAIN is spyware: they argue that the program can not catch the keystroke, to analyze the files on your hard drive, or provide information about the user to third parties. Moreover, this software can be easily removed using a standard function of Windows Add / Remove. It is unlikely that the GAIN program is able to make any impact on privacy or reliability of telephone calls made by users of Skype users to program KaZaA 3.0.; There is no effective way to analyze the content calls for targeted advertising without that these talks were proslusheny man, but the costs of such monitoring would be too high compared to the potential income from advertising. Nevertheless, civil society organizations should try to avoid using programs such as KaZaA. Since KaZaA is used primarily for file sharing, against the wishes of copyright owners, it is likely that users of KaZaA-s will be stored illegal copies of music and movies on their computers. Organization does not recommend to store such files on their computers, because the possession of a contracts collection may lead to prosecution.

Using Skype while connecting by dial-up (Dial-Up)

Using Skype has been tested in a Dial-Up Internet dial-up ISP when you connect to analog telephone line at speeds of 26 kbit / sec. The sound quality at such a speed significantly deteriorated. However, Skype offers acceptable sound quality for the user-friendly two-way conversation. In order to use the telephone line dial-up, appropriate to unload all programs that also use the Internet. For example, all web browsers and email programs should be turned off. Skype will also work better if subscribers will avoid talking at the same time, because it minimizes bandwidth requirements.
Using Skype in this way for low-speed lines, dial-up, Skype offers sound quality that is noticeably inferior analog telephone lines. Nevertheless, the advantage of Skype – its low cost and safety, resulting from the use of encryption. In situations where international calls are too expensive or when the play calls by the State or telecommunications services – a cause for concern, the use of  Skype should be encouraged.

Reliability Program Skype

Is the program Skype? Is it safe to use it for? Much more secure if the call made on Skype, compared with analog or ISDN phone calls? What is the reliability of Skype over other VoIP-systems? Answering these questions is not so easy. Reliability – this is a very abstract thing that is difficult to analyze separately: in order to assess the reliability of Skype, is necessary to consider certain kinds of threats and then decide whether the principle can work for this program to confront these threats? In addition, Skype security analysis is complicated for several reasons: firstly, the reliability of Skype calls depends on many factors, including the reliability of the computer on which you installed Skype and a network that is used for conversations. Secondly, because the Skype protocol is proprietary and closed, the only source of information – it is a statement of the company itself about  the reliability of the program, and the information that can be obtained in technical analysis of the software. Thirdly, as Skype – is a system of ad-hoc peer-to-peer, its overall reliability depends on third parties who are in the network (but unknown to those who directly communicate by Skype). In the end, as the Skype program can update itself every time a new startup, security of the entire system can change without warning or changes that can be clearly noticed.

Following distinctive features of system reliability are the key to the importance for organizations working in the field of civil society, using the program Skype:

Privacy
Does the system to eavesdrop on Skype conversations to outsiders?
Identification
If you call another user in the conversation on Skype, are you sure that you get called just before the user whose name you used when recruiting?
Accessibility
Is it always works Skype, if both Users have access to the Internet, or may be occasions when you do not see the user even if both of you have downloaded this program? Can the current
conversation is interrupted?
Resiliency
If the network or infrastructure Skype broken or damaged in some way, whether users of Skype Obliged to communicate while the network damaged?
Sustainability
If the network or infrastructure Skype broken or damaged so that Skype can no longer operate, whether Skype users to quickly restore contact with one another?
Integrity (talk)
Is lost if part of the conversation when you send them on Skype? Some go there sent Files intact?
Compatibility
How to use Skype software may affect the use of a user’s computer or a network of other applications? Other programs use ad hoc access to peer-to-peer come with spyware modules with
«spyware»; what about Skype?

To answer these questions, I corresponded with Kate James (Kat James), which is representative of Skype’s public relations and media in the United States, Toivo Annus (Toivo Annus) – Skype developer Kelly Larrabee (Kelly Larabee) – another spokesperson Skype. I also briefly talked on the issue with Kelly Larrabee on the phone. Besides, I conducted a preliminary analysis Skype protocol packets transmitted over the network, capturing all the information packages before and after Skype Vonk, who comes and come with the computer on which software is used
Skype.
Privacy

How do I declare the creators of Skype, the program encrypts and compresses the information differently, which is transmitted via the Internet. That is, analyzing the information packages, I could easily see unencoded open my text messages. But at the time when I can safely say that Skype is reliable in terms of accidental eavesdropping, I can not say whether it could protect against more sophisticated attacks. The reliability of the information that is sent in encrypted or compressed form, depends on many factors, including the use of special algorithms for encryption and compression as encryption keys are selected and how the exchange of the keys (known as key management), performance of these algorithms and protocol that uses these algorithms as well as the performance of these
algorithms and protocols in this software. Analysis of the packets sent between users of Skype, shows that the combination of these protocols are used to register online, search for other users and make phone calls. It seems that
 the program uses the HTTP-version protocol to communicate with the Skype-server ui.skype.com (which is apparently located in Amsterdam) to perform user identification and password and register directly on the server Skype. A modified version of HTTP-protocol used to transmit information to other Skype-to customers. As a result, encoded protocol used to transmit voice and text messages and files.
Using Skype on a computer, Macintosh, I made a phone call from Boston (Massachusetts, USA) in Budapest (Hungary), within which to exchange instant messages, and also sent the file.  All information packages have been me on hold. After analyzing them, I found that my Skype-client in Boston, first contact with a computer in the UK apparently in order to check if I use the latest version of Skype-client and then search the network Skype, in order to find the right I respondent. (The technology used by Skype-ohm for search and directory management, similar to that used a system called PeerEnabler company Joltid, «original managers and developers that – came  from companies and network KaZaA FastTrack peer-to-peer» Press Attache Skype insist that Skype does not use any network PeerEnabler FastTrack and another program with similar characteristics.)
After the search ends, were exchanged on a series of information packets from a computer in Hungary, which continued throughout the conversation. All these packages will not yield to my decoding. Perhaps because they were encoded, compressed or undocumented system compression. Based on the analysis of recorded information packets, I can conclude that while the ongoing exchange of information between Skype-clients can be encrypted, the search on behalf of the users of Skype, including the search needed to initiate Skype Vonk amenable to monitoring network Skype. This means that even the underprivileged members of the network can perform traffic analysis and determine what one user calls another. It is not known, allows the principle of the Skype network to view some of the nodal points of all search queries and logs of calls, or instead, each nodal point can only see part of the overall traffic.

What if Skype actually uses encryption?

The company Skype claims that its systems use RSA encryption algorithm for key exchange and 256-bit AES for bulk encryption. However, Skype does not publish either its key exchange algorithms, nor its network protocol, and, despite repeated requests, refuses to reveal the principle underlying the identification system of its certificates, or the implementation of encryption. Therefore impossible to confirm statements by the company relating to the encryption process. It is possible that the data is encoded and, but not reliably enough. Even if Skype otokol and provides encryption, it is possible that the Skype system sends encryption keys for voice channels (which may be encoded by another set of keys), or different stores keys so hard drive. Access to these keys would enable third parties to decipher the recorded Skype dialects. Such a function is conditionally secret key could be built into Skype, or for testing
 or at the request of police or intelligence services. Even if at the moment Skype does not have such supervisory functions, they can be added in the future and modified the client and then will be distributed across a network Skype, or to all users or those who meet certain criteria you choose. Skype uses encryption, but not at a high enough level. Even if Skype and uses the RSA, then the inefficient use of the algorithm can not provide good protection. Due to the fact that at the moment Skype has not published its protocol, it is impossible to say whether the protocol that uses RSA, sufficiently reliable or not. Should take into account the above situation. Talking on Skype is much more confidential than talking on a traditional analog or ISDN-telephone. Listen to this talk can anyone who has physical
access to a telephone line at any point between any of the parties talking.
Reliable encryption of Skype general

 Skype is also more reliable than today’s VoIP-system, because the coding is not part of most VoIP-proposals. Nevertheless, VoIP-talk may protect spending VoIP-traffic through a virtual private network (VPN). System, using VoIP over a VPN, may be more reliable than Skype, provided that the VPN is properly configured. It is important to understand that the reliability of Skype could be undermined by the presence of spyware spyware or other types of tracking programs that are running on your computer For example, programs such as Netbus and Back Orifice allow outsiders to include a computer microphone and send recordings via the Internet on someone else’s computer. Such a program can not only eavesdrop on Skype dialects, but also any others that occur in the office, which is a computer program loaded with Skype. There are other points concerning the safety program Skype, which users should be aware of: Although the impression that the Skype-client does not write and keep Skype words, it can record the history of text messages in the archive file for each user. Skype allows you to record conversations made by default, in other words, all text messages are saved until the user takes the reverse action. These files can be recovered by spyware spyware, other remote sensing applications, or when an unauthorized physical access to a computer system.
Since all Skype users downloaded the same so-called “cloud”, any Skype user can find out whether any other user in the program at this moment. It seems that Skype is trying to send packets between the parties to talk directly via the internet, but if the direct route available, it is possible that Skype instead sends packets through other computers that are running this program. These computers are called mediators nodal points (backbones). Nevyyasneno whether the nodal point to monitor the voice traffic that passes through them. Skype representatives argue that such monitoring is not possible due to the use of encryption. It is logical to assume that indeed such monitoring is impossible. It is possible that employees of Skype thinks that such monitoring is impossible, but there is a deficiency in their protocol
or device system that makes such monitoring possible. Many of these deficiencies have been found in other cryptographic protocols, after they have been used. Options SkypeIn and Skype Out can use encryption up to Skype gateway, but then calls decoded and sent via standard telephone network of public access. That is, at this point, calls can be subjected to illegal wiretapping and monitoring.
Ultimately it must be remembered that the reliability of the system Skype tazhe depends entirely on the conscience of Skype’s programmers and the organization of the Skype-servers. It is possible that the system has loopholes that allow Skype or other companies to eavesdrop or record Skype dialects. In theory, Skype developers could even build “loophole” in a system that can use a special program to activate the microphone on your computer to a record all the sounds in the room on your hard disk or transmit the data over the Internet to another computer. Such
loopholes and traps can also be made to any Skype ogrammu either of these functions can be added later to the Skype ogrammam individual users.

Identification

Each Skype olzovatelya have a username and password. Each user name is registered to a specific email address. In order to enter into the system, the user must enter your name and password. If the password is lost, Skype will change the password and send new e-mail to the registered user. This approach is called identification and authorization based on the e-mail Skype-client also has the ability to “remember” the user names and passwords to automatically log into the system. The additional complexity of Skype is its network. It seems that the Skype network is used to authenticate user names and passwords, but it is not clear exactly how this is done. For example, the nodes on the Skype network can send an encrypted combination of user names and passwords back to the Skype-server for authentication. Also they can send back an unencrypted combination of user names and passwords. Skype network can be in general is not involved, and all communication between Skype-clients can serve other purposes. However, if the network is Skype still involved in this, perhaps some variants of attacks:
Skype-client can find the name and password registered users of Skype, to then use this information to the bad purposes. If a Skype user oluchet access to Skype-network through a malicious Internet provider, it is possible that this provider can send the information from the user on the Skype site attacker. Thus, this ISP can learn any of the passwords Skype. Also, the attacker node can simulate a real identity, which will allow the customer to come in as the other Skype user, even if the password for that user is not known. Since Skype is a voice communication system, it users can identify the voice of the people with whom they communicate. That is the voice of a biometric quality. However, this does not work when there is communication only through the exchange of written messages and files.
Under normal circumstances, it seems that Skype Identification System provides the same level of identification, as well as other systems based on user names and passwords, such as AOL or HotMail. That is, most people can control their own mailboxes, but some criminals can get someone else’s password by guessing, social engineering, the use of keyloggers, either through intercepted communications to be used for password recovery. Also, computer administrators to give passwords, install new, or some other way to enable the attacker to impersonate the
 authorized user. At the same time, we can assume that the person with whom you communicate in Skype is actually the one whose name you see, but an absolute guarantee that you do not.

Accessibility

One of the great engineering achievements of the twentieth century – access to public telephone network. In many countries, users are experiencing outages neznaitelnye only in the amount of 5 minutes per user per year or even less, which is equivalent to 99.99905% availability. Although the original structure of the Internet imply that the network survive the loss of some critical linkages (see following chapter, “fault tolerance”), it has only recently began to developers and manufacturers of Internet equipment. Quality Internet Service as a whole has outperformed the telephone. Thus, it is possible that phone calls over the Internet less accessible than calls to telephone networks of public access. (Some commentators have observed that the availability of telephone networks is reduced in connection with deregulation, and that the availability of a separate system is less important, given the prevalence of multiple overlapping wireless networks.) Additional factors may undermine the potential availability of Skype. Since Skype-client depends on the identification of a user name and password, can a case where the whole network Skype
cease to function if the identity of Skype-server shut down, or for other reasons will no longer be available. Existing VoIP-systems do not have this problem, although those systems that rely on a single service gateway will experience a general breakdown, if this gateway fails. (For example, all users will not be able to use Vonage phone service, if the gateway Vonage goes down.)

Resiliency

It is often said that the Internet was invented in order to withstand nuclear war. The truth is that the network with packet switching have been developed in order to exchange information between nodes in the network could continue even if a direct connection between these nodes destroyed. Ability system to continue to work even after such an injury is called fault tolerance. The device allows Internet ISPs choose how they want to see Failover their systems. If an organization is connected to the Internet via your mail server with a single DSL-line, and this line goes down, then the mail will not work. On the other hand, if the organization has two DSL-line, e-mail will operate under failure of one of these lines. Redundant systems are usually more expensive than a system with a single alarm point. In addition, fault-tolerant systems in rare cases can provide better performance of routine than not fault-tolerant. As a result, the majority of Internet users and Internet service providers do not use the system that can withstand accidental failure of one or more of its components. It is not known whether the identity of Skype-server withstand interruptions in the network or attack. 
Sustainability

Network packet switched unusually stable. In most cases the Internet connection can be restored more quickly than in traditional telephone networks, through the deployment of wireless networking technologies. An additional advantage of other Skype VoIP-systems that these systems have been developed, taking into account mobile phone users. They do not depend on the change of IP addresses of users. As a result, Skype and other VoIP-systems are generally more suited to the disruption in the network. If the building goes down the network, you can simply take the computer or VoIP-phone, transfer them to another place and reconnect. Once you register your computer on the network Skype, you can make and receive calls regardless of your new location. On the other hand, Skype-client almost certainly could not have worked if Skype-network inverse identification is unreachable. This can happen as a result of violations of the network, with some types of hacker attacks, hostile invasion as well as in the case of closure of the parent company. In this case the Skype network could become unavailable for some or even all users of Skype.

The integrity of the conversation

The integrity of the conversation, secured Skyp-ohm is not fully understood. Perhaps the conversation, made with the help of Skype, can break off or distorted before they reach your interlocutor. Thus, Skype does not guarantee that text messages and files will be delivered in the form in which they are sent. However, in practice, Skype is well transmits voice and text messages and files as transmitted without distortion. But when using Skype for 802.11 wireless networks, voice quality suffers considerably.

Compatibility

Clearly, network administrators, concerned users downloaded software ensuring the use of which may have unpredictable consequences. Many universities, for example, have complained that students who use file-sharing systems like KaZaA, consume large amounts of traffic and potentially expose their schools prosecution by the owners, whose copyrights are violated. Community KaZaA-s can also be divided into the contents of their computers,
without even being aware of it. Since communication via Skype is limited only by voice, the total load on the network created by “backbones” should be doubled, because of the implementation of this node functions of the authorized site and duplication of communication. We do not know how you can avoid it. Skype can also serve as a source of spyware «spyware». Although the creators of the program say that their program is not equipped with spyware or adware modules, it is possible that they do not speak the truth, or their policy change in the future. Skype may have vulnerabilities in their system, which can be used by third parties.

It should be noted that most of the risks that arise in connection with the use of program Skype, did not differ from the risks of e-mail or other personal means of communication. In fact, the use of Skype software may be less risky for the general integrity of the system, simply because Skype was originally intended for voice communication. But we must be careful when using Skype to transfer files. Compared with KaZaA and other file-sharing program, Skype – provides less risk because the exchange always takes place between some people, rather than in situations where the location of these files is through the search and they are downloaded from potentially unknown sources. On the other hand Skype – a risky program, because programs like KaZaA have built-in virus protection, which scans the program when they are downloaded, but Skype does not seem to have such protection. 

Recommendations

In general, Skype gives the impression of the program more reliable than traditional analog or ISDN telephony, but more reliable, VoIP systems, using virtual private networks (VPNs). There is potential for cracking the Skype system experienced specialist or targeted by an attacker. If you use Skype, can be useful following recommendations:
Make sure that each computer that is running Skype, free from spyware «spyware» and additional «adware» modules, remote-control programs, worms, and viruses. All computers on which software is used Windows, should have the latest anti-virus and anti-spyware programs.
Although there is a small risk when using Skype to communicate with users of KaZaA 3.0, program KaZaA 3.0 should not be used as a replacement for Skype, given the potential liability that arises in the exchange of proprietary files without the permission of the owners of these patents. The combination of user name and password for Skype should not be used for any other programs. The username used for Skype, should not be easily guessed. It should not be associated with a user name, organization, or well-known facts about the user. User names and passwords should be changed on a regular basis, especially if Skype is used to transmit sensitive information. With regular changing of usernames attacker becomes more difficult to trace the actions of a specific user. A regular change of passwords reduces the time period during which this password may be used. Skype users must take into account that the system at any time can be unavailable for an indefinite time. Consequently, it is desirable to always have alternative ways to communicate with each other.
Do not be completely sure that a well-known to you the user name hides the type of person who used the same name yesterday. It is possible that quite a stranger can sit at a computer you know and use Skype without their permission, or their account may be hacked and stolen. Always make sure once more alone in the identity of the person with whom you communicate, especially if you have to exchange sensitive information. Although, Skype claims that the Skype network can not be used to spread computer viruses, the truth of this assertion has not yet proven. In particular, a buffer overflow in the voice decoder enables another Skype user to execute commands in the system, in which the user works. In addition, files transferred via Skype may contain viruses or spyware «spyware».
Remember, just because Skype is likely encoded conversation decoded at the other end of conversation. There is no way to verify that the person with whom you are speaking, he did not record your conversation with him. Using coded negotiations can not be a substitute for your care in the content of what you say on Skype.