Skype's contradictions show its strength

Skype is succeeding despite being closed, uncertainly secure and greedy for other people's bandwidth. It's important to understand why

It's just over two years old and is still making headlines. Skype is more than a telephone replacement service, it's a superb illustration of many fault lines in tech today's.

It's peer-to-peer — or is it? Although Skype makes a big play of being decentralised and user to user, it actually relies on super-peers to relay messages between users behind address-translating routers. That's most of us. If however you're in a position to act as one of those relays, your free software will start soaking up your expensive bandwidth: one American university found hundreds of megabits per second flooding in and out of its network as it relayed most of the US Skype traffic.

It's secure — or is it? Although it promises industry-standard encryption it's not secure enough for those who insist on seeing the source code, which Skype is keeping close to its chest. It's too secure for the French government, which has banned it from its universities ostensibly because it doesn't like tons of unproven software on its networks — in which case, whither Windows? — but more likely because it disapproves strongly of thousands of overseas students connected back home via encrypted voice.

It's free — or is it? Even if you're not paying for other people's calls over your bandwidth, you'll have to fork out for some beta services. And while it interfaces nicely with the public phone system, it doesn't want to talk to other voice over IP systems — that freedom is bought by restrictions and closed code. But it still has that maverick, counter-cultural sheen which truly free software attracts. A good trick.

Yet the ambiguities haven't hurt its popularity, or the ability of people on either side of each argument to misunderstand the views of the others. A typical case is an answer given to a Skype fan in a VoIP forum, who was asking how to use the service without having their PC turned on. "You want to use SIP," said one reply. "It's much better, because it's open. Of course, you may have to configure some proxies".

Skype is so widespread in a field with plenty of more open alternatives precisely because it knows that most people wouldn't know proxy configuration from a disease of the Dark Ages. People will choose convenience over just about anything, a lesson often lost on software vendors and those responsible for making systems secure. For all its weaknesses, Skype understands those who use it — a lesson too important to ignore.