GSM-to-Skype Bridge Lets You Lose Those Roaming Fees

Here’s the scenario: you’re going to be traveling somewhere and you’ll be charged roaming fees if you use your cellphone. But there is free WiFi available in this place. You can save yourself money by leaving your SIM card at home and using a GSM-to-Skype bridge to take calls on your phone via WiFi.

[Trax] is using a USB GSM modem to take cellphone calls on a PC. He leaves his sim card in this modem so that it can make and receive calls and text messages through your normal telephone number. For some reason, the USB connection only provides control of this modem and doesn’t pass bi-directional audio. To make this happen, he built an audio interface cable using two transformers and a few passive components to connect the modem to the computer’s audio card.

On the software side of things, an application written in Delphi 7 manages the modem, the audio stream, and the Skype application. When a call is incoming it sets up a Skype connection with your handset via the Internet, passing along the caller ID data in the process. If you choose to answer the Skype session the application will pick up the GSM call and you’ll be connected. It works the same way when placing an outgoing call.

This seems easier to manage than a rig that physically pushes a cellphone’s buttons via the Internet.

[Thanks Mure]

Bluetooth Multimedia Remote

[Mathieu] spent three months developing this multimedia remote control. It connects to a PC via USB or Bluetooth and communicates with Winamp to pull down track information for display on a Nokia LCD screen. It can also be used as a wireless headset via the two on-board jacks. [Mettieu] thinks it’s just a small hop away from working as a Skype client if you take the time to write a plugin for that API.

Eavesdropping Encrypted Compressed Voice

A team from Johns Hopkins University has discovered a way to eavesdrop on encrypted voice streams. Voice data like the kind used by Skype for its VoIP service sends encrypted packets of varying sizes for different sounds. The team learned that by simply measureing the size of the packets, they could determine what was being said with a high rate of accuracy. VoIP providers often use a variable bit rate to use bandwidth more efficiently, but it is this compression that makes audio streams vulnerable to eavesdropping.

The team’s software is still in its early stages of development, yet incapable of parsing entire conversations. It is capable, though, of finding pre-determined keywords and inferring common phrases bases on the words it detects. It also has a higher rate of accuracy in identifying long complicated words than short ones. The team’s goal was not to eavesdrop, but to expose the vulnerability; team member [Charles Wright] notes, “we hope we have caught this threat before it becomes too serious.”

[via Schneier on Security]
[photo: altemark]

GPL Vs. Skype Back In Court

UPDATE: Skype has withdrawn their appeal and accepted the original judgment.

Tomorrow the High District Court of Munich will hear Skype argue against the validity of the GPL. Last June, the court issued an injunction against Skype for selling the SMC WSKP 100, a Linux-based WiFi VoIP phone. After the initial GPL violation, a flier with the URL for the source was added to the package. The GPL wasn’t provided and the court found this insufficient for fulfilling the requirements of the GPL. Skype is appealing and claims that the GPL as a whole violates anti-trust regulation. The case against Skype was brought by OpenMoko‘s original system architect, Harald Welte, as part of his work for


[sprite_tm] made my morning by sending in his latest work. After opening up his new SMC WSKP100 (Skype wifi phone) to identify the hardware differences, he managed to shrink a flash image from the SMCWSP100 to fit on his new toy. Then he spent some time hacking the kernel from the former to work on his phone. The result? A SIP operational phone that’ll connect to his asterix server at half the price of SMC’s official SIP phone.