Legal Aspects

This page documents our position on legal aspects of the project.

Since there is a lot of uncertainty and confusion regarding the legality of any independent open source work in GSM,
we explicitly state that this is a legitimate project.

  • We do not infringe on any copyright
  • We do not reveal any trade secrets
  • We do not break any digital restrictions (DRM)
  • We do not implement or break any encryption algorithm


This project honors the copyright of third parties.

Specifically, the source code published by us does not infringe on copyrights of others like Motorola, TI, Vitelcom or Compal.

The software we publish for the GSM baseband is either original development by the project engineers or source code that is taken from sources licensed under GNU GPL.

Information Sources

We outline that we have only used public sources of information in the development of this project. There is no infringement on trade secrets of any sort.

Documentation on the GSM protocols

The GSM protocols are fully documented and specified by the 3GPP. They are publicly available for everyone.
There are no trade secrets involved in imlpementing the GSM protocols, including the Um air interface betwee phone and network.

The only parts that are undisclosed are the optional encryption methods called A5. Despite their secrecy, they have been thoroughly documented and broken in
academic research and resulting publications. There is no trade secret in that encryption anymore.

Furthermore, in those phones that our software runs on, the A5 encryption is implemented as a black box in hardware. Our software contains no information
about the GSM A5 encryption at all.

Documentation on Phones

Service Manuals including circuit descriptions and full schematics are widely available for all major phones, including the Motorola phones that we started this project on.

Such service manuals are authored by the phone maker and distributed to cellphone repair shops around the world. They are intended to aid understanding the phone hardware.

There are dozens of web sites in various countries around the world that make those schematics available. There is no serious attempt by any phone maker we know of to
halt the unofficial circulation of service manuals.

We officially buy the respective phones, and we wish to simply make our own software interoperable with the hardware.

The Vitelcom TSM30 source code

In 2005, the complete source code of the software running on the Vitelcom TSM30 phone was uploaded to the popular open source website, from where it is publicly
availalbe for download. According to statistics, it has been downloaded thousands of times ever since. As the download was never removed and no action has
been taken by the copyright holders, we assume that the source code was legitimately published, but under a non-permissive license. We do not use any of that copyrighted
code in our software, and we do not distribute that source code. We therefore do not infringe its copyright.

Even if its publication was unauthorized, its public availability for five years clearly outlines that any information contained in it can no longer be considered a trade
secret. Therfore, any information we deducted form it about how the digital baseband hardware works is not a trade secret either.

The leaked Ti Calypso documentation

At various places on the internet, two documents with register-level details on the TI Calypso DBB circuit have been published. While those documents contain notices
of confidentiality, their availability online once again indicates that the information contained in the documents is no secret, at least not ever since somebody might
have broken an NDA and publicly disclosed the information.

Using modified phones on carrier networks

Note: So far, our custom software does not activate the transmitter in the phone. Therefore, it works in receive-only mode as of now.

There are many reasons why we do not recommend or endorse operating our software on carrier networks
  • the software modifies the RF parameters of the phone, which are part of the regulatory approval
    • regulatory approval of the phones is lost once our software is installed
    • operating equipment without regulatory approval is illegal in probably almost all jurisdictions
  • our software is in early development stage
  • the terms and conditions of carrier networks vary, but will likely not allow the use of uncertified/unauthorized phones

We therefore only use our software with our own GSM test networks, e.g. using OpenBTS or OpenBSC with BS-11 or nanoBTS.


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