#Signal private contact discovery full#
#Signal private contact discovery code#

'However, this is in the range of a few seconds even in mobile networks for the synchronization of up to 1000 contacts,' said Rechberger. There may be some latency due to the cryptographic calculations and data transfers only during the initial registration.

Prototype tests have shown that even with 100 million data records, data matching is within a tolerable time frame. Compared to older chip generations, these chips speed up cryptographic calculations by a factor of 35. Successful tests should pave the way for more privacyĪdditional efficiency is promised by the use of modern security chips which are included in most smartphones that have come onto the market in the past seven years. This bilateral data encryption also means that no further information or sensitive data is revealed from the address books. Conversely, the service provider also does not receive any information about the address book entries of the users. There, the address book entries are encrypted with the service provider's secret key, but without the users being able to see the secret key. The service provider's encrypted database is sent to the user in a resource-saving manner-thanks to a compression technique specially developed by the researchers-and stored on the mobile phone. The shared contacts between the service provider and those people who use the messaging service are determined using intersection calculations. The ContactGuard application is based on new encryption protocols that are many times more efficient and secure than all previously existing approaches. This is a new method of contact discovery that significantly limits or completely avoids privacy threats and critical scenarios such as spying on contacts or reselling data and exploiting sensitive relationships. Rechberger has developed 'ContactGuard' together with his Institute colleague Daniel Kales and with the two researchers Christian Weinert and Thomas Schneider from TU Darmstadt. The cyber security expert is professor at the Institute of Applied Information Processing and Communications at Graz University of Technology and area manager for Data Security at the Know Center. All previous options are either completely insecure or at least do not offer any significant protection,' says Christian Rechberger, summarizing the problem. 'There are currently no satisfactory solutions for a contact discovery process by mobile messaging services. Service providers thus not only obtain the data of those individuals who have consented to the data processing themselves, they also obtain the data of those affected who have not installed the respective messaging service at all and thus have not given their consent to the processing and storage of their data.

#Signal private contact discovery full#

Now, you might counter that SGX is full of holes, and I would agree with you.This so-called 'mobile contact discovery' process constitutes a massive invasion of privacy. The actual algorithm is performed in plaintext in the enclave. Signal already uses SGX to implement contact search.

#Signal private contact discovery code#

(Typically the reverse process is used, to attest to a server that a client is running whatever DRM code the company wants.) If you trust Intel SGX (or other secure enclaves) it is theoretically possible for the server to attest to the client that a particular hash of code is running. And the extra-metadata scenario is the one being criticized, I think. However, there's nothing stopping a malicious server from logging a bunch of extra metadata on top of what they claim to log, which would be very interesting for nation states. Message content is protected by well-scrutinized and auditable client code. We should make a distinction between the server tampering with message content and message metadata.