Sigforgery: Breaking and Fixing Data Authenticity in Sigfox

Abstract

Sigfox is a popular communication and security protocol which allows setting up low-power wide-area networks for the Internet of Things. Currently, Sigfox networks operate in 72 countries, and cover 1.3 billion people. In this paper, we make an extensive analysis of the security mechanisms used to protect the radio interface in Sigfox. We describe news attacks against data authenticity, which is the only mandatory security property in Sigfox. Namely we describe how to replay frames, and how to compute forgeries. In addition, we highlight a flaw in the (optional) data encryption procedure. Our attacks do not exploit implementation or hardware bugs, nor do they imply a physical access to any equipment (e.g., legitimate end-device). They rely only on the peculiarities of the Sigfox security protocol. Our analysis is supported by practical experiments made in interaction with the Sigfox back-end network. These experiments validate our findings. Finally, we present efficient counter-measures which are likely straightforward to implement.

Appendices

A Practical Experiments

Fig. 1.

Experiment bench

Fig. 2.

Screen shots of forged frames accepted by the Sigfox back-end network. From top to bottom, the two pairs of frames correspond to the forgery types “clear_6” and “encrypted_5”. For each forgery type, the pair of genuine frames corresponds respectively to zero bytes and random bytes in the payload.

Figure 2 corresponds to screen shots made, from top to bottom, of two forged frames of type “clear_6” (the first original frame is made of 6 zero bytes, the second one of random bytes), and two forged frames of type “encrypted_5” (the first original frame is made of 5 zero bytes, the second one of random bytes) received on the back-end network. Table 5 lists an example of each forgery type (Fig. 1).

Table 5. Samples of forged frames. If the uplink frame is encrypted, the data received on the back-end is first decrypted, and then stored. The type “encrypted_4” has not been tested in real-life experiments.

B Sigfox Architecture

Fig. 3.

Sigfox architecture (source: [13])

C Sigfox Coverage in Several Geographic Areas

See (Fig. 4).

Fig. 4.

Sigfox coverage in several geographic areas (source: [14]). Actual deployments appear in , ongoing deployments appear in . (Color figure online)