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galileo-osnma

Crates.io Rust

galileo-osnma is a Rust implementation of the Galileo OSNMA (Open Service Navigation Message Authentication) protocol. This protocol is used by the Galileo GNSS to sign cryptographically the navigation message data transmitted by its satellites, in order to prevent spoofing. Briefly speaking, galileo-osnma can process the navigation message data and OSNMA cryptographic data and check all the cryptographic signatures against the ECDSA public key, in order to check the authenticity of the navigation data.

galileo-osnma does not require the Rust Standard library (it can be built with no_std), allocates all its data statically on the stack, and has a relatively small memory footprint for the data (~65 KiB if Slow MAC is used and data for 36 satellites in parallel is stored, and ~7 KiB if Slow MAC is not used and data for only 12 satellites in parallel is stored). This makes it possible to use the library in some embedded microcontrollers. A demo of galileo-osnma running in a Longan nano GD32VF103 board is provided in the osnma-longan-nano crate. This is a RISC-V microcontroller with 128 KiB of flash and 32 KiB of flash that is similar to the popular STM32F103 ARM Cortex-M3 microcontroller.

Documentation

The documentation for galileo-osnma is hosted in docs.rs.

The following reference documents from the Galileo system are relevant:

Quick start using Galmon

galileo-osnma comes with a small binary application that can read Galileo INAV pages using the Galmon transport protocol. This is located in the galmon-osnma folder.

A quick way to see this working is to use the Galmon Galileo navigation data feed, which streams from 86.82.68.237, TCP port 10000. From the galmon-osnma folder, we can run

nc 86.82.68.237 10000 | RUST_LOG=info cargo run --release OSNMA_PublicKey_20210920133026.pem

to see galileo-osnma processing the OSNMA and navigation data streamed by Galmon. The env_logger documentation describes how the logging information produced by this application can be configured.

Note that Galmon aggregates data from many receivers around the world, which is not the expected use case for galileo-osnma. Therefore, when running this, there can be some small problems with data or timestamps inconsistencies.

Alternatively, you can use one of the tools of Galmon with your own GNSS receiver. For instance, an uBlox receiver can be used as

ubxtool --wait --port /dev/ttyACM0 --station 1 --stdout --galileo | RUST_LOG=info cargo run --release OSNMA_PublicKey_20210920133026.pem

The OSNMA ECDSA public key needs to be obtained to run this application. This can be downloaded from the European GNSS Service Centre by registering to the public observation test phase. The registration takes a few days to be verified. The PEM file should only contain the public key, and not the elliptic curve parameters (the PEM file should only contain the -----BEGIN PUBLIC KEY----- line, the -----END PUBLIC KEY----- line, and the Base64 data between these two lines).

Development status

galileo-osnma already provides a solution that is usable during the puublic test phase of OSNMA. It can authenticate all the types of navigation data currently supported by OSNMA using the ECDSA P-256 public key. There are some features of the OSNMA protocol and some roadmap features that are not implemented yet. These are listed below.

Supported features:

  • Verification of DSM-KROOT using ECDSA P-256.
  • Verification of TESLA keys using the TESLA root key or another previously authenticated key in the chain.
  • Verification of the MACSEQ and ADKD fields of the MACK message using the MAC look-up table.
  • Verification of navigation data for ADKD=0, ADKD=4 and ADKD=12 using all the tags in the MACK messages.
  • Retrieval of DSM messages using OSNMA data.
  • Retrieval of MACK messages using OSNMA data.
  • Navigation data retrieval using INAV words.
  • Storage of the current TESLA key.
  • Storage and classification of MACK messages and navigation data.
  • Tag accumulation. 80 bit worth of tags are required to consider a piece of navigation data as authenticated.

Unsupported features:

  • Verification of DSM-KROOT using ECDSA P-521. A Rust implementation of this elliptic curve is needed. This curve is currently not being used in the public test phase of OSNMA.
  • Public key renewal. The parsing of DSM-PKR messages and the authentication using the Merkle tree is not implemented yet.
  • Change of TESLA chain scenarios. Currently it is assumed that there is only one TESLA chain being used. The handling of the scenarios defined in Section 5.5 of the OSNMA User ICD is not implemented.
  • Flexible ADKDs in the MAC look-up table. These are not currently defined for the OSNMA test phase.
  • Warm start, by loading a previously authenticated TESLA key.

Roadmap features. These are not features of OSNMA itself, but will add to the functionality and usability of galileo-osnma:

  • C API
  • Python API

License

Licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.