Skip to content

Verifying GEMS Libraries

Users may accidentaly modify a library file or download a corrupted version. Verifying the file's integrity against an official SHA-256 hash ensures:

  • The file has not been modified
  • Simulation results are reproducible
  • Debugging is simplified by eliminating file inconsistencies

What is a SHA-256 hash?

A SHA-256 hash is a unique fingerprint of a file. - Any change — even a single character — produces a completely different hash. - Identical files always produce the same hash.

Where to find the official hash

Each library's official SHA-256 hash is published alongside the library in the GitHub repository, as a .sha256 file:

libraries/
  basic_models_library.yml
  basic_models_library.yml.sha256   ← official hash is here
  ...

Always use the hash corresponding to the exact version you downloaded. You can find the .sha256 files in the libraries/ directory on GitHub.

Example content of basic_models_library.yml.sha256:

4809d2...  basic_models_library.yml

How to compute the hash locally

sha256sum or Get-FileHash are already installed in Linux/macOS and Windows. So, no installation is needed for these commands

Linux / macOS

sha256sum basic_models_library.yml

Windows (PowerShell)

Get-FileHash basic_models_library.yml -Algorithm SHA256

Windows (alternative)

certutil -hashfile basic_models_library.yml SHA256

How to verify the library

Online

  1. Download the library file from Github (e.g. ...) as well as the corresponding .sha256 file.

Offline

  1. Create your test case offline, manipulating the library and building a system.

  2. Consistency check before running the simulation:

    • Compute the hash of your downloaded file using one of the commands above
    • Compare the two hash values :
    Result Meaning
    Hashes match The file is identical to the official release
    Hashes differ The file has been modified, corrupted, or is not the official version
Example verification We can compare the two basic-models-library SHA
Official: 4809d22d8...
Local: 4809d22d8...
Result: Match (file is identical)