Signature Files

X4 uses RSA signature files for DRM/integrity verification of official content.

Format

• Every official file has a corresponding .sig file
• Signature catalogs: *_sig.cat/*_sig.dat contain .sig entries for catalog-packed files
• Each .sig file is exactly 1024 bytes (8192-bit RSA signature)
• Signed with Egosoft’s private key, verified with their public key embedded in the game

Impact on mods

• Mods cannot and do not need to generate signature files
• The game logs Could not find signature file for unsigned mod files – this is expected and harmless
• The error appears once per session, then is suppressed (or use fileio debug filter for all)
• This does not affect mod functionality in any way

---