Hidder

Hidder acts as the client half of a pair whose other half is the ModSeeker Paper plugin, and the two exchange data through a custom plugin messaging channel built into Minecraft. When a player joins a server running ModSeeker, the check runs in the background and finishes in under a second, and the mod does not require any manual configuration. Collected data covers installed mods, resource packs and shaders, and it is encrypted before it leaves the client so that only the target server can read it.

The security design rests on authentication, confidentiality and integrity. Each connection uses a challenge-response handshake in which the server generates a random nonce. Before transmission, the mod list is wrapped in hybrid encryption: a freshly generated AES-256 session key protects the content, and that key is then locked with the server's RSA public key. Responses carry a session-bound HMAC and timestamps, and the cryptographic operations run inside a compiled native library. The mod also identifies the launcher using native operating system inspection, since a self-reported launcher name can be guessed.

Hidder is open source under the GNU Affero General Public License v3.0 or later, and its source code is public. Files are published for Fabric only, for 1.21.4, 1.21.7, 1.21.8, 1.21.9, 1.21.10, 1.21.11, 26.1 and 26.1.1, with v2.0-26.1 as the latest file for 26.1.1.