SeedGuard

SeedGuard is a security plugin for Paper 1.21.11 that helps protect SMP servers from common methods used to obtain the world seed.

The plugin is designed for server owners who want to significantly increase the difficulty of seed extraction by players using seed-cracker mods, exploits, packet-based methods, and technical abuse of structure/NBT mechanics.

About the plugin

SeedGuard does not promise absolute mathematical impossibility of recovering the seed in every theoretical scenario.

Instead, it blocks and complicates the most common and practical seed leak paths on multiplayer servers.

Features

1. Fake seed

The plugin intercepts important outgoing packets and replaces the real hashed seed with a fake value.

Protection is applied in key scenarios:

• joining the server
• respawning / state changes where the client receives world data again

This makes it harder for client-side mods and tools to read the real seed directly from network data.

2. Command blocking

The plugin blocks:

• /seed
• /minecraft:seed
• /bukkit:seed
• /spigot:seed
• /paper:seed

3. Command hiding

Blocked commands are removed from:

• the list of available commands
• tab-completion suggestions
• command suggestions where possible

4. Structure and Jigsaw

The plugin can block:

• placing structure blocks
• breaking structure blocks
• interacting with structure blocks
• placing jigsaw blocks
• breaking jigsaw blocks
• using jigsaw-related functionality

5. Packet protection

SeedGuard blocks technical packets related to:

• block/entity NBT queries
• structure update/generate
• jigsaw update
• debug subscription-like requests

6. Fake seed modes

The following modes are supported:

• per_player_stable — a stable fake seed for each player
• random_each_join — a new fake seed on every join
• fixed — the same configured fake seed for everyone

Recommended mode

For most SMP servers, it is recommended to use:

fake-seed:
  mode: "per_player_stable"

Configuration

The plugin allows you to individually enable or disable:

• join packet protection
• respawn packet protection
• structure packet blocking
• jigsaw packet blocking
• NBT query packet blocking
• debug packet blocking
• command list updating on player join
• console logging of blocked attempts

Permission

seedguard.bypass

Players with this permission bypass the plugin’s restrictions.

Compatibility

• Server: Paper
• Minecraft version: 1.21.11
• Java: 21 recommended

Important

SeedGuard is a hardening plugin, not a “magic button”. It is designed to make real-world seed leak methods much less convenient and to block the most common practical seed leak paths on SMP servers.

Installation

1. Download the latest version
2. Move the .jar file into the plugins folder
3. Start or restart the server
4. Configure config.yml if needed
5. Make sure to replace the default salt with your own long random string

Recommendations

• Use Paper 1.21.11
• Use Java 21
• Replace the default salt in the config before using the plugin on a live server

Why use SeedGuard

SeedGuard is a good choice if you want to:

• make seed-cracker mods less effective
• close easy seed leak paths
• improve the security of a public or private SMP
• limit technical abuse related to structure/NBT packet paths