AntiSeedCracker

Version: 3.5.0  |  Target: Minecraft 26.1.2  |  Author: SunsetRQ7_

AntiSeedCracker is a professional, multi-layer world seed protection plugin for Paper, Purpur, and Folia. It blocks every known technique a player can use to recover your world seed, protecting your server from ESP clients, ghost clients, and seed-cracking tools such as SeedCrackerX.

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Features

Protection Layer	Description
Login & Respawn Packet Spoofing	Replaces the hashed seed in JOIN_GAME and RESPAWN network packets with a per-player cryptographically random fake seed. Operates at the Netty I/O level via PacketEvents before any client ever receives the real value.
Dynamic Seed Rotation	Periodically assigns each online player a new random fake seed (configurable interval, minimum 30 s). Only affects the network-facing hashed seed, never the generation seed. Defeats crackers that accumulate packets across multiple sessions.
Seed Integrity Monitor	Read-only watchdog that compares each world's live generation seed against its value at startup and warns in the console if it ever drifts. Never writes to the seed itself — see Correctness & Large-Server Notes for why.
Eye of Ender Redirection	Intercepts thrown Eyes of Ender and redirects their velocity toward a per-player fake stronghold location. Applies a ±8° angular jitter to prevent exact triangulation across repeated throws.
/locate Spoofing	Cancels /locate and replies with convincingly fake coordinates. Stronghold queries use the player's stable fake location for consistency.
/seed Command Block	Blocks /seed, /minecraft:seed, /getseed, /worldseed, and any extra commands configured in config.yml for players, console, and RCON. Also strips seed commands from tab-complete results.
End Spike Randomization	Shuffles the bedrock cap heights of all 10 End obsidian pillars at world load and after each dragon respawn cycle. Breaks the vanilla height fingerprint {76, 79, 82 … 103} that uniquely identifies the seed.
End City Glass Replacement	Replaces magenta stained glass in End City chunks (scanning only the structure's bounding box, not the full chunk column) with purpur blocks on first load. Prevents long-range visual fingerprinting of the distinctive glass pattern.
Treasure & Explorer Map Scrambling	Intercepts MAP_DATA packets and randomises the on-map position of every structure icon (buried treasure, woodland mansion, ocean monument, and others).
Slime Chunk Obfuscation (opt-in)	Cancels natural slime spawns in configured worlds so tools sampling spawn/no-spawn per chunk get no signal. Disables slime farms in those worlds — off by default.
Structure Reconnaissance Monitor	Detects (logs only, never blocks) when a player visits an unusual number of seed-cracking-relevant structures in a short window — the exact structure set SeedCrackerX-style tools use for bit accumulation. Structure list is fully configurable; the chunk-qualifies cache is evicted on chunk unload instead of growing for the entire server uptime. See Threat Model below.
Command Probing Monitor	Detects (logs only, never blocks) a player triggering several blocked seed commands in a short window — a pattern consistent with a script/macro probing for a command-blocker bypass rather than one curious /seed.
/execute-Wrapping Protection	/seed, /locate, and every extra blocked command are also checked against the command an /execute ... run ... chain ultimately dispatches to (recursively, for nested chains), closing a well-known Bukkit command-blocker gap where PlayerCommandPreprocessEvent never re-fires for vanilla's internal command re-dispatch.
Audit Log	Appends every blocked command, spoofed packet, redirected Eye, and recon flag to a flat-file TSV log in plugins/AntiSeedCracker/logs/. Zero external dependencies — no SQLite.

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Compatibility

Platform	Supported	Verified
Paper 26.1.2	✔	✔ Live-tested on build 74, zero errors, seed integrity verified byte-for-byte on disk
Folia 26.1.2	✔ (region-threaded scheduling)	✔ Live-tested on build 8, zero errors, seed integrity verified byte-for-byte on disk
Purpur 26.1.2	✔ (Paper-compatible)	—
Spigot / CraftBukkit	✘ Not supported — the plugin uses Paper-only APIs (Adventure, AsyncScheduler)	—

Runtime: Java 25 or higher is required.

Metrics

Anonymous usage statistics are collected via bStats. This can be disabled globally in plugins/bStats/config.yml.

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Installation

1. Download AntiSeedCracker-3.5.0.jar from Releases.
2. Place it in your server's plugins/ folder.
3. Start or restart the server.
4. Edit plugins/AntiSeedCracker/config.yml to your preference.
5. Run /asc reload to apply changes without restarting.

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Commands

Command	Description	Permission
/asc reload	Reloads config and restarts all protection tasks	antiseedcracker.admin.manage
/asc toggle <feature> [true|false]	Flips (or explicitly sets) one feature live — persists to config.yml and reloads automatically. Tab-completes feature names.	antiseedcracker.admin.manage
/asc status	Shows which protection layers are active	antiseedcracker.admin.status
/asc stats	Displays aggregate event counts from the audit log	antiseedcracker.admin.status
/asc info	Shows version, author, platform, and update status	antiseedcracker.admin.status
/asc help	Lists the subcommands the sender has permission to use	antiseedcracker.admin.status

antiseedcracker.admin is the umbrella permission (default: op) and grants both antiseedcracker.admin.status (read-only) and antiseedcracker.admin.manage (state-changing) as children, so you can hand trusted moderators view-only access without letting them change config. Toggleable feature names for /asc toggle: login, respawn, rotation, endspikes, endcities, locate, integrity, slime, recon, treasuremap, database, probing.

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Configuration

seed_obfuscation:
  intercept_login: true
  intercept_respawn: true

seed_rotation:
  enabled: true
  interval_seconds: 60

structure_protection:
  end_spikes:
    enabled: true
    worlds:
      - world_the_end
    modify_world: true
  end_cities:
    enabled: true
    worlds:
      - world_the_end
    modify_world: true
  spoof_locate_command:
    enabled: true
    max_offset: 2000

seed_integrity_monitor:
  enabled: true

slime_chunk_obfuscation:
  enabled: false
  worlds: []

structure_recon_monitor:
  enabled: true
  threshold: 6
  window_seconds: 900
  # Leave empty to use the built-in default list — see Configuration section below.
  tracked_structures: []

command_probing_monitor:
  enabled: true
  threshold: 5
  window_seconds: 30

eye_of_ender_protection:
  enabled: true
  worlds:
    - world
  fake_stronghold_min_distance: 800
  fake_stronghold_max_distance: 4000

update_checker:
  enabled: true
  modrinth_id: "YOUR_MODRINTH_PROJECT_ID"

database:
  enabled: true
  log_events: true
  max_event_age_days: 30

treasure_map_protection:
  enabled: true

messages:
  seed_blocked_player: "&c[AntiSeedCracker] Access to world seed information is restricted."
  seed_blocked_console: "&c[AntiSeedCracker] Seed access is restricted. The real seed is never exposed."

extra_blocked_commands:
  - "seedcracker"
  - "seedfind"
  - "worldseedinfo"

modify_world Warning

Setting modify_world: true for End spikes or End cities permanently changes world data. Spike bedrock caps are moved to shuffled positions and End City magenta glass is replaced with purpur blocks. These changes persist across restarts. Set to false to disable physical world modifications while keeping all other protection layers active.

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World Safety

AntiSeedCracker never reads, stores, or logs the real world seed. The only world modifications performed are:

• Moving bedrock cap blocks on End obsidian pillars (when end_spikes.modify_world: true).
• Replacing magenta stained glass in End City chunks with purpur blocks (when end_cities.modify_world: true).

Both modifications use physicsUpdate: false to prevent block-update cascades. Each chunk is tagged with a Persistent Data Container key so the modification runs at most once per chunk across all server restarts. No terrain, biome, or structure data outside these specific block types is ever altered.

AntiSeedCracker never writes to a world's generation seed, at any point, for any reason. Earlier versions did (see below) — this caused real damage and has been removed entirely.

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Correctness & Large-Server Notes

Version 3.3.0 fixes a serious bug present in 3.2.0 and earlier. The old "Plugin API Protection" feature patched the live in-memory seed field that Minecraft's own chunk generator reads, once per second, forever, on every loaded world. That field isn't a copy — it's the exact same value the vanilla decoration step (trees, ores, ravines, structure placement) re-reads fresh for every chunk it generates, not just once at world load. The result: any chunk decorated while that field held a fake value got seeded from randomness instead of your real seed, causing visibly broken terrain/structure generation, and the constant reflection-based writing added avoidable overhead and cross-plugin risk on busy servers.

This has been completely removed. In its place, SeedIntegrityMonitor only reads world.getSeed() on a low-frequency timer and logs a warning if it ever changes — it never writes to it. This was verified by booting real Paper 26.1.2 and Folia 26.1.2 servers with explicit known seeds and confirming, at the raw NBT byte level in world_gen_settings.dat, that the seed never drifted after extended runtime.

Other large-server changes in this release:

• EndCityProtector now scans only the generated structure's bounding box instead of the entire chunk column (previously up to 256 vertical blocks × 256 columns per End City chunk).
• The periodic player-seed safety-net task runs every 15s instead of every 1s (it no longer has any seed-patching work to do).

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Threat Model: LiquidBounce & SeedCrackerX Research

This release includes research into how modern cheat clients and cracking tools actually recover seeds, so protections target real techniques rather than guesses:

• SeedCrackerX (the dominant seed-cracking tool) primarily works by combining the exact coordinates of structures the player has legitimately found — shipwrecks, desert pyramids, jungle temples, swamp huts, pillager outposts, ocean monuments, igloos, and End Cities — until it has enough bits to brute-force the seed. This is not a network exploit. A player standing at a real structure already knows their own coordinates; no plugin can hide a player's position from themselves without breaking movement entirely. This is a fundamental limitation of any server-side plugin, not just this one — treat any tool's claim of "100% uncrackable" against this technique with skepticism.
• What we added because of this: StructureReconMonitor watches for the specific pattern SeedCrackerX data-gathering produces — visiting several of those exact structure types in a short time window — and logs it for admin review. It never blocks or punishes, matching this plugin's design; it just gives you visibility into likely automated cracking activity.
• Slime-chunk sampling is another real technique (spawn/no-spawn per chunk leaks a bit of seed information). slime_chunk_obfuscation (opt-in, off by default) cancels natural slime spawns in configured worlds to deny this signal — at the cost of disabling slime farms there.
• LiquidBounce's XRay and StorageESP modules (block/ore/chest ESP) are a different threat entirely — they exploit full chunk data the server must send for rendering, and have nothing to do with the world seed. This is not something a seed-protection plugin should attempt to solve by reimplementing chunk obfuscation (high risk, likely to break vanilla behavior — exactly what large-server admins told us to stop doing). Use Paper's built-in anti-xray (anticheat.anti-xray in paper-world-defaults.yml) for that threat class; it's mature, maintained, and the correct tool for the job. We surveyed the public source/issue trackers of LiquidBounce, Wurst, and Meteor Client directly: seed-cracking integration has been repeatedly requested against all three and never merged, and none of them ship any feature that detects or reacts to a server spoofing/rotating the hashed-seed packet field, faking stronghold triangulation, or scrambling map icons. Their ESP/X-ray modules only render blocks and entities the server already sent in chunk data — confirmed directly from LiquidBounce's own module docs — which is exactly why that threat class is out of this plugin's scope.
• Packet-level hashed-seed spoofing (login/respawn) and /locate spoofing still close off the older, simpler leak vectors that predate SeedCrackerX's structure-based method. Be honest about how load-bearing this layer is, though: the hashed seed is a narrow, low-information channel (originally just cosmetic biome-border noise), and a well-informed cracker that has enough structure-position bits can simply deprioritize or ignore an inconsistent hash rather than being blocked by it. Treat hashed-seed spoofing/rotation as raising the bar against unsophisticated tools, not as a load-bearing defense on its own — the structure-, End-spike-, and End-City-level protections matter more against a serious attacker.
• /execute-wrapping bypass. Vanilla's /execute ... run <command> re-dispatches its trailing command internally without re-firing PlayerCommandPreprocessEvent — a documented, long-standing Bukkit/Spigot architectural gap (command re-dispatch via Server#dispatchCommand or Brigadier's internal redirect never re-triggers that event). A command-blocker that only pattern-matches the literal typed message would let /execute run seed (or nested /execute as @s run execute run seed) straight through. Fixed in 3.5.0: every blocking check also recursively resolves what an /execute chain ultimately dispatches to before deciding whether to block it.
• Known remaining limitation, by design: commands issued by a command block or a data-pack /function never fire PlayerCommandPreprocessEvent at all (not even the outer event /execute at least still fires) — there is no supported Paper/Bukkit API hook for either. Closing this would require NMS-level hooks into Brigadier's command dispatcher, which this plugin deliberately avoids for the same reason it avoids reflection-based seed patching (see Correctness & Large-Server Notes): version-fragile, cross-plugin-risky code that breaks on every Minecraft update. Mitigate by restricting who can place command blocks or edit data packs (both already require elevated permissions/file access on a well-run server) rather than expecting a plugin to police vanilla mechanics with no exposed event.
• Other anti-seed-cracker projects, for comparison. akshualy/AntiSeedCracker (ProtocolLib-based, Spigot 1.20.4–1.21) covers hashed-seed spoofing plus End spike/City modification, similar core scope to this plugin's packet+structure layers. zAntiCracker takes a pure behavioral-heuristic approach instead of packet spoofing — a "suspicion score" from command spam, structure-scan rate, and packet rate, with optional auto-kick; we deliberately don't kick (see Design Principles) and a patient/slow cracker script can trivially stay under rate-based thresholds, but its command-probing concept is genuinely useful as a detection signal, which is why 3.5.0 adds the non-punishing command_probing_monitor. On the Fabric side (a fundamentally different, server-generation-layer approach not available to Paper/Spigot plugins), DrexHD/SeedGuard and Earthcomputer/SecureSeed re-randomize or cryptographically replace the per-feature seeds vanilla derives from the world seed, so structure-position triangulation no longer correlates to anything real — architecturally stronger against the "unblockable" triangulation vector than any packet-layer defense, but it requires Fabric server-side and isn't something the Bukkit/Paper API exposes a hook for. If you can run Fabric, that class of plugin closes a gap this one structurally cannot.

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Folia Threading Model

All block mutations are dispatched to the region thread owning the relevant chunk via RegionScheduler (Folia) or the main thread (Paper). Packet interceptors run on the Netty I/O thread and only perform ConcurrentHashMap lookups. The seed rotation and player-seed safety-net tasks run on the AsyncScheduler (Paper/Folia).

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Known Bypass Mitigations

Attack Vector	Mitigation
Login/Respawn packet interception	PacketEvents HIGHEST-priority intercept
/seed, /getseed, /worldseed	PlayerCommandPreprocessEvent + ServerCommandEvent + RemoteServerCommandEvent blocking
/execute ... run seed (or nested) wrapping	Recursive /execute chain resolution before the block check — see Threat Model
Eye of Ender triangulation	Per-player fake stronghold + ±8° jitter
/locate structure triangulation	Spoofed coordinate output, cached per player+structure so repeated queries stay consistent
Treasure / explorer maps	MAP_DATA packet decoration scrambling, deterministic per map+icon (no visible jitter on refresh)
End spike height fingerprinting	Full Fisher-Yates shuffle of pillar cap heights
End City visual fingerprinting	Magenta glass block replacement (bounding-box scoped)
SeedCrackerX-style structure recon	Detection + audit logging (cannot be prevented — see Threat Model)
Command-blocker bypass scripting/probing	Detection + audit logging (never blocks — see Threat Model)
Slime-chunk seed sampling	Optional natural-spawn cancellation
Tab-complete exposure	TabCompleteEvent filtering
RCON seed commands	RemoteServerCommandEvent blocking
Command-block / data-pack /function execution	Known limitation, not interceptable via Bukkit API — see Threat Model
Block/ore ESP (XRay, StorageESP)	Out of scope — use Paper's native anti-xray

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Building from Source

Requires Maven 3.6+ and JDK 25. The project compiles against folia-api 26.1.2 (Java 25 class files) and produces a Java 25 output jar.

# Windows (adjust to wherever your JDK 25 is actually installed, e.g. under
# "C:\Program Files\Eclipse Adoptium\" for Temurin builds)
set JAVA_HOME=C:\Program Files\Java\jdk-25
mvn clean package

# Linux / macOS
export JAVA_HOME=/path/to/jdk-25
mvn clean package

The shaded jar is produced at target/AntiSeedCracker-3.5.0.jar. PacketEvents 2.13.0 and bStats 3.2.1 are bundled and relocated under me.sunsetrqsv.antiseedcracker.lib.

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Design Principles

• Never punish players. AntiSeedCracker never kicks or bans anyone — it silently feeds cheat clients useless data.
• Never touch the real seed. The plugin never reads, stores, transmits, or logs the actual world seed.
• Never corrupt the world. All optional world modifications are single-block, physics-free, idempotent, and clearly documented.
• Fully asynchronous. Packet work happens on Netty I/O threads; periodic tasks run on async schedulers; block mutations are dispatched to the owning region thread on Folia.

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License

Released under the MIT License. Free to use, modify, and redistribute.