nklave

🌐 Site · 📚 Docs · 📦 crates.io package · 🔬 Cryptuon Research

Policy-enforcing trust boundary for PoS validators — the slashing firewall in front of your signing keys.

Nklave is a signing security layer that makes slashable signing impossible by construction. It sits between validator clients and signing keys, enforcing EIP-3076 slashing-prevention rules and configurable policies before any signature is produced — so a compromised or buggy validator client cannot produce a slashable signature, even when the host is fully compromised.

Why this matters in 2026: restaking multiplies your slashing surface

For most of proof-of-stake's history, a validator key faced exactly one slashing surface: the consensus layer of the chain it validated. Restaking changed that. As EigenLayer-style restaking and Actively Validated Services (AVS) go mainstream, the same staked capital and — increasingly — the same keys are opted into multiple independent slashing regimes at once. Each AVS defines its own slashing conditions. Each one is a new way to lose stake, governed by code you did not write.

That shift makes the boundary between "what asked for a signature" and "what actually gets signed" the single most valuable control point a staking operation has. A policy firewall that sits in front of the signing keys — refusing anything that violates a rule before the key is touched, and logging every decision — stops being a nice-to-have and becomes critical infrastructure.

nklave is that firewall. Today it enforces the consensus-layer slashing rules that account for the overwhelming majority of real-world slashing incidents (double proposals, double votes, surround votes on Ethereum; height/round double-signing on CometBFT), with EIP-3076 interchange import/export for migration. Its policy layer evaluates every request to an explicit allow-or-refuse decision before the key is reached — exactly the shape you need as restaking pushes more, and more heterogeneous, signing constraints down onto the same keys.

Honest scope: nklave enforces protocol-level slashing prevention (EIP-3076 and equivalents). AVS-specific slashing conditions are defined per-service and are not built in — but the policy engine is designed so operators can express additional guardrails as first-class policies. See ROADMAP.md for where restaking-aware policy work is headed.

┌─────────────────┐         ┌─────────────────────────────────┐         ┌─────────────────┐
│ Validator Client│         │            Nklave               │         │  Signing Keys   │
│                 │  Sign   │  ┌───────────────────────────┐  │         │                 │
│  - Lighthouse   │ ──────▶ │  │     Policy Engine         │  │ ──────▶ │  - BLS (ETH2)   │
│  - Teku         │         │  │  ┌─────────────────────┐  │  │         │  - Ed25519      │
│  - Prysm        │ ◀────── │  │  │ Slashing Protection │  │  │ ◀────── │    (Cosmos)     │
│  - Lodestar     │  Sig/   │  │  └─────────────────────┘  │  │  Sign   │                 │
│                 │  Refuse │  └───────────────────────────┘  │         │                 │
└─────────────────┘         └─────────────────────────────────┘         └─────────────────┘
                                         │
                                         ▼
                            ┌───────────────────────┐
                            │   Append-Only Log     │
                            │   + Checkpoints       │
                            └───────────────────────┘

Quick Start

Docker

docker run -p 9000:9000 ghcr.io/cryptuon/nklave

From Source

cargo install nklave-server
nklave --keys-dir ./keys --data-dir ./data

With Docker Compose

git clone https://github.com/cryptuon/nklave
cd nklave
docker compose -f docker/docker-compose.yml up

Features

• Enforce before the key is touched - The policy chain evaluates every request first; a refused request never reaches the keystore or HSM. Slashable signing is impossible by construction, even if the host is compromised.
• Web3Signer Compatible - Drop-in replacement for existing validator setups
• Slashing Protection - Enforces EIP-3076 and custom rules at the signing layer
• First-class policy engine - Slashing rules live in a dedicated policy module (nklave-core::policy) that returns an explicit Allow/Refuse(code) decision per request — a real enforcement layer, not a config afterthought, and the extension point that matters as restaking pushes more signing constraints onto the same keys
• Multi-Chain - Ethereum (BLS), Cosmos/CometBFT (Ed25519), extensible to others
• Audit Trail - Append-only decision logs with cryptographic chaining
• State Integrity - Rollback-resistant checkpoints prevent state manipulation
• Embedded UI - Vue.js dashboard for monitoring and operations
• High Availability - Primary/passive replication with automatic failover

Crates

Crate	Description
nklave-core	Core signing logic, BLS/Ed25519 keys, slashing protection rules
nklave-api	Web3Signer-compatible HTTP API with embedded UI
nklave-storage	Append-only logs, checkpoints, EIP-3076 interchange
nklave-server	Main server binary with TLS, metrics, configuration
nklave-cosmos	Cosmos/CometBFT remote signer protocol
nklave-cli	CLI tools for key management and operations

API Endpoints

# Health checks
GET  /livez                          # Liveness probe
GET  /readyz                         # Readiness probe
GET  /health                         # Detailed health status

# Web3Signer API
GET  /api/v1/eth2/publicKeys         # List validator public keys
POST /api/v1/eth2/sign/:pubkey       # Sign a message

# Admin
POST /reload                         # Reload keys from disk
GET  /status                         # Server status
POST /admin/checkpoint               # Force checkpoint

Configuration

Environment variables:

Variable	Default	Description
NKLAVE_LISTEN_ADDR	127.0.0.1:9000	Server listen address
NKLAVE_KEYS_DIR	./keys	Validator keystores directory
NKLAVE_DATA_DIR	./data	State and logs directory
NKLAVE_KEYSTORE_PASSWORD	-	Password for encrypted keystores
NKLAVE_API_TOKENS	-	Comma-separated bearer tokens
NKLAVE_METRICS_ADDR	-	Prometheus metrics endpoint
RUST_LOG	nklave=info	Log level

Documentation

Full documentation at docs.cryptuon.com/nklave:

• Architecture
• Deployment Guide
• Threat Model
• Slashing Policy
• API Reference

See ROADMAP.md for the project vision, milestones, and the cheapest path to a production deployment.

Contributing

Contributions are welcome. Please open an issue to discuss significant changes before submitting a PR.

# Run tests
cargo test --all

# Run with coverage
cargo llvm-cov --all-features

# Run benchmarks
cargo bench -p nklave-core

License

MIT License - Cryptuon Research · [email protected]

---

Part of Cryptuon Research

nklave is one of 20 open-source blockchain-infrastructure projects from Cryptuon Research — blockchain theory, shipped as protocols.

Related projects: Tesseract · Switchboard · StreamSync

Docs: docs.cryptuon.com/nklave · Contact: [email protected]