Nitro Enclaves Wallet Signer C++

Secure multi-chain wallet signing service using AWS Nitro Enclaves with KMS attestation-based key protection.

Architecture

Text version (ASCII)

┌─────────────────────────────────────────────────────────────────────┐
│                        EC2 Instance (m7i.xlarge)                    │
│                                                                     │
│  ┌─────────────────────────┐         ┌────────────────────────────┐ │
│  │      Parent Process     │  vsock  │         Enclave            │ │
│  │                         │ ══════> │                            │ │
│  │  • Read ciphertext from │ :5000   │  ┌──────────────────────┐  │ │
│  │    DynamoDB             │ ──────> │  │  C++ Signing Service │  │ │
│  │  • Fetch IAM temp creds │         │  │  • ECDSA (EVM)       │  │ │
│  │  • Send sign requests   │         │  │  • Schnorr (Bitcoin) │  │ │
│  │                         │         │  │  • Ed25519 (Solana)  │  │ │
│  └─────────────────────────┘         │  │  • BLS (Beacon)      │  │ │
│                                      │  └──────────────────────┘  │ │
│  ┌─────────────────────────┐         │                            │ │
│  │     vsock-proxy         │         │  ┌──────────────────────┐  │ │
│  │     (port 8000)         │ <────── │  │  kmstool_enclave_cli │  │ │
│  │         │               │  vsock  │  │  • KMS Decrypt       │  │ │
│  │         ▼               │ :8000   │  │  • NSM attestation   │  │ │
│  │  kms.amazonaws.com:443  │         │  └──────────────────────┘  │ │
│  └─────────────────────────┘         └────────────────────────────┘ │
└─────────────────────────────────────────────────────────────────────┘
                    │                              ▲
                    ▼                              │
         ┌──────────────────┐            ┌─────────────────┐
         │    DynamoDB      │            │    AWS KMS      │
         │ (encrypted keys) │            │  (PCR0 policy)  │
         └──────────────────┘            └─────────────────┘

Security: Private keys never leave enclave memory. KMS only decrypts when attestation (PCR0) matches.

Supported Chains

Type	Algorithm	Curve	Chains
evm	ECDSA	secp256k1	Ethereum, BSC, Polygon, Arbitrum, Avalanche
bitcoin	Schnorr (BIP-340)	secp256k1	Bitcoin (Taproot)
solana	EdDSA	Ed25519	Solana, Aptos, Sui, TON, Cosmos
beacon	BLS	BLS12-381	Ethereum Beacon Chain (validators)

Prerequisites

• AWS CLI with configured credential
• Terraform >= 1.0
• SSH client

Quick Start

# Provision AWS infra + store test keys + generate .env
# --profile defaults to "default", --region to ap-northeast-1
./setup.sh --profile <your-aws-profile> --region <aws-region>

# Build kmstool (first time) + EIF + update KMS policy
./deploy.sh

# Start vsock-proxy + enclave
./start.sh

# KMS attestation decrypt → sign
./test.sh evm
./test.sh all                   # Test all chains

# Benchmark (dev/debug, plaintext key)
./test_signing.sh --bench

Project Structure

├── enclave/
│   ├── main.cpp                # Enclave: multi-chain signer + KMS decrypt_and_init
│   └── CMakeLists.txt          # Build: libsecp256k1 + libsodium + blst
├── parent/
│   └── main.cpp                # Parent: signing client + benchmark
├── infra/
│   └── main.tf                 # Terraform: VPC, EC2, KMS, DDB, IAM (tfvars auto-generated by setup.sh)
├── Dockerfile.enclave          # Enclave image (C++ signer + kmstool)
├── setup.sh                    # Provision infra + store test keys + generate .env
├── deploy.sh                   # Build kmstool + EIF + update KMS policy
├── start.sh                    # Start vsock-proxy + enclave
├── test.sh                     # Production test: KMS decrypt → sign (per chain)
└── test_signing.sh             # Dev test: multi-chain signing + benchmark

Performance

Tested on m7i.xlarge (4 vCPU, 16 GiB), enclave 2 vCPU / 1024 MiB, ap-northeast-1.

Chain	Total	KMS Decrypt	Sign P50	Sign P99	TPS
EVM (ECDSA)	~316ms	~315ms	251us	285us	3968
Bitcoin (Schnorr)	~306ms	~305ms	254us	279us	3906
Solana (Ed25519)	~188ms	~187ms	253us	287us	3831
Beacon (BLS)	~211ms	~210ms	607us	666us	1644

• KMS Decrypt: network round-trip, one-time if key cached in enclave memory
• Sign P50/P99: 1000 iterations with 50 warmup (test_signing.sh --bench)
• vsock overhead: ~200us per request, included in Sign latency

Cost: KMS Decrypt Strategy

KMS pricing (ap-northeast-1): $0.03 per 10,000 symmetric requests + $1/month per key.

Strategy	KMS calls	Cost (1M signs/month)	Latency	Security
Decrypt per sign	1M	$3.00	~300ms	Highest
Decrypt on enclave start	1	~$0	~250µs	High (enclave memory is isolated)
Decrypt periodically (e.g. 5min)	~8,640	~$0.03	~250µs	High

Recommended: decrypt on enclave start — enclave memory cannot be accessed externally, so key-in-memory is safe. Re-decrypt only on enclave restart or key rotation.

Teardown

terraform -chdir=infra destroy -auto-approve