Piri Signing Service

A secure HTTP signing service for Storacha's Proof of Data Possession (PDP) operations on Filecoin.

Why This Service Exists

The Piri Signing Service acts as a secure bridge between Storacha's cold wallet and the PDP verification system on Filecoin. Instead of exposing private keys directly to multiple piri nodes, this service provides a centralized, auditable signing endpoint that:

1. Protects Storacha's private keys - Keys never leave the signing service
2. Enables distributed operations - Multiple piri nodes can request signatures without key access
3. Provides audit trails - All signing operations can be logged and monitored
4. Supports future authentication - Designed to evolve from blind signing to authenticated operations

Quick Start

1. Install the Service

go install github.com/storacha/piri-signing-service@latest

Or build from source:

git clone https://github.com/storacha/piri-signing-service.git
cd piri-signing-service
go build -o signing-service

2. Configure

Create a signer.yaml file in your working directory:

# Network configuration
host: localhost
port: 7446  # Spells SIGN on T9 keyboard

# Ethereum RPC endpoint (required)
rpc_url: https://api.calibration.node.glif.io/rpc/v1

# Contract address (required)
service_contract_address: "0x8b7aa0a68f5717e400F1C4D37F7a28f84f76dF91"

# Private key configuration (choose one)
signing_key: "0x0000000000000000000000000000000000000000"
# OR
# signing_key_path: /secure/path/to/key.hex
# OR
# signing_keystore_path: /secure/path/to/keystore.json
# signing_keystore_password: your-password

See signer.yaml.example for full configuration options.

3. Run

./signing-service

The service will start and display:

• Signer address (the address that will sign operations)
• Chain ID (detected from RPC endpoint)
• Contract address (for verification)
• Listening endpoint

Configuration

The service supports multiple configuration methods with the following priority:

1. Command-line flags (highest priority)
2. Environment variables
3. Configuration file (signer.yaml)
4. Default values (only for host and port)

Configuration Methods

Via Configuration File

Place a signer.yaml file in the current directory. See signer.yaml.example for a complete template.

Via Environment Variables

All configuration can be set via environment variables with the SIGNING_SERVICE_ prefix:

export SIGNING_SERVICE_RPC_URL=https://api.calibration.node.glif.io/rpc/v1
export SIGNING_SERVICE_SERVICE_CONTRACT_ADDRESS=0x8b7aa0a68f5717e400F1C4D37F7a28f84f76dF91
export SIGNING_SERVICE_SIGNING_KEY_PATH=/secure/path/to/key.hex

Via Command-line Flags

./signing-service \
  --rpc-url=https://api.calibration.node.glif.io/rpc/v1 \
  --contract-address=0x8b7aa0a68f5717e400F1C4D37F7a28f84f76dF91 \
  --signing-key-path=/secure/path/to/key.hex

Required Configuration

The following must be provided (no defaults):

• rpc_url - Ethereum RPC endpoint
• service_contract_address - FilecoinWarmStorageService contract address
• Either signing_key OR signing_key_path OR signing_keystore_path + signing_keystore_password

Service deployment

This project contains Terraform/OpenTofu deployment scripts for the service, generated using the storoku tool. The scripts are located in the deploy directory.

A GitHub Actions workflow will deploy the service when a new release is created. These deployments can also be triggered manually from a development environment.

Required environment variables that are not secrets are set in deploy/.env.production.local.tpl. More specifically, rpc_url and service_contract_address are defined there (as SIGNING_SERVICE_RPC_URL and SIGNING_SERVICE_SERVICE_CONTRACT_ADDRESS, respectively).

API Endpoints

Health Check

curl http://localhost:7446/healthcheck

Sign Create Dataset

curl -X POST http://localhost:7446/sign/create-dataset \
  -H "Content-Type: application/json" \
  -d '{
    "clientDatasetId": "1",
    "payeeAddress": "0xYourPayeeAddress",
    "metadata": {
      "key1": "value1",
      "key2": "value2"
    }
  }'

Sign Add Pieces

curl -X POST http://localhost:7446/sign/add-pieces \
  -H "Content-Type: application/json" \
  -d '{
    "clientDatasetId": "1",
    "pieces": ["piece1", "piece2"]
  }'

Sign Schedule Piece Removals

curl -X POST http://localhost:7446/sign/schedule-piece-removals \
  -H "Content-Type: application/json" \
  -d '{
    "clientDatasetId": "1",
    "pieces": ["piece1", "piece2"]
  }'

Sign Delete Dataset

curl -X POST http://localhost:7446/sign/delete-dataset \
  -H "Content-Type: application/json" \
  -d '{
    "clientDatasetId": "1"
  }'

Security Roadmap

The service is designed to evolve through multiple security phases:

Phase 1: Blind Signing (Current)

• Signs any properly formatted request
• No authentication required
• Suitable for trusted, private networks only
• ⚠️ WARNING: Do not expose to public internet

Phase 2: UCAN Authentication (Planned)

• Registered operators authenticate via UCAN tokens
• Each operator has specific permissions
• Audit trail of who requested each signature

Phase 3: Session Keys (Future)

• Temporary session keys for time-limited operations
• Reduced exposure of primary signing key
• Automatic key rotation

Phase 4: Hardware Security Module (Future)

• Cold wallet replaced with HSM or cloud KMS
• Hardware-level key protection
• Compliance with security standards

Production Deployment

Recommended Setup

1. Run on a secure, isolated network - Not exposed to public internet
2. Use environment variables or secure key management for sensitive configuration
3. Enable comprehensive logging for audit trails
4. Monitor all signing requests for anomalies
5. Implement rate limiting at the network level
6. Use TLS/HTTPS for all communications

Example Systemd Service

[Unit]
Description=Piri Signing Service
After=network.target

[Service]
Type=simple
User=signing-service
WorkingDirectory=/opt/signing-service
ExecStart=/opt/signing-service/signing-service
Restart=always
RestartSec=10

# Security hardening
NoNewPrivileges=true
PrivateTmp=true
ProtectSystem=strict
ProtectHome=true
ReadWritePaths=/opt/signing-service/logs

# Environment variables
Environment="SIGNING_SERVICE_RPC_URL=https://api.node.glif.io/rpc/v1"
EnvironmentFile=/etc/signing-service/env

[Install]
WantedBy=multi-user.target

Docker Deployment

FROM golang:1.21-alpine AS builder
WORKDIR /app
COPY . .
RUN go build -o signing-service

FROM alpine:latest
RUN apk --no-cache add ca-certificates
WORKDIR /root/
COPY --from=builder /app/signing-service .
EXPOSE 7446
CMD ["./signing-service"]

docker run -d \
  -p 7446:7446 \
  -v /secure/path/to/config:/root/signer.yaml:ro \
  -v /secure/path/to/keys:/keys:ro \
  --name signing-service \
  storacha/piri-signing-service

Monitoring

Key Metrics to Monitor

• Request rate per endpoint
• Response times
• Error rates
• Unique requesters (when authentication is added)
• Gas price at signature time
• Contract verification failures

Example Prometheus Metrics

The service exposes metrics at /metrics (when enabled):

signing_service_requests_total{endpoint="create_dataset"}
signing_service_request_duration_seconds{endpoint="create_dataset"}
signing_service_errors_total{endpoint="create_dataset",error="validation_failed"}
signing_service_signer_address{address="0x..."}

Troubleshooting

Common Issues

Service won't start

• Check all required configuration is provided
• Verify RPC endpoint is reachable
• Ensure private key file has correct permissions (600)

"Invalid contract address"

• Verify the contract address is a valid Ethereum address
• Ensure it matches the deployed FilecoinWarmStorageService contract

"Failed to get chain ID"

• Check RPC endpoint is correct and accessible
• Verify network connectivity

"Invalid signature" from contract

• Ensure chain ID matches the network
• Verify contract address is correct
• Check that the signer address has appropriate permissions

Development

Running Tests

go test ./...

Building for Different Platforms

# Linux
GOOS=linux GOARCH=amd64 go build -o signing-service-linux

# macOS
GOOS=darwin GOARCH=amd64 go build -o signing-service-darwin

# Windows
GOOS=windows GOARCH=amd64 go build -o signing-service.exe

Support

For issues, feature requests, or questions:

• GitHub Issues: https://github.com/storacha/piri-signing-service/issues
• Documentation: https://docs.storacha.com/signing-service

License

[License details here]