Settrum

Private settlement infrastructure for regulated financial institutions. Built on a permissioned Substrate blockchain with a REST API layer for institutional integrations.

Overview

Settrum provides a complete settlement layer for institutions that require a private, auditable, and deterministic record of asset movements. Operators register on-chain with collateral, define assets, and submit settlements that are finalized and proven through a structured lifecycle. Cross-operator atomic settlements are supported natively.

All settlement logic executes in a Byzantine fault-tolerant blockchain with 6-second finality. The REST API provides a familiar HTTP interface for integrating with existing institutional systems.

Architecture

┌─────────────────────────────────────────────┐
│               settrum-api                   │
│         Actix Web · JWT · PostgreSQL        │
└────────────────────┬────────────────────────┘
                     │ WebSocket RPC
┌────────────────────▼────────────────────────┐
│              settrum-node                   │
│  ┌──────────────────────────────────────┐   │
│  │             Runtime                  │   │
│  │  operators · asset-registry          │   │
│  │  settlement-engine · proofs          │   │
│  │  cross-settlement                    │   │
│  └──────────────────────────────────────┘   │
│  Aura block authoring · GRANDPA finality    │
└─────────────────────────────────────────────┘

Pallets

Pallet	Responsibility
pallet-operators	Operator registration, collateral management, status lifecycle (Active / Suspended / Terminated)
pallet-asset-registry	Multi-type asset registry (Fiat, Commodity, Security, InternalLedger) with supply tracking per issuer
pallet-settlement-engine	Settlement execution — Issue, Redeem, Transfer, Lock, Unlock — with balance and locked-balance accounting
pallet-settlement-proofs	Proof submission and verification across five proof types: Signature, Oracle, Multisig, ZeroKnowledge, Documentary
pallet-cross-settlement	Multi-leg atomic cross-operator settlements with participant approval workflow and expiry

API

The REST API runs on /api/v1. All write endpoints require a JWT obtained via /auth/login.

Resource	Endpoints
Auth	POST /auth/login
Operators	POST /operators · GET /operators · GET /operators/{id} · GET /operators/me · PUT /operators/{id}/status
Assets	POST /assets · GET /assets · GET /assets/{id} · PUT /assets/{id}/supply
Settlements	POST /settlements · GET /settlements · GET /settlements/{id} · POST /settlements/{id}/finalize
Balances	GET /balances/{asset_id}/{account_id} · GET /balances/locked/{asset_id}/{account_id}
Proofs	POST /proofs · GET /proofs/{id} · PUT /proofs/{id}/verify
Cross-Settlements	POST /cross-settlements · GET /cross-settlements/{id} · POST /cross-settlements/{id}/approve · POST /cross-settlements/{id}/execute
Health	GET /health · GET /status

Stack

Layer	Technology
Blockchain	Polkadot SDK polkadot-stable2512-3
Consensus	Aura (block authoring) + GRANDPA (finality) · 6-second blocks
API server	Rust · Actix Web 4
Database	PostgreSQL 15
Auth	JWT HS256 per operator
Build	Rust 1.75+ stable · single binary per component

Requirements

• Rust 1.75+ (rustup target add wasm32-unknown-unknown)
• PostgreSQL 15+
• Docker and Docker Compose (for local deployment)

Running Locally

cp .env.example .env
# Fill in DATABASE_URL, JWT_SECRET, ADMIN_API_KEY

docker compose up

Service	Address
Node RPC	ws://localhost:9944
API	http://localhost:8080
PostgreSQL	localhost:5432

Configuration

All API configuration is via environment variables. See .env.example for the full list. Required variables:

Variable	Description
DATABASE_URL	PostgreSQL connection string
JWT_SECRET	Signing secret for operator JWTs (min 64 chars)
ADMIN_API_KEY	Admin API key for privileged operations (min 64 chars)

Building from Source

# Build all components
cargo build --release --workspace

# Run pallet tests
cargo test --workspace

# Lint
cargo clippy --workspace --all-targets --all-features -- -D warnings

# Node binary
./target/release/settrum-node --dev --tmp

# API (requires running node and PostgreSQL)
./target/release/settrum-api

Production Deployment

See docker-compose.prod.yml for a reference production stack including validator nodes, the API server, Nginx TLS termination, Prometheus, and Grafana.

Validator keys must be generated and injected before starting production nodes:

./settrum-node key generate --scheme sr25519
./settrum-node key insert --key-type aura --scheme sr25519 ...
./settrum-node key insert --key-type gran --scheme ed25519 ...

Security

• All settlement state is on-chain and cryptographically finalized before the API reflects it
• Operator authentication via JWT; administrative operations require a separate API key
• Rate limiting enforced per operator
• Database queries use parameterized statements throughout
• No unsafe Rust (#![forbid(unsafe_code)] in every crate)