15+ years shipping production software: Rust SDKs and core protocols, applied cryptography, crypto wallets, and iOS apps. Based in Stockholm, Sweden, open to remote.

Open to full-time roles. I prefer B2B invoicing through my company, Alexander Cyon Consulting AB, but I'm open to EOR.

📫 alex [at] cyonconsulting [dot] com · LinkedIn

• Spotify (2026–present): Principal iOS Engineer on a consumer-facing feature team, working in one of the world's largest iOS codebases (Swift, UIKit, Bazel). I do much of my day-to-day delivery with AI coding agents (Claude Code, OpenAI Codex).
• Parity Technologies / Polkadot (2025): Rust core-protocol work on polkadot-sdk covering consensus, runtime APIs and P2P networking.
• Radix DLT (2019–2025): Principal Cryptography & Middleware Engineer. I led and mentored 10 engineers and merged 500 PRs across 18 public repositories.
  • Authored Sargon, a Rust SDK with UniFFI bindings shared by the iOS and Android wallets: over 90% code reuse and 99% test coverage.
  • Designed Radix Connect, an end-to-end encrypted protocol between the browser and the wallet.
  • Designed the multi-factor authentication and threshold-signature system.
  • Built the Ledger hardware-wallet apps in C and Rust.
• Zilliqa (2018–2019): built Zhip, the first iOS wallet for Zilliqa, on my own Schnorr and ECDSA implementation over secp256k1. I was the first recipient of a Zilliqa ecosystem grant.
• Earlier (2010–2018): iOS lead, architect and developer for PayPal (iZettle), BookBeat (as founding mobile developer), Avanza Bank, Aftonbladet, Nordic Choice Hotels, Ericsson and Samsung.

540+ merged pull requests in 32 public repositories I don't own, including contributions to Apple swift-crypto and Mozilla UniFFI.

• klirr (Rust): zero-maintenance invoicing CLI, my most-starred project
• K1 (Swift): safe wrapper around bitcoin-core's libsecp256k1 (ECDSA, Schnorr/BIP-340, ECDH) with a CryptoKit-style API
• EllipticCurveKit and EquationKit (Swift): elliptic curve cryptography from scratch, built on symbolic algebra
• lera (Rust): write SwiftUI and Jetpack Compose ViewModels once, in Rust via UniFFI
• Makt (Swift): reverse-engineered the binary file formats of Heroes of Might and Magic III

Skills: Rust (Tokio, Axum, SQLx, UniFFI) · Swift (SwiftUI, UIKit, TCA) · Kotlin · TypeScript · Python · C · secp256k1 · Schnorr · ECDH · BLS12-381 · threshold signatures · MFA · blockchain/DLT · Ledger hardware wallets · CI/CD · AI-assisted development