08/18/2026
A hardware crypto wallet usually costs around $150. This team built one on an Arduino Uno in 36 hours.
Meet cryptX, a hackathon project from Rahul Balasubramanian, Navin Narayanan, Sakthi Sadayappan, and Akshat Goyal. The name comes from a cryptex, the portable puzzle box built to guard secrets, which is exactly what this device does for your Solana keys.
The team reverse-engineered the Ledger Nano S to understand how private keys stay isolated, then rebuilt that trust boundary themselves. Users create a 6-digit PIN, back up a BIP-39 seed phrase displayed word by word on a small LCD, and physically confirm every signing request with two buttons before a transaction ever reaches the chain. Challenge-response authentication using SipHash-2-4 ties the device identity to the physical silicon it runs on.
The part that makes it feel like a product, though, is the security layer. A Google Gemini agent monitors every connection, PIN attempt, and transaction event, turning raw device logs into real risk assessments. Repeated auth failures or a mid-transaction disconnect gets the device blacklisted automatically. All of it surfaces in a live Next.js dashboard alongside on-chain balances and transaction history.
See the full build at the link in our Instastory đź”—