Stellar Community Fund

Nebula Wallet

SCF #41

SCF #42

Description

Nebula is a post-quantum crypto wallet for Stellar. It lets users send XLM using XMSS signatures a NIST-standardized hash-based scheme that is not broken by quantum computers with on-chain enforcement via a ZK proof, no classical ECDSA or ed25519 anywhere in the signing path. The flow: the user signs a transaction locally with their XMSS private key. An SP1 zkVM circuit proves that a valid XMSS signature over the transaction exists, without revealing the key or the signature. Sindri compiles this to a compact Groth16 proof. The Soroban smart contract verifies the proof on-chain using Stellar's native BN254 host functions, checks replay protection via a wallet nonce, and transfers XLM to the destination. The contract never sees the user's private key. The destination and amount are cryptographically bound inside the proof no relay or intermediary can redirect the funds. A ships a Rust CLI with an interactive TUI, a Chrome browser extension, and a relay server that works around a current Stellar testnet limitation (BN254 pairing disabled in RPC simulation). The full end-to-end flow is live on Stellar testnet.