Nullifier.cash is a privacy-preserving transaction mixer on Solana that uses zero-knowledge proofs (zkSNARKs) to break the link between deposit and withdrawal addresses. Users can deposit SOL and withdraw to fresh addresses after a time delay, providing transaction privacy while maintaining the security and speed of the Solana blockchain. The protocol uses Groth16 zkSNARK verification, SHA256-based cryptographic commitments, and Poseidon hash functions for Merkle tree proofs to ensure maximum privacy.