Stop Saying ‘We Need Privacy’
Title: Stop Saying ‘We Need Privacy’
The article argues that "privacy" is not a single concept but rather five distinct problems in the context of blockchain and cryptocurrency. When people demand privacy, they are often referring to one of the following:
1. **Intent Privacy:** Hiding transaction details from observers before execution to prevent front-running by MEV bots. Solutions include private transaction delivery (e.g., Flashbots Protect) and encrypted mempools (e.g., Shutter Network).
2. **Value Privacy:** Concealing the amounts transferred. This is achieved through shielded systems (e.g., Zcash, Penumbra) that use cryptographic proofs to verify transactions without revealing values. Privacy can still be compromised by user behavior patterns.
3. **Graph Privacy:** Protecting the relationships and patterns of who transacts with whom. Techniques include pooled unlinkability (e.g., Tornado Cash mixers) and stealth addresses (e.g., ERC-5564) to break direct on-chain links between transactions.
4. **State Privacy:** Keeping DeFi positions, balances, and liquidation thresholds hidden. This requires storing state as private records and using zero-knowledge proofs (ZK-proofs) to validate state changes without revealing underlying data (e.g., Aztec). Composability and edge interactions remain challenges.
5. **Execution Privacy:** Hiding the computation logic itself, crucial for strategies like auctions or liquidations. Methods include using Trusted Execution Environments (TEEs) (e.g., Secret Network) or ZK-proofs for private execution.
The article concludes that privacy often fails at the edges, such as at the RPC (Remote Procedure Call) layer, where providers can collect IP addresses and wallet information. The key is to ask which surface is being protected and where information might leak when users interact with the real world, rather than seeking a single winning privacy model.
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