# Ethereum Privacy Of Reads

_Contributed by [alxkzmn](https://github.com/alxkzmn), [sinu](https://github.com/sinui0), [0xvikasrushi](https://github.com/0xvikasrushi)_

Ethereum users are forced to choose between privacy (running their own node) and practicality (using RPC providers), creating a trade-off that undermines Ethereum's principles of decentralization and user sovereignty. This document aims to explore possible ways to narrow this gap.

## Problem

Reconstruction of [subject identity](https://www.sciencedirect.com/topics/computer-science/subject-identity) (physical or onchain) from Ethereum state requests.

## Rationale

Most users access Ethereum through RPC providers rather than running their own nodes, creating a fundamental privacy vulnerability. While running a personal node would solve this issue, it remains costly and impractical for standard users, especially on resource-constrained devices like smartphones. Local storage of Ethereum's World State is prohibitively expensive for consumer hardware.

### Privacy Exposure

Standard RPC calls (`eth_getBalance`, `eth_call`, `eth_getStorageAt`) expose critical metadata that enables deanonymization:

- **Query Content**: Specific addresses, contract slots, and transaction details being accessed
- **Behavioral Patterns**: Query timing, frequency, and access patterns that reveal user habits
- **Network Metadata**: User's IP address and device fingerprints processed by providers
- **Identity Correlation**: Ability to link on-chain addresses to physical identities through request patterns

### Security Implications

The privacy exposure has tangible security consequences:

- **Physical Security**: Wealth correlation through balance queries can be dangerous for individuals
- **Censorship Risk**: Centralized providers can monitor and restrict access to specific addresses, contracts, or ban users from certain countries
- **Surveillance**: Government and corporate entities can profile user behavior through RPC metadata
- **Data Breaches**: Centralized logging of user queries creates honeypots for malicious actors

### User Requirements

- Sync wallets quickly without downloading full blockchain state
- Operate on low-resource devices (mobile, embedded systems)
- Perform financial transactions without surveillance
- Access Ethereum state without revealing intentions or identity

## Solution Paths

### Node Requirements

If we lower node requirements, users would be more likely to access Ethereum through their own nodes in a private manner.

**Light Clients**: Clients like Helios verify state proofs from peers without storing full blockchain data, reducing storage and bandwidth requirements. However, they currently rely on centralized RPC providers and implementing peer-to-peer networking remains challenging.

**Portal Network**: Distributes Ethereum data across multiple nodes, reducing individual storage requirements and decentralizing data access. Comes with higher latency costs but eliminates reliance on centralized state providers.

**Partial Statelessness**: Future Ethereum proposals suggest nodes will move towards storing only subsets of state data, making node operation more accessible to resource-constrained devices.

**Limitations**: Individual peers still learn about queries they serve, and current implementations face networking complexity and latency trade-offs.

### Private RPCs

There are two ways around private RPCs:

#### Visible Query - Obfuscated Identity

**Network-level Privacy**: Using Tor, mixing networks, or similar routing protocols to anonymize the user's identity while queries remain visible to the server.

**Limitations**: Query content is still visible to the server, requires additional trust assumptions.

#### Obfuscated Query - Visible Identity

**Private Information Retrieval (PIR)**: Clients send encrypted/masked queries to servers, which process them homomorphically. The server cannot determine which specific item was retrieved, but the client's identity may be visible.

**TEEs + ORAM**: Secure enclaves process user queries and forward them to backend nodes without exposing query content to the relay operator. Requires trust in TEE hardware.

**Limitations**: High server-side costs, limited scalability for large databases, potential IP-based tracking.

### Rotating RPCs

Wallets rotate queries across multiple RPC providers, ensuring no single provider sees the user's full query history. This distributes the data and makes it harder for any one entity to profile the user.

**Limitations:**

- Each provider still learns about specific queries sent to them
- If providers collude, they can reconstruct user activity
- Limited number of reliable RPC providers available
- Does not hide query content or user's IP address
- Only makes deanonymization slightly harder

## Observations

zkEVM proofs will let stateless clients easily verify blocks, eroding the incentive to store Ethereum’s full state. Profit-driven dApps (e.g., Uniswap) will keep only their needed slices, centralizing state access and undermining decentralization.

## Next Steps

We recognize this issue as a priority to address and recommend taking action.

### Key Recommendation

Establish a dedicated working group, formed mainly by engineers, to take ownership of the task.

### Proposed Approach

Tackle the problem incrementally, as an example:

- **Initial Action**: Implement rotating RPCs and collaborate with wallets to adopt this change.
- **Subsequent Steps**: Provide guidance and examples for integrating the Tor protocol.

A phased approach enables immediate action.

## Resources

- [Consensys Privacy Notice](https://consensys.io/privacy-notice)
- [DarkFi - Set-up a Tor-enabled node](https://darkrenaissance.github.io/darkfi/misc/nodes/tor-guide.html)
- [Hopr](https://hoprnet.org/)
- [The Crypto Anarchist Manifesto](https://groups.csail.mit.edu/mac/classes/6.805/articles/crypto/cypherpunks/may-crypto-manifesto.html)
- [Peer2PIR: Private Queries for IPFS](https://arxiv.org/abs/2405.17307)
- [Vitalik Buterin on Ethereum Privacy @Web3Privacy hackathon, Berlin 2025](https://www.youtube.com/watch?v=oCANLFSCPq8)
- [Why 'wrench attacks' on wealthy crypto holders are on the rise](https://apnews.com/article/crypto-bitcoin-kidnapping-wrench-attack-ddc7263c25ba590f85648e1682576971)