NOSTR Censorship Improvement Proposal

Hello everyone, I just wanted to pass along a draft of a proposal that I created this evening to try to eliminate or greatly reduce censorship on NOSTR. Please review it when you can and feel free to share any feedback that you have. Thank you. 

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# **NIP-21mm: Hash-Linked Messages and Lightweight Client Relays for Censorship Resistance**

**Date**: March 17, 2025  
**Author**:Bitcoin_Fan_1@protonmail.com 
**Status**: Draft  
**Category**: Protocol Improvement  

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## **Abstract**

This proposal introduces a method to enhance censorship resistance in the Nostr protocol by implementing hash-linked message structures and lightweight client relay functionality. The goal is to ensure that users can verify the integrity and authenticity of their messages while minimizing reliance on external relays. This approach creates a cryptographically verifiable chain of messages for each user and allows users to act as the first relay for their own messages.

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## **Motivation**

Currently, Nostr relies on relays to distribute user-signed messages across the network. However, there is no way for users to ensure that relays are not censoring or tampering with their messages. This lack of transparency undermines the protocol's censorship resistance.

The proposed solution addresses this issue by:
1. Structuring messages in a hash-linked format, enabling verifiable integrity across a user's entire message history.
2. Introducing lightweight relay functionality within client software, allowing users to act as the first relay for their own messages.
3. Providing mechanisms for other clients to verify message authenticity against the user's original relay.

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## **Specification**

### **1. Message Structure**
Each message sent by a user will include additional fields to create a cryptographically verifiable chain of messages. The structure is as follows:

#### **First Message (Message 0)**
The first message sent by a user includes:
- The standard Nostr message data (e.g., `content`, `pubkey`, `created_at`, etc.).
- A SHA256 hash of:
  - The message content.
  - The Unix timestamp (`created_at`) in seconds when the message was created.
  - A sequential message number (`msg_number`), starting at `0`.
- A digital signature of the above hash using the user's private key.

#### **Subsequent Messages**
Each subsequent message includes:
- The standard Nostr message data.
- A SHA256 hash of:
  - The current message content.
  - The Unix timestamp (`created_at`).
  - The sequential message number (`msg_number`).
  - The hash of the previous message in the sequence.
- A digital signature of the above hash using the user's private key.

This creates a hash-linked chain of messages, similar to a blockchain but specific to each user.

### **2. Lightweight Client Relay**
Each Nostr client will include optional lightweight relay functionality to act as the first point of transmission for its user's messages. This relay will:
- Store all messages sent by the user locally.
- Broadcast these messages to one or more external relays for wider distribution.
- Publicly display the hash of each transmitted message for verification purposes.

### **3. Verification by Receiving Clients**
Receiving clients can verify the authenticity and integrity of a user's messages by:
1. Querying the user's personal relay (if available) to retrieve the original message and its hash.
2. Comparing the retrieved hash with hashes stored on other relays.
3. Validating that each message's hash matches its signature and that the chain of hashes is intact.

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## **Rationale**

The proposed changes enhance censorship resistance by:
1. Ensuring that any attempt to censor or tamper with messages is detectable through cryptographic verification.
2. Reducing reliance on external relays by allowing users to act as their own initial relay.
3. Preserving compatibility with existing Nostr infrastructure while introducing optional enhancements.

By linking messages in a cryptographically verifiable chain, users gain greater control over their data without requiring significant changes to existing protocols.

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## **Backward Compatibility**

This proposal is backward-compatible with existing Nostr clients and relays, as it does not alter the core protocol's requirements. Clients and relays that do not implement these changes can still process standard Nostr messages but will not benefit from enhanced verification features.

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## **Security Considerations**

1. **Hash Collision Resistance**: The use of SHA256 ensures that it is computationally infeasible to generate two different inputs with the same hash, preserving message integrity.
2. **Private Key Security**: As with existing Nostr functionality, users must safeguard their private keys to prevent unauthorized signing of messages..
3. **Relay Availability**: If a user's personal relay is offline, verification may be delayed until it becomes available again. External relays can serve as backups in such cases.

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## **Implementation Plan**

1. Add support for hash-linked message structures in Nostr clients.
2. Develop lightweight relay functionality as an optional feature in client software.
3. Update receiving clients to verify hashes against personal relays when available.

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## **Future Work**

1. Explore incentives for external relays to store and distribute verifiable hash-linked messages.
2. Investigate additional cryptographic techniques (e.g., Merkle trees) to optimize storage and verification processes.

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## **Conclusion**

This proposal enhances Nostr's censorship resistance by introducing cryptographically verifiable message chains and empowering users with lightweight client relay functionality. By enabling transparent verification of message authenticity and integrity, it strengthens trust in the protocol while preserving its decentralized nature.

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Received on Tuesday, 18 March 2025 08:00:29 UTC