README-first/README-endorser-context.md

Endorser.ch Context

Project Overview

Endorser.ch is an API for creating and querying claims in privacy-preserving ways. The system allows users to make cryptographically signed claims (attestations) and confirmations while maintaining control over their personal identifiers' visibility.

Core Principles

1. Privacy-Preserving: Store and retrieve textual data publicly while ensuring identifier visibility is fully controlled by each user.

2. Accessibility: Provide service without cost to users in selected communities, with rate-limiting to manage usage.

3. Verification: Support only cryptographically signed claims and confirmations, ensuring authenticity.

4. Discovery: Enable discovery of other users through visibility networks or users' preferred messaging networks.

5. Utility: Support specific use cases like counting confirmations or aggregating claim totals.

Key Technical Concepts

Decentralized Identifiers (DIDs)

• The system uses DIDs as the primary user identification mechanism
• Visibility of DIDs is controlled by the user
• Hidden DIDs are represented as HIDDEN_TEXT in responses

Claims and Confirmations

• Claims are attestations made by users about events, actions, or tenures
• Confirmations are verification of claims by other users
• All claims and confirmations are cryptographically signed using JWTs

Merkle-Chained Claims

• Claims are chained together using cryptographic merkle hashes
• The entire system maintains a most-recent merkle hash of all claims
• Each user has their own most-recent merkle hash available
• Observers with visibility permissions can verify they have the latest data
• This enables data integrity verification for both individual users and the entire system
• Supports efficient synchronization and verification of claim histories

Visibility Control

• Users explicitly control who can see their identifiers
• Visibility can be granted or revoked between users
• Claims may be visible but with identifiers hidden

Location-Based Features

• System supports geospatial data for claims and profiles
• Location data can be searched and retrieved in privacy-preserving ways
• Tile-based location indexing for efficient spatial queries

User Profiles

• Users can create and update profiles with descriptions and locations
• Profiles are searchable by text and location
• Visibility rules apply to profile data

Implementation Goals

1. Simple-to-deploy service with minimal dependencies
2. Fast response times for common operations
3. Well-defined rules for visibility and access control
4. Scalable architecture for growing user bases
5. Resistance to abuse through rate-limiting and verification requirements

Top Use Cases

1. Attendance verification for events
2. Community participation tracking
3. Location-based claim verification
4. Peer-to-peer endorsements with privacy controls
5. Building trust networks with controlled visibility