baseid-trust

Build decentralized reputation networks where trust is expressed as Verifiable Credentials, aggregated into a graph, and proven via BBS+ zero-knowledge predicates.

Key Features

• Reputation Attestations — VC-encoded endorsements with domain, score, and weight
• Trust Graph — DID nodes with attestation edges, path queries, domain filtering
• Three Algorithms — DirectOnly, TransitiveTrust (PageRank), ReputationWeighted
• BBS+ Score Proofs — prove “reputation > 80” without revealing the actual score
• Domain-Specific — separate scores for software, legal, finance, etc.

Quick Start

use baseid_trust::*;

// Build a trust graph
let mut graph = TrustGraph::new();

// Alice endorses Bob in software development
let att = AttestationBuilder::new("did:key:alice", "did:key:bob")
    .domain("software")
    .score(85)
    .weight(0.9)
    .evidence("https://github.com/bob/project")
    .build()?;

graph.add_attestation(&att);

// Compute trust score
let score = TrustAlgorithm::DirectOnly.compute(&graph, "did:key:bob", "software");
println!("Score: {:.1}, Confidence: {:.1}", score.score, score.confidence);
// Score: 85.0, Confidence: 0.2

// Add more endorsers to increase confidence
let att2 = AttestationBuilder::new("did:key:carol", "did:key:bob")
    .domain("software").score(90).weight(1.0).build()?;
graph.add_attestation(&att2);

let score = TrustAlgorithm::DirectOnly.compute(&graph, "did:key:bob", "software");
// Score: ~87.4, Confidence: 0.4 (2/5 endorsers)

Trust Algorithms

Algorithm	Description	Best For
DirectOnly	Weighted average of direct attestations	Simple reputation queries
TransitiveTrust	PageRank-style propagation through network	Discovering indirect trust
ReputationWeighted	Attestor’s own score multiplies their weight	Preventing gaming by low-rep nodes

TransitiveTrust Example

// A endorses B, B endorses C — trust propagates A→B→C
let score = TrustAlgorithm::TransitiveTrust {
    damping: 0.85,
    iterations: 20,
}.compute(&graph, "did:key:c", "software");
// C has transitive trust from A through B

ReputationWeighted Example

// High-reputation endorser's attestation counts more
let score = TrustAlgorithm::ReputationWeighted { depth: 2 }
    .compute(&graph, "did:key:bob", "software");
// Alice's endorsement (if she has high rep) weighs more than unknown's

Privacy-Preserving Score Proofs

Prove reputation exceeds a threshold without revealing the actual score:

use baseid_trust::*;
use baseid_bbs::BbsKeyPair;

let kp = BbsKeyPair::generate()?;

// Issue reputation as BBS+ credential
let att = AttestationBuilder::new("did:key:alice", "did:key:bob")
    .domain("software").score(90).build()?;
let credential = issue_reputation_credential(&att, &kp)?;

// Prove score > 80 (verifier learns domain but NOT actual score)
let proof = prove_score_threshold(&credential, 80, &kp)?;

// Verify the proof
let valid = verify_score_proof(&proof)?;
assert!(valid); // Score 90 > threshold 80

Graph Operations

Operation	Method	Returns
Add attestation	graph.add_attestation(&att)	Edge ID
Query by subject	graph.attestations_for(did)	Edges
Query by domain	graph.attestations_for_domain(did, domain)	Edges
Find trust path	graph.find_path(from, to)	DID path
Remove issuer	graph.remove_issuer(did)	—
Graph stats	graph.node_count(), graph.edge_count()	Counts

Key Types

Type	Description
ReputationAttestation	VC-encoded reputation with domain, score, weight, evidence
AttestationBuilder	Fluent builder for creating attestations
TrustGraph	DID nodes + attestation edges + queries
TrustAlgorithm	DirectOnly, TransitiveTrust, ReputationWeighted
TrustScore	Computed score with confidence and breakdown
TrustNode / TrustEdge	Graph primitives

Server API

When using baseid-server, trust operations are available via REST:

Method	Endpoint	Description
POST	/api/trust/attestations	Add a reputation attestation
GET	/api/trust/attestations/:did	Get attestations for a subject
POST	/api/trust/score	Compute trust score (supports algorithm selection)
GET	/api/trust/graph/stats	Graph statistics

Related Crates

• baseid-bbs — BBS+ signatures for ZK score proofs
• baseid-verifier-core — TrustRegistry integration
• baseid-core — ClaimSet, AssuranceLevel