Architecture

Layer Design

BaseID follows a 5-layer architecture where each layer depends only on layers below it:

Layer	Crates	Purpose
Core	baseid-core, baseid-crypto	Shared types, cryptographic primitives
Identity	baseid-did	DID methods and resolution
Credentials	baseid-vc, baseid-sd-jwt, baseid-mdl	Credential format implementations
Protocols	baseid-oid4vci, baseid-oid4vp, baseid-siop, baseid-didcomm	Communication protocols
Application	baseid-wallet-core, baseid-issuer-core, baseid-verifier-core	Business logic orchestration

Dependency Graph

┌─────────────────────────────────────────────┐
│  Application: wallet-core, issuer-core, ... │
├─────────────────────────────────────────────┤
│  Protocols: oid4vci, oid4vp, siop, didcomm  │
├─────────────────────────────────────────────┤
│  Credentials: vc, sd-jwt, mdl               │
├─────────────────────────────────────────────┤
│  Identity: did                              │
├─────────────────────────────────────────────┤
│  Core: baseid-core, baseid-crypto           │
└─────────────────────────────────────────────┘

Key Design Principles

Pure Rust

No runtime dependencies, memory-safe, cross-platform. The entire stack compiles to native code, WASM, and can be wrapped for mobile via FFI.

Bilingual Errors

All BaseID errors implement the BilingualError trait, providing messages in English and French (with support for additional languages). This is a core requirement for Canadian government deployments.

Trait-Based Lifecycle

The credential lifecycle is modeled with three core traits:

• CredentialIssuer — creates and signs credentials
• CredentialVerifier — validates credentials and extracts claims
• CredentialPresenter — selects and presents credentials

Each credential format implements these traits, enabling format-agnostic application logic.

Format-Agnostic Credential Handling

The AnyCredential enum wraps all supported formats (VC, mDL, SD-JWT), allowing application code to handle credentials without knowing their specific format.

Crate Map

src/rust/crates/
├── baseid-core/         # Shared types and traits
├── baseid-crypto/       # Key generation, signing, verification
├── baseid-did/          # DID methods (did:key, did:web, did:jwk)
├── baseid-vc/           # W3C Verifiable Credentials (JWT-VC)
├── baseid-sd-jwt/       # SD-JWT Verifiable Credentials
├── baseid-mdl/          # ISO 18013-5 mobile driving licences
├── baseid-oid4vci/      # OpenID for Verifiable Credential Issuance
├── baseid-oid4vp/       # OpenID for Verifiable Presentations
├── baseid-siop/         # Self-Issued OpenID Provider v2
├── baseid-didcomm/      # DIDComm v2 messaging
├── baseid-wallet-core/  # Wallet business logic
├── baseid-issuer-core/  # Issuer business logic
└── baseid-verifier-core/# Verifier business logic