Cross-Language Interoperability

PDTF 2.0 provides four language implementations that are proven to be interoperable through shared deterministic test vectors.

The Interop Promise

A credential signed in any language can be verified in any other language. This isn’t aspirational — it’s tested on every commit.

Operation	TypeScript	Rust	Python	C#
Key generation	✅	✅	✅	✅
did:key derivation	✅	✅	✅	✅
VC signing (eddsa-jcs-2022)	✅	✅	✅	✅
VC verification	✅	✅	✅	✅
Status list create/check	✅	✅	✅	✅
TIR path matching	✅	✅	✅	✅
DID document resolution	✅	✅	✅	✅

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How It Works

Shared Test Vectors

The TypeScript reference implementation generates test-vectors/vectors.json from a fixed Ed25519 seed. Every other language consumes these vectors and validates its output matches exactly.

@pdtf/core (TypeScript)
    │
    ├── generates test-vectors/vectors.json
    │       │
    │       ├── pdtf-core (Rust) consumes → 6 integration tests
    │       ├── pdtf-core (Python) consumes → 10 pytest tests
    │       └── Pdtf.Core (C#) consumes → 9 xUnit tests
    │
    └── self-validates → 17 vitest tests

What’s in the Vector File

{
  "keys": {
    "seed": "ababab...",
    "publicKeyHex": "248acb...",
    "did": "did:key:z6Mk...",
    "publicKeyMultibase": "z6Mk..."
  },
  "signing": [
    {
      "name": "minimal-vc",
      "unsignedVc": { ... },
      "signedVc": { ... },
      "proofValue": "z3vv14hX..."
    }
  ],
  "verification": [
    { "name": "valid-signature", "expectedValid": true },
    { "name": "tampered-subject", "expectedValid": false },
    { "name": "wrong-key", "expectedValid": false }
  ],
  "statusList": { ... },
  "tirPathMatching": [ ... ]
}

What’s Proven

Test Category	What’s Compared	Pass Criteria
Key derivation	did:key string from raw public key	Exact string match
Signing	Proof value from same unsigned VC + key + timestamp	Byte-identical Ed25519 signatures
Verification	Valid/tampered/wrong-key outcomes	Boolean match
Status lists	Decoded bit arrays from encoded bitstrings	Logical equivalence (decoded bytes identical)
TIR matching	Pattern + path → match result	Boolean match

Note on gzip: Different gzip implementations may produce different compressed byte sequences for the same data. Status list tests compare decoded content (logical equivalence), not raw base64 strings. This is by design — the W3C Bitstring Status List spec defines the logical format, not the compression output.

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Test Matrix

Language	Framework	Tests	Status
TypeScript	Vitest	68 (17 vector)	✅ Passing
Rust	cargo test	84 (6 cross-lang)	✅ Passing
Python	pytest	10	✅ Passing
C#	xUnit	9 cross-lang + 5 unit	✅ Written (needs .NET SDK)

Total: 172+ tests across 4 languages.

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Adding a New Language

To add PDTF support in a new language:

1. Implement the core operations: key generation, JCS canonicalization, SHA-256, Ed25519 signing, base58-btc encoding
2. Download test-vectors/vectors.json from the core-rs repository
3. Write tests that consume the vectors — every test category must pass
4. Submit a PR to add your language to the interop matrix

The vector file is the contract. If your implementation produces the same outputs for the same inputs, it’s compatible.

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Regenerating Vectors

cd core-ts
npx tsx scripts/generate-vectors.ts
# Copies to test-vectors/vectors.json

# Then copy to Rust repo
cp test-vectors/vectors.json ../core-rs/test-vectors/

⚠️ Do not change the seed or timestamps — all existing tests depend on deterministic output.