Borrowing it
Nothing to install: this file belongs to sparq-org/sparq. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/sparq-org/sparq/main/.claude/skills/verifiable-credentials-zk/SKILL.mdgit clone --depth 1 https://github.com/sparq-org/sparqWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/sparq-org/sparq/verifiable-credentials-zk)<a href="https://agentmods.dev/skills/sparq-org/sparq/verifiable-credentials-zk"><img src="https://agentmods.dev/badge/skills/sparq-org/sparq/verifiable-credentials-zk/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/sparq-org/sparq/verifiable-credentials-zk"><img src="https://agentmods.dev/badge/skills/sparq-org/sparq/verifiable-credentials-zk.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00097 | $0.01120 |
| Opus 5 | $0.00048 | $0.00560 |
| Sonnet 5 | $0.00019 | $0.00224 |
| Haiku 4.5 | $0.00010 | $0.00112 |
Grade A, and why
verifiable-credentials-zk scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 100 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Verifiable Credentials in a ZK pipeline
Patterns for the cryptographic seam between W3C Verifiable Credentials and the Noir circuits in this workspace.
Signature scheme trade-offs
| Scheme | Native selective disclosure? | In-circuit verification cost | Ecosystem alignment | When to pick |
|---|---|---|---|---|
| BBS+ | Yes (per-message blinding) | High — pairing-friendly group ops are heavy in BN254 / Grumpkin | Strong (W3C VC, IRTF draft) | When selective disclosure is the dominant feature and the verifier outside the circuit can do the heavy lifting (verifying a BBS+ proof of knowledge, not the signature directly). |
| SD-JWT-VC | Yes (salted-hash disclosures) | Moderate — hashing only | Strong (IETF, OAuth ecosystem) | When you want JWT-shaped tokens, simple disclosures, no pairings. |
| EdDSA | No (sign whole document) | Low — Ed25519 verifications are cheap | Universal | When the whole credential is disclosed, or when the prover holds a separate "compiled" representation that the SPARQL evaluator commits to. |
For the paper's first version, EdDSA + a separate prover-side commitment is the simplest defensible choice. BBS+ becomes attractive once the paper has demonstrated the pipeline end-to-end.
Commitment schemes
- Pedersen — additive homomorphism; classic for committing to field-element vectors.
- Poseidon — sponge-friendly, fast in Noir-style circuits. Default choice unless additivity is needed.
- Merkle tree (Poseidon-leaved) — when the circuit needs sparse random-access into a large committed set (e.g. selecting a few triples from a 10k-triple graph).
- KZG / IPA polynomial commitment — overkill for a paper prototype unless you need batched openings.
Encoding RDF triples into field elements
A triple (s, p, o) becomes three field elements via a hash with
domain separation:
h_s = Poseidon(b"rdf-term-v1" ‖ s_bytes)
h_p = Poseidon(b"rdf-term-v1" ‖ p_bytes)
h_o = Poseidon(b"rdf-term-v1" ‖ o_bytes)
triple_hash = Poseidon(b"rdf-triple-v1" ‖ h_s ‖ h_p ‖ h_o)
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 11d ago First seen · 100 lines · 97 tokens per session scan A 8073f98f6221
verifiable-credentials-zk is a skill published in the GitHub repository sparq-org/sparq (12 stars, last pushed today), licensed MIT. It adds 97 tokens to every session and 1,120 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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