zk-proofs

A guide to using zero-knowledge proofs on Stellar, a blockchain platform, so a smart contract can verify a claim without revealing the underlying private data. It covers Groth16, BN254, Poseidon, BLS12-381, and tools such as Circom, Noir, and RISC Zero.

In plain words
What is it for?
Use it to build on-chain proof verifiers, privacy pools, confidential tokens, or Merkle-tree commitments, and to connect proof output from supported tools to Stellar contracts.
Why use it?
It helps developers choose and verify the correct proof primitives, protocol support, and SDK support before building privacy features.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/stellar/stellar-dev-skill/zk-proofs
Any agent
npx skills add stellar/stellar-dev-skill --skill zk-proofs
Clone the repo
git clone --depth 1 https://github.com/stellar/stellar-dev-skill

Made for: Claude Code, Codex.

Per session 90 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,987 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00090 $0.03987
Opus 5 $0.00045 $0.01994
Sonnet 5 $0.00018 $0.00797
Haiku 4.5 $0.00009 $0.00399

Measured 2d ago against content hash 7549d4e4ae49, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

zk-proofs 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 2d 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.

skills/zk-proofs/SKILL.md · 240 lines

How it starts

The opening of the file, as written. The whole thing — 240 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Zero-Knowledge Proofs & Privacy

ZK verification on Stellar. Capability is protocol- and SDK-version dependent — always verify CAP status, network version, and soroban-sdk host-function support before relying on a primitive.

Last verified against Protocol 27 (mainnet, August 2026). CAP-0074/0075 shipped in Protocol 25 "X-Ray" and CAP-0080 (BN254 MSM, Fr arithmetic, on-curve checks) in Protocol 26 — if a doc tells you BN254 or Poseidon is "proposed", it predates that.

When to use this skill

  • Implementing a Groth16 (or other SNARK) verifier as a Stellar smart contract
  • Wiring Circom, Noir, or RISC Zero output to on-chain verification
  • Building privacy pools, confidential tokens, or Merkle-tree-backed commitments
  • Using the BN254 / Poseidon host functions (Protocol 25+)
  • Contract patterns and deployment → ../smart-contracts/development.md
  • Verifier security review → ../smart-contracts/security.md
  • CAPs referenced here → ../standards/SKILL.md

What's available — verify before building

Primitive CAP Status
BLS12-381 ops (G1/G2 add, mul, MSM, pairing check, hash-to-curve, Fr arithmetic) CAP-0059 Available (Protocol 22+)
BN254 base ops (G1 add/mul, pairing check — crypto::bn254) CAP-0074 Available (Protocol 25+)
BN254 G1 MSM, Fr arithmetic (fr_add/sub/mul/pow/inv), on-curve checks CAP-0080 Available (Protocol 26+)
Poseidon/Poseidon2 permutation primitives (not complete hash functions) CAP-0075 Available (Protocol 25+)

Before implementation, always confirm:

  1. CAP status in the preamble (Accepted/Implemented vs draft)
  2. Target network protocol version (software versions)
  3. soroban-sdk release support for the host functions you need

Read the full file on GitHub · 240 lines

Changes

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.

  1. 2d ago First seen · 240 lines · 90 tokens per session scan A 7549d4e4ae49

Subscribe to this mod's changes

zk-proofs is a skill published in the GitHub repository stellar/stellar-dev-skill (51 stars, last pushed 4d ago), licensed Apache-2.0. It adds 90 tokens to every session and 3,987 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 2026-08-30.

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