# FractalAI Post-Quantum Signature Verification

> FractalAI Post-Quantum Signature Verification is a paid API for AI agents from fractalai.net.co, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Verifies a post-quantum cryptographic signature (ML-DSA-65 / Dilithium-2) over a message and returns a signed attestation of the verdict

## Facts

- Endpoint: POST https://fractalai.net.co/api/x402/verify-proof
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fractalai-post-quantum-signature-verification-22541fc8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vBbTMeerS6aDfUMHPXKGv

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability fractalai-post-quantum-signature-verification-22541fc8 -d '<json body>'
```

Example prompt: Can you verify this ML-DSA-65 post-quantum signature — here's the base64 message, the base64 signature, and the base64 public key — and give me a signed attestation receipt I can use as proof it was validated?

## When to prefer this

Choose this endpoint when you need a verifiable, server-attested proof of post-quantum signature validation — not just a local library check. Ideal when you need an auditable receipt (the server's own ML-DSA-65 attestation signature) that a third party can independently verify offline. Prefer this over self-contained library verification when operating in regulated, audit-required, or zero-trust environments where an external attestation from an independent party strengthens non-repudiation. Also suitable when you need automatic scheme detection between Dilithium-2 and ML-DSA-65 (NIST FIPS 204).

## Known failure modes

- Invalid or malformed base64 input for message, signature, or public key returns an error
- Signature length mismatch (not 2420 bytes for Dilithium-2 or 3293 bytes for ML-DSA-65) causes rejection
- Public key length mismatch causes scheme auto-detection to fail
- Payment failure or insufficient USDC balance prevents the call from being processed
- Server-side attestation signer temporarily unavailable returns null signature with served_signature_error flag but still delivers the paid verdict
- Incorrect or mismatched public key/signature pair returns valid=false

## How this service works

The first AI-native Layer 1 blockchain built from scratch in Rust. Post-quantum cryptography (CRYSTALS-Dilithium), Proof of Fractal Work consensus, WASM smart contracts, and 460+ RPC endpoints. Mine FRAC tokens with fractal analysis instead of hash puzzles.

## Output

A JSON object containing: a boolean 'valid' field indicating whether the client's post-quantum signature is authentic; 'verified_algorithm' identifying whether ML-DSA-65 or Dilithium-2 was detected; echoed 'input_signature' and 'input_public_key' for reproducibility; a server-generated ML-DSA-65 attestation 'signature' (3309 bytes) over a canonical signed_message string; the server's 'public_key' (1952 bytes) for offline verification; and optionally a 'payment' settlement receipt with transaction hash and payer details.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "message": {
   "type": "string",
   "description": "The UTF-8 message that was signed. Provide message OR message_b64. For an ML-DSA-65 signature this must be the EXACT bytes the client signed."
  },
  "signature": {
   "type": "string",
   "description": "The base64 post-quantum signature to verify. Scheme auto-detected by size: 3309 bytes → ML-DSA-65 / Dilithium-3 (verified locally); 2420 bytes → Dilithium-2 / ML-DSA-44 (verified via the node PQC API). Required."
  },
  "public_key": {
   "type": "string",
   "description": "The base64 public key to verify against. 1952 bytes → ML-DSA-65 / Dilithium-3; 1312 bytes → Dilithium-2 / ML-DSA-44. Must match the signature scheme. Required."
  },
  "message_b64": {
   "type": "string",
   "description": "The base64-encoded exact bytes that were signed (use this if the original signer signed raw bytes, e.g. our /api/x402/sign). Provide message OR message_b64. For ML-DSA-65 the verifier checks ml_dsa65.verify(signature, base64-decode(message_b64), public_key) — pass the exact signed message (include any domain prefix the signer used)."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "schema": {
  "type": "object",
  "required": [
   "valid",
   "algorithm",
   "verified_algorithm",
   "input_signature",
   "input_public_key"
  ],
  "properties": {
   "valid": {
    "type": "boolean",
    "description": "True iff the supplied client signature (ML-DSA-65 or Dilithium-2, auto-detected) is valid over the message for the public key."
   },
   "payment": {
    "type": "object",
    "description": "Settlement receipt (scheme, network, asset, txHash, payer, settled)."
   },
   "algorithm": {
    "type": "string",
    "description": "ml-dsa-65 — algorithm of THIS route's attestation signature over the verdict (NOT necessarily the client input scheme; see verified_algorithm)."
   },
   "signature": {
    "type": "string",
    "description": "Base64 ML-DSA-65 / Dilithium-3 (NIST FIPS 204) signature (3309 bytes) by this server over the EXACT bytes echoed in `signed_message` = FRACTALAI-x402-served-v1\\nx402-verify-proof\\n<attestation_digest> (route-separated, 3 lines), attesting the verdict. Verify offline: ml_dsa65.verify(b64(signature), utf8(signed_message), b64(public_key)). Null (with served_signature_error) if the served signer was momentarily unavailable — the paid verdict is still served."
   },
   "public_key": {
    "type": "string",
    "description": "Base64 ML-DSA-65 public key (1952 bytes) that verifies the attestation signature. Null if the served signer was unavailable."
   },
   "message_b64": {
    "type": "string",
    "description": "The exact base64 bytes that were verified (echoed for reproducibility)."
   },
   "signed_message": {
    "type": "string",
    "description": "The EXACT UTF-8 bytes the served signature covers (FRACTALAI-x402-served-v1\\nx402-verify-proof\\n<attestation_digest>). Pass verbatim to ml_dsa65.verify — do not reconstruct it yourself."
   },
   "algorithm_label": {
    "type": "string",
    "description": "ML-DSA-65 / Dilithium-3 (NIST FIPS 204)"
   },
   "input_signature": {
    "type": "string",
    "description": "The exact base64 client signature that was verified (echoed so a third party can recompute attestation_digest from this response alone)."
   },
   "input_public_key": {
    "type": "string",
    "description": "The exact base64 client public key that was verified (echoed for attestation_digest reconstruction)."
   },
   "attestation_digest": {
    "type": "string",
    "description": "sha256 hex over JSON({valid, verified_algorithm, message_b64, message_hash, signature:
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fractalai-post-quantum-signature-verification-22541fc8/health.json
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