# Post-Quantum Confidentiality for Agent Payment Metadata: Hybrid ML-KEM Decision Procedure

> Post-Quantum Confidentiality for Agent Payment Metadata: Hybrid ML-KEM Decision Procedure is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-18).

Returns a decision procedure for agents on when and how to use hybrid ML-KEM (Kyber) key encapsulation to encrypt x402 payment metadata before it reaches a facilitator, wallet, or settlement rail.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/post-quantum-confidentiality-for-agent-payment-m?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-18
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/post-quantum-confidentiality-for-agent-payment-metadata-hybrid-ml-kem-eb5df322
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_73HsH0x86U2jH6u_LvzAW

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 post-quantum-confidentiality-for-agent-payment-metadata-hybrid-ml-kem-eb5df322
```

Example prompt: Give me the decision procedure for encrypting x402 payment metadata using hybrid ML-KEM — I need to know when to negotiate hybrid Kyber plus ECDH, how to handle a classical-only peer downgrade warning, and the key-rotation cadence for payment-derived keys.

## When to prefer this

Choose this endpoint when an agent needs specific, authoritative guidance on post-quantum encryption for x402 payment metadata — particularly the hybrid ML-KEM (Kyber) handshake, per-rail KEM support across Base/Solana/XRPL/TRON/Casper, downgrade handling, and key rotation. Prefer it over general cryptography references when the context is specifically x402 agent payment flows and settlement rail compatibility.

## Known failure modes

- Payment required but not provided — returns 402 with payment instructions
- Invalid query parameter values (e.g. meta not 0 or 1) — likely 400 or ignored
- Topic override not recognized — may return generic procedure without topic specificity
- Service unavailable on k2so.wrong.systems — network or 5xx error
- Procedure generated as 'deterministic' may be stale if rail KEM support has changed

## How this service works

Decision procedure for agents that need to encrypt x402 payment metadata before it touches a facilitator, wallet callback, or settlement rail. Covers the hybrid ML-KEM (Kyber) key encapsulation handshake: when to negotiate hybrid ML-KEM plus classical ECDH, when a classical-only peer triggers a downgrade warning, per-rail KEM support checks for Base, Solana, XRPL, TRON, Casper and CSPR, ciphertext integrity verification before decryption, key-rotation cadence for payment-derived keys, and the

## Output

A JSON object containing a plain-prose decision procedure (120+ words) covering hybrid ML-KEM negotiation logic, per-rail KEM support (Base, Solana, XRPL, TRON, Casper/CSPR), downgrade warning conditions, ciphertext integrity verification steps, and key-rotation cadence for payment-derived keys. Also includes metadata: service slug, generation timestamp, model used, and generation source (llm, reasoning, or deterministic).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "post-quantum confidentiality for agent payment metadata: hybrid ML-KEM paid response",
     "$schema": "https://json-schema.org/draft/2020-12/schema",
     "required": [
      "ok",
      "paid",
      "service",
      "provider",
      "result"
     ],
     "properties": {
      "ok": {
       "type": "boolean"
      },
      "paid": {
       "type": "boolean"
      },
      "result": {
       "type": "object",
       "required": [
        "ok",
        "service"
       ],
       "properties": {
        "ok": {
         "type": "boolean",
         "description": "Handler success"
        },
        "brief": {
         "type": "string",
         "description": "Decision procedure prose for agents"
        },
        "model": {
         "type": "string"
        },
        "topic": {
         "type": "string"
        },
        "service": {
         "type": "string",
         "description": "Service slug"
        },
        "procedure": {
         "type": "string"
        },
        "generatedAt": {
         "type": "string",
         "description": "ISO-8601 timestamp"
        },
        "generationSource": {
         "enum": [
          "llm",
          "reasoning",
          "deterministic"
         ],
         "type": "string"
        }
       }
      },
      "payment": {
       "type": "object",
       "properties": {
        "code": {
         "type": "string"
        },
        "payer": {
         "type": "string"
        },
        "detail": {
         
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "paid": true,
  "result": {
   "ok": true,
   "brief": "plain prose decision procedure (120+ words)",
   "model": "deepseek/deepseek-v4-flash-0731",
   "topic": "string topic",
   "service": "post-quantum-confidentiality-for-agent-payment-m",
   "procedure": "same as brief",
   "generatedAt": "2026-01-01T00:00:00.000Z",
   "generationSource": "deterministic"
  },
  "service": "post-quantum-confidentiality-for-agent-payment-m",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/post-quantum-confidentiality-for-agent-payment-metadata-hybrid-ml-kem-eb5df322/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from k2so.wrong.systems](https://www.zero.xyz/host/k2so.wrong.systems/llms.txt)