---
title: "Counterparty co-signs a commitment (non-repudiation)"
method: POST
path: "/cosign"
---

# Counterparty co-signs a commitment (non-repudiation)

`POST /cosign`

## Request

- Base URL: `https://touchstone.cv`
- URL: `https://touchstone.cv/cosign`
- Auth: none declared

## Request body

- object
  - `recorder_id` string, required
  - `seq` integer, required
  - `counterparty_pubkey` string, required: base64 Ed25519 public key
  - `counterparty_sig` string, required: base64 Ed25519 signature over the same signed_content

## Response `200`

Co-signed

- object
  - `grade` 'verified' | 'claimed'

## Other responses

- `409`: Already co-signed

---

[API](https://skmtc.dev/touchstone/apis/touchstone-api.md) · [All operations](https://skmtc.dev/touchstone/apis/touchstone-api/llms.txt) · [OpenAPI document](https://skmtc.dev/touchstone/apis/touchstone-api/revisions/11ffeafa6a85?raw)