> ## Documentation Index
> Fetch the complete documentation index at: https://developer.copper.co/llms.txt
> Use this file to discover all available pages before exploring further.

# Sign transaction

Create a request to Copper Unlimited Online to sign the transaction. After signing, when the transaction is in the completed status,
the signed transaction will be uploaded to the Copper Platform automatically.


## OpenAPI

````yaml copper-unlimited-open-api post /sign-async
openapi: 3.1.0
info:
  title: Copper Unlimited Online API
  description: API for signing transactions asynchronously with Copper Unlimited Online
  version: 1.0.0
servers:
  - url: http://0.0.0.0:3010
    description: Local server
security: []
paths:
  /sign-async:
    post:
      summary: Sign transaction asynchronously
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SignAsyncRequest'
      responses:
        '200':
          description: Transaction signed successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SignAsyncResponse'
components:
  schemas:
    SignAsyncRequest:
      type: object
      properties:
        type:
          type: string
          enum:
            - request
        keyPassword:
          description: The password from the shard
          type: string
        keyFilename:
          description: The filename of the key
          type: string
        transactionRequestId:
          description: The transaction request id
          type: string
        masterPassword:
          description: The organization master password
          type: string
        apiKey:
          description: The Copper's Platform API Key
          type: string
        apiSecret:
          description: The Copper's Platform API Key
          type: string
        signRequest:
          description: All this fields from order.extra.transactionRequest
          type: object
      required:
        - type
        - keyPassword
        - keyFilename
        - transactionRequestId
        - masterPassword
        - apiKey
        - apiSecret
        - signRequest
    SignAsyncResponse:
      type: object
      properties:
        transactionRequestId:
          type: string
        sessionKey:
          type: string
        sessionTimestamp:
          type: string
          examples:
            - '1608296004000'

````