Signal Certificates API

openapi: 3.1.0
info:
  title: Signal Server Accounts Certificates API
  description: The Signal Server API is the backend REST API that supports the Signal Private Messenger applications on Android, Desktop, and iOS. Built as a Dropwizard application, it provides REST controllers for account registration and management, message delivery, pre-key bundle distribution, device provisioning, profile management, and attachment handling. The server handles user registration via phone number verification, encrypted message routing, push notification delivery, and pre-key bundle management. While Signal does not offer an official public REST API for third-party use, the server source code is available for inspection and self-hosting. All communication is end-to-end encrypted using the Signal Protocol.
  version: '2.0'
  contact:
    name: Signal Support
    url: https://support.signal.org/
  termsOfService: https://signal.org/legal/
  license:
    name: AGPL-3.0
    url: https://github.com/signalapp/Signal-Server/blob/main/LICENSE
servers:
- url: https://chat.signal.org
  description: Signal Production Server
security:
- basicAuth: []
tags:
- name: Certificates
  description: Certificate endpoints for retrieving delivery certificates used in sealed sender message delivery.
paths:
  /v1/certificate/delivery:
    get:
      operationId: getDeliveryCertificate
      summary: Get a sealed sender delivery certificate
      description: Returns a delivery certificate for the authenticated account. This certificate is used in sealed sender message delivery, which hides the sender's identity from the server during message transmission.
      tags:
      - Certificates
      parameters:
      - name: includeE164
        in: query
        required: false
        description: Whether to include the E164 phone number in the certificate.
        schema:
          type: boolean
          default: true
      responses:
        '200':
          description: Delivery certificate returned successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/DeliveryCertificate'
        '401':
          description: Authentication required
components:
  schemas:
    DeliveryCertificate:
      type: object
      properties:
        certificate:
          type: string
          description: The Base64-encoded sealed sender delivery certificate signed by the server.
  securitySchemes:
    basicAuth:
      type: http
      scheme: basic
      description: HTTP Basic authentication using the account UUID (or phone number) and password. The password is established during account registration.
    bearerAuth:
      type: http
      scheme: bearer
      description: Bearer token authentication used for certain provisioning and registration flows.
externalDocs:
  description: Signal Server Source Code
  url: https://github.com/signalapp/Signal-Server