# Customer Creation

{% hint style="info" %}
This step assumes you have successfully authenticated your API credentials using [authentication](https://docs.offblocks.xyz/developer-guides/step-by-step-guide/authentication "mention") and have followed [request-signatures](https://docs.offblocks.xyz/developer-guides/api-integration/request-signatures "mention") and [idempotency](https://docs.offblocks.xyz/developer-guides/api-integration/idempotency "mention") guides to configure your requests
{% endhint %}

Now that you can make authenticated requests to the API, you are officially ready to onboard new customers with our platform. To do so, you need to use `/customers` `POST` request.

{% openapi src="<https://1545901005-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTToCQFhAYRMgObGgbSjC%2Fuploads%2FV89o79d3urx40FHQswwW%2Foffblocks-api-spec_master_api.yaml?alt=media&token=762e0468-4f4f-407e-9281-df4ee98be768>" path="/customers" method="post" expanded="true" %}
[offblocks-api-spec\_master\_api.yaml](https://1545901005-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTToCQFhAYRMgObGgbSjC%2Fuploads%2FV89o79d3urx40FHQswwW%2Foffblocks-api-spec_master_api.yaml?alt=media\&token=762e0468-4f4f-407e-9281-df4ee98be768)
{% endopenapi %}

Specified `chainId` is expected to follow the convention outlined in [#account-identifier](https://docs.offblocks.xyz/api-integration/blockchain-identifiers#account-identifier "mention"). For example, in order to onboard a customer using zkSync Era wallet with address `0x22227A31dd842196A246d8f3b775998560eAa61d` on Goerli Testnet, you can submit a following request:

```json
{
  "chainId": "eip155:280:0x22227A31dd842196A246d8f3b775998560eAa61d",
  "externalId": "27c9aa3b-f12d-43b9-8e91-5264ccc998de"
}
```

If a customer with specified `chainId` and `externalId` is not onboarded in our system yet, you will receive a response with status `201 (Created)` which looks similar to the following:

{% code overflow="wrap" %}

```json
{
    "chainId": "eip155:280:0x22227A31dd842196A246d8f3b775998560eAa61d",
    "challenge": "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",
    "createdAt": "2024-01-12T14:53:02.65345725Z",
    "externalId": "27c9aa3b-f12d-43b9-8e91-5264ccc998de",
    "id": "04c5851c-4386-5bd9-9f89-08312f8aee3a",
    "status": "initiating",
    "updatedAt": "2024-01-12T14:53:02.65345725Z"
}
```

{% endcode %}

If everything went well, you will receive a customer challenge to sign as a base64 encoded string. This is required to proceed to verification stage. Please, follow [sign-in-with-x](https://docs.offblocks.xyz/developer-guides/api-integration/sign-in-with-x "mention") guide for more details on signing a customer challenge.

In order to submit a signed challenge, use a `POST` request to `/customers/{customerId}/challenge/sign` endpoint.

{% openapi src="<https://1545901005-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTToCQFhAYRMgObGgbSjC%2Fuploads%2FV89o79d3urx40FHQswwW%2Foffblocks-api-spec_master_api.yaml?alt=media&token=762e0468-4f4f-407e-9281-df4ee98be768>" path="/customers/{customerId}/challenge/sign" method="post" expanded="true" %}
[offblocks-api-spec\_master\_api.yaml](https://1545901005-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTToCQFhAYRMgObGgbSjC%2Fuploads%2FV89o79d3urx40FHQswwW%2Foffblocks-api-spec_master_api.yaml?alt=media\&token=762e0468-4f4f-407e-9281-df4ee98be768)
{% endopenapi %}

{% code overflow="wrap" %}

```json
{
  "ownerId": "eip155:280:0x43158f45b5EbD7b1179130131DF00393928C2691",
  "challenge": "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",
  "signature": "MHg4M2IxM2RhYjE2MjI3MjAxMWQzMzQ4NDFkZjE5NTQ1MjUwNDI1NjczMjhhZDdjMDVjOTYyYjAwNWVlZDg3MGI2NDhjMjA0ZjBiZmZjZjUyYjM3NTE0MGIwYzg0OTA4ZTQ2MzMyNWIxZGZlNWJiYjAzMjU5NzYyNDgyODM0YWYzNzFi"
}
```

{% endcode %}

Please, not that the signature also must be a base64 encoded string. If signature is verified, you will receive an empty response with status code `204 (No Content)`.

If, for any reason, the original challenge is lost or cannot be signed immediately, you can fetch it again using a dedicated endpoint. If we encounter an error during signature validation via `/sign` endpoint, a new challenge will be issued for you to retrieve.

We enforce a 1 hour expiration window via our API for all issued challenges for security purposes. If a challenge hasn't been signed within 1 hour from issue, we will generate a new one and make it available through this endpoint.

{% openapi src="<https://1545901005-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTToCQFhAYRMgObGgbSjC%2Fuploads%2FV89o79d3urx40FHQswwW%2Foffblocks-api-spec_master_api.yaml?alt=media&token=762e0468-4f4f-407e-9281-df4ee98be768>" path="/customers/{customerId}/challenge" method="get" expanded="true" %}
[offblocks-api-spec\_master\_api.yaml](https://1545901005-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTToCQFhAYRMgObGgbSjC%2Fuploads%2FV89o79d3urx40FHQswwW%2Foffblocks-api-spec_master_api.yaml?alt=media\&token=762e0468-4f4f-407e-9281-df4ee98be768)
{% endopenapi %}