# Sign in With X

{% hint style="info" %}
This functionality is currently only supported on EVM networks and is 100% compliant with [EIP-4361 (Sign in With Ethereum)](https://eips.ethereum.org/EIPS/eip-4361). We will be adding support for more networks soon.
{% endhint %}

To verify a customer's externally-owned account ownership, we require a challenge to be signed with the private key. This mechanism is outlined in [CAIP-122](https://chainagnostic.org/CAIPs/caip-122), originally known as "Sign in With Ethereum" (SIWE) but expanded to support other blockchains. When a new customer object is created in our system, we generate a challenge following the standardised structure, expecting it to be signed and verified before proceeding with user onboarding. The challenge returned by the endpoint is a Base64-encoded string.

{% openapi src="/files/ZuFqAH96VVGgwQAJ2vzc" path="/customers" method="post" %}
[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 %}

When a new user is created on supported chains, you will receive a Base64 encoded challenge, which resembles the following:

```
api.sandbox.offblocks.xyz wants you to sign in with your Ethereum account:
0x43158f45b5EbD7b1179130130DF00393928C2691

OffBlocks wants to verify ownership of your wallet. By connecting your wallet and using OffBlocks, you agree to our Terms of services and Privacy Policy

URI: https://api.sandbox.offblocks.xyz
Version: 1
Chain ID: 300
Nonce: 5ufoiEqDaFvmfo78
Issued At: 2024-01-17T18:21:53Z
```

In order to proceed with ownership verification, your customer needs to sign this challenge with their private key. Please, follow [SIWE documentation](https://docs.login.xyz/) to learn more about signing SIWE challenges using community supported libraries. For testing purposes, you can use [MyCrypto](https://app.mycrypto.com/sign-message) signing tools to sign a challenge for test accounts.

If everything was successful, you will have a HEX-formatted signature ready to be submitted to our API. For example, if using MyCrypto, it will produce a following message for the above challenge:

```json
{
  "address": "0x43158f45b5EbD7b1179130130DF00393928C2691",
  "msg": "api.sandbox.offblocks.xyz wants you to sign in with your Ethereum account:\n0x43158f45b5EbD7b1179130130DF00393928C2691\n\nOffBlocks wants to verify ownership of your wallet. By connecting your wallet and using OffBlocks, you agree to our Terms of services and Privacy Policy\n\nURI: https://api.sandbox.offblocks.xyz\nVersion: 1\nChain ID: 300\nNonce: 5ufoiEqDaFvmfo78\nIssued At: 2024-01-17T18:21:53Z",
  "sig": "0xd2472857a11a29b612fda39b3a381cc88a8e6d085333cb7e2536ea38e71664be5e88ada8f5de966eff4f7c9cf59429b9a24814d878e779db34b612d4091c26ba1c",
  "version": "2"
}
```

To submit a signed challenge, please encode a HEX signature as Base64 string and send it using the corresponding endpoint.

{% openapi src="/files/ZuFqAH96VVGgwQAJ2vzc" path="/customers/{customerId}/challenge/sign" method="post" %}
[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 %}

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="/files/ZuFqAH96VVGgwQAJ2vzc" path="/customers/{customerId}/challenge" method="get" %}
[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 %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.offblocks.xyz/developer-guides/api-integration/sign-in-with-x.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.