User Signatures

You can use MetaKeep to generate signatures for messages using the private key of the asymmetric key pair. The signature can be verified using the public key.

Calling sign

You can ask the user to sign a bigint by using thesignMessage function in MetaKeep SDK. The bigint is converted to a big-endian byte array and then converted to a hex string. The hex string is then sent to the signMessage function along with the reason. The function expects a non-empty reason which is shown to the user at the time of message signing.

The operation result is returned in the callback object passed to the signMessage function or the Promise object returned by the signMessage function.

await sdk.signMessage(
    // bigint as big-endian byte hex string
    "0x0000260e66bea5cc8114947584de9f68574710c9e472378d4595febfd51eb853",
    // signing reason
    "reason",
);

sdk.signMessage(
    // bigint as big-endian byte hex string
    "0x0000260e66bea5cc8114947584de9f68574710c9e472378d4595febfd51eb853",
    // signing reason
    "reason",
    // Callback
    Callback(
        onSuccess = { response: JsonResponse ->
            Log.d("onSuccess", response.toString())
        },
        onFailure = { error: JsonResponse ->
            Log.d("onFailure", error.toString())
        },
    ),
)

sdk.signMessage(
  // bigint as big-endian byte hex string
  message: "0x0000260e66bea5cc8114947584de9f68574710c9e472378d4595febfd51eb853",
  // signing reason
  reason: "reason",
  // Callback
  callback: Callback(
    onSuccess: { (result: JsonResponse) in
      print("onSuccess")
      print(result.description)
    },
    onFailure: { (error: JsonResponse) in
      print("onFailure")
      print(error.description)
    }
  )
)

await sdk.signMessage(
    // bigint as big-endian byte hex string
    "0x0000260e66bea5cc8114947584de9f68574710c9e472378d4595febfd51eb853",
    // signing reason
    "reason",
);

await sdk.signMessage(
    // bigint as big-endian byte hex string
    "0x0000260e66bea5cc8114947584de9f68574710c9e472378d4595febfd51eb853",
    // signing reason
    "reason",
);

Response

On success, the callback onSuccess or the Promise resolve function is called with the signature inside a JSON object. The signature is a 64-byte compressed EdDSA signature in hex format as defined in RFC 8032.

This is what the response looks like:

{
    "status": "SUCCESS",
    // 64-byte compressed EdDSA signature in hex format
    "signature": "0x20ba78dcc23893aefaa3c8c2c9d99598831265e3ce32638d3cfda6c4d2028c8ade8b897c9d4542259204224ff59b72f7fea835727df8cee40cafd3a6d101ff02"
}

Here's a reference implementation of this code for JS SDK: https://jsfiddle.net/passbird/14er9xoy/

Error status

Callback onFailure or the Promise reject function is called when the user cancels the operation or if there's an error. The error object contains a status field, a string indicating the status of the operation. Here's what the error object looks like:

{
  status: "USER_CONSENT_DENIED"
}

Here's a table of all possible error status returned by the SDK:

Status	Description
USER_REQUEST_DENIED	The user has denied the sign operation. In this case, you should ask the user if they want to try again.
INVALID_REQUEST	Invalid data passed to sign operation. Please get in touch with us if you are unable to fix this.
INVALID_MESSAGE	The message to sign is not valid. Make sure that it's a valid hex string.
APP_ID_REQUIRED	No `app-id` was provided when initializing the SDK. You can find the app ID in the MetaKeep Developer Console.
APP_NOT_FOUND	The provided `app-id` is invalid. You can find the correct `app-id` in the MetaKeep Developer Console.
SOMETHING_WENT_WRONG	An unknown error happened. Please get in touch with us if you continue seeing this error.