> For the complete documentation index, see [llms.txt](https://docs.truecaller.com/truecaller-sdk/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.truecaller.com/truecaller-sdk/ios/server-side-response-validation.md).

# Server Side Response Validation

TruecallerSDK provides two optional delegate methods to check the authenticity of the profile you receive. Note that TruecallerSDK readily offers a simplified way to request and receive a user profile via required delegate methods and verifies the content before forwarding it your app.

**Server side Truecaller Profile authenticity check**

The delegate method didReceiveTrueProfileResponse: will return a TCTrueProfileResponse instance. Inside TCTrueProfileResponse class there are 3 important fields, payload, signature and signatureAlgorithm. Payload is a Base64 encoding of the json object containing all profile info of the user. Signature contains the payload's signature. You can forward these fields along with the signing algorithm back to your backend and verify the authenticity of the information by doing the following:

1. Fetch Truecaller public keys using this api: <https://api4.truecaller.com/v1/key> (we recommend you cache these keys for future use and refresh the cache only if you cannot verify the signature);
2. Loop through the public keys and try to verify the signature and payloa&#x64;**.**

**Request-Response correlation check**

Every request created with TruecallerSDK has a unique identifier namely 'requestNonce'. This identifier is bundled into the response for assuring a correlation between a request and a response. If you want you can check this correlation yourself by:

1. Get the request nonce at willRequestProfileWithNonce: method
2. In didReceiveTrueProfileResponse: verify that the previously retrieved identifier matches the one in TCTrueProfileResponse.requestNonce.


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