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Fetch the complete documentation index at: https://docs.lt.cryptoprocessing.com/llms.txt

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Learn how to authenticate API requests and avoid common setup issues.

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Required headers

Include the following headers with every request, except for /ping:
HeaderRequiredDescription
Content-TypeYesMust be application/json
X-Processing-KeyYesYour API key
X-Processing-SignatureYesHMAC-SHA512 signature of the request body, generated using your secret key

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How to generate the signature

Generate the signature from the exact JSON string sent in the request body:
  1. Take the exact request body string that you are going to send.
  2. Use your secret key as the HMAC key.
  3. Compute the HMAC signature using the SHA-512 algorithm and encode the result as a lowercase hexadecimal string.
  4. Send that value in the X-Processing-Signature header.
The signature must be generated from the exact request body sent to the API.If the body changes after signing, the request will be rejected.Make sure that:
  • The JSON is not reformatted or pretty-printed after signing
  • Field order does not change
  • No extra whitespace or line breaks are added
  • Your HTTP client does not modify the body before sending it

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Verify your implementation

Generate a signature for the following JSON body using AbCdEfG123456 as the secret key: 
{"currency":"BTC","foreign_id":"123456"}
Expected result: 
03c25fcf7cd35e7d995e402cd5d51edd72d48e1471e865907967809a0c189ba55b90815f20e2bb10f82c7a9e9d865546fda58989c2ae9e8e2ff7bc29195fa1ec

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Common pitfalls

Most authentication errors are caused by differences between the signed body and the sent body. Check the following:
  • The JSON used for signing is identical to the JSON sent
  • Field order has not changed
  • No additional whitespace or line breaks were introduced
  • Your HTTP client did not modify the request body
  • The signature is hex-encoded (not Base64)
  • Header names match exactly:
    • X-Processing-Key
    • X-Processing-Signature
Last modified on May 7, 2026