Handlers.add(
  "sign-message",
  Handlers.utils.hasMatchingTag("Action", "Sign"),
  function(msg)
    local messageToSign = msg.Data
    local signature = Crypto.sign(messageToSign)
    return {
      Data = signature,
      Tags = {
        { name = "Original-Message", value = messageToSign },
        { name = "Signature-Type", value = "arweave" }
      }
    }
  end
)