diff --git a/lib/vonbraun/http_signature.ex b/lib/vonbraun/http_signature.ex
index 0c46b9c..6493b81 100644
--- a/lib/vonbraun/http_signature.ex
+++ b/lib/vonbraun/http_signature.ex
@@ -3,10 +3,6 @@ defmodule HTTPSignature do
   Implements RFC 9421 HTTP Signatures using the Digest header.
   """
 
-  @algo :sha256
-  # Load this securely in production
-  @key "secret_key"
-
   @spec create_signature_header(map(), list(), String.t(), binary()) :: String.t()
   def create_signature_header(headers, include_headers, key_id, body) do
     digest = compute_digest(body)
@@ -42,7 +38,7 @@ defmodule HTTPSignature do
   end
 
   defp sign(data) do
-    :crypto.hash(@algo, [@key, data])
+    :crypto.hash(:sha256, [Vonbraun.KeyAgent.get_private_key(), data])
     |> Base.encode64()
     |> String.downcase()
   end