diff --git a/digsigserver/server.py b/digsigserver/server.py
index 5a48c20..0a37120 100644
--- a/digsigserver/server.py
+++ b/digsigserver/server.py
@@ -198,26 +198,39 @@ async def sign_handler_fitimage(req: request):
         f = validate_upload(req, "artifact")
         if not f:
             return text("Invalid artifact", status=400)
+        dtb = validate_upload(req, "dtb")
         with tempfile.TemporaryDirectory() as workdir:
             try:
-                s = FitImageSigner(app, workdir)
+                s = FitImageSigner(app, workdir, req.form.get("machine") or "imx")
             except ValueError:
                 return text("Invalid parameters", status=400)
 
-            with open(os.path.join(workdir, "artifact"), "wb") as artifact:
-                artifact.write(f.body)
+            fitimage_path = os.path.join(workdir, "fitImage")
+            with open(fitimage_path, "wb") as fitimage:
+                fitimage.write(f.body)
+
+            dtb_path = None
+            if dtb:
+                dtb_path = os.path.join(workdir, dtb.name or "u-boot.dtb")
+                with open(dtb_path, "wb") as dtb_file:
+                    dtb_file.write(dtb.body)
 
             outfile = tempfile.NamedTemporaryFile(delete=False)
             outfile.close()
             if await asyncio.get_running_loop().run_in_executor(None, s.sign,
-                                   artifact.name,
-                                   None,
+                                   fitimage_path,
+                                   dtb_path,
                                    req.form.get("external_data_offset"),
                                    req.form.get("mark_required"),
                                    req.form.get("algo"),
                                    req.form.get("keyname")):
-                await return_file(req, artifact.name, "artifact.signed")
-                response = None
+                if dtb_path:
+                    dtb_name = os.path.basename(dtb_path)
+                    response = await return_tarball(req, workdir, return_filename="signed-fitImage.tar.gz",
+                                                   files_to_return=["fitImage", dtb_name])
+                else:
+                    await return_file(req, fitimage_path, "fitImage.signed")
+                    response = None
             else:
                 response = text("Signing error", status=500)
         return response
diff --git a/digsigserver/signers/fitimagesign.py b/digsigserver/signers/fitimagesign.py
index 75c9692..ebdfeb5 100644
--- a/digsigserver/signers/fitimagesign.py
+++ b/digsigserver/signers/fitimagesign.py
@@ -1,5 +1,7 @@
 import os
 import copy
+import re
+import subprocess
 from typing import Optional
 from digsigserver.signers import Signer
 
@@ -10,8 +12,8 @@ class FitImageSigner (Signer):
 
     keytag = 'fitimagesign'
 
-    def __init__(self, app: Sanic, workdir: str):
-        super().__init__(app, workdir, "imx")
+    def __init__(self, app: Sanic, workdir: str, machine: str = "imx"):
+        super().__init__(app, workdir, machine)
 
     def _prepare_path(self) -> dict:
         env = dict(copy.deepcopy(os.environ))
@@ -20,14 +22,77 @@ def _prepare_path(self) -> dict:
             env['PATH'] += ':' + curpath
         return env
 
+    @staticmethod
+    def _normalize_keyname(keyname: Optional[str]) -> Optional[str]:
+        if not keyname:
+            return None
+        resolved = keyname.strip()
+        if not resolved:
+            return None
+        if resolved.endswith('.key'):
+            resolved = resolved[:-4]
+        return resolved or None
+
+    def _keyname_from_dtb(self, dtb: Optional[str]) -> Optional[str]:
+        if not dtb or not os.path.exists(dtb):
+            return None
+        try:
+            with open(dtb, 'rb') as f:
+                content = f.read().decode('latin-1', errors='ignore')
+        except OSError:
+            return None
+
+        # U-Boot signature keys are typically named key-<name>.
+        match = re.search(r'key-([A-Za-z0-9_.-]+)', content)
+        if match:
+            return match.group(1)
+        return None
+
+    def _keyname_from_fitimage(self, fitimage: str, env: dict) -> Optional[str]:
+        try:
+            proc = subprocess.run(
+                ['mkimage', '-l', fitimage],
+                stdin=subprocess.DEVNULL,
+                cwd=self.workdir,
+                env=env,
+                check=True,
+                capture_output=True,
+                encoding='utf-8'
+            )
+        except (subprocess.CalledProcessError, FileNotFoundError):
+            return None
+
+        # Example: "Sign algo:    sha256,rsa2048:dev_vb"
+        match = re.search(r'Sign algo:\s+[^:\n]+:([A-Za-z0-9_.-]+)', proc.stdout)
+        if match:
+            return match.group(1)
+        return None
+
+    def _resolve_keyname(self, keyname: Optional[str], dtb: Optional[str], fitimage: str, env: dict) -> str:
+        resolved = self._normalize_keyname(keyname)
+        if resolved:
+            return resolved
+        resolved = self._keyname_from_dtb(dtb)
+        if resolved:
+            logger.info("Resolved fitImage keyname from dtb: %s", resolved)
+            return resolved
+        resolved = self._keyname_from_fitimage(fitimage, env)
+        if resolved:
+            logger.info("Resolved fitImage keyname from fitImage metadata: %s", resolved)
+            return resolved
+        logger.info("Using default fitImage keyname: dev")
+        return 'dev'
+
     def sign(self, fitimage: str,
              dtb: Optional[str],
              external_data_offset: Optional[str],
              mark_required: Optional[bool],
              algo: Optional[str],
-             keyname: str = "dev.key") -> bool:
-        private_key = self.keys.get("{}.key".format(keyname))
+             keyname: Optional[str] = None) -> bool:
         env = self._prepare_path()
+        selected_keyname = self._resolve_keyname(keyname, dtb, fitimage, env)
+        private_key = self.keys.get("{}.key".format(selected_keyname))
+        self.keys.get("{}.crt".format(selected_keyname))
         cmd = [ 'mkimage', '-F', '-k', os.path.dirname(private_key) ]
         if external_data_offset:
             cmd += [ '-p', external_data_offset ]