diff --git a/scripts/imgtool/version.py b/scripts/imgtool/version.py
new file mode 100644
index 0000000..eac3667
--- /dev/null
+++ b/scripts/imgtool/version.py
@@ -0,0 +1,27 @@
+"""
+Semi Semantic Versioning
+
+Implements a subset of semantic versioning that is supportable by the image header.
+"""
+
+from collections import namedtuple
+import re
+
+SemiSemVersion = namedtuple('SemiSemVersion', ['major', 'minor', 'revision', 'build'])
+
+version_re = re.compile(r"""^([1-9]\d*)(\.([1-9]\d*)(\.([1-9]\d*)(\+([a-z1-9-][a-z0-9-]*))?)?)?$""")
+def decode_version(text):
+    """Decode the version string, which should be of the form maj.min.rev+build"""
+    # print("decode:", text)
+    m = version_re.match(text)
+    if m:
+        result = SemiSemVersion(
+                int(m.group(1)) if m.group(1) else 0,
+                int(m.group(3)) if m.group(3) else 0,
+                int(m.group(5)) if m.group(5) else 0,
+                int(m.group(7)) if m.group(7) else 0)
+        return result
+    else:
+        msg = "Invalid version number, should be maj.min.rev+build with later parts optional"
+        raise argparse.ArgumentTypeError(msg)
+