diff --git a/scripts/imgtool.py b/scripts/imgtool.py
new file mode 100755
index 0000000..4f5e56b
--- /dev/null
+++ b/scripts/imgtool.py
@@ -0,0 +1,94 @@
+#! /usr/bin/env python3
+
+import argparse
+from imgtool import keys
+from imgtool import image
+from imgtool import version
+import sys
+
+def gen_rsa2048(args):
+    keys.RSA2048.generate().export_private(args.keyfile)
+def gen_ecdsa_p256(args):
+    keys.ecdsa256p1.generate().export_private(args.keyfile)
+def gen_ecdsa_p224(args):
+    print("TODO: p-224 not yet implemented")
+
+keygens = {
+        'rsa-2048': gen_rsa2048,
+        'ecdsa-p256': gen_ecdsa_p256,
+        'ecdsa-p224': gen_ecdsa_p224, }
+
+def do_keygen(args):
+    if args.type not in keygens:
+        msg = "Unexpected key type: {}".format(args.type)
+        raise argparse.ArgumentTypeError(msg)
+    keygens[args.type](args)
+
+def do_getpub(args):
+    key = keys.load(args.key)
+    key.emit_c()
+
+def do_sign(args):
+    align = args.align
+    # print('sign:', args)
+    img = image.Image.load(args.infile, version=args.version,
+            header_size=args.header_size,
+            pad=args.pad)
+    key = keys.load(args.key)
+    img.sign(key)
+
+    if args.pad:
+        img.pad_to(args.pad, args.align)
+
+    img.save(args.outfile)
+
+subcmds = {
+        'keygen': do_keygen,
+        'getpub': do_getpub,
+        'sign': do_sign, }
+
+def alignment_value(text):
+    value = int(text)
+    if value not in [1, 2, 4, 8]:
+        msg = "{} must be one of 1, 2, 4 or 8".format(value)
+        raise argparse.ArgumentTypeError(msg)
+    return value
+
+def intparse(text):
+    """Parse a command line argument as an integer.
+
+    Accepts 0x and other prefixes to allow other bases to be used."""
+    return int(text, 0)
+
+def args():
+    parser = argparse.ArgumentParser()
+    subs = parser.add_subparsers(help='subcommand help', dest='subcmd')
+
+    keygenp = subs.add_parser('keygen', help='Generate pub/private keypair')
+    keygenp.add_argument('-k', '--key', metavar='filename', required=True)
+    keygenp.add_argument('-t', '--type', metavar='type',
+            choices=['rsa-2048', 'ecdsa-p224', 'ecdsa-p256'],
+            required=True)
+
+    getpub = subs.add_parser('getpub', help='Get public key from keypair')
+    getpub.add_argument('-k', '--key', metavar='filename', required=True)
+
+    sign = subs.add_parser('sign', help='Sign an image with a private key')
+    sign.add_argument('-k', '--key', metavar='filename', required=True)
+    sign.add_argument("--align", type=alignment_value, required=True)
+    sign.add_argument("-v", "--version", type=version.decode_version, required=True)
+    sign.add_argument("-H", "--header-size", type=intparse, required=True)
+    sign.add_argument("--pad", type=intparse,
+            help='Pad image to this many bytes, adding trailer magic')
+    sign.add_argument("infile")
+    sign.add_argument("outfile")
+
+    args = parser.parse_args()
+    if args.subcmd is None:
+        print('Must specify a subcommand', file=sys.stderr)
+        sys.exit(1)
+
+    subcmds[args.subcmd](args)
+
+if __name__ == '__main__':
+    args()