diff --git a/src/wormhole/test/test_util.py b/src/wormhole/test/test_util.py
new file mode 100644
index 0000000..3c916a4
--- /dev/null
+++ b/src/wormhole/test/test_util.py
@@ -0,0 +1,39 @@
+import unicodedata
+from twisted.trial import unittest
+from .. import util
+
+class Utils(unittest.TestCase):
+    def test_to_bytes(self):
+        b = util.to_bytes(u"abc")
+        self.assertIsInstance(b, type(b""))
+        self.assertEqual(b, b"abc")
+
+        A = unicodedata.lookup("LATIN SMALL LETTER A WITH DIAERESIS")
+        b = util.to_bytes(A + u"bc")
+        self.assertIsInstance(b, type(b""))
+        self.assertEqual(b, b"\xc3\xa4\x62\x63")
+
+    def test_bytes_to_hexstr(self):
+        b = b"\x00\x45\x91\xfe\xff"
+        hexstr = util.bytes_to_hexstr(b)
+        self.assertIsInstance(hexstr, type(u""))
+        self.assertEqual(hexstr, u"004591feff")
+
+    def test_hexstr_to_bytes(self):
+        hexstr = u"004591feff"
+        b = util.hexstr_to_bytes(hexstr)
+        hexstr = util.bytes_to_hexstr(b)
+        self.assertIsInstance(b, type(b""))
+        self.assertEqual(b, b"\x00\x45\x91\xfe\xff")
+
+    def test_dict_to_bytes(self):
+        d = {"a": "b"}
+        b = util.dict_to_bytes(d)
+        self.assertIsInstance(b, type(b""))
+        self.assertEqual(b, b'{"a": "b"}')
+
+    def test_bytes_to_dict(self):
+        b = b'{"a": "b", "c": 2}'
+        d = util.bytes_to_dict(b)
+        self.assertIsInstance(d, dict)
+        self.assertEqual(d, {u"a": u"b", u"c": 2})
diff --git a/src/wormhole/util.py b/src/wormhole/util.py
new file mode 100644
index 0000000..43dccfe
--- /dev/null
+++ b/src/wormhole/util.py
@@ -0,0 +1,25 @@
+import json, unicodedata
+from binascii import hexlify, unhexlify
+
+def to_bytes(u):
+    return unicodedata.normalize("NFC", u).encode("utf-8")
+def bytes_to_hexstr(b):
+    assert isinstance(b, type(b""))
+    hexstr = hexlify(b).decode("ascii")
+    assert isinstance(hexstr, type(u""))
+    return hexstr
+def hexstr_to_bytes(hexstr):
+    assert isinstance(hexstr, type(u""))
+    b = unhexlify(hexstr.encode("ascii"))
+    assert isinstance(b, type(b""))
+    return b
+def dict_to_bytes(d):
+    assert isinstance(d, dict)
+    b = json.dumps(d).encode("utf-8")
+    assert isinstance(b, type(b""))
+    return b
+def bytes_to_dict(b):
+    assert isinstance(b, type(b""))
+    d = json.loads(b.decode("utf-8"))
+    assert isinstance(d, dict)
+    return d
diff --git a/src/wormhole/wormhole.py b/src/wormhole/wormhole.py
index a8f4eef..efc11c7 100644
--- a/src/wormhole/wormhole.py
+++ b/src/wormhole/wormhole.py
@@ -1,5 +1,5 @@
 from __future__ import print_function, absolute_import
-import os, sys, json, re, unicodedata
+import os, sys, json, re
 from six.moves.urllib_parse import urlparse
 from binascii import hexlify, unhexlify
 from twisted.internet import defer, endpoints, error
@@ -18,6 +18,7 @@ from . import codes
 from .errors import (WrongPasswordError, UsageError, WelcomeError,
                      WormholeClosedError)
 from .timing import DebugTiming
+from .util import to_bytes
 from hkdf import Hkdf
 
 def HKDF(skm, outlen, salt=None, CTXinfo=b""):
@@ -28,8 +29,6 @@ CONFMSG_MAC_LENGTH = 256//8
 def make_confmsg(confkey, nonce):
     return nonce+HKDF(confkey, CONFMSG_MAC_LENGTH, nonce)
 
-def to_bytes(u):
-    return unicodedata.normalize("NFC", u).encode("utf-8")
 
 # We send the following messages through the relay server to the far side (by
 # sending "add" commands to the server, and getting "message" responses):