diff --git a/Doc/library/binascii.rst b/Doc/library/binascii.rst
index 2f7851a..a34c843 100644
--- a/Doc/library/binascii.rst
+++ b/Doc/library/binascii.rst
@@ -18,6 +18,11 @@
 low-level functions written in C for greater speed that are used by the
 higher-level modules.
 
+.. note::
+
+   Encoding and decoding functions do not accept Unicode strings.  Only bytestring
+   and bytearray objects can be processed.
+
 The :mod:`binascii` module defines the following functions:
 
 
@@ -54,6 +59,9 @@
    data. More than one line may be passed at a time. If the optional argument
    *header* is present and true, underscores will be decoded as spaces.
 
+   .. versionchanged:: 3.2
+      accept only bytestring or bytearray object as input.
+
 
 .. function:: b2a_qp(data, quotetabs=False, istext=True, header=False)
 
@@ -83,6 +91,9 @@
    decompressed data, unless data input data ends in an orphaned repeat indicator,
    in which case the :exc:`Incomplete` exception is raised.
 
+   .. versionchanged:: 3.2
+      accept only bytestring or bytearray object as input.
+
 
 .. function:: rlecode_hqx(data)
 
@@ -139,6 +150,9 @@
    of hexadecimal digits (which can be upper or lower case), otherwise a
    :exc:`TypeError` is raised.
 
+   .. versionchanged:: 3.2
+      accept only bytestring or bytearray object as input.
+
 
 .. exception:: Error
 
@@ -164,4 +178,3 @@
 
    Module :mod:`quopri`
       Support for quoted-printable encoding used in MIME email messages.
-
diff --git a/Lib/email/base64mime.py b/Lib/email/base64mime.py
index 6cbfdf6..f3bbac1 100644
--- a/Lib/email/base64mime.py
+++ b/Lib/email/base64mime.py
@@ -74,12 +74,12 @@
 
 
 def body_encode(s, maxlinelen=76, eol=NL):
-    """Encode a string with base64.
+    r"""Encode a string with base64.
 
     Each line will be wrapped at, at most, maxlinelen characters (defaults to
     76 characters).
 
-    Each line of encoded text will end with eol, which defaults to "\\n".  Set
+    Each line of encoded text will end with eol, which defaults to "\n".  Set
     this to "\r\n" if you will be using the result of this function directly
     in an email.
     """
diff --git a/Lib/email/message.py b/Lib/email/message.py
index 27a577d..520d63d 100644
--- a/Lib/email/message.py
+++ b/Lib/email/message.py
@@ -198,17 +198,19 @@
             return None
         cte = self.get('content-transfer-encoding', '').lower()
         if cte == 'quoted-printable':
+            if isinstance(payload, str):
+                payload = payload.encode('ascii')
             return utils._qdecode(payload)
         elif cte == 'base64':
             try:
                 if isinstance(payload, str):
-                    payload = payload.encode('raw-unicode-escape')
+                    payload = payload.encode('ascii')
                 return base64.b64decode(payload)
             except binascii.Error:
                 # Incorrect padding
                 pass
         elif cte in ('x-uuencode', 'uuencode', 'uue', 'x-uue'):
-            in_file = BytesIO(payload.encode('raw-unicode-escape'))
+            in_file = BytesIO(payload.encode('ascii'))
             out_file = BytesIO()
             try:
                 uu.decode(in_file, out_file, quiet=True)
diff --git a/Lib/test/test_binascii.py b/Lib/test/test_binascii.py
index 3c6d88f..1e9e888 100644
--- a/Lib/test/test_binascii.py
+++ b/Lib/test/test_binascii.py
@@ -55,7 +55,7 @@
                              "{!r} != {!r}".format(fb, fa, res, raw))
             self.assertIsInstance(res, bytes)
             self.assertIsInstance(a, bytes)
-            self.assertLess(max(c for c in a), 128)
+            self.assertLess(max(a), 128)
         self.assertIsInstance(binascii.crc_hqx(raw, 0), int)
         self.assertIsInstance(binascii.crc32(raw), int)
 
@@ -167,7 +167,7 @@
     def test_qp(self):
         # A test for SF bug 534347 (segfaults without the proper fix)
         try:
-            binascii.a2b_qp("", **{1:1})
+            binascii.a2b_qp(b"", **{1:1})
         except TypeError:
             pass
         else:
@@ -179,12 +179,10 @@
         self.assertEqual(binascii.a2b_qp(b"=00\r\n=00"), b"\x00\r\n\x00")
         self.assertEqual(
             binascii.b2a_qp(b"\xff\r\n\xff\n\xff"),
-            b"=FF\r\n=FF\r\n=FF"
-        )
+            b"=FF\r\n=FF\r\n=FF")
         self.assertEqual(
             binascii.b2a_qp(b"0"*75+b"\xff\r\n\xff\r\n\xff"),
-            b"0"*75+b"=\r\n=FF\r\n=FF\r\n=FF"
-        )
+            b"0"*75+b"=\r\n=FF\r\n=FF\r\n=FF")
 
         self.assertEqual(binascii.b2a_qp(b'\0\n'), b'=00\n')
         self.assertEqual(binascii.b2a_qp(b'\0\n', quotetabs=True), b'=00\n')
@@ -210,13 +208,15 @@
             except Exception as err:
                 self.fail("{}({!r}) raises {!r}".format(func, empty, err))
 
-    def test_no_binary_strings(self):
-        # b2a_ must not accept strings
-        for f in (binascii.b2a_uu, binascii.b2a_base64,
-                  binascii.b2a_hqx, binascii.b2a_qp,
-                  binascii.hexlify, binascii.rlecode_hqx,
-                  binascii.crc_hqx, binascii.crc32):
-            self.assertRaises(TypeError, f, "test")
+    def test_unicode_strings(self):
+        # Unicode strings are not accepted.
+        for func in all_functions:
+            try:
+                self.assertRaises(TypeError, getattr(binascii, func), "test")
+            except Exception as err:
+                self.fail('{}("test") raises {!r}'.format(func, err))
+        # crc_hqx needs 2 arguments
+        self.assertRaises(TypeError, binascii.crc_hqx, "test", 0)
 
 
 class ArrayBinASCIITest(BinASCIITest):
diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
index b923f45..6ca35ca 100644
--- a/Lib/test/test_struct.py
+++ b/Lib/test/test_struct.py
@@ -213,6 +213,7 @@
                     expected = '%x' % expected
                     if len(expected) & 1:
                         expected = "0" + expected
+                    expected = expected.encode('ascii')
                     expected = unhexlify(expected)
                     expected = (b"\x00" * (self.bytesize - len(expected)) +
                                 expected)
diff --git a/Misc/NEWS b/Misc/NEWS
index 3f565f6..2437614 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -473,6 +473,10 @@
 Library
 -------
 
+- Issue #4770: Restrict binascii module to accept only bytes (as specified).
+  And fix the email package to encode to ASCII instead of
+  ``raw-unicode-escape`` before ASCII-to-binary decoding.
+
 - Issue #9384: python -m tkinter will now display a simple demo applet.
 
 - The default size of the re module's compiled regular expression cache has
diff --git a/Modules/binascii.c b/Modules/binascii.c
index d21404b..23ce3f0 100644
--- a/Modules/binascii.c
+++ b/Modules/binascii.c
@@ -546,7 +546,7 @@
     Py_ssize_t len;
     int done = 0;
 
-    if ( !PyArg_ParseTuple(args, "s*:a2b_hqx", &pascii) )
+    if ( !PyArg_ParseTuple(args, "y*:a2b_hqx", &pascii) )
         return NULL;
     ascii_data = pascii.buf;
     len = pascii.len;
@@ -750,7 +750,7 @@
     PyObject *rv;
     Py_ssize_t in_len, out_len, out_len_left;
 
-    if ( !PyArg_ParseTuple(args, "s*:rledecode_hqx", &pin) )
+    if ( !PyArg_ParseTuple(args, "y*:rledecode_hqx", &pin) )
         return NULL;
     in_data = pin.buf;
     in_len = pin.len;
@@ -1121,7 +1121,7 @@
     char* retbuf;
     Py_ssize_t i, j;
 
-    if (!PyArg_ParseTuple(args, "s*:a2b_hex", &parg))
+    if (!PyArg_ParseTuple(args, "y*:a2b_hex", &parg))
         return NULL;
     argbuf = parg.buf;
     arglen = parg.len;
@@ -1199,7 +1199,7 @@
     static char *kwlist[] = {"data", "header", NULL};
     int header = 0;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "s*|i", kwlist, &pdata,
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "y*|i", kwlist, &pdata,
           &header))
         return NULL;
     data = pdata.buf;