news.texi              |  4 ++++
 pygost/__init__.py     |  2 +-
 pygost/gost3410.py     | 18 +++++++++++++-----
 pygost/gost3410_vko.py |  4 +++-

diff --git a/news.texi b/news.texi
index 110503cd5e1bbc517f983e6fda843ea389281fe8d4da757bbbe825a552ac1a73..9abd0b3f955321f950a922f9e6680f043b90059d5ee9c3d6dd110682be7021a3 100644
--- a/news.texi
+++ b/news.texi
@@ -3,6 +3,10 @@ @unnumbered News
 
 @table @strong
 
+@anchor{Release 5.13}
+@item 5.13
+Ability to use masked 34.10 private keys.
+
 @anchor{Release 5.12}
 @item 5.12
 Fixed incorrect digest calculation when using @code{GOST34112012*.update()}
diff --git a/pygost/__init__.py b/pygost/__init__.py
index 032adc8b2e2c305420fd59ba7828193e9f85561ac7ebde32c5e3e982cf7f749d..7b1183a6e6474f958ba3f550f8888e83508581e37d98850e1fa99665ab09221d 100644
--- a/pygost/__init__.py
+++ b/pygost/__init__.py
@@ -3,4 +3,4 @@
 PyGOST is free software: see the file COPYING for copying conditions.
 """
 
-__version__ = "5.12"
+__version__ = "5.13"
diff --git a/pygost/gost3410.py b/pygost/gost3410.py
index c3c63a0f48e0c231bed9c768a85df14e5bcb9112f2ae3f53f45d1a9a50f93a2f..4128eb31b792b6393c623978535ebd7a7386bd2ef998b4aec266605a91e7df1f 100644
--- a/pygost/gost3410.py
+++ b/pygost/gost3410.py
@@ -242,7 +242,7 @@     _curve.name = _name
 DEFAULT_CURVE = CURVES["id-tc26-gost-3410-12-256-paramSetB"]
 
 
-def public_key(curve, prv):
+def public_key(curve, prv, mask=None):
     """Generate public key from the private one
 
     :param GOST3410Curve curve: curve to use
@@ -250,10 +250,13 @@     :param long prv: private key
     :returns: public key's parts, X and Y
     :rtype: (long, long)
     """
-    return curve.exp(prv)
+    pub = curve.exp(prv)
+    if mask is not None:
+        pub = curve.exp(mask, pub[0], pub[1])
+    return pub
 
 
-def sign(curve, prv, digest, rand=None):
+def sign(curve, prv, digest, rand=None, mask=None):
     """Calculate signature for provided digest
 
     :param GOST3410Curve curve: curve to use
@@ -278,13 +281,18 @@             raise ValueError("rand length != %d" % size)
         k = bytes2long(rand) % q
         if k == 0:
             continue
-        r, _ = curve.exp(k)
+        r, y = curve.exp(k)
+        if mask is not None:
+            r, y = curve.exp(mask, x=r, y=y)
         r %= q
         if r == 0:
             continue
         d = prv * r
         k *= e
-        s = (d + k) % q
+        s = d + k
+        if mask is not None:
+            s *= mask
+        s %= q
         if s == 0:
             continue
         break
diff --git a/pygost/gost3410_vko.py b/pygost/gost3410_vko.py
index a44199b5bed0c8c268d6c21396974239f6a1be85b4fba3cd4115c67652068582..f820aee5a3f4be55c6677667c3b6af00414728e98f1e71d07dd6c0bf32365381 100644
--- a/pygost/gost3410_vko.py
+++ b/pygost/gost3410_vko.py
@@ -32,11 +32,13 @@     """
     return bytes2long(ukm[::-1])
 
 
-def kek(curve, prv, pub, ukm):
+def kek(curve, prv, pub, ukm, mask=None):
     if not curve.contains(pub):
         raise ValueError("pub is not on the curve")
     key = curve.exp(prv, pub[0], pub[1])
     key = curve.exp(curve.cofactor * ukm, key[0], key[1])
+    if mask is not None:
+        key = curve.exp(mask, key[0], key[1])
     return pub_marshal(key)