34.11-2012 PBKDF2

[pygost.git] / pygost / pbkdf2.py

diff --git a/pygost/pbkdf2.py b/pygost/pbkdf2.py
new file mode 100644 (file)
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--- /dev/null
+++ b/pygost/pbkdf2.py
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+# coding: utf-8
+""" PBKDF2 implementation suitable for GOST R 34.11-94/34.11-2012.
+
+This implementation is based on Python 3.5.2 source code's one.
+PyGOST does not register itself in hashlib anyway, so use it instead.
+"""
+
+
+from pygost.utils import bytes2long
+from pygost.utils import long2bytes
+from pygost.utils import strxor
+from pygost.utils import xrange  # pylint: disable=redefined-builtin
+
+
+def pbkdf2(hasher, password, salt, iterations, dklen):
+    """PBKDF2 implementation suitable for GOST R 34.11-94/34.11-2012
+    """
+    inner = hasher()
+    outer = hasher()
+    password = password + b"\x00" * (inner.block_size - len(password))
+    inner.update(strxor(password, len(password) * b"\x36"))
+    outer.update(strxor(password, len(password) * b"\x5C"))
+
+    def prf(msg):
+        icpy = inner.copy()
+        ocpy = outer.copy()
+        icpy.update(msg)
+        ocpy.update(icpy.digest())
+        return ocpy.digest()
+
+    dkey = b''
+    loop = 1
+    while len(dkey) < dklen:
+        prev = prf(salt + long2bytes(loop, 4))
+        rkey = bytes2long(prev)
+        for _ in xrange(iterations - 1):
+            prev = prf(prev)
+            rkey ^= bytes2long(prev)
+        loop += 1
+        dkey += long2bytes(rkey, inner.digest_size)
+    return dkey[:dklen]