Auto fill Streebog's cache

[pygost.git] / pygost / gost34112012.py

diff --git a/pygost/gost34112012.py b/pygost/gost34112012.py
index ac20edd790741dd915fd52d3f8fc1494eaacfdca..ae7627bf23703cb4b8903385b32abb61d521bb67 100644 (file)
--- a/pygost/gost34112012.py
+++ b/pygost/gost34112012.py
@@ -163,6 +163,26 @@ C = [hexdec("".join(s))[::-1] for s in (
 )]
 
 
+def _lcache():
+    cache = []
+    for byteN in xrange(8):
+        cache.append([0 for _ in xrange(256)])
+    for byteN in xrange(8):
+        for byteVal in xrange(256):
+            res64 = 0
+            val = byteVal
+            for bitN in xrange(8):
+                if val & 0x80 > 0:
+                    res64 ^= A[(7 - byteN) * 8 + bitN]
+                val <<= 1
+            cache[byteN][byteVal] = res64
+    return cache
+
+
+# Trade memory for CPU for part of L() calculations
+LCache = _lcache()
+
+
 def add512bit(a, b):
     """Add two 512 integers
     """
@@ -202,12 +222,9 @@ def PS(data):
 def L(data):
     res = []
     for i in range(8):
-        val = unpack("<Q", data[i * 8:i * 8 + 8])[0]
         res64 = 0
-        for j in range(BLOCKSIZE):
-            if val & 0x8000000000000000:
-                res64 ^= A[j]
-            val <<= 1
+        for j in range(8):
+            res64 ^= LCache[j][data[8 * i + j]]
         res.append(pack("<Q", res64))
     return b"".join(res)