From 274e21920d28168d0c5b6acb6a763e88d5366f6f Mon Sep 17 00:00:00 2001
From: Donald Stufft <donald@stufft.io>
Date: Sun, 17 Mar 2013 17:59:32 -0400
Subject: [PATCH] Generate the shared key upfront
---
nacl/public.py | 34 +++++++++++++---------------------
1 file changed, 13 insertions(+), 21 deletions(-)
diff --git a/nacl/public.py b/nacl/public.py
index d9e45f70..36a590d8 100644
--- a/nacl/public.py
+++ b/nacl/public.py
@@ -108,7 +108,17 @@ class Box(object):
self._public_key = public_key
self._private_key = private_key
- self._shared_key = None
+ _shared_key_size = nacl.lib.crypto_box_BEFORENMBYTES
+ _shared_key = nacl.ffi.new("unsigned char[]", _shared_key_size)
+
+ if not nacl.lib.crypto_box_beforenm(
+ _shared_key,
+ self._public_key.encode(encoder=encoding.RawEncoder),
+ self._private_key.encode(encoder=encoding.RawEncoder),
+ ):
+ raise CryptoError("Failed to derive shared key")
+
+ self._shared_key = nacl.ffi.buffer(_shared_key, _shared_key_size)[:]
def encrypt(self, plaintext, nonce, encoder=encoding.RawEncoder):
"""
@@ -136,7 +146,7 @@ class Box(object):
padded,
len(padded),
nonce,
- self._beforenm()
+ self._shared_key,
):
raise CryptoError("Encryption failed")
@@ -170,7 +180,7 @@ class Box(object):
padded,
len(padded),
nonce,
- self._beforenm()
+ self._shared_key,
):
raise CryptoError(
"Decryption failed. Ciphertext failed verification")
@@ -179,21 +189,3 @@ class Box(object):
plaintext = nacl.ffi.buffer(plaintext, len(padded))[box_zeros:]
return plaintext
-
- def _beforenm(self):
- if self._shared_key is not None:
- return self._shared_key
-
- sharedkey_size = nacl.lib.crypto_box_BEFORENMBYTES
-
- k = nacl.ffi.new("unsigned char[]", sharedkey_size)
-
- if not nacl.lib.crypto_box_beforenm(
- k,
- self._public_key.encode(encoder=encoding.RawEncoder),
- self._private_key.encode(encoder=encoding.RawEncoder),
- ):
- raise CryptoError("Failed to derive shared key")
-
- self._shared_key = nacl.ffi.buffer(k, sharedkey_size)[:]
- return self._shared_key
--
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