From 068e8820d6f43c410d456dce0c2d730202df99ed Mon Sep 17 00:00:00 2001
From: Brian Warner <warner@lothar.com>
Date: Fri, 20 Jun 2014 16:01:20 -0700
Subject: [PATCH] expose and test crypto_scalarmult
fixes #65
---
src/nacl/_lib/crypto_scalarmult.h | 1 +
src/nacl/c/__init__.py | 3 ++-
src/nacl/c/crypto_scalarmult.py | 18 ++++++++++++++++++
tests/test_raw.py | 23 +++++++++++++++++++----
4 files changed, 40 insertions(+), 5 deletions(-)
diff --git a/src/nacl/_lib/crypto_scalarmult.h b/src/nacl/_lib/crypto_scalarmult.h
index dee5e849..e7990389 100644
--- a/src/nacl/_lib/crypto_scalarmult.h
+++ b/src/nacl/_lib/crypto_scalarmult.h
@@ -17,3 +17,4 @@ size_t crypto_scalarmult_bytes();
size_t crypto_scalarmult_scalarbytes();
int crypto_scalarmult_base(unsigned char *q, const unsigned char *n);
+int crypto_scalarmult(unsigned char *q, const unsigned char *n, const unsigned char *p);
diff --git a/src/nacl/c/__init__.py b/src/nacl/c/__init__.py
index 48b369a4..0a73a5ba 100644
--- a/src/nacl/c/__init__.py
+++ b/src/nacl/c/__init__.py
@@ -25,7 +25,7 @@ from nacl.c.crypto_hash import (
)
from nacl.c.crypto_scalarmult import (
crypto_scalarmult_BYTES, crypto_scalarmult_SCALARBYTES,
- crypto_scalarmult_base,
+ crypto_scalarmult, crypto_scalarmult_base,
)
from nacl.c.crypto_secretbox import (
crypto_secretbox_KEYBYTES, crypto_secretbox_NONCEBYTES,
@@ -63,6 +63,7 @@ __all__ = [
"crypto_scalarmult_BYTES",
"crypto_scalarmult_SCALARBYTES",
+ "crypto_scalarmult",
"crypto_scalarmult_base",
"crypto_secretbox_KEYBYTES",
diff --git a/src/nacl/c/crypto_scalarmult.py b/src/nacl/c/crypto_scalarmult.py
index b94841e4..f5ba2bac 100644
--- a/src/nacl/c/crypto_scalarmult.py
+++ b/src/nacl/c/crypto_scalarmult.py
@@ -36,3 +36,21 @@ def crypto_scalarmult_base(n):
"An error occurred while computing the scalar product")
return lib.ffi.buffer(q, crypto_scalarmult_SCALARBYTES)[:]
+
+
+def crypto_scalarmult(n, p):
+ """
+ Computes and returns the scalar product of the given group element and an
+ integer ``n``.
+
+ :param p: bytes
+ :param n: bytes
+ :rtype: bytes
+ """
+ q = lib.ffi.new("unsigned char[]", crypto_scalarmult_BYTES)
+
+ if lib.crypto_scalarmult(q, n, p) != 0:
+ raise CryptoError(
+ "An error occurred while computing the scalar product")
+
+ return lib.ffi.buffer(q, crypto_scalarmult_SCALARBYTES)[:]
diff --git a/tests/test_raw.py b/tests/test_raw.py
index a3a0ed4f..2a608749 100644
--- a/tests/test_raw.py
+++ b/tests/test_raw.py
@@ -12,7 +12,7 @@
# See the License for the specific language governing permissions and
# limitations under the License.
-from binascii import hexlify
+from binascii import hexlify, unhexlify
from nacl import c
import hashlib
@@ -108,6 +108,21 @@ def test_scalarmult():
x, xpub = secret_scalar()
assert len(x) == 32
y, ypub = secret_scalar()
-
- bx = c.crypto_scalarmult_base(x)
- assert tohex(bx) == tohex(xpub)
+ # the Curve25519 base point (generator)
+ base = unhexlify(b"09" + b"00"*31)
+
+ bx1 = c.crypto_scalarmult_base(x)
+ bx2 = c.crypto_scalarmult(x, base)
+ assert tohex(bx1) == tohex(bx2)
+ assert tohex(bx1) == tohex(xpub)
+
+ xby = c.crypto_scalarmult(x, c.crypto_scalarmult_base(y))
+ ybx = c.crypto_scalarmult(y, c.crypto_scalarmult_base(x))
+ assert tohex(xby) == tohex(ybx)
+
+ z = unhexlify(b"10"*32)
+ bz1 = c.crypto_scalarmult_base(z)
+ assert tohex(bz1) == ("781faab908430150daccdd6f9d6c5086"
+ "e34f73a93ebbaa271765e5036edfc519")
+ bz2 = c.crypto_scalarmult(z, base)
+ assert tohex(bz1) == tohex(bz2)
--
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