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authorBodo Möller <bodo@openssl.org>2000-06-08 20:26:03 +0000
committerBodo Möller <bodo@openssl.org>2000-06-08 20:26:03 +0000
commitdc434bbcb0f63e03c64be1d977fae6c9411bfc5c (patch)
tree6bbbbf7a0c1d0d6d2b8cbffef94da36dbb65fc62 /crypto/bn/bn_lcl.h
parent947b3b8bafb2266410610ff17964c5b42a407846 (diff)
Slightly faster DSA verification (BN_mod_exp2_mont),
marginally faster BN_mod_exp for 1024 bit exponents.
Diffstat (limited to 'crypto/bn/bn_lcl.h')
-rw-r--r--crypto/bn/bn_lcl.h98
1 files changed, 98 insertions, 0 deletions
diff --git a/crypto/bn/bn_lcl.h b/crypto/bn/bn_lcl.h
index e36ccbc4c2..97c35ea595 100644
--- a/crypto/bn/bn_lcl.h
+++ b/crypto/bn/bn_lcl.h
@@ -55,6 +55,59 @@
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
+/* ====================================================================
+ * Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ * software must display the following acknowledgment:
+ * "This product includes software developed by the OpenSSL Project
+ * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ * endorse or promote products derived from this software without
+ * prior written permission. For written permission, please contact
+ * openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ * nor may "OpenSSL" appear in their names without prior written
+ * permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ * acknowledgment:
+ * "This product includes software developed by the OpenSSL Project
+ * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This product includes cryptographic software written by Eric Young
+ * (eay@cryptsoft.com). This product includes software written by Tim
+ * Hudson (tjh@cryptsoft.com).
+ *
+ */
#ifndef HEADER_BN_LCL_H
#define HEADER_BN_LCL_H
@@ -65,6 +118,51 @@
extern "C" {
#endif
+
+/*
+ * BN_window_bits_for_exponent_size -- macro for sliding window mod_exp functions
+ *
+ *
+ * For window size 'w' (w >= 2) and a random 'b' bits exponent,
+ * the number of multiplications is a constant plus on average
+ *
+ * 2^(w-1) + (b-w)/(w+1);
+ *
+ * here 2^(w-1) is for precomputing the table (we actually need
+ * entries only for windows that have the lowest bit set), and
+ * (b-w)/(w+1) is an approximation for the expected number of
+ * w-bit windows, not counting the first one.
+ *
+ * Thus we should use
+ *
+ * w >= 6 if b > 671
+ * w = 5 if 671 > b > 239
+ * w = 4 if 239 > b > 79
+ * w = 3 if 79 > b > 23
+ * w <= 2 if 23 > b
+ *
+ * (with draws in between). Very small exponents are often selected
+ * with low Hamming weight, so we use w = 1 for b <= 23.
+ */
+#if 1
+#define BN_window_bits_for_exponent_size(b) \
+ ((b) > 671 ? 6 : \
+ (b) > 239 ? 5 : \
+ (b) > 79 ? 4 : \
+ (b) > 23 ? 3 : 1)
+#else
+/* Old SSLeay/OpenSSL table.
+ * Maximum window size was 5, so this table differs for b==1024;
+ * but it coincides for other interesting values (b==160, b==512).
+ */
+#define BN_window_bits_for_exponent_size(b) \
+ ((b) > 255 ? 5 : \
+ (b) > 127 ? 4 : \
+ (b) > 17 ? 3 : 1)
+#endif
+
+
+
/* Pentium pro 16,16,16,32,64 */
/* Alpha 16,16,16,16.64 */
#define BN_MULL_SIZE_NORMAL (16) /* 32 */