File indexing completed on 2024-05-12 04:45:15
0001 /* 0002 Copyright (C) 1999-2007 The Botan Project. All rights reserved. 0003 0004 Redistribution and use in source and binary forms, for any use, with or without 0005 modification, is permitted provided that the following conditions are met: 0006 0007 1. Redistributions of source code must retain the above copyright notice, this 0008 list of conditions, and the following disclaimer. 0009 0010 2. Redistributions in binary form must reproduce the above copyright notice, 0011 this list of conditions, and the following disclaimer in the documentation 0012 and/or other materials provided with the distribution. 0013 0014 THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) "AS IS" AND ANY EXPRESS OR IMPLIED 0015 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 0016 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED. 0017 0018 IN NO EVENT SHALL THE AUTHOR(S) OR CONTRIBUTOR(S) BE LIABLE FOR ANY DIRECT, 0019 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 0020 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 0021 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 0022 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 0023 OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 0024 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 0025 */ 0026 // LICENSEHEADER_END 0027 namespace QCA { // WRAPNS_LINE 0028 /************************************************* 0029 * Utility Functions Source File * 0030 * (C) 1999-2007 The Botan Project * 0031 *************************************************/ 0032 0033 } // WRAPNS_LINE 0034 #include <botan/util.h> 0035 namespace QCA { // WRAPNS_LINE 0036 #ifndef BOTAN_TOOLS_ONLY 0037 } // WRAPNS_LINE 0038 #include <botan/bit_ops.h> 0039 namespace QCA { // WRAPNS_LINE 0040 #endif 0041 } // WRAPNS_LINE 0042 #include <algorithm> 0043 namespace QCA { // WRAPNS_LINE 0044 } // WRAPNS_LINE 0045 #include <cmath> 0046 namespace QCA { // WRAPNS_LINE 0047 0048 namespace Botan { 0049 0050 /************************************************* 0051 * Round up n to multiple of align_to * 0052 *************************************************/ 0053 u32bit round_up(u32bit n, u32bit align_to) 0054 { 0055 if (n % align_to || n == 0) 0056 n += align_to - (n % align_to); 0057 return n; 0058 } 0059 0060 /************************************************* 0061 * Round down n to multiple of align_to * 0062 *************************************************/ 0063 u32bit round_down(u32bit n, u32bit align_to) 0064 { 0065 return (n - (n % align_to)); 0066 } 0067 0068 #ifndef BOTAN_TOOLS_ONLY 0069 /************************************************* 0070 * Return the work required for solving DL * 0071 *************************************************/ 0072 u32bit dl_work_factor(u32bit n_bits) 0073 { 0074 const u32bit MIN_ESTIMATE = 64; 0075 0076 if (n_bits < 32) 0077 return 0; 0078 0079 const double log_x = n_bits / 1.44; 0080 0081 u32bit estimate = (u32bit)(2.76 * std::pow(log_x, 1.0 / 3.0) * std::pow(std::log(log_x), 2.0 / 3.0)); 0082 0083 return std::max(estimate, MIN_ESTIMATE); 0084 } 0085 0086 /************************************************* 0087 * Estimate the entropy of the buffer * 0088 *************************************************/ 0089 u32bit entropy_estimate(const byte buffer[], u32bit length) 0090 { 0091 if (length <= 4) 0092 return 0; 0093 0094 u32bit estimate = 0; 0095 byte last = 0, last_delta = 0, last_delta2 = 0; 0096 0097 for (u32bit j = 0; j != length; ++j) { 0098 byte delta = last ^ buffer[j]; 0099 last = buffer[j]; 0100 0101 byte delta2 = delta ^ last_delta; 0102 last_delta = delta; 0103 0104 byte delta3 = delta2 ^ last_delta2; 0105 last_delta2 = delta2; 0106 0107 byte min_delta = delta; 0108 if (min_delta > delta2) 0109 min_delta = delta2; 0110 if (min_delta > delta3) 0111 min_delta = delta3; 0112 0113 estimate += hamming_weight(min_delta); 0114 } 0115 0116 return (estimate / 2); 0117 } 0118 #endif 0119 0120 } 0121 } // WRAPNS_LINE