**** Merged from MCS ****
[mono-project.git] / mcs / class / Mono.Security / Mono.Math.Prime.Generator / SequentialSearchPrimeGeneratorBase.cs
blob87388d0011c84e22e50adbf9b4ec3eaa854940ff
1 //
2 // Mono.Math.Prime.Generator.SequentialSearchPrimeGeneratorBase.cs - Prime Generator
3 //
4 // Authors:
5 // Ben Maurer
6 //
7 // Copyright (c) 2003 Ben Maurer. All rights reserved
8 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
9 //
10 // Permission is hereby granted, free of charge, to any person obtaining
11 // a copy of this software and associated documentation files (the
12 // "Software"), to deal in the Software without restriction, including
13 // without limitation the rights to use, copy, modify, merge, publish,
14 // distribute, sublicense, and/or sell copies of the Software, and to
15 // permit persons to whom the Software is furnished to do so, subject to
16 // the following conditions:
17 //
18 // The above copyright notice and this permission notice shall be
19 // included in all copies or substantial portions of the Software.
20 //
21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
30 namespace Mono.Math.Prime.Generator {
32 #if INSIDE_CORLIB
33 internal
34 #else
35 public
36 #endif
37 class SequentialSearchPrimeGeneratorBase : PrimeGeneratorBase {
39 protected virtual BigInteger GenerateSearchBase (int bits, object context)
41 BigInteger ret = BigInteger.GenerateRandom (bits);
42 ret.SetBit (0);
43 return ret;
47 public override BigInteger GenerateNewPrime (int bits)
49 return GenerateNewPrime (bits, null);
53 public virtual BigInteger GenerateNewPrime (int bits, object context)
56 // STEP 1. Find a place to do a sequential search
58 BigInteger curVal = GenerateSearchBase (bits, context);
60 const uint primeProd1 = 3u* 5u * 7u * 11u * 13u * 17u * 19u * 23u * 29u;
62 uint pMod1 = curVal % primeProd1;
64 int DivisionBound = TrialDivisionBounds;
65 uint[] SmallPrimes = BigInteger.smallPrimes;
67 // STEP 2. Search for primes
69 while (true) {
72 // STEP 2.1 Sieve out numbers divisible by the first 9 primes
74 if (pMod1 % 3 == 0) goto biNotPrime;
75 if (pMod1 % 5 == 0) goto biNotPrime;
76 if (pMod1 % 7 == 0) goto biNotPrime;
77 if (pMod1 % 11 == 0) goto biNotPrime;
78 if (pMod1 % 13 == 0) goto biNotPrime;
79 if (pMod1 % 17 == 0) goto biNotPrime;
80 if (pMod1 % 19 == 0) goto biNotPrime;
81 if (pMod1 % 23 == 0) goto biNotPrime;
82 if (pMod1 % 29 == 0) goto biNotPrime;
85 // STEP 2.2 Sieve out all numbers divisible by the primes <= DivisionBound
87 for (int p = 10; p < SmallPrimes.Length && SmallPrimes [p] <= DivisionBound; p++) {
88 if (curVal % SmallPrimes [p] == 0)
89 goto biNotPrime;
93 // STEP 2.3 Is the potential prime acceptable?
95 if (!IsPrimeAcceptable (curVal, context))
96 goto biNotPrime;
99 // STEP 2.4 Filter out all primes that pass this step with a primality test
101 if (PrimalityTest (curVal, Confidence))
102 return curVal;
105 // STEP 2.4
107 biNotPrime:
108 pMod1 += 2;
109 if (pMod1 >= primeProd1)
110 pMod1 -= primeProd1;
111 curVal.Incr2 ();
115 protected virtual bool IsPrimeAcceptable (BigInteger bi, object context)
117 return true;