100 lines
3.2 KiB
C#
100 lines
3.2 KiB
C#
#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
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#pragma warning disable
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using System;
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namespace BestHTTP.SecureProtocol.Org.BouncyCastle.Math.EC.Multiplier
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{
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public class FixedPointUtilities
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{
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public static readonly string PRECOMP_NAME = "bc_fixed_point";
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public static int GetCombSize(ECCurve c)
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{
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BigInteger order = c.Order;
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return order == null ? c.FieldSize + 1 : order.BitLength;
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}
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public static FixedPointPreCompInfo GetFixedPointPreCompInfo(PreCompInfo preCompInfo)
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{
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return preCompInfo as FixedPointPreCompInfo;
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}
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public static FixedPointPreCompInfo Precompute(ECPoint p)
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{
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return (FixedPointPreCompInfo)p.Curve.Precompute(p, PRECOMP_NAME, new FixedPointCallback(p));
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}
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private class FixedPointCallback
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: IPreCompCallback
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{
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private readonly ECPoint m_p;
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internal FixedPointCallback(ECPoint p)
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{
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this.m_p = p;
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}
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public PreCompInfo Precompute(PreCompInfo existing)
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{
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FixedPointPreCompInfo existingFP = (existing is FixedPointPreCompInfo) ? (FixedPointPreCompInfo)existing : null;
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ECCurve c = m_p.Curve;
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int bits = FixedPointUtilities.GetCombSize(c);
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int minWidth = bits > 250 ? 6 : 5;
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int n = 1 << minWidth;
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if (CheckExisting(existingFP, n))
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return existingFP;
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int d = (bits + minWidth - 1) / minWidth;
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ECPoint[] pow2Table = new ECPoint[minWidth + 1];
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pow2Table[0] = m_p;
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for (int i = 1; i < minWidth; ++i)
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{
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pow2Table[i] = pow2Table[i - 1].TimesPow2(d);
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}
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// This will be the 'offset' value
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pow2Table[minWidth] = pow2Table[0].Subtract(pow2Table[1]);
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c.NormalizeAll(pow2Table);
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ECPoint[] lookupTable = new ECPoint[n];
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lookupTable[0] = pow2Table[0];
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for (int bit = minWidth - 1; bit >= 0; --bit)
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{
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ECPoint pow2 = pow2Table[bit];
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int step = 1 << bit;
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for (int i = step; i < n; i += (step << 1))
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{
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lookupTable[i] = lookupTable[i - step].Add(pow2);
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}
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}
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c.NormalizeAll(lookupTable);
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FixedPointPreCompInfo result = new FixedPointPreCompInfo();
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result.LookupTable = c.CreateCacheSafeLookupTable(lookupTable, 0, lookupTable.Length);
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result.Offset = pow2Table[minWidth];
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result.Width = minWidth;
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return result;
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}
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private bool CheckExisting(FixedPointPreCompInfo existingFP, int n)
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{
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return existingFP != null && CheckTable(existingFP.LookupTable, n);
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}
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private bool CheckTable(ECLookupTable table, int n)
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{
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return table != null && table.Size >= n;
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}
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}
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}
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}
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#pragma warning restore
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#endif
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