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/*
KeePass Password Safe - The Open-Source Password Manager
Copyright (C) 2003-2019 Dominik Reichl <dominik.reichl@t-online.de>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
namespace KeePassLib.Cryptography.KeyDerivation
{
public abstract class KdfEngine
{
public abstract PwUuid Uuid
{
get;
}
public abstract string Name
{
get;
}
public virtual KdfParameters GetDefaultParameters()
{
return new KdfParameters(this.Uuid);
}
/// <summary>
/// Generate random seeds and store them in <paramref name="p" />.
/// </summary>
public virtual void Randomize(KdfParameters p)
{
Debug.Assert(p != null);
Debug.Assert(p.KdfUuid.Equals(this.Uuid));
}
public abstract byte[] Transform(byte[] pbMsg, KdfParameters p);
public virtual KdfParameters GetBestParameters(uint uMilliseconds)
{
throw new NotImplementedException();
}
protected void MaximizeParamUInt64(KdfParameters p, string strName,
ulong uMin, ulong uMax, uint uMilliseconds, bool bInterpSearch)
{
if(p == null) { Debug.Assert(false); return; }
if(string.IsNullOrEmpty(strName)) { Debug.Assert(false); return; }
if(uMin > uMax) { Debug.Assert(false); return; }
if(uMax > (ulong.MaxValue >> 1))
{
Debug.Assert(false);
uMax = ulong.MaxValue >> 1;
if(uMin > uMax) { p.SetUInt64(strName, uMin); return; }
}
byte[] pbMsg = new byte[32];
for(int i = 0; i < pbMsg.Length; ++i) pbMsg[i] = (byte)i;
ulong uLow = uMin;
ulong uHigh = uMin + 1UL;
long tLow = 0;
long tHigh = 0;
long tTarget = (long)uMilliseconds;
// Determine range
while(uHigh <= uMax)
{
p.SetUInt64(strName, uHigh);
// GC.Collect();
Stopwatch sw = Stopwatch.StartNew();
Transform(pbMsg, p);
sw.Stop();
tHigh = sw.ElapsedMilliseconds;
if(tHigh > tTarget) break;
uLow = uHigh;
tLow = tHigh;
uHigh <<= 1;
}
if(uHigh > uMax) { uHigh = uMax; tHigh = 0; }
if(uLow > uHigh) uLow = uHigh; // Skips to end
// Find optimal number of iterations
while((uHigh - uLow) >= 2UL)
{
ulong u = (uHigh + uLow) >> 1; // Binary search
// Interpolation search, if possible
if(bInterpSearch && (tLow > 0) && (tHigh > tTarget) &&
(tLow <= tTarget))
{
u = uLow + (((uHigh - uLow) * (ulong)(tTarget - tLow)) /
(ulong)(tHigh - tLow));
if((u >= uLow) && (u <= uHigh))
{
u = Math.Max(u, uLow + 1UL);
u = Math.Min(u, uHigh - 1UL);
}
else
{
Debug.Assert(false);
u = (uHigh + uLow) >> 1;
}
}
p.SetUInt64(strName, u);
// GC.Collect();
Stopwatch sw = Stopwatch.StartNew();
Transform(pbMsg, p);
sw.Stop();
long t = sw.ElapsedMilliseconds;
if(t == tTarget) { uLow = u; break; }
else if(t > tTarget) { uHigh = u; tHigh = t; }
else { uLow = u; tLow = t; }
}
p.SetUInt64(strName, uLow);
}
}
}
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