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2023-06-21 12:46:23 -04:00
commit c70248a520
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namespace Org.BouncyCastle.Math.EC.Multiplier
{
/**
* Interface for classes encapsulating a point multiplication algorithm
* for <code>ECPoint</code>s.
*/
internal interface ECMultiplier
{
/**
* Multiplies the <code>ECPoint p</code> by <code>k</code>, i.e.
* <code>p</code> is added <code>k</code> times to itself.
* @param p The <code>ECPoint</code> to be multiplied.
* @param k The factor by which <code>p</code> i multiplied.
* @return <code>p</code> multiplied by <code>k</code>.
*/
ECPoint Multiply(ECPoint p, BigInteger k, PreCompInfo preCompInfo);
}
}

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namespace Org.BouncyCastle.Math.EC.Multiplier
{
/**
* Class implementing the NAF (Non-Adjacent Form) multiplication algorithm.
*/
internal class FpNafMultiplier
: ECMultiplier
{
/**
* D.3.2 pg 101
* @see org.bouncycastle.math.ec.multiplier.ECMultiplier#multiply(org.bouncycastle.math.ec.ECPoint, java.math.BigInteger)
*/
public ECPoint Multiply(ECPoint p, BigInteger k, PreCompInfo preCompInfo)
{
// TODO Probably should try to add this
// BigInteger e = k.Mod(n); // n == order of p
BigInteger e = k;
BigInteger h = e.Multiply(BigInteger.Three);
ECPoint neg = p.Negate();
ECPoint R = p;
for (int i = h.BitLength - 2; i > 0; --i)
{
R = R.Twice();
bool hBit = h.TestBit(i);
bool eBit = e.TestBit(i);
if (hBit != eBit)
{
R = R.Add(hBit ? p : neg);
}
}
return R;
}
}
}

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namespace Org.BouncyCastle.Math.EC.Multiplier
{
/**
* Interface for classes storing precomputation data for multiplication
* algorithms. Used as a Memento (see GOF patterns) for
* <code>WNafMultiplier</code>.
*/
internal interface PreCompInfo
{
}
}

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namespace Org.BouncyCastle.Math.EC.Multiplier
{
internal class ReferenceMultiplier
: ECMultiplier
{
/**
* Simple shift-and-add multiplication. Serves as reference implementation
* to verify (possibly faster) implementations in
* {@link org.bouncycastle.math.ec.ECPoint ECPoint}.
*
* @param p The point to multiply.
* @param k The factor by which to multiply.
* @return The result of the point multiplication <code>k * p</code>.
*/
public ECPoint Multiply(ECPoint p, BigInteger k, PreCompInfo preCompInfo)
{
ECPoint q = p.Curve.Infinity;
int t = k.BitLength;
for (int i = 0; i < t; i++)
{
if (k.TestBit(i))
{
q = q.Add(p);
}
p = p.Twice();
}
return q;
}
}
}

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using System;
namespace Org.BouncyCastle.Math.EC.Multiplier
{
/**
* Class implementing the WNAF (Window Non-Adjacent Form) multiplication
* algorithm.
*/
internal class WNafMultiplier
: ECMultiplier
{
/**
* Computes the Window NAF (non-adjacent Form) of an integer.
* @param width The width <code>w</code> of the Window NAF. The width is
* defined as the minimal number <code>w</code>, such that for any
* <code>w</code> consecutive digits in the resulting representation, at
* most one is non-zero.
* @param k The integer of which the Window NAF is computed.
* @return The Window NAF of the given width, such that the following holds:
* <code>k = &#8722;<sub>i=0</sub><sup>l-1</sup> k<sub>i</sub>2<sup>i</sup>
* </code>, where the <code>k<sub>i</sub></code> denote the elements of the
* returned <code>sbyte[]</code>.
*/
public sbyte[] WindowNaf(sbyte width, BigInteger k)
{
// The window NAF is at most 1 element longer than the binary
// representation of the integer k. sbyte can be used instead of short or
// int unless the window width is larger than 8. For larger width use
// short or int. However, a width of more than 8 is not efficient for
// m = log2(q) smaller than 2305 Bits. Note: Values for m larger than
// 1000 Bits are currently not used in practice.
sbyte[] wnaf = new sbyte[k.BitLength + 1];
// 2^width as short and BigInteger
short pow2wB = (short)(1 << width);
BigInteger pow2wBI = BigInteger.ValueOf(pow2wB);
int i = 0;
// The actual length of the WNAF
int length = 0;
// while k >= 1
while (k.SignValue > 0)
{
// if k is odd
if (k.TestBit(0))
{
// k Mod 2^width
BigInteger remainder = k.Mod(pow2wBI);
// if remainder > 2^(width - 1) - 1
if (remainder.TestBit(width - 1))
{
wnaf[i] = (sbyte)(remainder.IntValue - pow2wB);
}
else
{
wnaf[i] = (sbyte)remainder.IntValue;
}
// wnaf[i] is now in [-2^(width-1), 2^(width-1)-1]
k = k.Subtract(BigInteger.ValueOf(wnaf[i]));
length = i;
}
else
{
wnaf[i] = 0;
}
// k = k/2
k = k.ShiftRight(1);
i++;
}
length++;
// Reduce the WNAF array to its actual length
sbyte[] wnafShort = new sbyte[length];
Array.Copy(wnaf, 0, wnafShort, 0, length);
return wnafShort;
}
/**
* Multiplies <code>this</code> by an integer <code>k</code> using the
* Window NAF method.
* @param k The integer by which <code>this</code> is multiplied.
* @return A new <code>ECPoint</code> which equals <code>this</code>
* multiplied by <code>k</code>.
*/
public ECPoint Multiply(ECPoint p, BigInteger k, PreCompInfo preCompInfo)
{
WNafPreCompInfo wnafPreCompInfo;
if ((preCompInfo != null) && (preCompInfo is WNafPreCompInfo))
{
wnafPreCompInfo = (WNafPreCompInfo)preCompInfo;
}
else
{
// Ignore empty PreCompInfo or PreCompInfo of incorrect type
wnafPreCompInfo = new WNafPreCompInfo();
}
// floor(log2(k))
int m = k.BitLength;
// width of the Window NAF
sbyte width;
// Required length of precomputation array
int reqPreCompLen;
// Determine optimal width and corresponding length of precomputation
// array based on literature values
if (m < 13)
{
width = 2;
reqPreCompLen = 1;
}
else
{
if (m < 41)
{
width = 3;
reqPreCompLen = 2;
}
else
{
if (m < 121)
{
width = 4;
reqPreCompLen = 4;
}
else
{
if (m < 337)
{
width = 5;
reqPreCompLen = 8;
}
else
{
if (m < 897)
{
width = 6;
reqPreCompLen = 16;
}
else
{
if (m < 2305)
{
width = 7;
reqPreCompLen = 32;
}
else
{
width = 8;
reqPreCompLen = 127;
}
}
}
}
}
}
// The length of the precomputation array
int preCompLen = 1;
ECPoint[] preComp = wnafPreCompInfo.GetPreComp();
ECPoint twiceP = wnafPreCompInfo.GetTwiceP();
// Check if the precomputed ECPoints already exist
if (preComp == null)
{
// Precomputation must be performed from scratch, create an empty
// precomputation array of desired length
preComp = new ECPoint[]{ p };
}
else
{
// Take the already precomputed ECPoints to start with
preCompLen = preComp.Length;
}
if (twiceP == null)
{
// Compute twice(p)
twiceP = p.Twice();
}
if (preCompLen < reqPreCompLen)
{
// Precomputation array must be made bigger, copy existing preComp
// array into the larger new preComp array
ECPoint[] oldPreComp = preComp;
preComp = new ECPoint[reqPreCompLen];
Array.Copy(oldPreComp, 0, preComp, 0, preCompLen);
for (int i = preCompLen; i < reqPreCompLen; i++)
{
// Compute the new ECPoints for the precomputation array.
// The values 1, 3, 5, ..., 2^(width-1)-1 times p are
// computed
preComp[i] = twiceP.Add(preComp[i - 1]);
}
}
// Compute the Window NAF of the desired width
sbyte[] wnaf = WindowNaf(width, k);
int l = wnaf.Length;
// Apply the Window NAF to p using the precomputed ECPoint values.
ECPoint q = p.Curve.Infinity;
for (int i = l - 1; i >= 0; i--)
{
q = q.Twice();
if (wnaf[i] != 0)
{
if (wnaf[i] > 0)
{
q = q.Add(preComp[(wnaf[i] - 1)/2]);
}
else
{
// wnaf[i] < 0
q = q.Subtract(preComp[(-wnaf[i] - 1)/2]);
}
}
}
// Set PreCompInfo in ECPoint, such that it is available for next
// multiplication.
wnafPreCompInfo.SetPreComp(preComp);
wnafPreCompInfo.SetTwiceP(twiceP);
p.SetPreCompInfo(wnafPreCompInfo);
return q;
}
}
}

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namespace Org.BouncyCastle.Math.EC.Multiplier
{
/**
* Class holding precomputation data for the WNAF (Window Non-Adjacent Form)
* algorithm.
*/
internal class WNafPreCompInfo
: PreCompInfo
{
/**
* Array holding the precomputed <code>ECPoint</code>s used for the Window
* NAF multiplication in <code>
* {@link org.bouncycastle.math.ec.multiplier.WNafMultiplier.multiply()
* WNafMultiplier.multiply()}</code>.
*/
private ECPoint[] preComp = null;
/**
* Holds an <code>ECPoint</code> representing twice(this). Used for the
* Window NAF multiplication in <code>
* {@link org.bouncycastle.math.ec.multiplier.WNafMultiplier.multiply()
* WNafMultiplier.multiply()}</code>.
*/
private ECPoint twiceP = null;
internal ECPoint[] GetPreComp()
{
return preComp;
}
internal void SetPreComp(ECPoint[] preComp)
{
this.preComp = preComp;
}
internal ECPoint GetTwiceP()
{
return twiceP;
}
internal void SetTwiceP(ECPoint twiceThis)
{
this.twiceP = twiceThis;
}
}
}

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using System;
using Org.BouncyCastle.Math.EC.Abc;
namespace Org.BouncyCastle.Math.EC.Multiplier
{
/**
* Class implementing the WTNAF (Window
* <code>&#964;</code>-adic Non-Adjacent Form) algorithm.
*/
internal class WTauNafMultiplier
: ECMultiplier
{
/**
* Multiplies a {@link org.bouncycastle.math.ec.F2mPoint F2mPoint}
* by <code>k</code> using the reduced <code>&#964;</code>-adic NAF (RTNAF)
* method.
* @param p The F2mPoint to multiply.
* @param k The integer by which to multiply <code>k</code>.
* @return <code>p</code> multiplied by <code>k</code>.
*/
public ECPoint Multiply(ECPoint point, BigInteger k, PreCompInfo preCompInfo)
{
if (!(point is F2mPoint))
throw new ArgumentException("Only F2mPoint can be used in WTauNafMultiplier");
F2mPoint p = (F2mPoint)point;
F2mCurve curve = (F2mCurve) p.Curve;
int m = curve.M;
sbyte a = (sbyte) curve.A.ToBigInteger().IntValue;
sbyte mu = curve.GetMu();
BigInteger[] s = curve.GetSi();
ZTauElement rho = Tnaf.PartModReduction(k, m, a, s, mu, (sbyte)10);
return MultiplyWTnaf(p, rho, preCompInfo, a, mu);
}
/**
* Multiplies a {@link org.bouncycastle.math.ec.F2mPoint F2mPoint}
* by an element <code>&#955;</code> of <code><b>Z</b>[&#964;]</code> using
* the <code>&#964;</code>-adic NAF (TNAF) method.
* @param p The F2mPoint to multiply.
* @param lambda The element <code>&#955;</code> of
* <code><b>Z</b>[&#964;]</code> of which to compute the
* <code>[&#964;]</code>-adic NAF.
* @return <code>p</code> multiplied by <code>&#955;</code>.
*/
private F2mPoint MultiplyWTnaf(F2mPoint p, ZTauElement lambda,
PreCompInfo preCompInfo, sbyte a, sbyte mu)
{
ZTauElement[] alpha;
if (a == 0)
{
alpha = Tnaf.Alpha0;
}
else
{
// a == 1
alpha = Tnaf.Alpha1;
}
BigInteger tw = Tnaf.GetTw(mu, Tnaf.Width);
sbyte[]u = Tnaf.TauAdicWNaf(mu, lambda, Tnaf.Width,
BigInteger.ValueOf(Tnaf.Pow2Width), tw, alpha);
return MultiplyFromWTnaf(p, u, preCompInfo);
}
/**
* Multiplies a {@link org.bouncycastle.math.ec.F2mPoint F2mPoint}
* by an element <code>&#955;</code> of <code><b>Z</b>[&#964;]</code>
* using the window <code>&#964;</code>-adic NAF (TNAF) method, given the
* WTNAF of <code>&#955;</code>.
* @param p The F2mPoint to multiply.
* @param u The the WTNAF of <code>&#955;</code>..
* @return <code>&#955; * p</code>
*/
private static F2mPoint MultiplyFromWTnaf(F2mPoint p, sbyte[] u,
PreCompInfo preCompInfo)
{
F2mCurve curve = (F2mCurve)p.Curve;
sbyte a = (sbyte) curve.A.ToBigInteger().IntValue;
F2mPoint[] pu;
if ((preCompInfo == null) || !(preCompInfo is WTauNafPreCompInfo))
{
pu = Tnaf.GetPreComp(p, a);
p.SetPreCompInfo(new WTauNafPreCompInfo(pu));
}
else
{
pu = ((WTauNafPreCompInfo)preCompInfo).GetPreComp();
}
// q = infinity
F2mPoint q = (F2mPoint) p.Curve.Infinity;
for (int i = u.Length - 1; i >= 0; i--)
{
q = Tnaf.Tau(q);
if (u[i] != 0)
{
if (u[i] > 0)
{
q = q.AddSimple(pu[u[i]]);
}
else
{
// u[i] < 0
q = q.SubtractSimple(pu[-u[i]]);
}
}
}
return q;
}
}
}

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namespace Org.BouncyCastle.Math.EC.Multiplier
{
/**
* Class holding precomputation data for the WTNAF (Window
* <code>&#964;</code>-adic Non-Adjacent Form) algorithm.
*/
internal class WTauNafPreCompInfo
: PreCompInfo
{
/**
* Array holding the precomputed <code>F2mPoint</code>s used for the
* WTNAF multiplication in <code>
* {@link org.bouncycastle.math.ec.multiplier.WTauNafMultiplier.multiply()
* WTauNafMultiplier.multiply()}</code>.
*/
private readonly F2mPoint[] preComp;
/**
* Constructor for <code>WTauNafPreCompInfo</code>
* @param preComp Array holding the precomputed <code>F2mPoint</code>s
* used for the WTNAF multiplication in <code>
* {@link org.bouncycastle.math.ec.multiplier.WTauNafMultiplier.multiply()
* WTauNafMultiplier.multiply()}</code>.
*/
internal WTauNafPreCompInfo(F2mPoint[] preComp)
{
this.preComp = preComp;
}
/**
* @return the array holding the precomputed <code>F2mPoint</code>s
* used for the WTNAF multiplication in <code>
* {@link org.bouncycastle.math.ec.multiplier.WTauNafMultiplier.multiply()
* WTauNafMultiplier.multiply()}</code>.
*/
internal F2mPoint[] GetPreComp()
{
return preComp;
}
}
}