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using System;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Pqc.Crypto.Crystals.Kyber
{
internal class KyberIndCpa
{
private readonly KyberEngine m_engine;
private Symmetric m_symmetric;
internal KyberIndCpa(KyberEngine mEngine)
{
m_engine = mEngine;
m_symmetric = mEngine.Symmetric;
}
private int GenerateMatrixNBlocks => ((12 * KyberEngine.N / 8 * (1 << 12) / KyberEngine.Q + m_symmetric.XofBlockBytes) / m_symmetric.XofBlockBytes);
private void GenerateMatrix(PolyVec[] a, byte[] seed, bool transposed)
{
int K = m_engine.K;
byte[] buf = new byte[GenerateMatrixNBlocks * m_symmetric.XofBlockBytes + 2];
for (int i = 0; i < K; i++)
{
for (int j = 0; j < K; j++)
{
if (transposed)
{
m_symmetric.XofAbsorb(seed, (byte) i, (byte) j);
}
else
{
m_symmetric.XofAbsorb(seed, (byte) j, (byte) i);
}
m_symmetric.XofSqueezeBlocks(buf, 0, GenerateMatrixNBlocks * m_symmetric.XofBlockBytes);
int buflen = GenerateMatrixNBlocks * m_symmetric.XofBlockBytes;
int ctr = RejectionSampling(a[i].m_vec[j].m_coeffs, 0, KyberEngine.N, buf, buflen);
while (ctr < KyberEngine.N)
{
int off = buflen % 3;
for (int k = 0; k < off; k++)
{
buf[k] = buf[buflen - off + k];
}
m_symmetric.XofSqueezeBlocks(buf, off, m_symmetric.XofBlockBytes * 2);
buflen = off + m_symmetric.XofBlockBytes;
ctr += RejectionSampling(a[i].m_vec[j].m_coeffs, ctr, KyberEngine.N - ctr, buf, buflen);
}
}
}
return;
}
private int RejectionSampling(short[] r, int off, int len, byte[] buf, int buflen)
{
int ctr = 0, pos = 0;
while (ctr < len && pos + 3 <= buflen)
{
ushort val0 = (ushort) ((((ushort) (buf[pos + 0] & 0xFF) >> 0) | ((ushort)(buf[pos + 1] & 0xFF) << 8)) & 0xFFF);
ushort val1 = (ushort) ((((ushort) (buf[pos + 1] & 0xFF) >> 4) | ((ushort)(buf[pos + 2] & 0xFF) << 4)) & 0xFFF);
pos += 3;
if (val0 < KyberEngine.Q)
{
r[off + ctr++] = (short)val0;
}
if (ctr < len && val1 < KyberEngine.Q)
{
r[off + ctr++] = (short)val1;
}
}
return ctr;
}
internal void GenerateKeyPair(out byte[] pk, out byte[] sk)
{
int K = m_engine.K;
byte[] buf = new byte[2 * KyberEngine.SymBytes];
byte nonce = 0;
PolyVec[] Matrix = new PolyVec[K];
PolyVec e = new PolyVec(m_engine), pkpv = new PolyVec(m_engine), skpv = new PolyVec(m_engine);
byte[] d = new byte[32];
m_engine.RandomBytes(d, 32);
m_symmetric.Hash_g(buf, d);
byte[] PublicSeed = Arrays.CopyOfRange(buf, 0, KyberEngine.SymBytes);
byte[] NoiseSeed = Arrays.CopyOfRange(buf, KyberEngine.SymBytes, 2 * KyberEngine.SymBytes);
for (int i = 0; i < K; i++)
{
Matrix[i] = new PolyVec(m_engine);
}
GenerateMatrix(Matrix, PublicSeed, false);
for (int i = 0; i < K; i++)
{
skpv.m_vec[i].GetNoiseEta1(NoiseSeed, nonce++);
}
for (int i = 0; i < K; i++)
{
e.m_vec[i].GetNoiseEta1(NoiseSeed, nonce++);
}
skpv.Ntt();
e.Ntt();
for (int i = 0; i < K; i++)
{
PolyVec.PointwiseAccountMontgomery(pkpv.m_vec[i], Matrix[i], skpv, m_engine);
pkpv.m_vec[i].ToMont();
}
pkpv.Add(e);
pkpv.Reduce();
PackSecretKey(out sk, skpv);
PackPublicKey(out pk, pkpv, PublicSeed);
}
private void PackSecretKey(out byte[] sk, PolyVec skpv)
{
sk = new byte[m_engine.PolyVecBytes];
skpv.ToBytes(sk);
}
private void UnpackSecretKey(PolyVec skpv, byte[] sk)
{
skpv.FromBytes(sk);
}
private void PackPublicKey(out byte[] pk, PolyVec pkpv, byte[] seed)
{
int i;
pk = new byte[m_engine.IndCpaPublicKeyBytes];
pkpv.ToBytes(pk);
Array.Copy(seed, 0, pk, m_engine.PolyVecBytes, KyberEngine.SymBytes);
}
private void UnpackPublicKey(PolyVec pkpv, byte[] seed, byte[] pk)
{
int i;
pkpv.FromBytes(pk);
Array.Copy(pk, m_engine.PolyVecBytes, seed, 0, KyberEngine.SymBytes);
}
public void Encrypt(byte[] c, byte[] m, byte[] pk, byte[] coins)
{
int K = m_engine.K;
byte[] seed = new byte[KyberEngine.SymBytes];
byte nonce = 0;
PolyVec sp = new PolyVec(m_engine), pkpv = new PolyVec(m_engine), ep = new PolyVec(m_engine), bp = new PolyVec(m_engine);
PolyVec[] MatrixTransposed = new PolyVec[K];
Poly v = new Poly(m_engine), k = new Poly(m_engine), epp = new Poly(m_engine);
UnpackPublicKey(pkpv, seed, pk);
k.FromMsg(m);
for (int i = 0; i < K; i++)
{
MatrixTransposed[i] = new PolyVec(m_engine);
}
GenerateMatrix(MatrixTransposed, seed, true);
for (int i = 0; i < K; i++)
{
sp.m_vec[i].GetNoiseEta1(coins, nonce++);
}
for (int i = 0; i < K; i++)
{
ep.m_vec[i].GetNoiseEta2(coins, nonce++);
}
epp.GetNoiseEta2(coins, nonce++);
sp.Ntt();
for (int i = 0; i < K; i++)
{
PolyVec.PointwiseAccountMontgomery(bp.m_vec[i], MatrixTransposed[i], sp, m_engine);
}
PolyVec.PointwiseAccountMontgomery(v, pkpv, sp, m_engine);
bp.InverseNttToMont();
v.PolyInverseNttToMont();
bp.Add(ep);
v.Add(epp);
v.Add(k);
bp.Reduce();
v.PolyReduce();
PackCipherText(c, bp, v);
}
private void PackCipherText(byte[] r, PolyVec b, Poly v)
{
b.CompressPolyVec(r);
v.CompressPoly(r, m_engine.PolyVecCompressedBytes);
}
private void UnpackCipherText(PolyVec b, Poly v, byte[] c)
{
b.DecompressPolyVec(c);
v.DecompressPoly(c, m_engine.PolyVecCompressedBytes);
}
internal void Decrypt(byte[] m, byte[] c, byte[] sk)
{
PolyVec bp = new PolyVec(m_engine), skpv = new PolyVec(m_engine);
Poly v = new Poly(m_engine), mp = new Poly(m_engine);
UnpackCipherText(bp, v, c);
UnpackSecretKey(skpv, sk);
bp.Ntt();
PolyVec.PointwiseAccountMontgomery(mp, skpv, bp, m_engine);
mp.PolyInverseNttToMont();
mp.Subtract(v);
mp.PolyReduce();
mp.ToMsg(m);
}
}
}
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