/// <summary>
/// Encrypt a plain text message
/// </summary>
///
/// <param name="Input">The plain text</param>
///
/// <returns>The cipher text</returns>
public byte[] Encrypt(byte[] Input)
{
if (!_isEncryption)
throw new CryptoAsymmetricSignException("FujisakiCipher:Encrypt", "The cipher is not initialized for encryption!", new ArgumentException());
// generate random vector r of length k bits
GF2Vector r = new GF2Vector(_K, _rndEngine);
// convert r to byte array
byte[] rBytes = r.GetEncoded();
// compute (r||input)
byte[] rm = ByteUtils.Concatenate(rBytes, Input);
// compute H(r||input)
_dgtEngine.BlockUpdate(rm, 0, rm.Length);
byte[] hrm = new byte[_dgtEngine.DigestSize];
_dgtEngine.DoFinal(hrm, 0);
// convert H(r||input) to error vector z
GF2Vector z = CCA2Conversions.Encode(_N, _T, hrm);
// compute c1 = E(r, z)
byte[] c1 = CCA2Primitives.Encrypt((MPKCPublicKey)_asmKey, r, z).GetEncoded();
byte[] c2;
// get PRNG object
using (KDF2Drbg sr0 = new KDF2Drbg(GetDigest(_cprParams.Digest)))
{
// seed PRNG with r'
sr0.Initialize(rBytes);
// generate random c2
c2 = new byte[Input.Length];
sr0.Generate(c2);
}
// XOR with input
for (int i = 0; i < Input.Length; i++)
c2[i] ^= Input[i];
// return (c1||c2)
return ByteUtils.Concatenate(c1, c2);
}
public byte[] Encrypt(byte[] Input)
{
if (!_isEncryption)
throw new CryptoAsymmetricSignException("PointchevalCipher:Encrypt", "The cipher is not initialized for encryption!", new ArgumentException());
int kDiv8 = _K >> 3;
// generate random r of length k div 8 bytes
byte[] r = new byte[kDiv8];
_rndEngine.GetBytes(r);
// generate random vector r' of length k bits
GF2Vector rPrime = new GF2Vector(_K, _rndEngine);
// convert r' to byte array
byte[] rPrimeBytes = rPrime.GetEncoded();
// compute (input||r)
byte[] mr = ByteUtils.Concatenate(Input, r);
// compute H(input||r)
_dgtEngine.BlockUpdate(mr, 0, mr.Length);
byte[] hmr = new byte[_dgtEngine.DigestSize];
_dgtEngine.DoFinal(hmr, 0);
// convert H(input||r) to error vector z
GF2Vector z = CCA2Conversions.Encode(_N, _T, hmr);
// compute c1 = E(rPrime, z)
byte[] c1 = CCA2Primitives.Encrypt((MPKCPublicKey)_asmKey, rPrime, z).GetEncoded();
byte[] c2;
// get PRNG object
using (KDF2Drbg sr0 = new KDF2Drbg(GetDigest(_cprParams.Digest)))
{
// seed PRNG with r'
sr0.Initialize(rPrimeBytes);
// generate random c2
c2 = new byte[Input.Length + kDiv8];
sr0.Generate(c2);
}
// XOR with input
for (int i = 0; i < Input.Length; i++)
c2[i] ^= Input[i];
// XOR with r
for (int i = 0; i < kDiv8; i++)
c2[Input.Length + i] ^= r[i];
// return (c1||c2)
return ByteUtils.Concatenate(c1, c2);
}