private Srp6(string initialVector, string modulus, int generator, byte[] identityHash)
{
HashAlgorithm = "SHA1";
PasswordIterations = 2;
KeySize = 256;
InitialVector = initialVector;
IdentityHash = identityHash;
Modulus = BigIntegerExtensions.CreateBigInteger(modulus, 16);
Generator = BigIntegerExtensions.CreateBigInteger("" + generator, 10);
Multiplier = BigIntegerExtensions.CreateBigInteger("3", 10);
}
public void SetSessionKey(String pubKeyString, String scrambler = null)
{
BigInteger pubKey = BigIntegerExtensions.CreateBigInteger(pubKeyString, 16);
if (IsServerInstance) // Server SessionKey
{
// (Av^u) ^ b (mod N)
SessionKey = pubKey.Multiply(Verifier.ModPow(Scrambler, Modulus)).ModPow(PrivateKey, Modulus);
}
else // Client SessionKey
{
Scrambler = BigIntegerExtensions.CreateBigInteger(scrambler, 16);
BigInteger temp = PrivateKey.Add(Scrambler.Multiply(SaltedIdentityHash));
SessionKey = pubKey.Subtract((Generator.ModPow(SaltedIdentityHash, Modulus))
.Multiply(Multiplier)).ModPow(temp, Modulus);
}
}
// Client Constructor, salt not generated by client
public Srp6(byte[] identityHash, String modulus, int generator,
String salt, string initialVector = "OFRna73m*aze01xY")
: this(initialVector, modulus, generator, identityHash)
{
// This SRP6 instance is a client instance
IsServerInstance = false;
// Convert the salt string to a BigInteger
Salt = BigIntegerExtensions.CreateBigInteger(salt, 16);
// Set the salted identity hash
SaltedIdentityHash = Salt.CreateSaltedIdentityHash(identityHash);
// Generate a pseudo prime to use for the private key
PrivateKey = BigIntegerExtensions.GeneratePseudoPrime(128, 100, new Random());
// g^a (mod N)
PublicKey = Generator.ModPow(PrivateKey, Modulus);
}
// Server Constructor, Radix 16 strings, 256-bit predef values
public Srp6(byte[] identityHash, string modulus, int generator, string inputSalt,
int scramblerBits, string initialVector = "OFRna73m*aze01xY")
: this(initialVector, modulus, generator, identityHash)
{
// This SRP6 instance is a server instance
IsServerInstance = true;
// Generate the Salt
Salt = BigIntegerExtensions.CreateBigInteger(inputSalt, 16);
// Set the salted identity hash, scrambler, and verifier
Scrambler = BigIntegerExtensions.CreateBigInteger(scramblerBits, new Random());
SaltedIdentityHash = Salt.CreateSaltedIdentityHash(identityHash);
Verifier = Generator.ModPow(SaltedIdentityHash, Modulus);
// Random 128 bit number that is a probable prime
PrivateKey = BigIntegerExtensions.GeneratePseudoPrime(128, 100, new Random());
// kv + g^b (mod N)
PublicKey = Multiplier.Multiply(Verifier).Add(Generator.ModPow(PrivateKey, Modulus));
}
public static BigInteger CreateSaltedIdentityHash(this BigInteger salt, byte[] identityHash)
{
return(BigIntegerExtensions.CreateBigInteger(
Concatenate(salt.ToByteArray(), identityHash).Sha1Hash().ToHexString(), 16));
}
public static BigInteger generateSalt(int saltBits)
{
return(BigIntegerExtensions.CreateBigInteger(saltBits, new Random()));
}