private static BigInteger calculateAgreement(
AsymmetricCipherKeyPair U1,
AsymmetricCipherKeyPair U2,
AsymmetricCipherKeyPair V1,
AsymmetricCipherKeyPair V2)
{
ECMqvBasicAgreement u = new ECMqvBasicAgreement();
u.Init(new MqvPrivateParameters(
(ECPrivateKeyParameters)U1.Private,
(ECPrivateKeyParameters)U2.Private,
(ECPublicKeyParameters)U2.Public));
BigInteger ux = u.CalculateAgreement(new MqvPublicParameters(
(ECPublicKeyParameters)V1.Public,
(ECPublicKeyParameters)V2.Public));
ECMqvBasicAgreement v = new ECMqvBasicAgreement();
v.Init(new MqvPrivateParameters(
(ECPrivateKeyParameters)V1.Private,
(ECPrivateKeyParameters)V2.Private,
(ECPublicKeyParameters)V2.Public));
BigInteger vx = v.CalculateAgreement(new MqvPublicParameters(
(ECPublicKeyParameters)U1.Public,
(ECPublicKeyParameters)U2.Public));
if (ux.Equals(vx))
{
return(ux);
}
return(null);
}
/**
* X9.62 - 1998,<br/>
* J.3.1, Page 152, ECDSA over the field Fp<br/>
* an example with 192 bit prime
*/
private static IBigInteger CalculateAgreement(
IAsymmetricCipherKeyPair u1,
IAsymmetricCipherKeyPair u2,
IAsymmetricCipherKeyPair v1,
IAsymmetricCipherKeyPair v2)
{
var u = new ECMqvBasicAgreement();
u.Init(new MqvPrivateParameters(
(ECPrivateKeyParameters)u1.Private,
(ECPrivateKeyParameters)u2.Private,
(ECPublicKeyParameters)u2.Public));
IBigInteger ux = u.CalculateAgreement(new MqvPublicParameters(
(ECPublicKeyParameters)v1.Public,
(ECPublicKeyParameters)v2.Public));
var v = new ECMqvBasicAgreement();
v.Init(new MqvPrivateParameters(
(ECPrivateKeyParameters)v1.Private,
(ECPrivateKeyParameters)v2.Private,
(ECPublicKeyParameters)v2.Public));
IBigInteger vx = v.CalculateAgreement(new MqvPublicParameters(
(ECPublicKeyParameters)u1.Public,
(ECPublicKeyParameters)u2.Public));
if (ux.Equals(vx))
{
return(ux);
}
return(null);
}
/// <summary>
/// Derives a shared secret key from a private key and another persons public key
/// </summary>
/// <param name="myPrivateKey">the private key which is used</param>
/// <param name="otherPartyPublicKey">the public key of the other person</param>
/// <returns></returns>
public byte[] DeriveKey(byte[] myPrivateKey, byte[] otherPartyPublicKey)
{
ECPrivateKeyParameters privKey = null;
try
{
privKey = (ECPrivateKeyParameters)CreateAsymmetricKeyParameterFromPrivateKeyInfo(myPrivateKey);
}
catch (InvalidCastException exception)
{
string message = "Private Key Import Failed!\n" +
$"{exception.Message}.\n" +
"The contents of the source do not represent a valid EC private key parameter\n" +
"Verify that the public key is not corrupted.\n" +
"- or - Verify that the correct key is selected.";
throw new CryptoException(message, exception);
}
var mqvParameters = new MqvPrivateParameters(privKey, privKey);
var a1 = new ECMqvBasicAgreement();
a1.Init(mqvParameters);
ECPublicKeyParameters pubKey = null;
try
{
pubKey = (ECPublicKeyParameters)CreateAsymmetricKeyParameterFromPublicKeyInfo(otherPartyPublicKey);
}
catch (InvalidCastException exception)
{
string message = "Public Key Import Failed!\n" +
$"{exception.Message}.\n" +
"The contents of the source do not represent a valid EC public key parameter\n" +
"Verify that the public key is not corrupted.\n" +
"- or - Verify that the correct key is selected.";
throw new CryptoException(message, exception);
}
var mqvPubParameters = new MqvPublicParameters(pubKey, pubKey);
BigInteger k = null;
try
{
k = a1.CalculateAgreement(mqvPubParameters);
}
catch (InvalidOperationException exception)
{
string message = "Key Deriviation Failed!\n" +
$"{exception.Message}.\n" +
"The public key does not use the same domain parameters as the private key.\n" +
"Verify that the correct public key is selected.";
throw new CryptoException(message, exception);
}
return(k.ToByteArrayUnsigned());
}
