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package cz.crcs.ectester.common.ec;
import cz.crcs.ectester.applet.EC_Consts;
import cz.crcs.ectester.common.util.ByteUtil;
import javacard.security.KeyPair;
import java.math.BigInteger;
import java.security.spec.*;
/**
* An Elliptic curve, contains parameters Fp/F2M, A, B, G, R, (K)?.
*
* @author Jan Jancar johny@neuromancer.sk
*/
public class EC_Curve extends EC_Params {
private short bits;
private byte field;
private String desc;
/**
* @param bits
* @param field KeyPair.ALG_EC_FP or KeyPair.ALG_EC_F2M
*/
public EC_Curve(short bits, byte field) {
super(field == KeyPair.ALG_EC_FP ? EC_Consts.PARAMETERS_DOMAIN_FP : EC_Consts.PARAMETERS_DOMAIN_F2M);
this.bits = bits;
this.field = field;
}
public EC_Curve(String id, short bits, byte field) {
this(bits, field);
this.id = id;
}
public EC_Curve(String id, short bits, byte field, String desc) {
this(id, bits, field);
this.desc = desc;
}
public short getBits() {
return bits;
}
public byte getField() {
return field;
}
public String getDesc() {
return desc;
}
@Override
public String toString() {
return "<" + getId() + "> " + (field == KeyPair.ALG_EC_FP ? "Prime" : "Binary") + " field Elliptic curve (" + String.valueOf(bits) + "b)" + (desc == null ? "" : ": " + desc);
}
public ECParameterSpec toSpec() {
ECField field;
if (this.field == KeyPair.ALG_EC_FP) {
field = new ECFieldFp(new BigInteger(1, getData(0)));
} else {
byte[][] fieldData = getParam(EC_Consts.PARAMETER_F2M);
int m = ByteUtil.getShort(fieldData[0], 0);
int e1 = ByteUtil.getShort(fieldData[1], 0);
int e2 = ByteUtil.getShort(fieldData[2], 0);
int e3 = ByteUtil.getShort(fieldData[3], 0);
int[] powers = new int[]{e1, e2, e3};
field = new ECFieldF2m(m, powers);
}
BigInteger a = new BigInteger(1, getParam(EC_Consts.PARAMETER_A)[0]);
BigInteger b = new BigInteger(1, getParam(EC_Consts.PARAMETER_B)[0]);
EllipticCurve curve = new EllipticCurve(field, a, b);
byte[][] G = getParam(EC_Consts.PARAMETER_G);
BigInteger gx = new BigInteger(1, G[0]);
BigInteger gy = new BigInteger(1, G[1]);
ECPoint generator = new ECPoint(gx, gy);
BigInteger n = new BigInteger(1, getParam(EC_Consts.PARAMETER_R)[0]);
int h = ByteUtil.getShort(getParam(EC_Consts.PARAMETER_K)[0], 0);
return new ECParameterSpec(curve, generator, n, h);
}
public static EC_Curve fromSpec(ECParameterSpec spec) {
EllipticCurve curve = spec.getCurve();
ECField field = curve.getField();
short bits = (short) field.getFieldSize();
byte[][] params;
int paramIndex = 0;
byte fieldType;
if (field instanceof ECFieldFp) {
ECFieldFp primeField = (ECFieldFp) field;
params = new byte[7][];
params[paramIndex++] = primeField.getP().toByteArray();
fieldType = KeyPair.ALG_EC_FP;
} else if (field instanceof ECFieldF2m) {
ECFieldF2m binaryField = (ECFieldF2m) field;
params = new byte[10][];
params[paramIndex] = new byte[2];
ByteUtil.setShort(params[paramIndex++], 0, (short) binaryField.getM());
int[] powers = binaryField.getMidTermsOfReductionPolynomial();
for (int i = 0; i < 3; ++i) {
params[paramIndex] = new byte[2];
ByteUtil.setShort(params[paramIndex++], 0, (short) powers[i]);
}
fieldType = KeyPair.ALG_EC_F2M;
} else {
throw new IllegalArgumentException("ECParameterSpec with an unknown field.");
}
ECPoint generator = spec.getGenerator();
params[paramIndex++] = curve.getA().toByteArray();
params[paramIndex++] = curve.getB().toByteArray();
params[paramIndex++] = generator.getAffineX().toByteArray();
params[paramIndex++] = generator.getAffineY().toByteArray();
params[paramIndex++] = spec.getOrder().toByteArray();
params[paramIndex] = new byte[2];
ByteUtil.setShort(params[paramIndex], 0, (short) spec.getCofactor());
EC_Curve result = new EC_Curve(bits, fieldType);
result.readByteArray(params);
return result;
}
}
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