【发布时间】：2013-03-21 13:34:18
【问题描述】：
我正在对 NIST 指定的曲线“p192”执行椭圆曲线点算术运算。出于测试目的，我采用了NIST Routine document for the curve p192 中显示的示例点。 我得到了加点和加倍点的正确答案，但对于标量乘法，我的答案不正确。由于这个原因，我无法达到是否
$ k^{-1}(kP) = P $
在哪里
$ k^{-1}.k = 1 mod p $
请帮助我了解我在哪里犯了错误。
package a;
import java.math.BigInteger;
import java.security.spec.ECPoint;
public class ScalarMultiply {
private static final BigInteger ONE = new BigInteger("1");;
static BigInteger TWO = new BigInteger("2");
static BigInteger p = new BigInteger("6277101735386680763835789423207666416083908700390324961279");
public static ECPoint scalmult(ECPoint P, BigInteger k){
ECPoint R =P,S = P;
int length = k.bitLength();
//System.out.println("length is" + length);
byte[] binarray = new byte[length];
for(int i=0;i<=length-1;i++){
binarray[i] = k.mod(TWO).byteValue();
k = k.divide(TWO);
}
for(int i=0;i<=length-1;i++){
System.out.print("" + binarray[i]);
}
for(int i = length - 2;i > 0;i--){
R = doublePoint(R);
if(binarray[i]== 1)
R = addPoint(R, S);
}
return R;
}
public static ECPoint addPoint(ECPoint r, ECPoint s) {
BigInteger slope = (r.getAffineY().subtract(s.getAffineY())).multiply(r.getAffineX().subtract(s.getAffineX()).modInverse(p)).mod(p);
BigInteger Xout = (slope.modPow(TWO, p).subtract(r.getAffineX())).subtract(s.getAffineX()).mod(p);
BigInteger Yout = r.getAffineY().negate().mod(p);
Yout = Yout.add(slope.multiply(r.getAffineX().subtract(Xout))).mod(p);
ECPoint out = new ECPoint(Xout, Yout);
return out;
}
public static ECPoint doublePoint(ECPoint r) {
// TODO Auto-generated method stub
BigInteger slope = (r.getAffineX().pow(2)).multiply(new BigInteger("3"));
slope = slope.add(new BigInteger("3"));
slope = slope.multiply((r.getAffineY().multiply(TWO)).modInverse(p));
BigInteger Xout = slope.pow(2).subtract(r.getAffineX().multiply(new BigInteger("2"))).mod(p);
BigInteger Yout = (r.getAffineY().negate()).add(slope.multiply(r.getAffineX().subtract(Xout))).mod(p);
ECPoint out = new ECPoint(Xout, Yout);
return out;
}
}
主类是
package a;
import java.math.BigInteger;
import java.security.spec.ECPoint;
public class EccArithmetic {
/**
* @param args
*/
public static void main(String[] args) {
BigInteger xs = new BigInteger("d458e7d127ae671b0c330266d246769353a012073e97acf8", 16);
BigInteger ys = new BigInteger
("325930500d851f336bddc050cf7fb11b5673a1645086df3b", 16);
BigInteger xt = new BigInteger
("f22c4395213e9ebe67ddecdd87fdbd01be16fb059b9753a4", 16);
BigInteger yt = new BigInteger
("264424096af2b3597796db48f8dfb41fa9cecc97691a9c79", 16);
ECPoint S = new ECPoint(xs,ys);
ECPoint T = new ECPoint(xt,yt);
// Verifying addition
ECPoint Rst = ScalarMultiply.addPoint(S, T);
BigInteger xst = new BigInteger
("48e1e4096b9b8e5ca9d0f1f077b8abf58e843894de4d0290", 16); // Specified value of x of point R for addition in NIST Routine example
System.out.println("\nx-coordinate of point Rst is : " + Rst.getAffineX());
System.out.println("\ny-coordinate of point Rst is : " + Rst.getAffineY());
if(Rst.getAffineX().equals(xst))
System.out.println("Adding is correct");
//Verifying Doubling
BigInteger xr = new BigInteger
("30c5bc6b8c7da25354b373dc14dd8a0eba42d25a3f6e6962", 16); // Specified value of x of point R for doubling in NIST Routine example
BigInteger yr = new BigInteger
("0dde14bc4249a721c407aedbf011e2ddbbcb2968c9d889cf", 16);
ECPoint R2s = new ECPoint(xr, yr); // Specified value of y of point R for doubling in NIST Routine example
System.out.println("\nx-coordinate of point R2s is : " + R2s.getAffineX());
System.out.println("\ny-coordinate of point R2s is : " + R2s.getAffineY());
System.out.println("\nx-coordinate of calculated point is : " +
ScalarMultiply.doublePoint(S).getAffineX());
System.out.println("\ny-coordinate of calculated point is : " +
ScalarMultiply.doublePoint(S).getAffineY());
if(R2s.getAffineX().equals(ScalarMultiply.doublePoint(S).getAffineX()))
System.out.println("Doubling is correct");
xr = new BigInteger("1faee4205a4f669d2d0a8f25e3bcec9a62a6952965bf6d31", 16); // Specified value of x of point R for scalar Multiplication in NIST Routine example
yr = new BigInteger("5ff2cdfa508a2581892367087c696f179e7a4d7e8260fb06", 16); // Specified value of y of point R for scalar Multiplication in NIST Routine example
ECPoint Rds = new ECPoint(xr, yr);
BigInteger d = new BigInteger
("a78a236d60baec0c5dd41b33a542463a8255391af64c74ee", 16);
//Rs = new ECPoint(ScalarMultiply.scalmult(S, d).getAffineX(), yr);
System.out.println("\nx-coordinate of point Rds is : " + Rds.getAffineX());
System.out.println("\nx-coordinate of point Rds is : " + Rds.getAffineY());
System.out.println("\nx-coordinate of calculated point is : " + ScalarMultiply.scalmult(S,
d).getAffineX());
System.out.println("\nx-coordinate of calculated point is : " + ScalarMultiply.scalmult(S,
d).getAffineY());
if(Rds.getAffineX().equals(ScalarMultiply.scalmult(S, d).getAffineX()))
System.out.println("Scalar Multiplication is correct");
}
}
【问题讨论】：
-
加倍看起来不对。而且我不希望 a*(bP) = P 仅仅因为基础字段 F_q 中的 ab = 1 mod q。
标签： java elliptic-curve