status-im/status-keycard-java
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add g2 point compression

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This commit is contained in:
Michele Balistreri
2022-06-01 10:10:58 +02:00
parent e2ef06329a
commit 2d40584919
1 changed files with 37 additions and 13 deletions
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lib/src/main/java/im/status/keycard/applet/BLS.java
+37 -13
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@@ -7,6 +7,18 @@ import java.security.MessageDigest;
import org.bouncycastle.util.Arrays;
public class BLS {
public static byte[] hash(byte[] msg) {
Fp[][] u = hashToField(msg, 2);
PointG2 q0 = isogenyMapG2(mapToCurveSimpleSWU9mod16(new Fp2(u[0][0], u[0][1])));
PointG2 q1 = isogenyMapG2(mapToCurveSimpleSWU9mod16(new Fp2(u[1][0], u[1][1])));
PointG2 r = q0.add(q1).clearCofactor();
return r.toByteArray(false);
}
public static byte[] compress(byte[] g2) {
return new PointG2(g2).toByteArray(true);
}
private BLS() {}
final static byte DST[] = {
@@ -245,14 +257,6 @@ public class BLS {
return new PointG2(numerator, y, denominator);
}
public static byte[] hash(byte[] msg) {
Fp[][] u = hashToField(msg, 2);
PointG2 q0 = isogenyMapG2(mapToCurveSimpleSWU9mod16(new Fp2(u[0][0], u[0][1])));
PointG2 q1 = isogenyMapG2(mapToCurveSimpleSWU9mod16(new Fp2(u[1][0], u[1][1])));
PointG2 r = q0.add(q1).clearCofactor();
return r.toByteArray();
}
static class Fp {
final static Fp ZERO = new Fp(BigInteger.ZERO);
final static Fp ONE = new Fp(BigInteger.ONE);
@@ -344,6 +348,10 @@ public class BLS {
this.im = im;
}
Fp2(byte[] buf, int off) {
this(new Fp(Arrays.copyOfRange(buf, off + Fp.SIZE, off + Fp2.SIZE)), new Fp(Arrays.copyOfRange(buf, off, off + Fp.SIZE)));
}
int sgn0() {
boolean sign0 = this.re.i.testBit(0);
return sign0 || (this.re.isZero() && this.re.i.testBit(0)) ? 1 : 0;
@@ -423,8 +431,8 @@ public class BLS {
}
void serialize(byte[] out, int off) {
this.re.serialize(out, off);
this.im.serialize(out, Fp.SIZE + off);
this.im.serialize(out, off);
this.re.serialize(out, Fp.SIZE + off);
}
@Override
@@ -699,6 +707,12 @@ public class BLS {
this.z = z;
}
PointG2(byte[] buf) {
this.x = new Fp2(buf, 0);
this.y = new Fp2(buf, Fp2.SIZE);
this.z = Fp2.ONE;
}
PointG2 add(PointG2 b) {
if (this.isZero()) {
return b;
@@ -815,11 +829,21 @@ public class BLS {
return new PointG2(this.x.mul(invZ), this.y.mul(invZ), Fp2.ONE);
}
byte[] toByteArray() {
byte[] toByteArray(boolean compressed) {
PointG2 p = this.toAffine();
byte[] result = new byte[Fp2.SIZE * 2];
byte[] result = new byte[Fp2.SIZE * (compressed ? 1 : 2)];
p.x.serialize(result, 0);
p.y.serialize(result, Fp2.SIZE);
if (compressed) {
result[0] |= (byte) 0x80;
BigInteger tmp = p.y.im.isZero() ? p.y.re.i.shiftLeft(1) : p.y.im.i.shiftLeft(1);
if (tmp.compareTo(P) > 0) {
result[0] |= 0x20;
}
} else {
p.y.serialize(result, Fp2.SIZE);
}
return result;
}