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JNI for mcl (experimental)

This library provides functionality to compute the optimal ate pairing over Barreto-Naehrig (BN) or BLS12-381 curves.

Initialization

Load the library mcljava.

import com.herumi.mcl.*;

System.loadLibrary(System.mapLibraryName("mcljava"));
Mcl.SystemInit(curveType); // curveType = Mcl.BN254 or Mcl.BLS12_381

Classes

  • G1 ; The cyclic group instantiated as E(Fp)[r] where where r = p + 1 - t.
  • G2 ; The cyclic group instantiated as the inverse image of E'(Fp^2)[r].
  • GT ; The cyclic group in the image of the optimal ate pairing.
    • e : G1 x G2 -> GT
  • Fr ; The finite field with characteristic r.

Methods and Functions

Fr

  • Fr::setInt(int x) ; set by x
  • Fr::setStr(String str) ; set by str such as "123", "0xfff", etc.
  • Fr::setByCSPRNG() ; randomly set
  • Mcl.neg(Fr y, Fr x) ; y = -x
  • Mcl.add(Fr z, Fr x, Fr y) ; z = x + y
  • Mcl.sub(Fr z, Fr x, Fr y) ; z = x - y
  • Mcl.mul(Fr z, Fr x, Fr y) ; z = x * y
  • Mcl.div(Fr z, Fr x, Fr y) ; z = x / y

G1

  • Mcl.neg(G1 y, G1 x) ; y = -x
  • Mcl.dbl(G1 y, G1 x) ; y = 2x
  • Mcl.add(G1 z, G1 x, G1 y) ; z = x + y
  • Mcl.sub(G1 z, G1 x, G1 y) ; z = x - y
  • Mcl.mul(G1 z, G1 x, Fr y) ; z = x * y
  • Mcl.verifyOrderG1(boolean doVerify) ; If set to true, setStr of G1 will automatically check subgroup membership. Set to false by default, meaning only a on curve check is done by default.

G2

  • Mcl.neg(G2 y, G2 x) ; y = -x
  • Mcl.dbl(G2 y, G2 x) ; y = 2x
  • Mcl.add(G2 z, G2 x, G2 y) ; z = x + y
  • Mcl.sub(G2 z, G2 x, G2 y) ; z = x - y
  • Mcl.mul(G2 z, G2 x, Fr y) ; z = x * y
  • Mcl.verifyOrderG2(boolean doVerify) ; If set to true, setStr of G2 will automatically check subgroup membership. Set to false by default, meaning only a on curve check is done by default.

GT

  • GT::setStr(String str) ; set by the result of toString() method
  • Mcl.mul(GT z, GT x, GT y) ; z = x * y
  • Mcl.pow(GT z, GT x, Fr y) ; z = x ^ y
  • Mcl.inv(GT y, GT x) ; y = x^{-1}

pairing

  • Mcl.pairing(GT e, G1 P, G2 Q) ; e = e(P, Q)

BLS signature sample

G2 Q = new G2();
Mcl.hashAndMapToG2(Q, "abc".getBytes());

Fr s = new Fr();
s.setByCSPRNG(); // secret key
G2 pub = new G2();
Mcl.mul(pub, Q, s); // public key = sQ

String m = "signature test";
G1 H = new G1();
Mcl.hashAndMapToG1(H, m.getBytes()); // H = Hash(m)
G1 sign = new G1();
Mcl.mul(sign, H, s); // signature of m = s H

GT e1 = new GT();
GT e2 = new GT();
Mcl.pairing(e1, H, pub); // e1 = e(H, s Q)
Mcl.pairing(e2, sign, Q); // e2 = e(s H, Q);
assertBool("verify signature", e1.equals(e2));

Make test

cd ffi/java
make test

Make test for Windows

Install swig and jre at first.

cd ffi/java
make_wrap
run-mcl

Sample code

MclTest.java