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88 lines
2.3 KiB
88 lines
2.3 KiB
# JNI for mcl (experimental)
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This library provides functionality to compute the optimal ate pairing
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over Barreto-Naehrig (BN) or BLS12-381 curves.
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# Initialization
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Load the library `mcljava`.
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```
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import com.herumi.mcl.*;
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System.loadLibrary(System.mapLibraryName("mcljava"));
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Mcl.SystemInit(curveType); // curveType = Mcl.BN254 or Mcl.BLS12_381
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```
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# Classes
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* `G1` ; The cyclic group instantiated as E(Fp)[r] where where r = p + 1 - t.
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* `G2` ; The cyclic group instantiated as the inverse image of E'(Fp^2)[r].
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* `GT` ; The cyclic group in the image of the optimal ate pairing.
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* `e : G1 x G2 -> GT`
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* `Fr` ; The finite field with characteristic r.
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# Methods and Functions
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## Fr
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* `Fr::setInt(int x)` ; set by x
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* `Fr::setStr(String str)` ; set by str such as "123", "0xfff", etc.
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* `Fr::setByCSPRNG()` ; randomly set
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* `Mcl.neg(Fr y, Fr x)` ; `y = -x`
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* `Mcl.add(Fr z, Fr x, Fr y)` ; `z = x + y`
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* `Mcl.sub(Fr z, Fr x, Fr y)` ; `z = x - y`
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* `Mcl.mul(Fr z, Fr x, Fr y)` ; `z = x * y`
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* `Mcl.div(Fr z, Fr x, Fr y)` ; `z = x / y`
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## G1
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* `Mcl.neg(G1 y, G1 x)` ; `y = -x`
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* `Mcl.dbl(G1 y, G1 x)` ; `y = 2x`
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* `Mcl.add(G1 z, G1 x, G1 y)` ; `z = x + y`
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* `Mcl.sub(G1 z, G1 x, G1 y)` ; `z = x - y`
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* `Mcl.mul(G1 z, G1 x, Fr y)` ; `z = x * y`
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## G2
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* `Mcl.neg(G2 y, G2 x)` ; `y = -x`
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* `Mcl.dbl(G2 y, G2 x)` ; `y = 2x`
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* `Mcl.add(G2 z, G2 x, G2 y)` ; `z = x + y`
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* `Mcl.sub(G2 z, G2 x, G2 y)` ; `z = x - y`
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* `Mcl.mul(G2 z, G2 x, Fr y)` ; `z = x * y`
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## GT
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* `GT::setStr(String str)` ; set by the result of `toString()` method
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* `Mcl.mul(GT z, GT x, GT y)` ; `z = x * y`
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* `Mcl.pow(GT z, GT x, Fr y)` ; `z = x ^ y`
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* `Mcl.inv(GT y, GT x)` ; `y = x^{-1}`
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## pairing
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* `Mcl.pairing(GT e, G1 P, G2 Q)` ; e = e(P, Q)
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# BLS signature sample
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```
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G2 Q = new G2();
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Mcl.hashAndMapToG2(Q, "abc".getBytes());
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Fr s = new Fr();
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s.setByCSPRNG(); // secret key
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G2 pub = new G2();
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Mcl.mul(pub, Q, s); // public key = sQ
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String m = "signature test";
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G1 H = new G1();
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Mcl.hashAndMapToG1(H, m.getBytes()); // H = Hash(m)
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G1 sign = new G1();
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Mcl.mul(sign, H, s); // signature of m = s H
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GT e1 = new GT();
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GT e2 = new GT();
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Mcl.pairing(e1, H, pub); // e1 = e(H, s Q)
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Mcl.pairing(e2, sign, Q); // e2 = e(s H, Q);
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assertBool("verify signature", e1.equals(e2));
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```
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# Make test
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```
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cd ffi/java
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make test
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```
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# Sample code
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[MclTest.java](https://github.com/herumi/mcl/blob/master/ffi/java/MclTest.java)
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