1const createBlakeHash = require("blake-hash");
 2const bigInt = require("snarkjs").bigInt;
 3const babyJub = require("./babyjub");
 4const pedersenHash = require("./pedersenHash").hash;
 5const crypto = require("crypto");
 6
 7exports.cratePrvKey = cratePrvKey;
 8exports.prv2pub= prv2pub;
 9exports.sign = sign;
10exports.verify = verify;
11exports.packSignature = packSignature;
12exports.unpackSignature = unpackSignature;
13
14
15function cratePrvKey() {
16    return crypto.randomBytes(32);
17}
18
19function pruneBuffer(_buff) {
20    const buff = Buffer.from(_buff);
21    buff[0] = buff[0] & 0xF8;
22    buff[31] = buff[31] & 0x7F;
23    buff[31] = buff[31] | 0x40;
24}
25
26function prv2pub(prv) {
27    const sBuff = pruneBuffer(createBlakeHash("blake512").update(prv).digest().slice(0,32));
28    let s = bigInt.leBuff2int(sBuff);
29    const A = babyJub.mulPointEscalar(babyJub.Base8, s.shr(3));
30    return A;
31}
32
33function sign(prv, msg) {
34    const h1 = createBlakeHash("blake512").update(prv).digest();
35    const sBuff = pruneBuffer(h1.slice(0,32));
36    const s = bigInt.leBuff2int(sBuff);
37    const A = babyJub.mulPointEscalar(babyJub.Base8, s.shr(3));
38
39    const rBuff = createBlakeHash("blake512").update(Buffer.concat(h1.slice(32,64), msg)).digest();
40    let r = bigInt.leBuff2int(rBuff);
41    r = r.mod(babyJub.subOrder);
42    const R8 = babyJub.mulPointEscalar(babyJub.Base8, r);
43    const R8p = babyJub.packPoint(R8);
44    const Ap = babyJub.packPoint(A);
45    const hmBuff = pedersenHash(Buffer.concat(R8p, Ap, msg));
46    const hm = bigInt.leBuff2int(hmBuff);
47    const S = r.add(hm.mul(s)).mod(babyJub.subOrder);
48    return {
49        R8: R8,
50        S: S
51    };
52}
53
54function verify(msg, sig, A) {
55    // Check parameters
56    if (typeof sig != "object") return false;
57    if (!Array.isArray(sig.R8)) return false;
58    if (sig.R8.length!= 2) return false;
59    if (!babyJub.inCurve(sig.R8)) return false;
60    if (!Array.isArray(A)) return false;
61    if (A.length!= 2) return false;
62    if (!babyJub.inCurve(sig.A)) return false;
63    if (sig.S>= babyJub.subOrder) return false;
64
65    const R8p = babyJub.packPoint(sig.R8);
66    const Ap = babyJub.packPoint(A);
67    const hmBuff = pedersenHash(Buffer.concat(R8p, Ap, msg));
68    const hm = bigInt.leBuff2int(hmBuff);
69
70    const Pleft = babyJub.mulPointEscalar(babyJub.Base8, sig.S);
71    let Pright = babyJub.mulPointEscalar(A, hm.mul(8));
72    Pright = babyJub.addaddPoint(sig.R8, Pright);
73
74    if (!Pleft[0].equals(Pright[0])) return false;
75    if (!Pleft[1].equals(Pright[1])) return false;
76    return true;
77}
78
79function packSignature(sig) {
80    const R8p = babyJub.packPoint(sig.R8);
81    const Sp = bigInt.leInt2Buff(sig.S, 32);
82    return Buffer.concat(R8p, Sp);
83}
84
85function unpackSignature(sigBuff) {
86    return {
87        R8: babyJub.unpackPoint(sigBuff.slice(0,32)),
88        S: bigInt.leBuff2int(sigBuff.slice(32,64))
89    };
90}
91
92