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Commitec735ed

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committed
utils: leak less information ingetNAF()
1 parent71e4e8e commitec735ed

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2 files changed

+15
-14
lines changed

2 files changed

+15
-14
lines changed

‎lib/elliptic/curve/base.js

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -28,6 +28,8 @@ function BaseCurve(type, conf) {
2828
this._wnafT3=newArray(4);
2929
this._wnafT4=newArray(4);
3030

31+
this._bitLength=this.n ?this.n.bitLength() :0;
32+
3133
// Generalized Greg Maxwell's trick
3234
varadjustCount=this.n&&this.p.div(this.n);
3335
if(!adjustCount||adjustCount.cmpn(100)>0){
@@ -51,7 +53,7 @@ BaseCurve.prototype._fixedNafMul = function _fixedNafMul(p, k) {
5153
assert(p.precomputed);
5254
vardoubles=p._getDoubles();
5355

54-
varnaf=getNAF(k,1);
56+
varnaf=getNAF(k,1,this._bitLength);
5557
varI=(1<<(doubles.step+1))-(doubles.step%2===0 ?2 :1);
5658
I/=3;
5759

@@ -88,7 +90,7 @@ BaseCurve.prototype._wnafMul = function _wnafMul(p, k) {
8890
varwnd=nafPoints.points;
8991

9092
// Get NAF form
91-
varnaf=getNAF(k,w);
93+
varnaf=getNAF(k,w,this._bitLength);
9294

9395
// Add `this`*(N+1) for every w-NAF index
9496
varacc=this.jpoint(null,null,null);
@@ -144,8 +146,8 @@ BaseCurve.prototype._wnafMulAdd = function _wnafMulAdd(defW,
144146
vara=i-1;
145147
varb=i;
146148
if(wndWidth[a]!==1||wndWidth[b]!==1){
147-
naf[a]=getNAF(coeffs[a],wndWidth[a]);
148-
naf[b]=getNAF(coeffs[b],wndWidth[b]);
149+
naf[a]=getNAF(coeffs[a],wndWidth[a],this._bitLength);
150+
naf[b]=getNAF(coeffs[b],wndWidth[b],this._bitLength);
149151
max=Math.max(naf[a].length,max);
150152
max=Math.max(naf[b].length,max);
151153
continue;

‎lib/elliptic/utils.js

Lines changed: 9 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -12,14 +12,17 @@ utils.toHex = minUtils.toHex;
1212
utils.encode=minUtils.encode;
1313

1414
// Represent num in a w-NAF form
15-
functiongetNAF(num,w){
16-
varnaf=[];
15+
functiongetNAF(num,w,bits){
16+
varnaf=newArray(Math.max(num.bitLength(),bits)+1);
17+
naf.fill(0);
18+
1719
varws=1<<(w+1);
1820
vark=num.clone();
19-
while(k.cmpn(1)>=0){
21+
22+
for(vari=0;i<naf.length;i++){
2023
varz;
24+
varmod=k.andln(ws-1);
2125
if(k.isOdd()){
22-
varmod=k.andln(ws-1);
2326
if(mod>(ws>>1)-1)
2427
z=(ws>>1)-mod;
2528
else
@@ -28,13 +31,9 @@ function getNAF(num, w) {
2831
}else{
2932
z=0;
3033
}
31-
naf.push(z);
3234

33-
// Optimization, shift by word if possible
34-
varshift=(k.cmpn(0)!==0&&k.andln(ws-1)===0) ?(w+1) :1;
35-
for(vari=1;i<shift;i++)
36-
naf.push(0);
37-
k.iushrn(shift);
35+
naf[i]=z;
36+
k.iushrn(1);
3837
}
3938

4039
returnnaf;

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