518 lines
13 KiB
JavaScript
518 lines
13 KiB
JavaScript
/**
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* Constructs a new bignum from another bignum, a number or a hex string.
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*/
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sjcl.bn = function(it) {
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this.initWith(it);
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};
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sjcl.bn.prototype = {
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radix: 24,
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maxMul: 8,
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_class: sjcl.bn,
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copy: function() {
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return new this._class(this);
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},
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/**
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* Initializes this with it, either as a bn, a number, or a hex string.
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*/
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initWith: function(it) {
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var i=0, k, n, l;
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switch(typeof it) {
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case "object":
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this.limbs = it.limbs.slice(0);
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break;
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case "number":
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this.limbs = [it];
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this.normalize();
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break;
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case "string":
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it = it.replace(/^0x/, '');
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this.limbs = [];
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// hack
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k = this.radix / 4;
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for (i=0; i < it.length; i+=k) {
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this.limbs.push(parseInt(it.substring(Math.max(it.length - i - k, 0), it.length - i),16));
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}
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break;
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default:
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this.limbs = [0];
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}
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return this;
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},
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/**
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* Returns true if "this" and "that" are equal. Calls fullReduce().
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* Equality test is in constant time.
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*/
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equals: function(that) {
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if (typeof that === "number") { that = new this._class(that); }
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var difference = 0, i;
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this.fullReduce();
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that.fullReduce();
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for (i = 0; i < this.limbs.length || i < that.limbs.length; i++) {
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difference |= this.getLimb(i) ^ that.getLimb(i);
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}
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return (difference === 0);
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},
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/**
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* Get the i'th limb of this, zero if i is too large.
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*/
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getLimb: function(i) {
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return (i >= this.limbs.length) ? 0 : this.limbs[i];
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},
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/**
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* Constant time comparison function.
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* Returns 1 if this >= that, or zero otherwise.
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*/
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greaterEquals: function(that) {
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if (typeof that === "number") { that = new this._class(that); }
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var less = 0, greater = 0, i, a, b;
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i = Math.max(this.limbs.length, that.limbs.length) - 1;
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for (; i>= 0; i--) {
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a = this.getLimb(i);
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b = that.getLimb(i);
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greater |= (b - a) & ~less;
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less |= (a - b) & ~greater;
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}
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return (greater | ~less) >>> 31;
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},
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/**
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* Convert to a hex string.
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*/
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toString: function() {
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this.fullReduce();
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var out="", i, s, l = this.limbs;
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for (i=0; i < this.limbs.length; i++) {
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s = l[i].toString(16);
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while (i < this.limbs.length - 1 && s.length < 6) {
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s = "0" + s;
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}
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out = s + out;
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}
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return "0x"+out;
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},
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/** this += that. Does not normalize. */
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addM: function(that) {
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if (typeof(that) !== "object") { that = new this._class(that); }
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var i, l=this.limbs, ll=that.limbs;
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for (i=l.length; i<ll.length; i++) {
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l[i] = 0;
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}
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for (i=0; i<ll.length; i++) {
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l[i] += ll[i];
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}
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return this;
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},
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/** this *= 2. Requires normalized; ends up normalized. */
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doubleM: function() {
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var i, carry=0, tmp, r=this.radix, m=this.radixMask, l=this.limbs;
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for (i=0; i<l.length; i++) {
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tmp = l[i];
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tmp = tmp+tmp+carry;
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l[i] = tmp & m;
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carry = tmp >> r;
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}
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if (carry) {
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l.push(carry);
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}
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return this;
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},
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/** this /= 2, rounded down. Requires normalized; ends up normalized. */
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halveM: function() {
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var i, carry=0, tmp, r=this.radix, l=this.limbs;
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for (i=l.length-1; i>=0; i--) {
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tmp = l[i];
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l[i] = (tmp+carry)>>1;
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carry = (tmp&1) << r;
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}
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if (!l[l.length-1]) {
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l.pop();
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}
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return this;
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},
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/** this -= that. Does not normalize. */
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subM: function(that) {
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if (typeof(that) !== "object") { that = new this._class(that); }
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var i, l=this.limbs, ll=that.limbs;
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for (i=l.length; i<ll.length; i++) {
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l[i] = 0;
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}
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for (i=0; i<ll.length; i++) {
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l[i] -= ll[i];
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}
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return this;
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},
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mod: function(that) {
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that = new sjcl.bn(that).normalize(); // copy before we begin
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var out = new sjcl.bn(this).normalize(), ci=0;
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for (; out.greaterEquals(that); ci++) {
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that.doubleM();
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}
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for (; ci > 0; ci--) {
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that.halveM();
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if (out.greaterEquals(that)) {
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out.subM(that).normalize();
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}
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}
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return out.trim();
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},
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/** return inverse mod prime p. p must be odd. Binary extended Euclidean algorithm mod p. */
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inverseMod: function(p) {
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var a = new sjcl.bn(1), b = new sjcl.bn(0), x = new sjcl.bn(this), y = new sjcl.bn(p), tmp, i, nz=1;
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if (!(p.limbs[0] & 1)) {
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throw (new sjcl.exception.invalid("inverseMod: p must be odd"));
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}
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// invariant: y is odd
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do {
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if (x.limbs[0] & 1) {
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if (!x.greaterEquals(y)) {
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// x < y; swap everything
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tmp = x; x = y; y = tmp;
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tmp = a; a = b; b = tmp;
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}
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x.subM(y);
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x.normalize();
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if (!a.greaterEquals(b)) {
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a.addM(p);
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}
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a.subM(b);
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}
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// cut everything in half
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x.halveM();
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if (a.limbs[0] & 1) {
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a.addM(p);
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}
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a.normalize();
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a.halveM();
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// check for termination: x ?= 0
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for (i=nz=0; i<x.limbs.length; i++) {
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nz |= x.limbs[i];
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}
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} while(nz);
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if (!y.equals(1)) {
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throw (new sjcl.exception.invalid("inverseMod: p and x must be relatively prime"));
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}
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return b;
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},
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/** this + that. Does not normalize. */
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add: function(that) {
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return this.copy().addM(that);
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},
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/** this - that. Does not normalize. */
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sub: function(that) {
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return this.copy().subM(that);
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},
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/** this * that. Normalizes and reduces. */
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mul: function(that) {
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if (typeof(that) === "number") { that = new this._class(that); }
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var i, j, a = this.limbs, b = that.limbs, al = a.length, bl = b.length, out = new this._class(), c = out.limbs, ai, ii=this.maxMul;
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for (i=0; i < this.limbs.length + that.limbs.length + 1; i++) {
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c[i] = 0;
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}
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for (i=0; i<al; i++) {
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ai = a[i];
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for (j=0; j<bl; j++) {
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c[i+j] += ai * b[j];
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}
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if (!--ii) {
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ii = this.maxMul;
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out.cnormalize();
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}
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}
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return out.cnormalize().reduce();
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},
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/** this ^ 2. Normalizes and reduces. */
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square: function() {
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return this.mul(this);
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},
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/** this ^ n. Uses square-and-multiply. Normalizes and reduces. */
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power: function(l) {
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if (typeof(l) === "number") {
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l = [l];
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} else if (l.limbs !== undefined) {
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l = l.normalize().limbs;
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}
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var i, j, out = new this._class(1), pow = this;
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for (i=0; i<l.length; i++) {
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for (j=0; j<this.radix; j++) {
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if (l[i] & (1<<j)) {
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out = out.mul(pow);
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}
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pow = pow.square();
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}
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}
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return out;
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},
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trim: function() {
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var l = this.limbs, p;
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do {
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p = l.pop();
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} while (l.length && p === 0);
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l.push(p);
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return this;
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},
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/** Reduce mod a modulus. Stubbed for subclassing. */
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reduce: function() {
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return this;
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},
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/** Reduce and normalize. */
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fullReduce: function() {
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return this.normalize();
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},
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/** Propagate carries. */
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normalize: function() {
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var carry=0, i, pv = this.placeVal, ipv = this.ipv, l, m, limbs = this.limbs, ll = limbs.length, mask = this.radixMask;
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for (i=0; i < ll || (carry !== 0 && carry !== -1); i++) {
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l = (limbs[i]||0) + carry;
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m = limbs[i] = l & mask;
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carry = (l-m)*ipv;
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}
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if (carry === -1) {
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limbs[i-1] -= this.placeVal;
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}
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return this;
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},
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/** Constant-time normalize. Does not allocate additional space. */
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cnormalize: function() {
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var carry=0, i, ipv = this.ipv, l, m, limbs = this.limbs, ll = limbs.length, mask = this.radixMask;
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for (i=0; i < ll-1; i++) {
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l = limbs[i] + carry;
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m = limbs[i] = l & mask;
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carry = (l-m)*ipv;
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}
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limbs[i] += carry;
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return this;
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},
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/** Serialize to a bit array */
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toBits: function(len) {
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this.fullReduce();
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len = len || this.exponent || this.limbs.length * this.radix;
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var i = Math.floor((len-1)/24), w=sjcl.bitArray, e = (len + 7 & -8) % this.radix || this.radix,
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out = [w.partial(e, this.getLimb(i))];
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for (i--; i >= 0; i--) {
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out = w.concat(out, [w.partial(this.radix, this.getLimb(i))]);
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}
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return out;
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},
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/** Return the length in bits, rounded up to the nearest byte. */
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bitLength: function() {
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this.fullReduce();
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var out = this.radix * (this.limbs.length - 1),
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b = this.limbs[this.limbs.length - 1];
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for (; b; b >>= 1) {
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out ++;
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}
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return out+7 & -8;
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}
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};
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sjcl.bn.fromBits = function(bits) {
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var Class = this, out = new Class(), words=[], w=sjcl.bitArray, t = this.prototype,
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l = Math.min(this.bitLength || 0x100000000, w.bitLength(bits)), e = l % t.radix || t.radix;
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words[0] = w.extract(bits, 0, e);
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for (; e < l; e += t.radix) {
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words.unshift(w.extract(bits, e, t.radix));
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}
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out.limbs = words;
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return out;
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};
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sjcl.bn.prototype.ipv = 1 / (sjcl.bn.prototype.placeVal = Math.pow(2,sjcl.bn.prototype.radix));
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sjcl.bn.prototype.radixMask = (1 << sjcl.bn.prototype.radix) - 1;
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/**
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* Creates a new subclass of bn, based on reduction modulo a pseudo-Mersenne prime,
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* i.e. a prime of the form 2^e + sum(a * 2^b),where the sum is negative and sparse.
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*/
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sjcl.bn.pseudoMersennePrime = function(exponent, coeff) {
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function p(it) {
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this.initWith(it);
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/*if (this.limbs[this.modOffset]) {
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this.reduce();
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}*/
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}
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var ppr = p.prototype = new sjcl.bn(), i, tmp, mo;
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mo = ppr.modOffset = Math.ceil(tmp = exponent / ppr.radix);
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ppr.exponent = exponent;
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ppr.offset = [];
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ppr.factor = [];
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ppr.minOffset = mo;
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ppr.fullMask = 0;
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ppr.fullOffset = [];
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ppr.fullFactor = [];
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ppr.modulus = p.modulus = new sjcl.bn(Math.pow(2,exponent));
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ppr.fullMask = 0|-Math.pow(2, exponent % ppr.radix);
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for (i=0; i<coeff.length; i++) {
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ppr.offset[i] = Math.floor(coeff[i][0] / ppr.radix - tmp);
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ppr.fullOffset[i] = Math.ceil(coeff[i][0] / ppr.radix - tmp);
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ppr.factor[i] = coeff[i][1] * Math.pow(1/2, exponent - coeff[i][0] + ppr.offset[i] * ppr.radix);
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ppr.fullFactor[i] = coeff[i][1] * Math.pow(1/2, exponent - coeff[i][0] + ppr.fullOffset[i] * ppr.radix);
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ppr.modulus.addM(new sjcl.bn(Math.pow(2,coeff[i][0])*coeff[i][1]));
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ppr.minOffset = Math.min(ppr.minOffset, -ppr.offset[i]); // conservative
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}
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ppr._class = p;
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ppr.modulus.cnormalize();
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/** Approximate reduction mod p. May leave a number which is negative or slightly larger than p. */
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ppr.reduce = function() {
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var i, k, l, mo = this.modOffset, limbs = this.limbs, aff, off = this.offset, ol = this.offset.length, fac = this.factor, ll;
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i = this.minOffset;
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while (limbs.length > mo) {
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l = limbs.pop();
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ll = limbs.length;
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for (k=0; k<ol; k++) {
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limbs[ll+off[k]] -= fac[k] * l;
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}
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i--;
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if (!i) {
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limbs.push(0);
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this.cnormalize();
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i = this.minOffset;
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}
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}
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this.cnormalize();
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return this;
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};
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ppr._strongReduce = (ppr.fullMask === -1) ? ppr.reduce : function() {
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var limbs = this.limbs, i = limbs.length - 1, k, l;
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this.reduce();
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if (i === this.modOffset - 1) {
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l = limbs[i] & this.fullMask;
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limbs[i] -= l;
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for (k=0; k<this.fullOffset.length; k++) {
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limbs[i+this.fullOffset[k]] -= this.fullFactor[k] * l;
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}
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this.normalize();
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}
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};
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/** mostly constant-time, very expensive full reduction. */
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ppr.fullReduce = function() {
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var greater, i;
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// massively above the modulus, may be negative
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this._strongReduce();
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// less than twice the modulus, may be negative
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this.addM(this.modulus);
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this.addM(this.modulus);
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this.normalize();
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// probably 2-3x the modulus
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this._strongReduce();
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// less than the power of 2. still may be more than
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// the modulus
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// HACK: pad out to this length
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for (i=this.limbs.length; i<this.modOffset; i++) {
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this.limbs[i] = 0;
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}
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// constant-time subtract modulus
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greater = this.greaterEquals(this.modulus);
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for (i=0; i<this.limbs.length; i++) {
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this.limbs[i] -= this.modulus.limbs[i] * greater;
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}
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this.cnormalize();
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return this;
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};
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ppr.inverse = function() {
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return (this.power(this.modulus.sub(2)));
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};
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p.fromBits = sjcl.bn.fromBits;
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return p;
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};
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// a small Mersenne prime
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sjcl.bn.prime = {
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p127: sjcl.bn.pseudoMersennePrime(127, [[0,-1]]),
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// Bernstein's prime for Curve25519
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p25519: sjcl.bn.pseudoMersennePrime(255, [[0,-19]]),
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// NIST primes
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p192: sjcl.bn.pseudoMersennePrime(192, [[0,-1],[64,-1]]),
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p224: sjcl.bn.pseudoMersennePrime(224, [[0,1],[96,-1]]),
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p256: sjcl.bn.pseudoMersennePrime(256, [[0,-1],[96,1],[192,1],[224,-1]]),
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p384: sjcl.bn.pseudoMersennePrime(384, [[0,-1],[32,1],[96,-1],[128,-1]]),
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p521: sjcl.bn.pseudoMersennePrime(521, [[0,-1]])
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};
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sjcl.bn.random = function(modulus, paranoia) {
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if (typeof modulus !== "object") { modulus = new sjcl.bn(modulus); }
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var words, i, l = modulus.limbs.length, m = modulus.limbs[l-1]+1, out = new sjcl.bn();
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while (true) {
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// get a sequence whose first digits make sense
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do {
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words = sjcl.random.randomWords(l, paranoia);
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if (words[l-1] < 0) { words[l-1] += 0x100000000; }
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} while (Math.floor(words[l-1] / m) === Math.floor(0x100000000 / m));
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words[l-1] %= m;
|
|
|
|
// mask off all the limbs
|
|
for (i=0; i<l-1; i++) {
|
|
words[i] &= modulus.radixMask;
|
|
}
|
|
|
|
// check the rest of the digitssj
|
|
out.limbs = words;
|
|
if (!out.greaterEquals(modulus)) {
|
|
return out;
|
|
}
|
|
}
|
|
};
|
|
|