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'use strict';

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var bn = require('bn.js');

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var elliptic = require('../../elliptic');

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var utils = elliptic.utils;

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var assert = utils.assert;

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function Signature(options, enc) {

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  if (options instanceof Signature)

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    return options;

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  if (this._importDER(options, enc))

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    return;

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  assert(options.r && options.s, 'Signature without r or s');

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  this.r = new bn(options.r, 16);

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  this.s = new bn(options.s, 16);

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}

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module.exports = Signature;

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Signature.prototype._importDER = function _importDER(data, enc) {

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  data = utils.toArray(data, enc);

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  if (data.length < 6 || data[0] !== 0x30 || data[2] !== 0x02)

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    return false;

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  var total = data[1];

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  if (1 + total > data.length)

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    return false;

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  var rlen = data[3];

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  // Short length notation

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  if (rlen >= 0x80)

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    return false;

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  if (4 + rlen + 2 >= data.length)

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    return false;

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  if (data[4 + rlen] !== 0x02)

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    return false;

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  var slen = data[5 + rlen];

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  // Short length notation

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  if (slen >= 0x80)

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    return false;

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  if (4 + rlen + 2 + slen > data.length)

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    return false;

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  this.r = new bn(data.slice(4, 4 + rlen));

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  this.s = new bn(data.slice(4 + rlen + 2, 4 + rlen + 2 + slen));

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  return true;

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};

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Signature.prototype.toDER = function toDER(enc) {

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  var r = this.r.toArray();

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  var s = this.s.toArray();

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  // Pad values

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  if (r[0] & 0x80)

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    r = [ 0 ].concat(r);

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  // Pad values

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  if (s[0] & 0x80)

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    s = [ 0 ].concat(s);

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  var total = r.length + s.length + 4;

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  var res = [ 0x30, total, 0x02, r.length ];

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  res = res.concat(r, [ 0x02, s.length ], s);

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  return utils.encode(res, enc);

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};

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