code: function _bnToBytes(b) {
    // prepend 0x00 if first byte >= 0x80
    var hex = b.toString(16);
    if(hex[0] >= '8') {
      hex = '00' + hex;
    }
    return forge.util.hexToBytes(hex);
  }
docs: Converts a positive BigInteger into 2's-complement big-endian bytes.
  
  @param b the big integer to convert.
  
  @return the bytes.