public static Tuple <int, int> ValidateTokenString(string value)
{
var charOffset = 0;
try
{
var tokenString = value.ToUpper();
var splittedTokenString = tokenString.Split('-');
// 4 parts
if (splittedTokenString.Length != 4)
{
throw new Exception();
}
// each part has 4 characters
for (var i = 0; i < 4; i++)
{
if (splittedTokenString[i].Length != 4)
{
throw new Exception();
}
}
// revert code to ints
var bytes = new int[8];
for (var i = 0; i < 2; i++)
{
var nstring = splittedTokenString[2 * i];
var cstring = splittedTokenString[2 * i + 1];
for (var k = 0; k < 4; k++)
{
var number = int.Parse(nstring[k].ToString());
var character = cstring[k];
var charValue = GetValueOfChar(character, charOffset);
bytes[i * 4 + k] = number * 26 + charValue;
if (i == 0 && k == 0)
{
// calculate char offset (first 5 bits of first value in bytes
var b = TokenRing.GetBitArrayFromInt(bytes[0]);
var bbool = new bool[32];
b.CopyTo(bbool, 0);
var bits5 = new bool[5];
Array.Copy(bbool, 0, bits5, 0, 5);
charOffset = TokenRing.GetIntFromBitArray(new BitArray(bits5));
}
}
}
//revert ints to bits
var completeRing = new TokenRing(64, 0);
for (var i = 0; i < 8; i++)
{
completeRing.AddBits(TokenRing.GetBitArrayFromInt(bytes[i]), 8);
}
//calculate offset
var allBits = completeRing.GetBits();
var offsetBits = new bool[6];
Array.Copy(allBits, 5, offsetBits, 0, 6);
var offset = TokenRing.GetIntFromBitArray(new BitArray(offsetBits));
// create ring
var ringBits = new bool[53];
Array.Copy(allBits, 11, ringBits, 0, 53);
var rotateRing = new TokenRing(47, 6);
rotateRing.AddBits(new BitArray(ringBits), 53);
//rotate ring
rotateRing.Rotate(-offset);
//check validity
if (!rotateRing.IsSealValid())
{
throw new Exception();
}
var baseBits = rotateRing.GetBits();
// electionId
var electionBits = new bool[7];
Array.Copy(baseBits, 31, electionBits, 0, 7);
var electionId = TokenRing.GetIntFromBitArray(new BitArray(electionBits));
// wahlkreisId
var wahlkreisBits = new bool[9];
Array.Copy(baseBits, 38, wahlkreisBits, 0, 9);
var wahlkreisId = TokenRing.GetIntFromBitArray(new BitArray(wahlkreisBits));
// check if electionId and wahlkreisId exists
using (var context = new ElectionDBEntities())
{
var election = context.Elections.SingleOrDefault(e => e.Id == electionId);
var wahlkreis = context.Wahlkreis.SingleOrDefault(w => w.Id == wahlkreisId);
if (election == null || wahlkreis == null)
{
throw new Exception();
}
return(Tuple.Create(electionId, wahlkreisId));
}
}
catch (Exception)
{
return(null);
}
}
