/* Detect single-character XOR
* One of the 60-character strings in this file has been encrypted by single-character XOR.
* Find it.
* (Your code from #3 should help.)
*/
static void Main(string[] args)
{
StreamReader reader = File.OpenText("cdata.txt");
char key;
string cleartext = string.Empty;
while (!reader.EndOfStream)
{
// If there is a 10% or greater match of digraphs/trigraphs/doubles, assume its english cleartext
cleartext = Transforms.FindKeyDecryptXor(reader.ReadLine(), out key);
if (Detectors.LikelyEnglish(cleartext) > 0.1)
{
System.Console.WriteLine(String.Format("Found text {0} with key {1} in input file", cleartext.Trim(), key));
}
}
System.Console.ReadKey();
}
static void Main(string[] args)
{
// string s1 = "this is a test";
//string s2 = "wokka wokka!!!";
//int hdist = CryptoUtils.Detectors.HammingDistance(s1, s2);
//hdist = CryptoUtils.Detectors.HammingDistance(Encoding.ASCII.GetBytes(s1.ToCharArray()), Encoding.ASCII.GetBytes(s2.ToCharArray()));
StreamReader reader = File.OpenText(".\\cdata6.txt");
byte[] inbytes = Convert.FromBase64String(reader.ReadToEnd());
int maxkeylen = 40;
double mineditdist = double.MaxValue;
MemoryStream memstr = new MemoryStream(inbytes);
Dictionary <double, List <int> > keylenmap = new Dictionary <double, List <int> >();
int index = 0;
int readct = 0;
int cdist = 0;
for (int i = 2; i < maxkeylen; i++)
{
byte[] b1 = new byte[i];
StringBuilder sb = new StringBuilder();
byte[] b2 = new byte[i];
while (memstr.Position < memstr.Length - i * 2)
{
memstr.Read(b1, 0, i);
memstr.Read(b2, 0, i);
cdist += Detectors.HammingDistance(b1, b2);
}
Console.WriteLine(String.Format("Keylen {0} HD {1}", i, cdist));
//if ((cdist / i) <= mineditdist)
//{
mineditdist = cdist / (double)i;
if (!keylenmap.ContainsKey(mineditdist))
{
keylenmap[mineditdist] = new List <int>();
}
keylenmap[mineditdist].Add(i);
//}
memstr.Seek(0, SeekOrigin.Begin);
}
double[] sortlist = keylenmap.Keys.ToArray();
Array.Sort(sortlist);
foreach (double d in new ArraySegment <double>(sortlist, 0, 20))
{
foreach (int l in keylenmap[d])
//for (int l = 2; l < 60; l++)
{
System.Console.WriteLine(String.Format("Keylen {0} has smallest HammingDistance {1}", l, d));
// Break the ciphertext
memstr.Seek(0, SeekOrigin.Begin);
List <byte[]> cblocks = new List <byte[]>();
// if inbytes count is not a multiple of keylength, pad it with 0s
if (((int)memstr.Length % l) != 0)
{
// Copy incoming memory stream to a new buffer with padding
int plen = (int)memstr.Length;
while (plen % l != 0)
{
plen++;
}
byte[] newbuf = new byte[plen];
memstr.Read(newbuf, 0, (int)memstr.Length);
memstr.Dispose();
memstr = new MemoryStream(newbuf);
}
int blockcount = (int)memstr.Length / l;
for (int i = 0; i < blockcount; i++)
{
byte[] block = new byte[l];
memstr.Read(block, 0, l);
cblocks.Add(block);
}
List <byte[]> tblocks = new List <byte[]>();
for (int bindex = 0; bindex < l; bindex++)
{
index = 0;
byte[] tblock = new byte[blockcount];
foreach (byte[] block in cblocks)
{
tblock[index] = block[bindex];
index++;
}
tblocks.Add(tblock);
}
List <char> keys = new List <char>();
List <string> ptext = new List <string>();
foreach (byte[] tblock in tblocks)
{
char key = char.MinValue;
ptext.Add(Transforms.FindKeyDecryptXor(string.Empty, out key, tblock));
keys.Add(key);
}
StringBuilder sb = new StringBuilder();
sb.Append(keys.ToArray());
System.Console.WriteLine(sb.ToString());
}
}
// From above, we know the probable key. Let user type in key from best looking output displayed above
System.Console.WriteLine("Enter the guessed key from the list above:");
string keystr = System.Console.ReadLine();
memstr.Seek(0, SeekOrigin.Begin);
System.Console.WriteLine(Transforms.DecryptRotXor(inbytes, keystr));
System.Console.ReadKey();
}
