public void Challenge19_Fixed_Nonce_CTR_Substitutions()
{
var(encryptedLines, plainTextLines) = ReadAndEncryptWithCTR("19.txt", 0);
var expectedChars = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM-'\".,:;!? ";
var keystream = Xor.GetCommonKeyStream(encryptedLines, expectedChars);
for (int j = 0; j < encryptedLines.Count; j++)
{
byte[] encryptedLine = encryptedLines[j];
var line = new char[encryptedLine.Length];
for (int i = 0; i < encryptedLine.Length; ++i)
{
line[i] = Convert.ToChar((byte)(encryptedLine[i] ^ keystream[i]));
}
var decryptedLowerCase = new string(line).ToLowerInvariant();
var originalLowerCase = plainTextLines[j].ToLowerInvariant();
switch (j)
{
case 4:
// i have passed with a nod of the head
Assert.Equal("i have passed with a nod of the hiln", decryptedLowerCase);
break;
case 27:
// he might have won fame in the end,
Assert.Equal("he might have won fame in the end ", decryptedLowerCase);
break;
case 37:
// he, too, has been changed in his turn,
Assert.Equal("he, too, has been changed in his xxxis", decryptedLowerCase);
break;
default:
Assert.Equal(originalLowerCase, decryptedLowerCase);
break;
}
}
}
