public void Challenge007()
{
var lines = File.ReadAllLines(Path.Combine(_dataPath, "Set001Challenge007.txt"));
var content = string.Join("", lines);
var buffer = Buffer.FromBase64(content);
var outputBuffer = new byte[buffer.Length];
var aes = Aes.Create();
aes.Mode = CipherMode.ECB;
aes.BlockSize = 128;
aes.Key = Encoding.ASCII.GetBytes("YELLOW SUBMARINE");
aes.CreateDecryptor().TransformBlock(buffer, 0, buffer.Length, outputBuffer, 0);
var text = new Buffer(outputBuffer).ToText();
text.Split('\n')[0].ShouldBe("I'm back and I'm ringin' the bell ");
}
public void Challenge006()
{
var lines = File.ReadAllLines(Path.Combine(_dataPath, "Set001Challenge006.txt"));
var content = string.Join("", lines);
var buffer = Buffer.FromBase64(content);
var likelihoods =
Enumerable.Range(2, 40).Select(blocksize => new {
BlockSize = blocksize,
Likelihood =
Enumerable.Range(0, 10).Select(block => {
var buffer1 = buffer.GetBlock(blocksize, block * 2);
var buffer2 = buffer.GetBlock(blocksize, block * 2 + 1);
return(buffer1.NormalisedHammingDistance(buffer2));
}).Average()
})
.OrderBy(m => m.Likelihood);
var blockSize = likelihoods.First().BlockSize;
var transposed = buffer.Select((value, index) => new { Value = value, Index = index })
.GroupBy(x => x.Index % blockSize)
.Select(grp => grp.Select(x => x.Value).ToArray())
.Select(m => new Buffer(m))
.Select(m => m.EnglishScore())
.Select(score => Convert.ToChar(score.Byte))
.ToArray();
var key = new string(transposed);
var message = (buffer ^ key).ToText();
blockSize.ShouldBe(29);
key.ShouldBe("Terminator X: Bring the noise");
message.Split('\n')[0].ShouldBe("I'm back and I'm ringin' the bell ");
}
