/// <summary>
/// Decrypts a set of Taylor Swift lyrics into the original byte data.
/// </summary>
/// <param name="data">The string representation of the Taylor Swift lyrics to decrypt.</param>
/// <param name="key">The 256 bit Key used to encrypt the data.</param>
/// <param name="iv">The 128 bit IV used to encrypt the data.</param>
public byte[] Decrypt(string data, byte[] key, byte[] iv)
{
// Validate key parameter
if (key == null)
{
throw new ArgumentNullException("key");
}
if (key.Length == 0)
{
throw new ArgumentException("The key parameter can not be empty.", "key");
}
if (key.Length * 8 != KeyBitSize)
{
throw new ArgumentException($"The key parameter must be {KeyBitSize} bits long.", "key");
}
// Validate iv parameter
if (iv == null)
{
throw new ArgumentNullException("iv");
}
if (iv.Length == 0)
{
throw new ArgumentException("The iv parameter can not be empty.", "iv");
}
if (iv.Length * 8 != BlockBitSize)
{
throw new ArgumentException($"The iv parameter must be {BlockBitSize} bits long.", "iv");
}
// Get fingerprint id's from the fingerprint strings
var fingerprintIds = new List <int>();
foreach (var lyric in data.Split('\n'))
{
if (lyric.Trim() == string.Empty)
{
continue;
}
fingerprintIds.Add(
_fingerprintManager.GetIndexOfFingerprint(
_fingerprintManager.GetFromLyric(lyric)));
}
var bitArray = new BitArray(fingerprintIds.Count * 10);
var index = 0;
foreach (var x in fingerprintIds)
{
var arr = new BitArray(new int[] { x });
bitArray.Set(index++, arr.Get(0));
bitArray.Set(index++, arr.Get(1));
bitArray.Set(index++, arr.Get(2));
bitArray.Set(index++, arr.Get(3));
bitArray.Set(index++, arr.Get(4));
bitArray.Set(index++, arr.Get(5));
bitArray.Set(index++, arr.Get(6));
bitArray.Set(index++, arr.Get(7));
bitArray.Set(index++, arr.Get(8));
bitArray.Set(index++, arr.Get(9));
}
var encryptedData = bitArray.ToByteArray();
// Remove Padding from encrypted data
var paddingLength = encryptedData[encryptedData.Length - 1];
Array.Resize(ref encryptedData, encryptedData.Length - paddingLength);
// Decrypt Data
var decryptedData = DecryptPayload(encryptedData, key, iv);
return(decryptedData);
}
