/// <summary>
/// Decrypts the given bytes using the entry encryption.
/// </summary>
public static byte[] Decrypt(byte[] entryBytes, string contentId, string passcode, MetaEntry meta)
{
var iv_key = Crypto.Sha256(
meta.GetBytes()
.Concat(Crypto.ComputeKeys(contentId, passcode, meta.KeyIndex))
.ToArray());
var tmp = new byte[entryBytes.Length];
Crypto.AesCbcCfb128Decrypt(tmp, entryBytes, tmp.Length, iv_key.Skip(16).Take(16).ToArray(), iv_key.Take(16).ToArray());
return(tmp);
}
private static byte[] Decrypt(byte[] entryBytes, byte[] keySeed, MetaEntry meta)
{
var iv_key = Crypto.Sha256(
meta.GetBytes()
.Concat(keySeed)
.ToArray());
var tmp = new byte[entryBytes.Length];
Crypto.AesCbcCfb128Decrypt(tmp, entryBytes, tmp.Length, iv_key.Skip(16).Take(16).ToArray(), iv_key.Take(16).ToArray());
return(tmp);
}
/// <summary>
/// Decrypts the given entry using the entry encryption.
/// Throws an exception if it can't be decrypted.
/// </summary>
public static byte[] Decrypt(byte[] entryBytes, Pkg pkg, MetaEntry meta)
{
if (meta.KeyIndex != 3)
{
throw new Exception("We only have the key for encryption key 3");
}
var iv_key = Crypto.Sha256(
meta.GetBytes()
.Concat(Crypto.RSA2048Decrypt(pkg.EntryKeys.Keys[3].key, RSAKeyset.PkgDerivedKey3Keyset))
.ToArray());
var tmp = new byte[entryBytes.Length];
Crypto.AesCbcCfb128Decrypt(tmp, entryBytes, tmp.Length, iv_key.Skip(16).Take(16).ToArray(), iv_key.Take(16).ToArray());
return(tmp);
}
/// <summary>
/// Writes the entry in an encrypted form to the given stream.
/// </summary>
public void WriteEncrypted(Stream s, string contentId, string passcode)
{
var iv_key = Crypto.Sha256(
meta.GetBytes()
.Concat(Crypto.ComputeKeys(contentId, passcode, meta.KeyIndex))
.ToArray());
var tmp = new byte[Length];
using (var ms = new MemoryStream(tmp))
{
Write(ms);
}
Crypto.AesCbcCfb128Encrypt(tmp, tmp, tmp.Length, iv_key.Skip(16).Take(16).ToArray(), iv_key.Take(16).ToArray());
s.Write(tmp, 0, tmp.Length);
}