/// <summary>
/// Gets user's decrypted Key used for symmetric encryption/decryption of the file.
/// </summary>
/// <param name="userId">Unique user identifier from the database.</param>
/// <param name="userPrivatKey">Users private RSA key used for decryption of encrypted FEK data.</param>
/// <returns>Decrypted Key used for symmetric encryption/decryption of the file.</returns>
public byte[] GetKey(int userId, RSAParameters userPrivateKey)
{
if (Users.ContainsKey(userId))
{
var usersFek = new FileEncryptionKey();
usersFek.ParseFek(Users[userId], userPrivateKey);
return(usersFek.Key);
}
else
{
throw new Exception("You don't have access to this file.");
}
}
/// <summary>
/// Share a file with other specific user on EnigmaEfs. File can be shared max. with 3 other users.
/// Key used for file encryption is encrypted for the shared user using their public RSA key.
/// </summary>
/// <param name="loggedInUserId">Unique identifier of the logged-in user.</param>
/// <param name="userId">Unique user identifier from the database.</param>
/// <param name="loggedInUserPrivateKey">Private RSA key of the logged-in user.</param>
/// <param name="userPublicKey">Users public RSA key.</param>
public void ShareFile(int loggedInUserId, int userId, RSAParameters loggedInUserPrivateKey, RSAParameters userPublicKey)
{
if (OwnerId == loggedInUserId)
{
if (Users.Count > 4)
{
throw new Exception("File can't be shared with more than 4 users.");
}
if (!Users.ContainsKey(userId))
{
var usersFek = new FileEncryptionKey();
usersFek.ParseFek(Users[loggedInUserId], loggedInUserPrivateKey);
Users.Add(userId, usersFek.UnparseFek(userPublicKey));
}
}
else
{
throw new Exception("Only file owner can share this file.");
}
}
