-- Restoring the certificate, but without the private key.
CREATE CERTIFICATE TDECert
FROM FILE = 'D:\mssql_cert\tde_cert.cert'
WITH PRIVATE KEY (
	FILE = N'D:\mssql_cert\admin_private.key',
	DECRYPTION BY PASSWORD = 'abcde1'
);
GO

-- We have the correct certificate and we've also restored the 
-- private key. Now everything should work. Finally! 
restore DATABASE [admindb]
FROM disk= N'D:\backup\admindb_20160923.bak'
WITH move 'admindb' TO N'D:\MSSQL\ADMIN\admindb_data.mdf',
     move 'admindb_log' TO N'D:\MSSQL\ADMIN\admindb_data_log.ldf';
GO

sp_addlogin 'db_manager','12345a','admindb';

create login db_manager
with password='12345a',
default_database=admindb;

USE admindb
go
EXEC sp_change_users_login 'Update_One', 'db_manager', 'db_manager'