sqlite database encryption

copied from http://sqlite.phxsoftware.com/forums/t/130.aspx

Encrypt sqlite by using System.Data.SQLite.dll is pretty simple.

To encrypt an existing unencrypted database, or to change the password of an encrypted database, open the database and then use the ChangePassword() function of SQLiteConnection:

// Opens an unencrypted database
SQLiteConnection cnn = new SQLiteConnection("Data Source=c:\\test.db3");
cnn.Open();
// Encrypts the database. The connection remains valid and usable afterwards.
cnn.ChangePassword("mypassword"); 

To decrypt an existing encrypted database call ChangePassword() with a NULL or "" password:

// Opens an encrypted database
SQLiteConnection cnn = new SQLiteConnection("Data Source=c:\\test.db3;Password=mypassword");
cnn.Open();
// Removes the encryption on an encrypted database.
cnn.ChangePassword(null); 

To open an existing encrypted database, or to create a new encrypted database, specify a password in the ConnectionString as shown in the previous example, or call the SetPassword() function before opening a new SQLiteConnection. Passwords specified in the ConnectionString must be cleartext, but passwords supplied in the SetPassword() function may be binary byte arrays.

// Opens an encrypted database by calling SetPassword()
SQLiteConnection cnn = new SQLiteConnection("Data Source=c:\\test.db3");
cnn.SetPassword(new byte[] { 0xFF, 0xEE, 0xDD, 0x10, 0x20, 0x30 });
cnn.Open();
// The connection is now usable

By default, the ATTACH keyword will use the same encryption key as the main database when attaching another database file to an existing connection. To change this behavior, you use the KEY modifier as follows:
If you are attaching an encrypted database using a cleartext password:

// Attach to a database using a different key than the main database
SQLiteConnection cnn = new SQLiteConnection("Data Source=c:\\test.db3");
cnn.Open();
cmd = new SQLiteCommand("ATTACH DATABASE 'c:\\pwd.db3' AS [Protected] KEY 'mypassword'", cnn);
cmd.ExecuteNonQuery();

To attach an encrypted database using a binary password:

// Attach to a database encrypted with a binary key
SQLiteConnection cnn = new SQLiteConnection("Data Source=c:\\test.db3");
cnn.Open();
cmd = new SQLiteCommand("ATTACH DATABASE 'c:\\pwd.db3' AS [Protected] KEY X'FFEEDD102030'", cnn);
cmd.ExecuteNonQuery();