We needed a new PRAGMA! These things happen.

With the release of SQLCipher 2.0, a PRAGMA was added (cipher_use_hmac) which disabled the new per-page HMAC protection feature before opening a database, so that a developer wishing to run SQLCipher 2.0 against a 1.x database could do so. This was important to us because we wanted to provide an easy way for developers to migrate to the new database format. Generally speaking, you'd want to do something like this:

1. Open the legacy database, set your key
2. Call PRAGMA cipher_use_hmac = OFF; before opening the legacy database
3. ATTACH a new, empty database, which will be encrypted by default and have HMAC on by default
4. Copy your database into the attached database using sqlcipher_export()

That scenario looks about like this on the command line:

$> ./sqlite3 my-legacy-encrypted.db
sqlite> PRAGMA key = 's3cr37';
sqlite> PRAGMA cipher_use_hmac = OFF;
sqlite> ATTACH DATABASE 'new-sqlcipher2.db' AS newdb;
sqlite> SELECT sqlcipher_export('newdb');
sqlite> DETACH DATABASE newdb;

But there are other scenarios, ones in which we really needed to be able to ATTACH one legacy database to another (e.g. data replication). Even though we'd have called PRAGMA cipher_use_hmac = OFF; when opening the first database, the ATTACH operation assumed the new default format, and would report back "database is encrypted or is not a database."

We didn't wish to modify the ATTACH command, and we didn't want to change the behavior of cipher_use_hmac, as the latter's behavior is necessary for developers who wish to migrate and upgrade their databases. Instead, Stephen came up with a new PRAGMA, cipher_default_use_hmac, which is a globally applied setting in SQLCipher, allowing you to turn HMAC protection on and off before you open or ATTACH another encrypted database, so you only need to bother with one setting in your app. Here's an example (where custom_data_replicator() is a made-up function):

$> ./sqlite3 my-legacy-encrypted.db
sqlite> PRAGMA cipher_default_use_hmac = OFF;
sqlite> PRAGMA key = 's3cr37';
sqlite> ATTACH DATABASE 'remote.db' AS remote;
sqlite> SELECT custom_data_replicator('remote');
sqlite> DETACH DATABASE remote;

Pretty dang handy and available now on the master branch—stay tuned to the mailing list for details on new tags and release numbers. You can see the changes here along with updated unit tests.

Meanwhile, I've made some mods to SQLCipherManager to support this specific scenario. Setting the property useHMACPageProtection causes the new global PRAGMA to be called before a database is opened, rather than the older cipher_use_hmac. This allows you to attach 1.x or 2.x databases at will, by changing the setting when you need to, like so:

self.dbManager = [SQLCipherManager sharedManager];
[self.dbManager setUseHMACPageProtection:NO];
@try {
  [self.dbManager execute:
    [NSString stringWithFormat: @"ATTACH DATABASE '%@' AS remote;", [replicaURL path]];
  [self.dbManager beginTransaction];
  [self.dbManager execute:@"SELECT custom_data_replicator('remote');"];
  [self.dbManager commitTransaction];
  [self.dbManager execute:@"DETACH DATABASE remote;"];
}
@catch (NSException *exception) {
  // SQLCipher's execute: command now provides handy exceptions!
  // For traditional error handling, use execute:error: instead.
  NSLog(@"Command failed: %@", [exception reason]);
}

One of the most frequent requests we receive for Strip is support for Android. Android is one of the largest mobile platforms next to iOS. To support this, we first needed to port SQLCipher onto the Android platform. SQLCipher is our open source extension to SQLite that allows for transparent 256-bit AES encryption of database files. We began last year working in conjunction with The Guardian Project on this process. This has required bundling a custom build of the ICU project to allow portability across Android versions 2.1 through 4.0.3 (Ice Cream Sandwich). You can read more on integrating SQLCipher for Android here. With this out of the way, we've been focusing on the application development work and are nearing completion for an initial delivery.

Unlike the iOS platform, where users upgrade to the lastest iOS release quickly, the Android platform is more fragmented due to manufacturers playing a role in the update distribution process - more about this here. That said, we have been working to target Android versions 2.1 and up for Strip on Android - targeting the majority of users. We have also tried to maintain a consistent user experience between the iOS application and Android where it makes sense. An example of where the iOS and Android platforms differ is in their drag and drop support. iOS provides a native drag and drop interaction within their UITableView, requiring you to set an editing mode and handle a few events. On Android however, support was added in 3.0 for drag and drop, prior to that you are left with the implementation details. If you want to be notified when we release Strip for Android, sign up here. We are very excited about adding support for the Android platform and hope you are as well. We will leave you with a screenshot of the upcoming Strip for Android. Thanks!

Strip for Android

Bret Morgan of Cowerks, a good friend of Zetetic, is organizing a cooperative learning program in late April designed to give participants a crash course in iPad/iPhone development.

The approach is unique; instead of a traditional "teacher leads, students learn" class model, participants will work together as a cooperative development group. Following the first half of the Stanford University CS193P iPhoneApplication Development curriculum, the goal is to cover a wide range of iOS topics in just 8 weeks of sessions:

• A Walkthrough of iOS 5
• Objective-C
• Views
• Autorotation, Protocols, & Gestures
• View Controllers
• UIToolbar and iPad Apps
• Controller Lifecycle & Image/Scroll/WebViews
• Table Views

With the course materials and group as a guide, attendees will work both collaboratively and on their own time to learn Objective-C and the relevant SDKs.

It's a really neat concept, so if you're in the NJ area and you've been waiting for a reason to learn iOS development, this could be a great opportunity. Classes start on April 23rd, and registration is open now with early-bird discounts at http://cowerks-ios.eventbrite.com.

Big news today, Stephen just announced the final release of SQLCipher 2.0! That’s our new(ish) blog for folks who want to subscribe to a news feed specific to the SQLCipher project. Check out the long list of improvements and stay tuned for more updates this week regarding the new features.

Another bit of SQLCipher news you may have missed, if you don’t follow the mailing list: we’ve created an SQLCipher “organization” on Github, and moved the main repo and various associated, supporting projects under it. Find it here on Github!