Monday, March 10, 2014

iOS Keychain: Sharing data between iOS apps !

Save data in keychain from one iOS app and access it from another iOS app (Xcode 5) !

Creating your first app that will write to the Keychain

Settings for project : 
  1. Add the Security.framework to your project.
  2. Download UICKeyChainStore  and add the UICKeyChainStore.h and UICKeyChainStore.m files from Lib folder to your project.
  3. Go to Target -> Capabilities -> Keychain Sharing. By default it is off. On this option.
  4. As you will on it, a file name projectName.entitlements will add in your "Project Navigator", with key "Keychain Access Groups" of type "Array" with one "Item" of type "String" and Value "$(AppIdentifierPrefix)$(CFBundleIdentifier)". For example : is the Bundle identifier then Value will be "$(AppIdentifierPrefix)". It will look like this : 

Now all you need to do is start using the UICKeyChainStore and you'll be saving data to the KeyChain.

Now, in your class import "UICKeyChainStore.h" and write the following code: 

[UICKeyChainStore setString:@"mySecretPassword" forKey:@"password" service:@"MyService"];

[UICKeyChainStore stringForKey:@"password" service:@"MyService"];

Specifying the service allows you to store keys for a particular service, maybe you have a Twitter or Facebook specific set of keys you wish to save.

As you can see we are not specifying the accessGroup. By default it will pick the first access-group specified in your projectName.entitlements when writing and will search across all access-groups when none is specified.

Allowing your second app to access your shared keychain data:

Settings for project : 
  1. Repeat above steps from 1 to 3 (for firstApp). It will look like this : 

We want access to the Keychain group $(AppIdentifierPrefix) for reading, but we still want the default writing to occur in our own keychain group so we still specify $(AppIdentifierPrefix) as the first / default group. Add one more item in "Keychain Access Groups" with Value $(AppIdentifierPrefix)

It will look like this: 

Now, read the value from the shared Keychain exactly how we did in our first app.

In your class import "UICKeyChainStore.h" and write the following code: 

[UICKeyChainStore stringForKey:@"password" service:@"MyService"];

This should return the value “mySecretPassword” :)

Happy Coding :)