KlugKeychain

<extensions>
    <extensionID>com.klug.keychain.Keychain</extensionID>
</extensions>

import com.klug.keychain.Keychain;

var keychain:Keychain = Keychain.getInstance();

// iOS: always true.
// macOS: true only if the app is signed with a keychain access group entitlement;
//        the extension checks this with a test write.
// Android, Windows: false, and every call is a safe no-op.
if ( !keychain.isSupported )
    useLocalStorage();   // your app's fallback, e.g. a SharedObject

const TRIAL_DAYS:Number = 7;

if ( keychain.has( "trialStarted" ) )
{
    var started:Number = Number( keychain.get( "trialStarted" ) );
    var days:Number = ( new Date().time - started ) / 86400000;
    if ( days > TRIAL_DAYS ) showPurchaseScreen();   // your app
}
else
{
    // stays in the keychain after the app is uninstalled and installed again
    keychain.set( "trialStarted", String( new Date().time ) );
}

// set() replaces an existing value; false = not stored
if ( !keychain.set( "accountId", accountId ) )
    trace( "keychain: value not stored" );

// get() returns "" when nothing is stored
var id:String = keychain.get( "accountId" );
if ( id == "" ) showSignIn();   // your app

// sign-out: remove what the app no longer needs;
// true also when the key was already gone
keychain.remove( "accountId" );