Develop Reference

Is there any simple way to protect the Android App and update it?

I developed an Android App and installed to three users' cellphones through Eclipse and USB connection. I don't want to put the App to google market. Now I got two problems:
How to protect the App and make it invalid in other cellphones. I know we cannot protect it 100%, I just don't want the App to be easily copied and run on other devices. What I have done was hard coding in my program to compare the AndroidID (save the AndroidID to a string and compare with current AndroidID). The problem is that if I have 100 users, I have to hard code 100 times.
How can I keep the users updated. Do I just upload the updated App to my own server and give them the link to download and install? In this case, the first problem comes out again: how to protect the App?

The first thing in my mind is that you can set a password that app requires the first time it run after installation and give that password only to enabled users

you could make the application check for the presence of some pre-determined "key" file and distribute the file separately.
For updating the app can download new apk files and use an intent to send the user to the Package Installer so that they can choose whether or not to install.

Mobile app install for a fixed time

I don't know is it possible or not. I want to know how it is possible that user can install my app (android , iPhone, phonegap based) for a fixed time , may be 1 month. After 1 month, user will be unable to run the app. Then if he uninstall and try to install again for next 1 month, it would prevent him to install.
Is it possible or not? if possible how?
-Arefin

There's no 100% secure way to do what you want, but you could do something like this:
Get a unique identifier for device where app is installed. There's
NOT perfect way to get this identifier, but here are some options:
Is there a unique Android device ID?
Make your app connect to your server and register that identifier
Your server can return whether or not your app was already installed there, so app can act accordingly.
A side effect would be that your app could not run without Internet connection, to prevent users from disconnecting from Internet to avoid this control.

You can also specify the validity option in when you're creating the keytool. The keytool is used when exporting the .apk file of an application.
Or
You could save the install date of application in Shared Preferences- that's when the app is being installed for the first time. Then check the number of days from current date and saved date, every time the app is started and allow access only if its within limits.
Removes the problem of Internet access.

How to Manage Offline Trial Expiration for an Android Application?

I have developed an application that I want to share with my clients. I want to share its trial, taking care of following points
Application should expire (i.e. User cannot move from main activity) after 30 Days
Internet connection is not required for my application so I don't want to manage trial expiration by managing a server where device's IMEI can be stored or sort of thing.
I want to restrict user from using application even if he uninstall and later on re-Install my app.
I want to protect application trial against a manual date changing hack normally applied by users
I was planning to maintain a file for my application with time token of first run saved in it which can be compared with GPS time on each run but the issue I am facing here is of file storage. If I save a file in Internal memory it gets deleted with application un-install and cannot be used when user reinstalls the app and if I store it on SD card/ External memory it is vulnerable to user deletion. I have investigated this issue from everywhere I can but got no success. Any idea or suggestion by you guys would be a relief. :-)

There will have internet access when the app is installed, or they wouldn't be able to install it.
Simply require that the user activate the app with a server the first time they use it. The app gets a "this app was first activated on yyyy-mm-dd" response from the server, and stores that info on a file in internal storage. From that point on, the user won't need to be on-line to use the app.

How to make app identify if it was installed on this device before and if yes then when(Date)?

I am making an app.Which has a free trial version and a premium version.The free version runs as premium for 7 days and after that it will prompt user to buy premium and exit.To do so I have come up with some ideas such as:
1)Identify the device uniquely and send that unique id and date to a server.And on start up check if this device's app is more than 7 days old if so block it.And when the user uninstalls the app and installs again upon registering to the server the app will be blocked.I have read about some ways of identifying a device uniquely.But as this link suggests none of them is reliable and won't work on every device and OS version.
2)I can write a file to sdcard indicating the app installation and check for that particular file on first run to detect re-installation.But that file can be easily deleted by the user and the app re-installed thus obtaining another trial for 7 days which is not acceptable.
Is there a way I can attain my goal?

These things can be done but, I encourage you to think again. What you're proposing is not good for your users and not good for users usually means lower app sales.
The app has to check with your server every time it starts. So I can't use it if I have no data connection or your server is down? Even if I paid for it?
Whatever you do, it can be defeated, especially if using date bound stuff.
I recommend that you think about adding value to the premium version, which is not in the free version, that will encourage people to buy. Or support the free one with advertising, which a lot of people will gladly pay a reasonable amount to get rid of. I recommend NOT releasing a free version which is in someway crippled but rather to make your paid version valuable to the user.

My suggestion is that -
Trial version -
Send a time stamp key(a key as hex string which holds current time and device serial number and trial or premium id) to the server when it is started. In server if any key is not stored, that means the app is started first time and save it for future checking. Server will send a time stamp key(key with server current time) to the device. And device will save this key in local database.
Next time when the app wii start again, the key will be sent to server and server will extract time and serial number from key and check with the first key(as identified first launch), if it exceeds 7 days as identified that the app has been expired.
If network is not available don't start the app.
Premium version -
Extract the trial or premium id from key, it is premium don't expire the app just keep continue the app.
It will work for all cases if user change the device time won't hamper this logic.

Android: saving info for trial application

I want to save some info regarding a trial version an application.
I want this info to be persistent in order to detect if the user removed the application and installed it again after the trial expiry.
what is the best place to store such info
thanks

Most of the times the solution to this problem is to keep an server side check,
But if you dont want to involve a server its better to give some limited functionality in your trail app and full in the paid version.
There are other methods too like Time Trial but again they all depends on persistent data so they also fails if the user uninstalls and installs again your applucation

Store it in external file.
it wont be deleted after user uninstalled the app.
but
Serverside check by Device ID is the good way ..

I'm working on the same "problem" at the moment (offline solution for trial time expired apps):
My findings: There is no way to ensure that a user never can reinstall & reuse a (time) trial app but there is a way to 'nearly' prevent it:
Use shared preferences / a database / file saved on internal storage containing the install timestamp.
If the device has an external storage card (most devices have) also save the timestamp on the sd card.
The only possiblity to use your application also after expiring is if the user 1. clears app data on the phone and 2. finds the timestamp file on the sd card and also kills this one.
If he "just kills" the first or second check the killed one can be restored on next app start.