The easiest way to securely erase a smart phone or tablet is to encrypt the device first, then do a factory reset. First, though, remember to back up any files you want to keep and remove the microSD and SIM cards.
Apple generally does a better job of securely erasing your personal data than Android. For the iPhone 3GS or later, third-generation iPod Touch or later, and all iPads, device data should automatically be encrypted if you have a passcode (screen lock) enabled. The passcode is used to generate an encryption key, and when you factory-reset your phone, the passcode and encryption key are securely deleted. Any data that’s left behind is securely scrambled, and thereby inaccessible to all but the highest-level data-recovery experts.
If you haven’t already set a passcode in iOS, you can do so by tapping Settings, then General, then Passcode.
Also check on this screen to make sure that data protection is enabled; if it isn’t, toggle it on.
Once encryption is enabled, head back into Settings, then General, then Reset. You’ll see a warning that the next step will erase all your media and data, followed by a red Erase button. Hit this and after a few minutes, your iPhone, iPad or iPod touch is ready to sell or trade.
Many Android phones and tablets, particularly older devices, don’t support hardware-based encryption. But you can enable encryption via software. Just know that encryption may slow your device’s performance, and it can’t be disabled without resetting your phone.
Plug in your Android device before encrypting, as the process can take more than an hour, depending on hardware and the amount of storage on your device.
You’ll also need to set up a PIN or password (not pattern unlock or face recognition) if you don’t have one already, as the device uses your password to generate the encryption keys. Go to Settings, then tap Security, then Screen Lock, and PIN or Password. Then create a PIN or password.
Now you’ll be able to encrypt your Android device. Go to Settings again, then Security, then Encrypt phone (or tablet). A warning screen will advise you that the process will take time and can’t be undone without resetting your phone or tablet. You’ll also have to provide your PIN or password before proceeding.
After your device has finished encrypting its data and rebooted, you’ll have to again enter your PIN or Password to get back into Android. Once there, you’re ready to factory-reset the device.
Because different device makers tweak Android to their own liking, the instructions for this next step (and Android instruction in general) will vary from device to device.
For recent Samsung devices, go to Settings, then Accounts. Scroll down to Backup Options, tap Backup and Reset, then Factory data reset.
For Nexus devises such as the Nexus 7, go to Settings, then scroll down to Backup & reset, right above Accounts. Tap that, and then hit Factory data reset.
The BlackBerry OS has changed so much over the years that providing detailed steps to encrypt and reset every device is impossible. But the basic steps are quite similar to those of iOS and Android, and should roughly line up with the instructions below.
Go to Options, Security Options, General Settings, and set a password.
Then set Content Protection to Enabled. Choose the option to encrypt your address book as well.
Once that’s done, make sure your phone or tablet is plugged in, then follow these detailed instructions from BlackBerry to reset. Or just dive into Settings, tap Security, then tap Security Wipe.
Enter your password, confirm that you want to reset the device, tap the Wipe Data button, and wait for the process to finish.
Most older Windows Phone 7 devices lack on-device encryption. Newer Windows Phone 8 devices do support encryption, but the average consumer can’t switch it on: Encryption must be enabled via one of two paid business-class services, either Microsoft’s Exchange business e-mail client or the Intune enterprise cloud-based device-management system.
That means device encryption isn’t an option for the average Windows Phone consumer, so you’ll have to go to a bit more trouble to securely erase your data.
To reset your Windows Phone, go to Settings, then About, then Reset phone. In Windows Phone 8, you’ll have to tap through two warning screens before deleting all your data.
Since you weren’t able to encrypt your old data before deleting it, you can then force the device to overwrite your old data by manually filling up the phone’s internal storage with nonpersonal files. Any small files that don’t contain personal data will work. MP3 files are a good choice, because most people have enough of them to fill up a phone.
Unfortunately, for older Windows Phones, you can’t just connect the phone to a PC and drag files over. For Windows Phone 7 devices, you’ll need to transfer the files via Zune software.
For Windows Phone 8, on a PC, you can drag files onto the device using Windows Explorer. For Macs, you can use the Windows Phone app.
However you get the music or other nonpersonal data onto the device, you’ll need to keep adding files until the phone is completely full. For added security, when the phone is full of music files, you can delete the files you added, then fill the device up again, and factory reset the phone a second time.