Encryption for SD Cards

by Jeff Grundy
The same software used to encrypt hard drives can protect data on SD cards or microSD cards.

The same software used to encrypt hard drives can protect data on SD cards or microSD cards.

Securing private or sensitive data is just as important as backing it up on a safe, reliable medium. While not used as often with PCs as USB flash drives or external hard drives, SD cards are a reliable medium for saving modest amounts of data when you need something compact or easy-to-hide. Simply hiding an SD card with sensitive data is not enough, though. If you want to ensure that data stored on an SD card remains private, encrypt the device to prevent unauthorized access if the device falls into the wrong hands.

How Encryption Works

When you encrypt a file, drive or card, the encryption utility scrambles the data into an unreadable state and generates a key or lets you create a password for unscrambling the data. The key or password is not included in the encrypted file and must be stored separately from the protected file. Simple encryption may require a password only, while a more advanced locking method requires use of a password and a key file. Essentially, a key file is simply a text file with a long string of random letters, numbers and characters that form a secondary, and very complex, password string. With sensitive encrypted data, it is common for users to store keys on a separate external device, such as a USB flash drive, rather than on the computer to which the encrypted drive attaches or connects.

Whole-Drive Encryption

As the name implies, whole-drive encryption encrypts the entire disk or volume on which data is stored. If you don’t want others to see the names of files on your SD card, then whole-drive encryption will prevent them from opening or accessing anything on the drive unless they know the correct password or key. If you have the Pro or Ultimate version of Windows 8, the operating system includes the effective and relatively straightforward encryption utility BitLocker. If you don’t have a Windows version that offers BitLocker, you can download a free application such as TrueCrypt, DiskCryptor or Free CompuSec. Installation of any of the encryption applications is relatively simple, and all share similar setup methods. After installation, select your SD card in the application, choose an encryption method and then wait for the utility to encrypt the card. After you encrypt the SD card, the utility encrypts any files you save to the device automatically.

File and Folder Encryption Programs

Unlike whole-drive encryption, file and folder locking methods enable you to encrypt specific data on an SD card. This type of encryption is convenient if you have files on an SD card you want to keep private, but also have data to which you want quick access without having to enter a password or provide a key file. Some whole-drive encryption programs offer file and folder locking as well. However, applications such as AxCrypt, AES Crypt and Sophos Free Encryption are much better suited for encrypting specific files and folder.

Using File or Folder Encryption

After installing a file-and-folder encryption application, encrypting data on your SD card is as simple as right-clicking the file or folder you want to lock and then selecting the name of the program on the context menu. Once you right-click the name of the encryption program, you can select a password or create key for the file or folder, wait for the program to encrypt the data and then delete the original. To open an encrypted file folder, double-click it , enter the password, browse to the key file if applicable and then click "OK" or "Open."

Potential Pitfalls

The same advantages that the security of encrypting your SD card offers -- the need for a password or key -- are also its potential dangers. If you forget the encryption password or lose the key file, accessing encrypted information on the SD card may be virtually impossible. With some encryption applications, such as BitLocker or TrueCrypt, it is possible to unlock encrypted drives if you access them normally with a password only and create a key just as a backup protocol. However, if you set up your SD card to require both forms of access for extra security you must have the password and the key to view your data. Consequently, when encrypting your SD card, use passwords that are easy for you to remember -- but hard for others to guess -- and store your encryption key on a USB drive that you keep in a safe place or upload it to a cloud or secure email account.

About the Author

Jeff Grundy has been writing computer-related articles and tutorials since 1995. Since that time, Grundy has written many guides to using various applications that are published on numerous how-to and tutorial sites. Born and raised in South Georgia, Grundy holds a Master of Science degree in mathematics from the Georgia Institute of Technology.

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