In the first example, sensitive user information is stored in cleartext.
In the second and third examples, the code encrypts sensitive information before saving it to the device.
public void testSetSharedPrefs(Context context, String name, String password)
{
{
// BAD - sensitive information saved in cleartext.
SharedPreferences sharedPrefs = context.getSharedPreferences("user_prefs", Context.MODE_PRIVATE);
Editor editor = sharedPrefs.edit();
editor.putString("name", name);
editor.putString("password", password);
editor.commit();
}
{
// GOOD - save sensitive information encrypted with a custom method.
SharedPreferences sharedPrefs = context.getSharedPreferences("user_prefs", Context.MODE_PRIVATE);
Editor editor = sharedPrefs.edit();
editor.putString("name", encrypt(name));
editor.putString("password", encrypt(password));
editor.commit();
}
{
// GOOD - sensitive information saved using the built-in `EncryptedSharedPreferences` class in androidx.
MasterKey masterKey = new MasterKey.Builder(context, MasterKey.DEFAULT_MASTER_KEY_ALIAS)
.setKeyScheme(MasterKey.KeyScheme.AES256_GCM)
.build();
SharedPreferences sharedPreferences = EncryptedSharedPreferences.create(
context,
"secret_shared_prefs",
masterKey,
EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString("name", name);
editor.putString("password", password);
editor.commit();
}
}
private static String encrypt(String cleartext) throws Exception {
// Use an encryption or hashing algorithm in real world. The demo below just returns its
// hash.
MessageDigest digest = MessageDigest.getInstance("SHA-256");
byte[] hash = digest.digest(cleartext.getBytes(StandardCharsets.UTF_8));
String encoded = Base64.getEncoder().encodeToString(hash);
return encoded;
}