SecurePreferences is an Android library that allows developers to securely store sensitive data like passwords, tokens, and settings in SharedPreferences. It encrypts the values using AES-128 encryption and stores each key as a SHA-256 hash. Developers can generate encryption keys from passwords or use default keys. The library provides easy methods to get, set, remove and clear encrypted values from SharedPreferences.

1. Secure-preferenceshttps://github.com/scottyab/secure-preferences
Jain
Newegg developer

2. What is
SharedPreferences
• Save and retrieve persistent key-value pairs of
primitive data types
• Save any primitive data: booleans, floats, ints,
longs, and strings

3. Why use Secure-
preferences
• Protect secret data
1.password
2.token
3.setting

4. Secure mechanism
• Encrypts the values using AES 128, CBC, and
PKCS5
• Each key is stored as a one way SHA 256 hash
• Both keys and values are base64 encoded before
storing into prefs xml file

5. Secure data

6. How to use
public SharedPreferences getSharedPreferences() {
if(mSecurePrefs==null){
mSecurePrefs = new SecurePreferences(this, "", "my_prefs.xml");
SecurePreferences.setLoggingEnabled(true);
}
return mSecurePrefs;
}

7. public SharedPreferences getSharedPreferences1000() {
try {
AesCbcWithIntegrity.SecretKeys myKey =
AesCbcWithIntegrity.generateKeyFromPassword(
Build.SERIAL,AesCbcWithIntegrity.generateSalt(),1000);
return new SecurePreferences(this, myKey, "my_prefs_1000.xml");
} catch (GeneralSecurityException e) {
Log.e(TAG, "Failed to create custom key for SecurePreferences", e);
}
return null;
}
How to use
public SharedPreferences getSharedPreferences() {
if(mSecurePrefs==null){
mSecurePrefs = new SecurePreferences(this, "", "my_prefs.xml");
SecurePreferences.setLoggingEnabled(true);
}
return mSecurePrefs;
}

8. How to use
public SharedPreferences getSharedPreferences() {
if(mSecurePrefs==null){
mSecurePrefs = new SecurePreferences(this, "", "my_prefs.xml");
SecurePreferences.setLoggingEnabled(true);
}
return mSecurePrefs;
}
public SharedPreferences getSharedPreferences1000() {
try {
AesCbcWithIntegrity.SecretKeys myKey =
AesCbcWithIntegrity.generateKeyFromPassword(
Build.SERIAL,AesCbcWithIntegrity.generateSalt(),1000);
return new SecurePreferences(this, myKey, "my_prefs_1000.xml");
} catch (GeneralSecurityException e) {
Log.e(TAG, "Failed to create custom key for SecurePreferences", e);
}
return null;
}
public SecurePreferences getUserPinBasedSharedPreferences(String password){
if(mUserPrefs==null) {
mUserPrefs = new SecurePreferences(this, password, "user_prefs.xml");
}
return mUserPrefs;
}

9. public void onGetButtonClick(View v) {
final String value = getSharedPref().getString(MainActivity.KEY, null);
toast(MainActivity.KEY + "'s, value= " + value);
}
public void onSetButtonClick(View v) {
getSharedPref().edit().putString(MainActivity.KEY, MainActivity.VALUE)
.commit();
toast(MainActivity.KEY + " with enc value:" + MainActivity.VALUE
+ ". Saved");
}
public void onRemoveButtonClick(View v) {
getSharedPref().edit().remove(MainActivity.KEY).commit();
toast("key:" + MainActivity.KEY + " removed from secure prefs");
}
public void onClearAllButtonClick(View v) {
getSharedPref().edit().clear().commit();
updateEncValueDisplay();
toast("All secure prefs cleared");
}

10. Put value
putString(String key, String value)
hashPrefKey(String prefKey)
encrypt(String cleartext)
encrypt(byte[] plaintext, SecretKeys secretKeys)
new CipherTextIvMac(byteCipherText, iv, integrityMac)
toString()
public static CipherTextIvMac encrypt(byte[] plaintext, SecretKeys secretKeys)
throws GeneralSecurityException {
byte[] iv = generateIv();
Cipher aesCipherForEncryption = Cipher.getInstance(CIPHER_TRANSFORMATION);
aesCipherForEncryption.init(Cipher.ENCRYPT_MODE, secretKeys.getConfidentialityKey(), new IvParameterSpec(iv));
/*
* Now we get back the IV that will actually be used. Some Android
* versions do funny stuff w/ the IV, so this is to work around bugs:
*/
iv = aesCipherForEncryption.getIV();
byte[] byteCipherText = aesCipherForEncryption.doFinal(plaintext);
byte[] ivCipherConcat = CipherTextIvMac.ivCipherConcat(iv, byteCipherText);
byte[] integrityMac = generateMac(ivCipherConcat, secretKeys.getIntegrityKey());
return new CipherTextIvMac(byteCipherText, iv, integrityMac);
}

11. putString(String key, String value)
hashPrefKey(String prefKey)
encrypt(String cleartext)
encrypt(byte[] plaintext, SecretKeys secretKeys)
new CipherTextIvMac(byteCipherText, iv, integrityMac)
toString()
public String toString() {
String ivString = Base64.encodeToString(iv, BASE64_FLAGS);
String cipherTextString = Base64.encodeToString(cipherText, BASE64_FLAGS);
String macString = Base64.encodeToString(mac, BASE64_FLAGS);
return String.format(ivString + ":" + macString + ":" + cipherTextString);
}
Put value

12. Get valuegetInt(String key, int defaultValue)
decrypt(final String ciphertext)
new AesCbcWithIntegrity.CipherTextIvMac(ciphertext)
decryptString(cipherTextIvMac, keys)
public static byte[] decrypt(CipherTextIvMac civ, SecretKeys secretKeys)
throws GeneralSecurityException {
byte[] ivCipherConcat = CipherTextIvMac.ivCipherConcat(civ.getIv(), civ.getCipherText());
byte[] computedMac = generateMac(ivCipherConcat, secretKeys.getIntegrityKey());
if (constantTimeEq(computedMac, civ.getMac())) {
Cipher aesCipherForDecryption = Cipher.getInstance(CIPHER_TRANSFORMATION);
aesCipherForDecryption.init(Cipher.DECRYPT_MODE, secretKeys.getConfidentialityKey(),
new IvParameterSpec(civ.getIv()));
return aesCipherForDecryption.doFinal(civ.getCipherText());
} else {
throw new GeneralSecurityException("MAC stored in civ does not match computed MAC.");
}
}
new String(decrypt(civ, secretKeys), encoding)

13. Q & A