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@JosiasSena

JosiasSena/DeCryptor.java

Last active September 12, 2023 12:40
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Encryptor and Decryptor for data encryption.decryption using the Android KeyStore.
Raw
DeCryptor.java
/**
_____ _____ _
| __ \ / ____| | |
| | | | ___| | _ __ _ _ _ __ | |_ ___ _ __
| | | |/ _ \ | | '__| | | | '_ \| __/ _ \| '__|
| |__| | __/ |____| | | |_| | |_) | || (_) | |
|_____/ \___|\_____|_| \__, | .__/ \__\___/|_|
__/ | |
|___/|_|
*/
class DeCryptor {
private static final String TRANSFORMATION = "AES/GCM/NoPadding";
private static final String ANDROID_KEY_STORE = "AndroidKeyStore";
private KeyStore keyStore;
DeCryptor() throws CertificateException, NoSuchAlgorithmException, KeyStoreException,
IOException {
initKeyStore();
}
private void initKeyStore() throws KeyStoreException, CertificateException,
NoSuchAlgorithmException, IOException {
keyStore = KeyStore.getInstance(ANDROID_KEY_STORE);
keyStore.load(null);
}
String decryptData(final String alias, final byte[] encryptedData, final byte[] encryptionIv)
throws UnrecoverableEntryException, NoSuchAlgorithmException, KeyStoreException,
NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, IOException,
BadPaddingException, IllegalBlockSizeException, InvalidAlgorithmParameterException {
final Cipher cipher = Cipher.getInstance(TRANSFORMATION);
final GCMParameterSpec spec = new GCMParameterSpec(128, encryptionIv);
cipher.init(Cipher.DECRYPT_MODE, getSecretKey(alias), spec);
return new String(cipher.doFinal(encryptedData), "UTF-8");
}
private SecretKey getSecretKey(final String alias) throws NoSuchAlgorithmException,
UnrecoverableEntryException, KeyStoreException {
return ((KeyStore.SecretKeyEntry) keyStore.getEntry(alias, null)).getSecretKey();
}
}
Raw
EnCryptor.java
/**
______ _____ _
| ____| / ____| | |
| |__ _ __ | | _ __ _ _ _ __ | |_ ___ _ __
| __| | '_ \| | | '__| | | | '_ \| __/ _ \| '__|
| |____| | | | |____| | | |_| | |_) | || (_) | |
|______|_| |_|\_____|_| \__, | .__/ \__\___/|_|
__/ | |
|___/|_|
*/
class EnCryptor {
private static final String TRANSFORMATION = "AES/GCM/NoPadding";
private static final String ANDROID_KEY_STORE = "AndroidKeyStore";
private byte[] encryption;
private byte[] iv;
EnCryptor() {
}
byte[] encryptText(final String alias, final String textToEncrypt)
throws UnrecoverableEntryException, NoSuchAlgorithmException, KeyStoreException,
NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, IOException,
InvalidAlgorithmParameterException, SignatureException, BadPaddingException,
IllegalBlockSizeException {
final Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(alias));
iv = cipher.getIV();
return (encryption = cipher.doFinal(textToEncrypt.getBytes("UTF-8")));
}
@NonNull
private SecretKey getSecretKey(final String alias) throws NoSuchAlgorithmException,
NoSuchProviderException, InvalidAlgorithmParameterException {
final KeyGenerator keyGenerator = KeyGenerator
.getInstance(KeyProperties.KEY_ALGORITHM_AES, ANDROID_KEY_STORE);
keyGenerator.init(new KeyGenParameterSpec.Builder(alias,
KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
.setBlockModes(KeyProperties.BLOCK_MODE_GCM)
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
.build());
return keyGenerator.generateKey();
}
byte[] getEncryption() {
return encryption;
}
byte[] getIv() {
return iv;
}
}
Raw
SampleUsage.java
/**
_____ _ _ _
/ ____| | | | | | |
| (___ __ _ _ __ ___ _ __ | | ___ | | | |___ __ _ __ _ ___
\___ \ / _` | '_ ` _ \| '_ \| |/ _ \ | | | / __|/ _` |/ _` |/ _ \
____) | (_| | | | | | | |_) | | __/ | |__| \__ \ (_| | (_| | __/
|_____/ \__,_|_| |_| |_| .__/|_|\___| \____/|___/\__,_|\__, |\___|
| | __/ |
|_| |___/
*/
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
private static final String SAMPLE_ALIAS = "MYALIAS";
@BindView (R.id.toolbar)
Toolbar toolbar;
@BindView (R.id.ed_text_to_encrypt)
EditText edTextToEncrypt;
@BindView (R.id.tv_encrypted_text)
TextView tvEncryptedText;
@BindView (R.id.tv_decrypted_text)
TextView tvDecryptedText;
private EnCryptor encryptor;
private DeCryptor decryptor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
setSupportActionBar(toolbar);
encryptor = new EnCryptor();
try {
decryptor = new DeCryptor();
} catch (CertificateException | NoSuchAlgorithmException | KeyStoreException |
IOException e) {
e.printStackTrace();
}
}
@OnClick ({R.id.btn_encrypt, R.id.btn_decrypt})
public void onClick(final View view) {
final int id = view.getId();
switch (id) {
case R.id.btn_encrypt:
encryptText();
break;
case R.id.btn_decrypt:
decryptText();
break;
}
}
private void decryptText() {
try {
tvDecryptedText.setText(decryptor
.decryptData(SAMPLE_ALIAS, encryptor.getEncryption(), encryptor.getIv()));
} catch (UnrecoverableEntryException | NoSuchAlgorithmException |
KeyStoreException | NoSuchPaddingException | NoSuchProviderException |
IOException | InvalidKeyException e) {
Log.e(TAG, "decryptData() called with: " + e.getMessage(), e);
} catch (IllegalBlockSizeException | BadPaddingException | InvalidAlgorithmParameterException e) {
e.printStackTrace();
}
}
private void encryptText() {
try {
final byte[] encryptedText = encryptor
.encryptText(SAMPLE_ALIAS, edTextToEncrypt.getText().toString());
tvEncryptedText.setText(Base64.encodeToString(encryptedText, Base64.DEFAULT));
} catch (UnrecoverableEntryException | NoSuchAlgorithmException | NoSuchProviderException |
KeyStoreException | IOException | NoSuchPaddingException | InvalidKeyException e) {
Log.e(TAG, "onClick() called with: " + e.getMessage(), e);
} catch (InvalidAlgorithmParameterException | SignatureException |
IllegalBlockSizeException | BadPaddingException e) {
e.printStackTrace();
}
}
}
@ankitbaderiya
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And how to delete key?

@Matthcw
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Matthcw commented Apr 8, 2021

Hi, what is the license on this code?

@JosiasSena
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Author

@Matthcw none, feel free to do whatever you want with it

@Matthcw
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Matthcw commented Apr 9, 2021 via email

@javimar
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javimar commented Sep 22, 2021

Hello, my question is if there is a way to retrieve a stored value with just knowing the alias. The thing is that the method to retreive it is coupled with the encryption and the iv... thanks!!

@AMoeid7
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AMoeid7 commented Jun 27, 2022

it gave error javax.crypto.illegalblocksizeexception while decrypting the code could you help me out

@Heritiana-william
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Thanks for sharing! This code is really helpful!
Anyway, can i use this code for encrypting/decrypting android fingerprint information (data)?

@luskan
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luskan commented Jul 13, 2023

If someone needs it, I have created Example app for this code: https://github.com/luskan/EncryptDecryptApp

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