Develop Reference

How to create accessible PrivateKeys?

I've stumpled upon following Problem:
I need to create a KeyPair where I need to access the PrivateKey's getEncoded() once, before inserting it into the AndroidKeyStore.
When generating a Key via AndroidKeyStore, the resulting Keys getEncoded() method returns null (as intended as an extra key protection mechanism).
This is how I generate a Key using a KeyGenParameterSpec (targeting only devices above Android.M):
public AlgorithmParameterSpec createSpec(){
Calendar start = new GregorianCalendar();
Calendar end = new GregorianCalendar();
end.add(Calendar.YEAR, 1);
String alias = "myKeyAlias";
AlgorithmParameterSpec spec = new KeyGenParameterSpec.Builder(alias,
KeyProperties.PURPOSE_SIGN | KeyProperties.PURPOSE_VERIFY |
KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
.setCertificateSubject(new X500Principal("CN=" + alias))
.setDigests(KeyProperties.DIGEST_SHA256)
.setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1)
.setCertificateSerialNumber(BigInteger.valueOf(1337))
.setCertificateNotBefore(start.getTime())
.setCertificateNotAfter(end.getTime())
.build();
return spec;
}
public KeyPair generateKeyPairInKeystore(AlgorithmParameterSpec spec){
KeyPairGenerator kpGenerator = KeyPairGenerator
.getInstance("RSA", "AndroidKeyStore");
kpGenerator.initialize(spec);
KeyPair kp = kpGenerator.generateKeyPair();
//here kp.getPrivate().getEncrypted() doesn't give me the key
return kp;
}
public KeyPair generateKeyPair(AlgorithmParameterSpec spec){
KeyPairGenerator kpGenerator = KeyPairGenerator
.getInstance(SecurityConstants.TYPE_RSA);
kpGenerator.initialize(spec);
KeyPair kp = kpGenerator.generateKeyPair();
//I cannot receive the encrypted Key here either
//kp.getPrivate().getEncrypted();
return kp;
}
These Keys are generated inside AndroidKeyStore so they are automatically stored there. But I cannot access getEncrypted() to send it to a trusted Server.
So what I'm missing is:
How to create a PrivateKey where getEncoded() is accessible?
How do I store it inside Androids secure KeyStore (as I need to provide Certificates along)?

Generate symmetric key and store in android keystore

I am attempting to do the following,
Generate a secret key for sqlcipher.
Store the secret in android keystore.
Retrieve secret from keystore.
I've found nearly everything I need, but I'm having trouble getting the below pieces of code working together.
Pre: Setup keystore
private void InitialiseKeystore() throws ... {
KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
keyStore.load(null);
boolean containsAlias = keyStore.containsAlias("com.example.myapp");
KeyPairGenerator kpg = KeyPairGenerator.getInstance(
KeyProperties.KEY_ALGORITHM_EC, "AndroidKeyStore");
if (!containsAlias) {
kpg.initialize(new KeyGenParameterSpec.Builder(
alias,
KeyProperties.PURPOSE_SIGN | KeyProperties.PURPOSE_VERIFY)
.setDigests(KeyProperties.DIGEST_SHA256,
KeyProperties.DIGEST_SHA512)
.build());
KeyPair kp = kpg.generateKeyPair();
}
Generating symmetric key
I found these good examples but they're creating public/private keys, as the same with many others, so a bit confused there, but I have the following.
KeyGenerator keyGen = KeyGenerator.getInstance("AES");
keyGen.init(128); //<------------------------------------- [ERRORS HERE]
SecretKey secretKey = keyGen.generateKey();
Storing in keystore
Reviewing the documentation, it seems I should use KeyStore.SecretKeyEntry to store secrets, so this is what I currently have,
KeyStore.SecretKeyEntry secretKeyEntry = new KeyStore.SecretKeyEntry(secretKey);
keyStore.setKeyEntry("key1", secretKeyEntry.getSecretKey().getEncoded(), null);
Retrieving from keystore
private static byte[] getRawSecret() throws Exception {
KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
keyStore.load(null);
byte[] raw = keyStore.getKey("key1", null).getEncoded();
return raw;
}
Here's where it goes wrong, in another function I'm trying to call getRawSecret().
SQLiteDatabase.openOrCreateDatabase(databaseFile, getRawSecret().toString(), null);
ERROR: Cannot initialize without a android.security.keystore.KeyGenParameterSpec parameter
So question, how do I create a symmetric key and store in keystore? As the error is telling me to use KeyGenParameterSpec but as in the examples linked above, this wants to create public/private keys. What am I doing wrong?

I used this to solve my issue,
Guide: https://medium.com/#josiassena/using-the-android-keystore-system-to-store-sensitive-information-3a56175a454b
Code: https://gist.github.com/JosiasSena/3bf4ca59777f7dedcaf41a495d96d984

android.security.KeyStoreException: Incompatible digest when signing with RSA

When I try to sign a hashed value in my android app that I get from outside, I get the above mentioned exception.
The code for generating the keypair is:
public static KeyPair generateKeyPair(Context context, String username) throws Exception {
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA, ANDROID_KEY_STORE);
Calendar start = Calendar.getInstance();
Calendar end = Calendar.getInstance();
end.add(Calendar.YEAR, 1);
AlgorithmParameterSpec parameterSpec;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
parameterSpec = new KeyGenParameterSpec.Builder(MY_KEY_ALIAS, KeyProperties.PURPOSE_SIGN)
.setKeySize(KEY_SIZE)
.setCertificateSubject(usernameToSubject(username))
.setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA1)
.setCertificateNotBefore(start.getTime())
.setCertificateNotAfter(end.getTime())
.setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1)
.build();
} else {
// Here I build the keys for older versions. This is not part of my problem
}
keyPairGenerator.initialize(parameterSpec);
return keyPairGenerator.generateKeyPair();
}
Later on I sign the hash I get from outside:
public static byte[] signHash(byte[] hashToSign) {
try {
KeyStore keyStore = KeyStore.getInstance(ANDROID_KEY_STORE);
keyStore.load(null);
KeyStore.PrivateKeyEntry keyEntry = (KeyStore.PrivateKeyEntry)keyStore.getEntry(MY_KEY_ALIAS, null);
PrivateKey privateKey = keyEntry.getPrivateKey();
DigestAlgorithmIdentifierFinder hashAlgorithmFinder = new DefaultDigestAlgorithmIdentifierFinder();
AlgorithmIdentifier hashingAlgorithmIdentifier = hashAlgorithmFinder.find(KeyProperties.DIGEST_SHA256);
DigestInfo digestInfo = new DigestInfo(hashingAlgorithmIdentifier, hashToSign);
byte[] hashToEncrypt = digestInfo.getEncoded();
Cipher cipher = Cipher.getInstance("RSA/ECB/Pkcs1Padding");
cipher.init(Cipher.ENCRYPT_MODE, privateKey); // <= the exception is thrown here
return cipher.doFinal(hashToEncrypt);
} catch (Throwable e) {
Log.e("KeyStoreWrapper", "Error while signing: ", e);
}
return "Could not sign the message.".getBytes(StandardCharsets.UTF_16LE);
}
The error I get is:
java.security.InvalidKeyException: Keystore operation failed
at android.security.KeyStore.getInvalidKeyException(KeyStore.java:1004)
at android.security.KeyStore.getInvalidKeyException(KeyStore.java:1024)
at android.security.keystore.KeyStoreCryptoOperationUtils.getInvalidKeyExceptionForInit(KeyStoreCryptoOperationUtils.java:53)
at android.security.keystore.KeyStoreCryptoOperationUtils.getExceptionForCipherInit(KeyStoreCryptoOperationUtils.java:89)
at android.security.keystore.AndroidKeyStoreCipherSpiBase.ensureKeystoreOperationInitialized(AndroidKeyStoreCipherSpiBase.java:263)
at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineInit(AndroidKeyStoreCipherSpiBase.java:108)
at javax.crypto.Cipher.tryTransformWithProvider(Cipher.java:612)
at javax.crypto.Cipher.tryCombinations(Cipher.java:532)
at javax.crypto.Cipher.getSpi(Cipher.java:437)
at javax.crypto.Cipher.init(Cipher.java:815)
at javax.crypto.Cipher.init(Cipher.java:774)
at de.new_frontiers.m2fa.security.KeyStoreWrapper.signHash(KeyStoreWrapper.java:186)
at de.new_frontiers.m2fa.bluetooth.BluetoothHandler.handleMessage(BluetoothHandler.java:93)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: android.security.KeyStoreException: Incompatible digest
at android.security.KeyStore.getKeyStoreException(KeyStore.java:944)
at android.security.KeyStore.getInvalidKeyException(KeyStore.java:1024) 
at android.security.keystore.KeyStoreCryptoOperationUtils.getInvalidKeyExceptionForInit(KeyStoreCryptoOperationUtils.java:53) 
at android.security.keystore.KeyStoreCryptoOperationUtils.getExceptionForCipherInit(KeyStoreCryptoOperationUtils.java:89) 
at android.security.keystore.AndroidKeyStoreCipherSpiBase.ensureKeystoreOperationInitialized(AndroidKeyStoreCipherSpiBase.java:263) 
at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineInit(AndroidKeyStoreCipherSpiBase.java:108) 
at javax.crypto.Cipher.tryTransformWithProvider(Cipher.java:612) 
at javax.crypto.Cipher.tryCombinations(Cipher.java:532) 
at javax.crypto.Cipher.getSpi(Cipher.java:437) 
at javax.crypto.Cipher.init(Cipher.java:815) 
at javax.crypto.Cipher.init(Cipher.java:774) 
at com.mycompany.security.KeyStoreWrapper.signHash(KeyStoreWrapper.java:186) 
In the android documentation I see:
For signing and verification operations a digest must be specified in
the additional_params argument of begin. If the specified digest is
not in the digests associated with the key, the operation must fail
with KM_ERROR_INCOMPATIBLE_DIGEST.
But as you can see I create the keypair with KeyProperties.DIGEST_SHA256 and set the DigestInfo to the same algorithm. So I don't understand why I get the error "Incompatible digest". Can anybody shed some light on this?
Oh, for anybody who is wondering why I don't use Signature.sign(): this would need the plaintext to sign then creates a hash, a DigestInfo and then encrypts it with the private key. I already get the hash from outside and this is something I cannot change.
 

Encryption with private key using RSA/ECB/PKCS1Padding is available on AndroidKeyStore from Android 18, so you should be able to perform a valid digital signature with the received hash.
I guess the problem is setting the key usage to sign and not for encryption (that is really what you want the key for). Try this:
parameterSpec = new KeyGenParameterSpec.Builder(MY_KEY_ALIAS, KeyProperties.PURPOSE_ENCRYPT | | KeyProperties.PURPOSE_DECRYPT)
.setKeySize(KEY_SIZE)
.setCertificateSubject(usernameToSubject(username))
.setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA1)
.setCertificateNotBefore(start.getTime())
.setCertificateNotAfter(end.getTime())
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
.build();
Check also that the hashToSign is really SHA-256 (32 bytes)

pedrofbs answer helped me to get things right in the end. I had already changed the purpose for the key to the value mentioned in my comment to his answer: KeyProperties.PURPOSE_SIGN|KeyProperties.PURPOSE_ENCRYPT|Key‌​Properties.PURPOSE_D‌​ECRYPT, but forgot to call .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1). So a big thank you, pedrofs, for spotting this!
Unfortunately it still did not work. Fiddling around with different settings on the key I realized that I hadn't protected the device I use for testing with a password, pin or something else. So adding .setUserAuthenticationRequired(false) to the KeyGenParameterSpec did the trick. I know that this is not safe and has to be changed but at the moment I'm just doing a proof of concept, so that's fine. :-)
In case somebody else stumbles upon this problem: here is the whole working code for the key generation:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
parameterSpec = new KeyGenParameterSpec.Builder(LOGON_KEY_ALIAS, KeyProperties.PURPOSE_SIGN|KeyProperties.PURPOSE_ENCRYPT|KeyProperties.PURPOSE_DECRYPT)
.setKeySize(KEY_SIZE)
.setUserAuthenticationRequired(false)
.setCertificateSubject(usernameToSubject(username))
.setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA1)//, KeyProperties.DIGEST_NONE, KeyProperties.DIGEST_SHA224, KeyProperties.DIGEST_SHA384, KeyProperties.DIGEST_SHA512, KeyProperties.DIGEST_MD5)
.setCertificateNotBefore(start.getTime())
.setCertificateNotAfter(end.getTime())
.setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1)
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
.build();
}

Android KeyStore - keys not always persisted

In my app we are using RSA key, that the app generate (using android key store) on the first launch. From unknown reason, the app failed to retrieved the key from the key store on some of the devices. I've checked the logs, and I could not find a correlation between this bug to a specific OS version or to a specific device model. Also, I know for sure the app tried to read it only after the key created. So - my question is that: As far as I know, android key store should be persistent. What can cause such a bug?
Bellow are relevant code samples.
Key generation:
try {
KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA", keyStore.getProvider());
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M){
KeyGenParameterSpec spec;
spec = new KeyGenParameterSpec.Builder(alias, KeyProperties.PURPOSE_DECRYPT | KeyProperties.PURPOSE_ENCRYPT| KeyProperties.PURPOSE_SIGN| KeyProperties.PURPOSE_VERIFY)
.setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512)
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
.setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1)
.setKeySize(2048)
.build();
generator.initialize(spec);
} else {
Calendar start = new GregorianCalendar();
Calendar end = new GregorianCalendar();
end.add(Calendar.YEAR, 500);
KeyPairGeneratorSpec spec = new KeyPairGeneratorSpec.Builder(context)
.setAlias(alias)
.setSubject(new X500Principal("CN="+ subject))
.setSerialNumber(BigInteger.valueOf(new Random().nextInt(Integer.MAX_VALUE)))
.setStartDate(start.getTime())
.setEndDate(end.getTime())
.setKeySize(2048)
.build();
generator.initialize(spec);
}
return generator.generateKeyPair();
} catch (Exception e) {
logger.warn("Failed to create private key in store", e);
return null;
}
The keystore itself intialized using the following code:
KeyStore androidKeyStore = KeyStore.getInstance("AndroidKeyStore");
androidKeyStore.load(null);
return androidKeyStore;
And we use the following code to retrieve the key, the bug is that on some devices the keystore returns null:
try {
Key key = keyStore.getKey(alias, null);
if (key == null){
logger.warn("Key not found in key store");
return null;
}
if (key instanceof PrivateKey) {
// Get certificate of public key
Certificate cert = keyStore.getCertificate(alias);
// Get public key
PublicKey publicKey = cert.getPublicKey();
// Return a key pair
return new KeyPair(publicKey, (PrivateKey) key);
} else {
logger.warn("Key found, but not from current type. type found: " + key.getClass().getSimpleName());
}
return null;
}catch (Exception e){
logger.warn("Failed to get private key in store", e);
return null;
}
Thanks,
Omer

Just in case someone will run into the same problem:
I've found out that Azure Active Directory library for android suffer from similar issue, and from reading the code I've saw they linked to two issues that are similar to this problem and to another issue we have. Because of that I am planing to use keystore based on p12 file, stored in the app private storage.

Is it that you appear to lose your keys immediately after generation or some time later they are lost? Take a look at this question AndroidKeyStore getEntry is consistently failing after certain point which links to this great article: http://doridori.github.io/android-security-the-forgetful-keystore/
The moral of this story is if you use the AndroidKeyStore be prepared to lose your keys under certain circumstances!

how to get Key_name for fingerprint scanner?

Fingerprint API preview for Android N is found here with Sample App Sample App .As of this writing, createKey() in this method specify key_name,i don't know about key_name,Please anyone tell about key_name
/** Alias for our key in the Android Key Store */
private static final String KEY_NAME = "my_key";
public void createKey() {
// The enrolling flow for fingerprint. This is where you ask the user to set up fingerprint
// for your flow. Use of keys is necessary if you need to know if the set of
// enrolled fingerprints has changed.
try {
mKeyStore.load(null);
// Set the alias of the entry in Android KeyStore where the key will appear
// and the constrains (purposes) in the constructor of the Builder
mKeyGenerator.init(new KeyGenParameterSpec.Builder(KEY_NAME,
KeyProperties.PURPOSE_ENCRYPT |
KeyProperties.PURPOSE_DECRYPT)
.setBlockModes(KeyProperties.BLOCK_MODE_CBC)
// Require the user to authenticate with a fingerprint to authorize every use
// of the key
.setUserAuthenticationRequired(true)
.setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_PKCS7)
.build());
mKeyGenerator.generateKey();
} catch (NoSuchAlgorithmException | InvalidAlgorithmParameterException
| CertificateException | IOException e) {
throw new RuntimeException(e);
}
}
this my part of code,here what is KEY_NAME and key_name get from where

Just run this cmd on your terminal
/home/nn1android01user/Documents/Keystor_alicante/gerber_keystore.jks ->
this is your keystore file path
gerber -> alias name
keytool -exportcert -alias gerber -keystore /home/nn1android01user/Documents/Keystor_alicante/gerber_keystore.jks | openssl sha1 -binary | openssl base64