Android's KeyStore getKey returning null

Question

I use this small snippet to store a KeyPair in Android's keystore :

KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
ks.load(null);
Certificate[] cert = new Certificate[1];
cert[0] = getCertificate(kp);
ks.setKeyEntry(PRIVATE_KEY_TAG, kp.getPrivate(), null, cert);
ks.setKeyEntry(PUBLIC_KEY_TAG, kp.getPublic(), null, cert);

But when i fetch a key from KeyStore, with ks.getKey(PUBLIC_KEY_TAG, null).getEncoded(), i get this exception :

Attempt to invoke interface method Key.getEncoded() on a null object

And when i try to encrypt a String through a Cipher, i get a :

Unknow key type passed to RSA

Any idea on why this KeyStore is causing problems ? Thanks.

http://stackoverflow.com/questions/5355466/converting-secret-key-into-a-string-and-vice-versa — Krupal Shah, Dec 20 '14 at 18:04
This is about converting Keys to Strings, i might use it in the future but i don't think it will help me with this problem, but thanks btw — Rogue, Dec 20 '14 at 18:05
@Krupal Ugh, different times, 44 points for that horrid code example, I had to rewrite it. — Maarten Bodewes, Dec 20 '14 at 20:26

Maarten Bodewes · Accepted Answer · 2014-12-20T20:35:57.557

2

You can retrieve the public key from the certificate instead. Key stores can be used to store the private key / certificate you hold yourself, or a trusted certificate of another entity. Java (and Android) key stores are mainly targeted at X5.09 based PKI. Storing a public key with a certificate does not make sense, the public key is already contained within the certificate.

So instead try:

ks.getCertificate(PRIVATE_KEY_TAG).getPublicKey().getEncoded();

edited Dec 20 '14 at 20:35

answered Dec 20 '14 at 19:56

Maarten Bodewes

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Yeah, but i still have to store the certificate, which is not working. And I still won't be able to get the private key from the certificate right ? – Rogue Dec 20 '14 at 20:30
YOu can store the private key and cert, get the cert and then get the public key. Just a second, I'll update... – Maarten Bodewes Dec 20 '14 at 20:32
That's a good optimization, however my problem is that i can't fetch anything from KeyStore, so i won't be able to fetch PrivateKey, any clue ? – Rogue Dec 20 '14 at 20:34
Yay, it's working this way, you rocks. I can't understand why this error occurs tho, but as long as it works... Thanks again ! – Rogue Dec 20 '14 at 20:47
Storing public keys is just not really supported. With `getKey` it looks for a private key with corresponding cert. – Maarten Bodewes Dec 20 '14 at 20:54
I see, it seems logical this way. Thanks ;) – Rogue Dec 20 '14 at 20:55
I'm getting this problem again, when i quit the application and start it back, it seems like KeyStore delete its content when app stop, is it possible ? – Rogue Dec 20 '14 at 21:40
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/67392/discussion-between-maarten-bodewes-owlstead-and-rogue). – Maarten Bodewes Dec 20 '14 at 21:41

Android's KeyStore getKey returning null

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