Basic Sample in keypair generation using android keystore in api level 18

generateKeyPairAndroidKeyStoreAPI18.java

/*
*
*	The API is outlined in the 'Security' section of the 4.3 new API introduction page, 
*	and details can be found in the official SDK reference, so we will only review it briefly. 
*	Instead of introducing yet another Android-specific API, key store access is exposed via standard JCE APIs, 
*	namely KeyGenerator and KeyStore. Both are backed by a new Android JCE provider, 
*	AndroidKeyStoreProvider and are accessed by passing "AndroidKeyStore" as the type 
*	parameter of the respective factory methods (those APIs were actually available in 4.2 as well, 
*	but were not public). For a full sample detailing their usage, 
*	refer to the BasicAndroidKeyStore project in the Android SDK. 
*	To introduce their usage briefly, first you create a KeyPairGeneratorSpec that describes 
*	the keys you want to generate (including a self-signed certificate), initialize a KeyPairGenerator 
*	with it and then generate the keys by calling generateKeyPair(). 
*	The most important parameter is the alias, which you then pass to KeyStore.getEntry() in order to get a handle to the 
*	generated keys later. 
*	There is currently no way to specify key size or type and generated keys default to 2048 bit RSA. 
*	Here's how all this looks  like:
*/

// generate a key pair
Context ctx = getContext();
Calendar notBefore = Calendar.getInstance()
Calendar notAfter = Calendar.getInstance();
notAfter.add(1, Calendar.YEAR);
KeyPairGeneratorSpec spec = new KeyPairGeneratorSpec.Builder(ctx)
                .setAlias("key1")
                .setSubject(
                        new X500Principal(String.format("CN=%s, OU=%s", alais,
                                ctx.getPackageName())))
                .setSerialNumber(BigInteger.ONE).setStartDate(notBefore.getTime())
                .setEndDate(notAfter.getTime()).build();

KeyPairGenerator kpGenerator = KeyPairGenerator.getInstance("RSA", "AndroidKeyStore");
kpGenerator.initialize(spec);
KeyPair kp = kpGenerator.generateKeyPair();

// in another part of the app, access the keys
KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
keyStore.load(null);
KeyStore.PrivateKeyEntry keyEntry = (KeyStore.PrivateKeyEntry)keyStore.getEntry("key1", null);
RSAPublicKey pubKey = (RSAPublicKey)keyEntry.getCertificate().getPublicKey();
RSAPrivateKey privKey = (RSAPrivateKey) keyEntry.getPrivateKey();

/* original sample code from https://nelenkov.blogspot.com */