Storing key using KeyStore in Android

问题

I am using KeyStore to protect my private key but when the line:

FileOutputStream fos = ctx.openFileOutput("bs.keystore", Context.MODE_PRIVATE);

is executed I have this exception:

'java.lang.NullPointerException'.

I don't understand where is the problem.

Code:

    private Context ctx;

    public DataSec(Context ctx) 
    {
    ctx = this.ctx;
    }

    public void genKey() throws Exception
    {
    SecretKey key = KeyGenerator.getInstance("AES").generateKey();

    KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
    ks.load(null, "clavedekey".toCharArray());

    PasswordProtection pass = new PasswordProtection("fedsgjk".toCharArray());
    KeyStore.SecretKeyEntry skEntry = new KeyStore.SecretKeyEntry(key);
    ks.setEntry("secretKeyAlias", skEntry, pass);

    FileOutputStream fos = ctx.openFileOutput("bs.keystore", Context.MODE_PRIVATE);
    ks.store(fos, "clavedekey".toCharArray());
    fos.close();        
    }

Thanks for the Help!

回答1:

Change:

public DataSec(Context ctx) 
{
ctx = this.ctx;
}

To

public DataSec(Context ctx) 
{
    this.ctx = ctx;
}

Right now, you're assigning the context parameter in the method to the same value as the global one, which is null. Due to this, your context doesn't actually get stored.

来源：https://stackoverflow.com/questions/14972316/storing-key-using-keystore-in-android