Extracting Private key from pkcs12 and text encryption

Question

I have .p12 file, I am extracting the private key using openssl, I have a password for extracting it.

openssl pkcs12 -in my.p12 -nocerts -out privateKey.pem

And after I get my private key, I'm trying to use that key for encryption:

 public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());
        KeyPair keyPair = readKeyPair(privateKey, "testpassword".toCharArray());
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, keyPair.getPublic());
        byte[] textEncrypted = cipher.doFinal("hello world".getBytes());
        System.out.println("encrypted: "+new String(textEncrypted));
        cipher.init(Cipher.DECRYPT_MODE, keyPair.getPrivate());
        byte[] textDecrypted = cipher.doFinal(textEncrypted);
        System.out.println("decrypted: "+new String(textDecrypted));
    }

    private static KeyPair readKeyPair(File privateKey, char[] keyPassword) throws IOException {
        FileReader fileReader = new FileReader(privateKey);
        PEMReader r = new PEMReader(fileReader, new DefaultPasswordFinder(keyPassword));
        try {
            return (KeyPair) r.readObject(); // this returns null
        } catch (IOException ex) {
            throw new IOException("The private key could not be decrypted", ex);
        } finally {
            r.close();
            fileReader.close();
        }
    }

r.readObject(); returns null. But when I create a private key by myself by this command:

openssl genrsa -out privkey.pem 2048

The above code works fine.

• How can I extract private key from p12 file properly?
• Or is there any way to use p12 file for encrypt/decrypt the text without extracting through command line?

I know it is just PKCS#12 is just archaive file which stores keys.

Solution

I don't know what is wrong with your code, but I have code that reads stuff from a key store. I read the file into a KeyStore instance and then access the key or entry as appropriate. Here are some of the relevant calls:

char[] password;
String alias;
java.security.KeyStore keyStore = KeyStore.getInstance("PKCS12", "BC");
keyStore.load(inputStream, password);
java.security.PrivateKey privateKey = (PrivateKey) keyStore.getKey(alias, password);
java.security.keystore.PrivateKeyEntry privateKeyEntry = (PrivateKeyEntry) keyStore.getEntry(alias, new KeyStore.PasswordProtection(password));

To find the alias of the entry you are interested in, I suggest using keytool (comes with JDK):

keytool -list -v -keystore keystore.pkcs12 -storetype pkcs12

You will be prompted for the keystore password and then get information like this:

Keystore type: PKCS12
Keystore provider: SunJSSE

Your keystore contains 1 entry

Alias name: thealias
Creation date: Aug 30, 2013
Entry type: PrivateKeyEntry
Certificate chain length: 2
[... lots of info about the certificates deleted ...]