Java Cryptography - Storing keys


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The Keys and certificates used/generated are stored in a data base called as keystore. By default this database is stored in a file named .keystore.

You can access the contents of this database using the KeyStore class of the java.security package. This manages three different entries namely, PrivateKeyEntry, SecretKeyEntry, TrustedCertificateEntry.

  • PrivateKeyEntry
  • SecretKeyEntry
  • TrustedCertificateEntry

Storing a Key in keystore

In this section, we will learn how to store a key in a keystore. To store a key in the keystore, follow the steps given below.

Step 1: Create a KeyStore object

The getInstance() method of the KeyStore class of the java.security package accepts a string value representing the type of the keystore and returns a KeyStore object.

Create an object of the KeyStore class using the getInstance() method as shown below.

//Creating the KeyStore object
KeyStore keyStore = KeyStore.getInstance("JCEKS");

Step 2: Load the KeyStore object

The load() method of the KeyStore class accepts a FileInputStream object representing the keystore file and a String parameter specifying the password of the KeyStore.

In general, the KeyStore is stored in the file named cacerts, in the location C:/Program Files/Java/jre1.8.0_101/lib/security/ and its default password is changeit, load it using the load() method as shown below.

//Loading the KeyStore object
char[] password = "changeit".toCharArray();
String path = "C:/Program Files/Java/jre1.8.0_101/lib/security/cacerts";
java.io.FileInputStream fis = new FileInputStream(path);
keyStore.load(fis, password);

Step 3: Create the KeyStore.ProtectionParameter object

Instantiate the KeyStore.ProtectionParameter as shown below.

//Creating the KeyStore.ProtectionParameter object
KeyStore.ProtectionParameter protectionParam = new KeyStore.PasswordProtection(password);

Step 4: Create a SecretKey object

Create the SecretKey (interface) object by instantiating its Sub class SecretKeySpec. While instantiating you need to pass password and algorithm as parameters to its constructor as shown below.

//Creating SecretKey object
SecretKey mySecretKey = new SecretKeySpec(new String(keyPassword).getBytes(), "DSA");

Step 5: Create a SecretKeyEntry object

Create an object of the SecretKeyEntry class by passing the SecretKey object created in the above step as shown below.

//Creating SecretKeyEntry object
KeyStore.SecretKeyEntry secretKeyEntry = new KeyStore.SecretKeyEntry(mySecretKey);

Step 6: Set an entry to the KeyStore

The setEntry() method of the KeyStore class accepts a String parameter representing the keystore entry alias, a SecretKeyEntry object, a ProtectionParameter object and, stores the entry under the given alias.

Set the entry to the keystore using the setEntry() method as shown below.

//Set the entry to the keystore
keyStore.setEntry("secretKeyAlias", secretKeyEntry, protectionParam);

Example

The following example stores keys into the keystore existing in the “cacerts” file (windows 10 operating system).

import java.io.FileInputStream;
import java.security.KeyStore;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class StoringIntoKeyStore{
   public static void main(String args[]) throws Exception {
      //Creating the KeyStore object
      KeyStore keyStore = KeyStore.getInstance("JCEKS");

      //Loading the KeyStore object
      char[] password = "changeit".toCharArray();
      String path = "C:/Program Files/Java/jre1.8.0_101/lib/security/cacerts";
      java.io.FileInputStream fis = new FileInputStream(path);
      keyStore.load(fis, password);
      
      //Creating the KeyStore.ProtectionParameter object
      KeyStore.ProtectionParameter protectionParam = new KeyStore.PasswordProtection(password);

      //Creating SecretKey object
      SecretKey mySecretKey = new SecretKeySpec("myPassword".getBytes(), "DSA");
      
      //Creating SecretKeyEntry object
      KeyStore.SecretKeyEntry secretKeyEntry = new KeyStore.SecretKeyEntry(mySecretKey);
      keyStore.setEntry("secretKeyAlias", secretKeyEntry, protectionParam);

      //Storing the KeyStore object
      java.io.FileOutputStream fos = null;
      fos = new java.io.FileOutputStream("newKeyStoreName");
      keyStore.store(fos, password);
      System.out.println("data stored");
   }
}

Output

The above program generates the following output −

System.out.println("data stored");

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