How can I export my private key from a Java Keytool keystore?

Question

I would like to export my private key from a Java Keytool keystore, so I can use it with openssl. How can I do that?

Answer 1

Use Java keytool to convert from JKS to P12...

Export from keytool's proprietary format (called "JKS") to standardized format PKCS #12:

keytool -importkeystore \
    -srckeystore keystore.jks \
    -destkeystore keystore.p12 \
    -deststoretype PKCS12 \
    -srcalias <jkskeyalias> \
    -deststorepass <password> \
    -destkeypass <password>

...then use openssl to export from P12 to PEM

Export certificate using openssl:

openssl pkcs12 -in keystore.p12  -nokeys -out cert.pem

Export unencrypted private key:

openssl pkcs12 -in keystore.p12  -nodes -nocerts -out key.pem

Answer 2

Since Java 6, you can import/export private keys into PKCS#12 (.p12) files using keytool, with the option -importkeystore (not available in previous versions).

For example:

keytool -importkeystore -srckeystore existing-store.jks -destkeystore new-store.p12 -deststoretype PKCS12

The PKCS12 keystore type is also supported as a standard keystore type in the default Oracle/Sun security provider.

Answer 3

Try "Keystore Explorer"

I agree with Bruno. Keytool is ultimate tool when dealing with Java keystore, but there is one fancy and quite powerful free tool: Keystore explorer

I use it a lot and never had a need for something else.

Answer 4

If anyone finds themselves here trying to get a private key out of a JCEKS type keystore, I found that the keytool and openssl instructions described in other answers did not work. I had to use the below Java class to get the key out.

import sun.misc.BASE64Encoder;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.security.*;

public class ExportPrivateKey
{
    private File keystoreFile;
    private String keyStoreType;
    private char[] keyStorePassword;
    private char[] keyPassword;
    private String alias;
    private File exportedFile;

    public void export() throws Exception {
        KeyStore keystore = KeyStore.getInstance(keyStoreType);
        BASE64Encoder encoder = new BASE64Encoder();
        keystore.load(new FileInputStream(keystoreFile), keyStorePassword);
        Key key = keystore.getKey(alias, keyPassword);
        String encoded = encoder.encode(key.getEncoded());
        FileWriter fw = new FileWriter(exportedFile);
        fw.write("---BEGIN PRIVATE KEY---\n");
        fw.write(encoded);
        fw.write("\n");
        fw.write("---END PRIVATE KEY---");
        fw.close();
    }

    public static void main(String args[]) throws Exception {
        ExportPrivateKey export = new ExportPrivateKey();
        export.keystoreFile = new File(args[0]);
        export.keyStoreType = args[1];
        export.keyStorePassword = args[2].toCharArray();
        export.alias = args[3];
        export.keyPassword = args[4].toCharArray();
        export.exportedFile = new File(args[5]);
        export.export();
    }
}

Usage:

javac ExportPrivateKey.java
java ExportPrivateKey <path_to_keystore> JCEKS <keystore_password> “<key_alias>” <key_password> <output_file_name>

Answer 5

There is a format that allows the moving of private keys is called PKCS#12. This format came later in the evolution of PKI certificates and related keystores as the need evolved. If you consider the chain of trust issues created by accessing and transporting the private key you can see why it was not included in the initial features but rather came after pressure by operational need. This is the core reason for the challenge.

Java keystores were one of the initial users of the PKCS#12 format but as importers not exporters. It appears the security design of Java keystores still does not support exporting private keys as a standard feature. Again, there are good security reasons for this fact. That said, private routines have been written as referenced here: http://www.startux.de/index.php/java/44-dealing-with-java-keystoresyvComment44

If at all possible I would consider creating a new keystore in OpenSSL and new keys rather than trying to pry out the private key from the Java keystore. By opening the Java keystore and extracting the private key one is moving beyond the designed security features. The export PKCS#12 feature has been desired for many years but still is not supported in Java. My thinking is that is for very good cryptologic reasons thus I would be leary of taking that step unless it was absolutely necessary.