Read public key from file in keystore

Question

Hi I want to extract public key from KeyStore using Java code

I am creating a keystore

keytool -genkey -alias mykeystore -keyalg RSA -keystore mykeystore.jks -keysize 2048

And exporting the public into another file

keytool -export -alias mykeystore -keystore mykeystore.jks -rfc -file publickey.cert

How can I get the Public Key String from keystore or the publickey.cert file using the Java code?

Thanks.

UPDATE

public static void main(String[] args) {

    try {

        FileInputStream is = new FileInputStream("/home/myuser/my-keystore/mykeystore.jks");
        KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
        String password = "myuserpass";
        char[] passwd = password.toCharArray();
        keystore.load(is, passwd);
        String alias = "mykeystore";
        Key key = keystore.getKey(alias, passwd);
        if (key instanceof PrivateKey) {
          // Get certificate of public key
          Certificate cert = keystore.getCertificate(alias);
          // Get public key
          PublicKey publicKey = cert.getPublicKey();

          String publicKeyString = Base64.encodeBase64String(publicKey
                    .getEncoded());
          System.out.println(publicKeyString);

        }

    } catch (Exception e) {
        e.printStackTrace();
    }
}

Then it is giving like

MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAiG2FjSuXrraYuh0TyRNiUvVCyaFlb7VY9AFIMSDdcY0JgNF0c4YVQxYxUCbYzmkLZD/rrYMe/8nxkWV0TMz2Y7GnvichjtWHL1ui58uC0+RtFMkYJ+ftwt9qBy9hvb/rVFTsvT5/b6CQXD8a6bFveMUluQZISLCV7i11XYzp81+w6M7+2fJAwezIJnIrgwv1K9YDjWaToaNXe7hnzzy0s8AdkjTk197+hg8dRfbvkr8XAddNsEMPeUA5iY+5VEpRNI925ZT/dxnaABA0z6i4JbVjeLl8r7ySG9R/2w/j2G+/YSRQc9BmRHPa0tBgH7wvQM+WRwD9WmST+5qeBIfH3QIDAQAB

When I do cat publickey.cert, it shows this

-----BEGIN CERTIFICATE-----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==
-----END CERTIFICATE-----

They keys are different, even in length. Why?

Answer 1

You can find a solution by just googleling for your question.

Example from java2s.com:

import java.io.FileInputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.cert.Certificate;

public class Main {
  public static void main(String[] argv) throws Exception {
    FileInputStream is = new FileInputStream("your.keystore");

    KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
    keystore.load(is, "my-keystore-password".toCharArray());

    String alias = "myalias";

    Key key = keystore.getKey(alias, "password".toCharArray());
    if (key instanceof PrivateKey) {
      // Get certificate of public key
      Certificate cert = keystore.getCertificate(alias);

      // Get public key
      PublicKey publicKey = cert.getPublicKey();

      // Return a key pair
      new KeyPair(publicKey, (PrivateKey) key);
    }
  }
}

See also:

• http://www.java2s.com/Code/Java/Security/RetrievingaKeyPairfromaKeyStore.htm
• How to retrieve my public and private key from the keystore we created

UPDATE:

See comments for additional information to the problem.