Java Tutorial/Security/Public Key Infrastructure X.509

Getting the Subject and Issuer Distinguished Names of an X509 Certificate

import java.io.FileInputStream;
import java.security.KeyStore;
import java.security.Principal;
import java.security.cert.X509Certificate;
import java.util.Enumeration;
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());
    Enumeration e = keystore.aliases();
    for (; e.hasMoreElements();) {
      String alias = (String) e.nextElement();
      java.security.cert.Certificate cert = keystore.getCertificate(alias);
      if (cert instanceof X509Certificate) {
        X509Certificate x509cert = (X509Certificate) cert;
        // Get subject
        Principal principal = x509cert.getSubjectDN();
        String subjectDn = principal.getName();
        // Get issuer
        principal = x509cert.getIssuerDN();
        String issuerDn = principal.getName();
      }
    }
  }
}

Listing the Most-Trusted Certificate Authorities (CA) in a Key Store

import java.io.File;
import java.io.FileInputStream;
import java.security.KeyStore;
import java.security.cert.PKIXParameters;
import java.security.cert.TrustAnchor;
import java.security.cert.X509Certificate;
import java.util.Iterator;
public class Main {
  public static void main(String[] argv) throws Exception {
    String filename = System.getProperty("java.home")
        + "/lib/security/cacerts".replace("/", File.separatorChar);
    FileInputStream is = new FileInputStream(filename);
    KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
    String password = "password";
    keystore.load(is, password.toCharArray());
    PKIXParameters params = new PKIXParameters(keystore);
    Iterator it = params.getTrustAnchors().iterator();
    for (; it.hasNext();) {
      TrustAnchor ta = (TrustAnchor) it.next();
      X509Certificate cert = ta.getTrustedCert();
      System.out.println(cert.getSigAlgName());
    }
  }
}

PKIX Demo

import java.io.FileInputStream;
import java.math.BigInteger;
import java.security.KeyStore;
import java.security.PublicKey;
import java.security.cert.CertPath;
import java.security.cert.CertPathValidator;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
import java.security.cert.PKIXCertPathValidatorResult;
import java.security.cert.PKIXParameters;
import java.security.cert.TrustAnchor;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.List;
public class MainClass {
  public static void main(String args[]) throws Exception {
    CertificateFactory cf = CertificateFactory.getInstance("X.509");
    List mylist = new ArrayList();
    FileInputStream in = new FileInputStream(args[0]);
    Certificate c = cf.generateCertificate(in);
    mylist.add(c);
    CertPath cp = cf.generateCertPath(mylist);
    FileInputStream kin = new FileInputStream(args[0]);
    KeyStore ks = KeyStore.getInstance("JKS");
    ks.load(kin, args[1].toCharArray());
    PKIXParameters params = new PKIXParameters(ks);
    params.setRevocationEnabled(false);
    CertPathValidator cpv = CertPathValidator.getInstance("PKIX");
    PKIXCertPathValidatorResult result = (PKIXCertPathValidatorResult) cpv.validate(cp, params);
    PublicKey pbk = result.getPublicKey();
    byte[] pkenc = pbk.getEncoded();
    BigInteger pk = new BigInteger(pkenc);
    System.out.println(pk.toString(16));
    TrustAnchor anc = result.getTrustAnchor();
    X509Certificate xc = anc.getTrustedCert();
    System.out.println(xc.getSubjectDN());
    System.out.println(xc.getIssuerDN());
  }
}