Generate certificates, public and private keys with Java [closed]

Solution 1:

You can generate Certificate in java dynamically, by using a pair or keys. (Public Key, Private Keys). Get These keys as BigInteger format and checking the following code to generate certificate.

RSAPrivateKeySpec serPrivateSpec = new RSAPrivateKeySpec(
    new BigInteger(val of pub key), new BigInteger(val of pri key));
fact = KeyFactory.getInstance("RSA");
PrivateKey serverPrivateKey = fact.generatePrivate(serPrivateSpec);

RSAPublicKeySpec serPublicSpec = new RSAPublicKeySpec(
    new BigInteger(agentCL.getSerPubMod()), new BigInteger(agentCL.getSerPubExp()));
PublicKey serverPublicKey = fact.generatePublic(serPublicSpec);

keyStore = KeyStore.getInstance(IMXAgentCL.STORE_TYPE);
keyStore.load(null, SOMEPWD.toCharArray());

Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

X509Certificate[] serverChain = new X509Certificate[1];
X509V3CertificateGenerator serverCertGen = new X509V3CertificateGenerator();
X500Principal serverSubjectName = new X500Principal("CN=OrganizationName");
serverCertGen.setSerialNumber(new BigInteger("123456789"));
// X509Certificate caCert=null;
serverCertGen.setIssuerDN(somename);
serverCertGen.setNotBefore(new Date());
serverCertGen.setNotAfter(new Date());
serverCertGen.setSubjectDN(somename);
serverCertGen.setPublicKey(serverPublicKey);
serverCertGen.setSignatureAlgorithm("MD5WithRSA");
// certGen.addExtension(X509Extensions.AuthorityKeyIdentifier, false,new
// AuthorityKeyIdentifierStructure(caCert));
serverCertGen.addExtension(X509Extensions.SubjectKeyIdentifier, false,
    new SubjectKeyIdentifierStructure(serverPublicKey));
serverChain[0] = serverCertGen.generateX509Certificate(serverPrivateKey, "BC"); // note: private key of CA

keyStore.setEntry("xyz",
    new KeyStore.PrivateKeyEntry(serverPrivateKey, serverChain),
    new KeyStore.PasswordProtection("".toCharArray()));

Hope this will help you.

Solution 2:

Legacy Warning Begin:

• This code only sets the CommonName/CN/Subject.
• The correct place now is the SubjectAltName.

From Chrome Deprecates Subject CN Matching:

Chrome 58 will require that certificates specify the hostname(s) to which they apply in the SubjectAltName field; values in the Subject field will be ignored."

Legacy Warning End

import java.io.FileOutputStream;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.cert.X509Certificate;
import java.util.Date;

import sun.security.x509.CertAndKeyGen;
import sun.security.x509.X500Name;

public class UseKeyTool {

    private static final int keysize = 1024;
    private static final String commonName = "www.test.de";
    private static final String organizationalUnit = "IT";
    private static final String organization = "test";
    private static final String city = "test";
    private static final String state = "test";
    private static final String country = "DE";
    private static final long validity = 1096; // 3 years
    private static final String alias = "tomcat";
    private static final char[] keyPass = "changeit".toCharArray();

    // copied most ideas from sun.security.tools.KeyTool.java

    @SuppressWarnings("restriction")
    public static void main(String[] args) throws Exception {

        KeyStore keyStore = KeyStore.getInstance("JKS");
        keyStore.load(null, null);

        CertAndKeyGen keypair = new CertAndKeyGen("RSA", "SHA1WithRSA", null);

        X500Name x500Name = new X500Name(commonName, organizationalUnit, organization, city, state, country);

        keypair.generate(keysize);
        PrivateKey privKey = keypair.getPrivateKey();

        X509Certificate[] chain = new X509Certificate[1];

        chain[0] = keypair.getSelfCertificate(x500Name, new Date(), (long) validity * 24 * 60 * 60);

        keyStore.setKeyEntry(alias, privKey, keyPass, chain);

        keyStore.store(new FileOutputStream(".keystore"), keyPass);



    }
}