Generating a selfcertificate programatically

[Jose Botella]

It seems that there is no way to generate a selfcertificate via a JRE API. For instance java.security.cert.CertificateFactory needs to read an already existing certificate (encoding) from an InputStream. While CertPathBuilder requires LDAP or a Collection of certificates.

I do not want to force the users to pay to a CA, any free alternatives?
In fact, I would like the program would allow the user to generate the selfcertificates, preventing the user of knowing/managing the keytool utility.
I know they are not said to be reliable. But I think the user can phone the owner/subject of the selfcertificate to find out the "digitall firm" and check its autenticity. This is how I would like my program worked.

[ June 28, 2004: Message edited by: Jose Botella ]

[ June 28, 2004: Message edited by: Jose Botella ]
[ June 29, 2004: Message edited by: Jose Botella ]

[Jose Botella]

Hey I have found the bouncycastle.org site. Now it seems I am on the track!

/* The program simulates the transfer of a selfcertificate, generated programatically,
 * say from Alice to Bob.
 * If the file named: transmitter.cert does not exist in the executing dir
 * a FileNotFoundException is caught. Then we create a public priate key pair and a 
 * certificate for the public key. We add both as an entry to a privateKS that should be
 * kept under secret. At last, we "export" the DER encoded form to a file named 
 * transmitter.cert. If the program is executed a second time, the file transmitter.cert
 * exists. We create a X509Certificate from it and add it to a "trusted" keystore.
 * In both cases we print a digest of the signature. The first execution of the program 
 * pretends to be in Alice computer. Alice generates a key pair and a certificate of the
 * public key. Then sends the certificate to Bob. Bob before adding the certificate to the
 * trusted keystore, phones Alice and ask her for for the digest of the certificate. If 
 *it is the same as the one he has seen (second execution of the program) the certificate
 *is for the public
 key from Alice.
 */
 
package josebotella.filetransfer.secure;
 
import java.security.*;
import java.security.cert.Certificate;
import java.security.cert.*;
import java.security.spec.*;
import java.io.*;
import java.util.*;
import java.math.*;
import org.bouncycastle.jce.X509V3CertificateGenerator;
import org.bouncycastle.jce.X509Principal;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
 
public class FileTranfer {
    private static char[] keyStorePass = 
        new char[] { 'p', 'a', 's', 's', 'w', 'o', 'r', 'd' };
    static X509V3CertificateGenerator  v3CertGen = new X509V3CertificateGenerator();
    static MessageDigest digester;
    
    public static void main (String[] args) throws Exception {   
        Security.addProvider(new BouncyCastleProvider());
        digester = MessageDigest.getInstance("MD5");
        String keystoreFile = "FileTransfer.privateKS";
        FileInputStream fis;
        KeyPairGenerator KPGen = null;
        KeyStore trustedKS = KeyStore.getInstance("JKS");
        KeyStore privateKS = KeyStore.getInstance("JKS");
        try { 
            fis = new FileInputStream("transmitter.cert");
            CertificateFactory factory = CertificateFactory.getInstance("X509");
            X509Certificate toBeTrusted = (X509Certificate) factory.generateCertificate(
                fis);         
            trustedKS.load(null, "unrelatedpass".toCharArray());
            trustedKS.setCertificateEntry("transmitterKeyPair.cert", toBeTrusted);
            //trustedKS.store( new FileOutputStream("Receiver.trustedKS"), keyStorePass ); 
            System.out.println(trustedKS.getCertificate("transmitterKeyPair.cert"));
            printDigest(toBeTrusted);
        } catch (FileNotFoundException e) { 
            fis = null; 
            privateKS.load(fis, keyStorePass);
            KPGen = KeyPairGenerator.getInstance("RSA");
            KPGen.initialize(1024);
            KeyPair KPair = KPGen.generateKeyPair();
            v3CertGen.setSerialNumber(BigInteger.valueOf(1));
            v3CertGen.setIssuerDN( new X509Principal("CN=Jose, OU=test, O=SOHO " +
                "L=Caceres, C=SP") );
            v3CertGen.setNotBefore(new Date(System.currentTimeMillis() - 1000L * 60 * 60 
                * 24 * 30));
            v3CertGen.setNotAfter(new Date(System.currentTimeMillis() + (1000L * 60 * 60 
                * 24 * 30)));
            v3CertGen.setSubjectDN(new X509Principal("CN=Jose, OU=test, O=SOHO " +
                "L=Caceres, C=SP") );
            v3CertGen.setPublicKey(KPair.getPublic());
            v3CertGen.setSignatureAlgorithm("MD5WithRSAEncryption");            
            X509Certificate PKCertificate = v3CertGen.generateX509Certificate(
                KPair.getPrivate());            
            privateKS.setKeyEntry( "transmitterKeyPair" , KPair.getPrivate() ,
                new char[] { 'e', 'n', 't', 'r', 'y', 'p', 'a', 's', 's' }   ,
                    new Certificate[] { PKCertificate } );
            //privateKS.store( new FileOutputStream(keystoreFile), keyStorePass ); 
            FileOutputStream fos = new FileOutputStream("transmitter.cert");
            fos.write(PKCertificate.getEncoded());
            fos.close();
            printDigest(PKCertificate);
        }           
    }
    
    static void printDigest(X509Certificate certi) {
        byte[] sig = certi.getSignature();          
        digester.update(sig);
        byte[] digest = digester.digest();
        for(int i = 0; i< digest.length; i++)
            System.out.print(digest[i]);
        System.out.println();
   }
    
}

Dou you think this practice is secure or unfeasible?