Import/export secret key

Question

Hello i have a simple program that crypt a string, and i want to
to know how i can export the secret key.
My idea is to save a secret string in a file and pass it to the program
that decrypt the string is it possible ???
thank
--sxr                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

OK. First - PLEASE learn how to use the [ code ] tags when posting samples. I didn't even realize you'd posted two classes until I tried to paste 'em into Eclipse.
Second - you're...confused. Crypting and Decrypt need to share two things: the ciphertext, and the KEY. The key is not available from the AlgorithmParameters. In Decrypt, you're creating a new key from your ciphertext (?!?)
Since I had a little spare time, I refactored your code somewhat. The only reason to use AlgorithmParameters is to pass in an InitialValue (IV), which CBC-mode needs. The IV is not sensitive data - it's OK to make it public.
So I just stuck the same IV into both files. You can extend the concept and store the IV as well, if you like.
The following classes work:import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
public class Crypting {
    private static String Password = "sunray";
    public static void main(String[] argvs) throws Exception {
        // Choose an Initial Value (IV)
        byte[] iv = {
            (byte)0x01, (byte)0x02, (byte)0x03, (byte)0x04,
            (byte)0x05, (byte)0x06, (byte)0x07, (byte)0x08,
        IvParameterSpec ivps = new IvParameterSpec(iv);
        File keyFile = new File("key.txt"); // File that will hold the SecretKey
        File cryptFile = new File("algo.txt"); // File that will hold the ciphertext
        // Creazione del generatore di chiave
        KeyGenerator kgen = KeyGenerator.getInstance("Blowfish");
        SecretKey skey = kgen.generateKey();
        // Creazione della chiave
        byte[] rawKey = skey.getEncoded();
        // Encrypt our data
        Cipher cipher = Cipher.getInstance("BLOWFISH/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, skey, ivps);
        byte[] encrypted = cipher.doFinal(Password.getBytes("UTF8"));
        // Store the KEY
        try {
            DataOutputStream out = new DataOutputStream(new FileOutputStream(keyFile));
            out.write(rawKey, 0, rawKey.length);
            out.close();
        } catch (Throwable e) {
            System.err.println(e);
        // Store the ENCRYPTED DATA
        try {
            DataOutputStream out2 = new DataOutputStream(new FileOutputStream(cryptFile));
            out2.write(encrypted, 0, encrypted.length);
            out2.close();
        } catch (Throwable e) {
            System.err.println(e);
    } // main()
} //Crypting
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
public class Decrypting {
    public static void main(String[] argv) throws Exception {
        // Choose an Initial Value (IV)
        byte[] iv = {
            (byte)0x01, (byte)0x02, (byte)0x03, (byte)0x04,
            (byte)0x05, (byte)0x06, (byte)0x07, (byte)0x08,
        IvParameterSpec ivps = new IvParameterSpec(iv);
        File keyFile = new File("key.txt"); // Where's the key?
        File cryptFile = new File("algo.txt"); // Where's the data?
        byte[] ciphertext = null; //ciphertext
        byte[] rawKey = null; // key data
        // Read the KEY BYTES
        try {
            DataInputStream in = new DataInputStream(new FileInputStream(keyFile));
            rawKey = new byte[(int)keyFile.length()];
            in.readFully(rawKey);
            in.close();
        } catch (FileNotFoundException e) {
            System.err.println(e);
        // Read the ENCRYPTED DATA
        try {
            DataInputStream in2 = new DataInputStream(new FileInputStream(cryptFile));
            ciphertext = new byte[(int)cryptFile.length()];
            in2.readFully(ciphertext);
            in2.close();
        } catch (FileNotFoundException e) {
            System.err.println(e);
        //make a key object
        SecretKeySpec key = new SecretKeySpec(rawKey, "Blowfish");
        //make a cipher object
        Cipher cipher = Cipher.getInstance("BLOWFISH/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, key, ivps);
        // Decrypt the DATA with the KEY
        byte[] original = cipher.doFinal(ciphertext);
        // Spit out the decrypted data
        String originalString = new String(original, "UTF8");
        System.out.println("\nPassword: " + originalString);
    } // main()
} // DEcrypt classYou really need to do some reading on how crypto works, if you mean to get past this point.
Good luck,
Grant