java - encrypt - ¿Por qué mi cifrado AES arroja una InvalidKeyException?

aes java implementation

Question

Actualmente estoy trabajando en una función que encripta / descifra un archivo específico con una clave secreta. He escrito tres clases, una que genera una clave, una que encripta un archivo con la clave y otra que descifra.

Generar la clave y cifrar el archivo funciona bien, pero cuando intento descifrar el archivo, se lanza una excepción en la línea: c.init(Cipher.DECRYPT_MODE, keySpec); :

java.security.InvalidKeyException: parámetros que faltan

Supongo que he hecho algo mal al transmitir la clave secreta a mi byte[] o algo está mal al descifrar el archivo.

Explicación rápida de las tres clases: KeyHandler crea una clave AES y la almacena en el disco duro. El nombre de la clave / texto sin cifrar / encriptado / descifrado está actualmente codificado con fines de prueba.

EncryptionHandler transfiere un archivo .txt en el disco en bytes, encripta el archivo con la clave secreta y luego escribe los bytes cifrados en el disco utilizando CipherOutputStream .

DecryptionHandler por supuesto, hace lo contrario de EncryptionHandler .

Aquí está el código:

    public class KeyHandler {
        Scanner scan = new Scanner(System.in);

        public KeyHandler(){
            try {
                startMenu();
            } catch (Exception e) {
                System.out.println("fel någonstanns :)");
            }
        }

        public void startMenu() throws Exception{

            System.out.println("Hej. Med detta program kan du generera en hemlig nyckel"+"/n"+"Vill du:"+"/n"+ "1. Generera en nyckel"+"/n"+"2. Avsluta");
            int val=Integer.parseInt(scan.nextLine());
        do{ 
            switch (val){
            case 1: generateKey(); break;
            case 2: System.exit(1);

            default: System.out.println("Du måste välja val 1 eller 2");
            }
        }
            while (val!=3);
        }

        public void generateKey() throws Exception{
            try {
                KeyGenerator gen = KeyGenerator.getInstance("AES");
                gen.init(128);

                SecretKey key=gen.generateKey();
                byte[] keyBytes = key.getEncoded();
                System.out.print("Ge nyckeln ett filnamn: ");
                String filename = scan.next();
                System.out.println("Genererar nyckeln...");
                FileOutputStream fileOut = new FileOutputStream(filename);
                fileOut.write(keyBytes);
                fileOut.close();
                System.out.println("Nyckeln är genererad med filnamnet: "+filename+"...");
                System.exit(1);
                 } catch (NoSuchAlgorithmException e) {
                    }

        }

        public static void main(String[] args){
            new KeyHandler();
        }

    }


    public class EncryptHandler {
        private String encryptedDataString;
        private Cipher ecipher; 

        AlgorithmParameterSpec paramSpec;
        byte[] iv;

        public EncryptHandler(String dataString, String secretKey, String encryptedDataString){
            this.encryptedDataString=encryptedDataString;
            try {
                encryptFile(dataString, secretKey);
            } catch (Exception e) {

            }
        }

            public void encryptFile(String dataString, String secretKey) throws Exception{

                    FileInputStream fis = new FileInputStream(secretKey);
                    ByteArrayOutputStream baos = new ByteArrayOutputStream();

                    int theByte = 0;
                    while ((theByte = fis.read()) != -1)
                    {
                      baos.write(theByte);
                    }
                    fis.close();

                    byte[] keyBytes = baos.toByteArray();
                    baos.close();
                    SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");

                try 
                { 
                ecipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); 
                ecipher.init(Cipher.ENCRYPT_MODE, keySpec);     

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

                System.out.println("Encrypting file...");
                try 
                { 

                    encryptStream(new FileInputStream(dataString),new FileOutputStream(encryptedDataString)); 
                }
                catch(Exception e){
                e.printStackTrace();
                }

                }
    public void encryptStream(InputStream in, OutputStream out){
                ByteArrayOutputStream bOut = new ByteArrayOutputStream();
                byte[] buf = new byte[1024]; 
                try { 
                out = new CipherOutputStream(out, ecipher); 

             // read the cleartext and write it to out
                int numRead = 0; 
                while ((numRead = in.read(buf)) >= 0) {
                out.write(buf, 0, numRead); 

                }
                bOut.writeTo(out);
                out.close();
                bOut.reset();

                } 
                catch (java.io.IOException e) 
                { 
                } 

                }


        public static void main(String[] args){
            String data = "test.txt";
            String keyFileName="a";
            String encryptedFile="krypterad.txt";
            //String encryptedFile =args[2];
            new EncryptHandler(data, keyFileName, encryptedFile);
        }

    }


public class DecryptHandler {
    public DecryptHandler(){

    try {
        decryptFile();
    } catch (Exception e) {
        System.out.println("något gick fel :) ");
        }
    }


    public void decryptFile()throws Exception{
        byte[] buf = new byte[1024]; 
        String keyFilename = "hemlig";
        FileInputStream fis = new FileInputStream(keyFilename);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        int theByte = 0;
        while ((theByte = fis.read()) != -1)
        {
          baos.write(theByte);
        }
        fis.close();

        byte[] keyBytes = baos.toByteArray();
        baos.close();
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");


        Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
                System.out.println("här");
        c.init(Cipher.DECRYPT_MODE, keySpec); 

        System.out.println("Decrypting file...");
        try{
        decryptStream(new FileInputStream("krypterad.txt"),new FileOutputStream("Dekryperad.txt"), c, buf);
        }
            catch (java.io.IOException e){

            }
            System.out.println("File decrypted!");
        }
    public void decryptStream(InputStream in, OutputStream out, Cipher dcipher, byte[] buf){
        try 
        { 

        in = new CipherInputStream(in, dcipher); 

        // Read in the decrypted bytes and write the cleartext to out 
        int numRead = 0; 


        while ((numRead = in.read(buf)) >= 0) 
        { 
        out.write(buf, 0, numRead);

        } 
        out.close();


        } 
        catch (java.io.IOException e){ 

        } 
    } 
    public static void main(String[]args){
        new DecryptHandler();
    }
}

Answer 1

Si usa un modo de encadenamiento de bloque como CBC, también debe proporcionar un IvParameterSpec al Cipher.

Entonces puedes inicializar un IvParameterSpec como este:

    // build the initialization vector.  This example is all zeros, but it 
    // could be any value or generated using a random number generator.
    byte[] iv = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
    IvParameterSpec ivspec = new IvParameterSpec(iv);

Luego, para el cifrado, cambie su código donde inicia el cifrado a esto:

ecipher.init(Cipher.ENCRYPT_MODE, keySpec, ivspec);

Y donde descifras:

c.init(Cipher.DECRYPT_MODE, keySpec, ivspec);

Así que su código completo debería verse así (Funciona para mí):

    public class KeyHandler {

    Scanner scan = new Scanner(System.in);

    public KeyHandler() {
        try {
            startMenu();
        } catch (Exception e) {
            System.out.println("fel någonstanns :)");
        }
    }

    public void startMenu() throws Exception {

        System.out.println("Hej. Med detta program kan du generera en hemlig nyckel" + "/n" + "Vill du:" + "/n" + "1. Generera en nyckel" + "/n" + "2. Avsluta");
        int val = Integer.parseInt(scan.nextLine());
        do {
            switch (val) {
                case 1:
                    generateKey();
                    break;
                case 2:
                    System.exit(1);

                default:
                    System.out.println("Du måste välja val 1 eller 2");
            }
        } while (val != 3);
    }

    public void generateKey() throws Exception {
        try {
            KeyGenerator gen = KeyGenerator.getInstance("AES");
            gen.init(128);

            SecretKey key = gen.generateKey();
            byte[] keyBytes = key.getEncoded();
            System.out.print("Ge nyckeln ett filnamn: ");
            String filename = scan.next();
            System.out.println("Genererar nyckeln...");
            FileOutputStream fileOut = new FileOutputStream(filename);
            fileOut.write(keyBytes);
            fileOut.close();
            System.out.println("Nyckeln är genererad med filnamnet: " + filename + "...");
            System.exit(1);
        } catch (NoSuchAlgorithmException e) {
        }

    }

    public static void main(String[] args) {
        new KeyHandler();
    }
}

public class EncryptHandler {

    private String encryptedDataString;
    private Cipher ecipher;
    AlgorithmParameterSpec paramSpec;
    byte[] iv;

    public EncryptHandler(String dataString, String secretKey, String encryptedDataString) {
        this.encryptedDataString = encryptedDataString;
        try {
            encryptFile(dataString, secretKey);
        } catch (Exception e) {
        }
    }

    public void encryptFile(String dataString, String secretKey) throws Exception {

        FileInputStream fis = new FileInputStream(secretKey);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        int theByte = 0;
        while ((theByte = fis.read()) != -1) {
            baos.write(theByte);
        }
        fis.close();

        byte[] keyBytes = baos.toByteArray();
        baos.close();
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");

        // build the initialization vector.  This example is all zeros, but it 
        // could be any value or generated using a random number generator.
        byte[] iv = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        IvParameterSpec ivspec = new IvParameterSpec(iv);

        try {
            ecipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            ecipher.init(Cipher.ENCRYPT_MODE, keySpec, ivspec);

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

        System.out.println("Encrypting file...");
        try {

            encryptStream(new FileInputStream(dataString), new FileOutputStream(encryptedDataString));
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public void encryptStream(InputStream in, OutputStream out) {
        ByteArrayOutputStream bOut = new ByteArrayOutputStream();
        byte[] buf = new byte[1024];
        try {
            out = new CipherOutputStream(out, ecipher);

            // read the cleartext and write it to out
            int numRead = 0;
            while ((numRead = in.read(buf)) >= 0) {
                out.write(buf, 0, numRead);

            }
            bOut.writeTo(out);
            out.close();
            bOut.reset();

        } catch (java.io.IOException e) {
        }

    }

    public static void main(String[] args) {
        String data = "test.txt";
        String keyFileName = "a";
        String encryptedFile = "krypterad.txt";
        //String encryptedFile =args[2];
        new EncryptHandler(data, keyFileName, encryptedFile);
    }
}

public class DecryptHandler {

    public DecryptHandler() {

        try {
            decryptFile();
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("något gick fel :) ");
        }
    }

    public void decryptFile() throws Exception {
        byte[] buf = new byte[1024];
        String keyFilename = "hemlig";
        FileInputStream fis = new FileInputStream(keyFilename);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        int theByte = 0;
        while ((theByte = fis.read()) != -1) {
            baos.write(theByte);
        }
        fis.close();

        byte[] keyBytes = baos.toByteArray();
        baos.close();
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");

        // build the initialization vector.  This example is all zeros, but it 
        // could be any value or generated using a random number generator.
        byte[] iv = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        IvParameterSpec ivspec = new IvParameterSpec(iv);

        Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
        System.out.println("här");
        c.init(Cipher.DECRYPT_MODE, keySpec, ivspec);

        System.out.println("Decrypting file...");
        try {
            decryptStream(new FileInputStream("krypterad.txt"), new FileOutputStream("Dekryperad.txt"), c, buf);
        } catch (java.io.IOException e) {
        }
        System.out.println("File decrypted!");
    }

    public void decryptStream(InputStream in, OutputStream out, Cipher dcipher, byte[] buf) {
        try {

            in = new CipherInputStream(in, dcipher);

            // Read in the decrypted bytes and write the cleartext to out 
            int numRead = 0;


            while ((numRead = in.read(buf)) >= 0) {
                out.write(buf, 0, numRead);

            }
            out.close();


        } catch (java.io.IOException e) {
        }
    }

    public static void main(String[] args) {
        new DecryptHandler();
    }
}