Pertanyaan Java AES dan menggunakan Key saya sendiri


Saya ingin mengenkripsi string menggunakan AES dengan kunci saya sendiri. Tapi saya mengalami masalah dengan sedikit panjang kunci. Dapatkah Anda meninjau kode saya dan melihat apa yang perlu saya perbaiki / ubah.

public static void main(String[] args) throws Exception {
    String username = "bob@google.org";
    String password = "Password1";
    String secretID = "BlahBlahBlah";
    String SALT2 = "deliciously salty";

    // Get the Key
    byte[] key = (SALT2 + username + password).getBytes();
    System.out.println((SALT2 + username + password).getBytes().length);

    // Need to pad key for AES
    // TODO: Best way?

    // Generate the secret key specs.
    SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");

    // Instantiate the cipher
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);

    byte[] encrypted = cipher.doFinal((secrectID).getBytes());
    System.out.println("encrypted string: " + asHex(encrypted));

    cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
    byte[] original = cipher.doFinal(encrypted);
    String originalString = new String(original);
    System.out.println("Original string: " + originalString + "\nOriginal string (Hex): " + asHex(original));
}

Sekarang saya mendapat pengecualian "Panjang kunci AES tidak valid: 86 byte". Apakah saya perlu memasukkan kunci saya? Bagaimana saya harus melakukannya?

Juga apakah saya perlu mengatur apa pun untuk ECB atau CBC?

Terima kasih


75
2017-08-10 17:24


asal


Jawaban:


Anda harus menggunakan SHA-1 untuk menghasilkan hash dari kunci Anda dan memangkas hasilnya menjadi 128 bit (16 byte).

Selain itu tidak menghasilkan array byte dari Strings through getBytes () menggunakan Charset default platform. Jadi kata sandi "blaöä" menghasilkan array byte yang berbeda pada platform yang berbeda.

byte[] key = (SALT2 + username + password).getBytes("UTF-8");
MessageDigest sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit

SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");

Edit: Jika Anda membutuhkan 256 bit sebagai ukuran kunci, Anda perlu mengunduh "Java Cryptography Extension (JCE) File Kebijakan Jurisdiksi Kekuatan Terbatas" Tautan unduhan Oracle, gunakan SHA-256 sebagai hash dan hapus Arrays.copyOf garis. "ECB" adalah Mode Cipher default dan "PKCS5Padding" padding default. Anda bisa menggunakan Mode Cipher dan Mode Padding yang berbeda melalui Cipher.getInstance string menggunakan format berikut: "Cipher / Mode / Padding"

Untuk AES menggunakan CTS dan PKCS5Padding string adalah: "AES / CTS / PKCS5Padding"


112
2017-08-10 19:21



Anda harus menggunakan KeyGenerator untuk menghasilkan Kunci,

Panjang kunci AES adalah 128, 192, dan 256 bit tergantung pada sandi yang ingin Anda gunakan.

Lihatlah tutorialnya sini 

Berikut adalah kode untuk Enkripsi Berbasis Kata Sandi, ini memiliki kata sandi yang dimasukkan melalui System.in Anda dapat mengubahnya untuk menggunakan kata sandi yang tersimpan jika Anda mau.

        PBEKeySpec pbeKeySpec;
        PBEParameterSpec pbeParamSpec;
        SecretKeyFactory keyFac;

        // Salt
        byte[] salt = {
            (byte)0xc7, (byte)0x73, (byte)0x21, (byte)0x8c,
            (byte)0x7e, (byte)0xc8, (byte)0xee, (byte)0x99
        };

        // Iteration count
        int count = 20;

        // Create PBE parameter set
        pbeParamSpec = new PBEParameterSpec(salt, count);

        // Prompt user for encryption password.
        // Collect user password as char array (using the
        // "readPassword" method from above), and convert
        // it into a SecretKey object, using a PBE key
        // factory.
        System.out.print("Enter encryption password:  ");
        System.out.flush();
        pbeKeySpec = new PBEKeySpec(readPassword(System.in));
        keyFac = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);

        // Create PBE Cipher
        Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");

        // Initialize PBE Cipher with key and parameters
        pbeCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec);

        // Our cleartext
        byte[] cleartext = "This is another example".getBytes();

        // Encrypt the cleartext
        byte[] ciphertext = pbeCipher.doFinal(cleartext);

13
2017-08-10 17:43



import java.security.Key;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import sun.misc.*;
import java.io.BufferedReader;
import java.io.FileReader;

public class AESFile 
{
private static String algorithm = "AES";
private static byte[] keyValue=new byte[] {'0','2','3','4','5','6','7','8','9','1','2','3','4','5','6','7'};// your key

    // Performs Encryption
    public static String encrypt(String plainText) throws Exception 
    {
            Key key = generateKey();
            Cipher chiper = Cipher.getInstance(algorithm);
            chiper.init(Cipher.ENCRYPT_MODE, key);
            byte[] encVal = chiper.doFinal(plainText.getBytes());
            String encryptedValue = new BASE64Encoder().encode(encVal);
            return encryptedValue;
    }

    // Performs decryption
    public static String decrypt(String encryptedText) throws Exception 
    {
            // generate key 
            Key key = generateKey();
            Cipher chiper = Cipher.getInstance(algorithm);
            chiper.init(Cipher.DECRYPT_MODE, key);
            byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedText);
            byte[] decValue = chiper.doFinal(decordedValue);
            String decryptedValue = new String(decValue);
            return decryptedValue;
    }

//generateKey() is used to generate a secret key for AES algorithm
    private static Key generateKey() throws Exception 
    {
            Key key = new SecretKeySpec(keyValue, algorithm);
            return key;
    }

    // performs encryption & decryption 
    public static void main(String[] args) throws Exception 
    {
        FileReader file = new FileReader("C://myprograms//plaintext.txt");
        BufferedReader reader = new BufferedReader(file);
        String text = "";
        String line = reader.readLine();
    while(line!= null)
        {
            text += line;
    line = reader.readLine();
        }
        reader.close();
    System.out.println(text);

            String plainText = text;
            String encryptedText = AESFile.encrypt(plainText);
            String decryptedText = AESFile.decrypt(encryptedText);

            System.out.println("Plain Text : " + plainText);
            System.out.println("Encrypted Text : " + encryptedText);
            System.out.println("Decrypted Text : " + decryptedText);
    }
}

5
2017-12-24 10:41



Pekerjaan ini akan berhasil.

public class CryptoUtils {

    private  final String TRANSFORMATION = "AES";
    private  final String encodekey = "1234543444555666";
    public  String encrypt(String inputFile)
            throws CryptoException {
        return doEncrypt(encodekey, inputFile);
    }


    public  String decrypt(String input)
            throws CryptoException {
    // return  doCrypto(Cipher.DECRYPT_MODE, key, inputFile);
    return doDecrypt(encodekey,input);
    }

    private  String doEncrypt(String encodekey, String inputStr)   throws CryptoException {
        try {

            Cipher cipher = Cipher.getInstance(TRANSFORMATION);

            byte[] key = encodekey.getBytes("UTF-8");
            MessageDigest sha = MessageDigest.getInstance("SHA-1");
            key = sha.digest(key);
            key = Arrays.copyOf(key, 16); // use only first 128 bit

            SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");

            cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);

            byte[] inputBytes = inputStr.getBytes();     
            byte[] outputBytes = cipher.doFinal(inputBytes);

            return Base64Utils.encodeToString(outputBytes);

        } catch (NoSuchPaddingException | NoSuchAlgorithmException
                | InvalidKeyException | BadPaddingException
                | IllegalBlockSizeException | IOException ex) {
            throw new CryptoException("Error encrypting/decrypting file", ex);
       }
     }


    public  String doDecrypt(String encodekey,String encrptedStr) { 
          try {     

              Cipher dcipher = Cipher.getInstance(TRANSFORMATION);
              dcipher = Cipher.getInstance("AES");
              byte[] key = encodekey.getBytes("UTF-8");
              MessageDigest sha = MessageDigest.getInstance("SHA-1");
              key = sha.digest(key);
              key = Arrays.copyOf(key, 16); // use only first 128 bit

              SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");

              dcipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
            // decode with base64 to get bytes

              byte[] dec = Base64Utils.decode(encrptedStr.getBytes());  
              byte[] utf8 = dcipher.doFinal(dec);

              // create new string based on the specified charset
              return new String(utf8, "UTF8");

          } catch (Exception e) {

            e.printStackTrace();

          }
      return null;
      }
 }

2
2018-04-06 20:45



    byte[] seed = (SALT2 + username + password).getBytes();
    SecureRandom random = new SecureRandom(seed);
    KeyGenerator generator;
    generator = KeyGenerator.getInstance("AES");
    generator.init(random);
    generator.init(256);
    Key keyObj = generator.generateKey();

0
2018-05-31 23:38