Encrypt and Decrypt in Java

Question

I would like to store an encrypted password in a Java file   I saw at a solution using javax crypto  but the problem with that was that the key was being generated on the fly and it was random    This password will be then taken and decrypted in the Java program in runtime   Given that I am going to store an already encrypted password in a file - I want to get the  right text when decrypting it    Is there a way to tell the javax crypto method    key   KeyGenerator getInstance algorithm  generateKey     Can this be replaced with my own key generated once based on some private key    Can anyone point me to some resources on how to do this

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public class GenerateEncryptedPassword        public static void main String   args            Scanner sc  new Scanner System in               System out println  Please enter the password that needs to be encrypted              String input   sc next             try               String encryptedPassword  AESencrp encrypt input               System out println  Encrypted password generated is    encryptedPassword             catch  Exception ex                Logger getLogger GenerateEncryptedPassword class getName    log Level SEVERE  null  ex

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You may want to use the jasypt library  Java Simplified Encryption   which is quite easy to use    Also  it s recommended to check against the encrypted password rather than decrypting the encrypted password   To use jasypt  if you re using maven  you can include jasypt into your pom xml file as follows   lt dependency gt       lt groupId gt org jasypt lt  groupId gt       lt artifactId gt jasypt lt  artifactId gt       lt version gt 1 9 3 lt  version gt       lt scope gt compile lt  scope gt   lt  dependency gt   And then to encrypt the password  you can use StrongPasswordEncryptor public static String encryptPassword String inputPassword        StrongPasswordEncryptor encryptor   new StrongPasswordEncryptor        return encryptor encryptPassword inputPassword      Note  the encrypted password is different every time you call encryptPassword but the checkPassword method can still check that the unencrypted password still matches each of the encrypted passwords  And to check the unencrypted password against the encrypted password  you can use the checkPassword method  public static boolean checkPassword String inputPassword  String encryptedStoredPassword        StrongPasswordEncryptor encryptor   new StrongPasswordEncryptor        return encryptor checkPassword inputPassword  encryptedStoredPassword      The page below provides detailed information on the complexities involved in creating safe encrypted passwords  http   www jasypt org howtoencryptuserpasswords html

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KeyGenerator is used to generate keys  You may want to check KeySpec  SecretKey and SecretKeyFactory classes  http   docs oracle com javase 1 5 0 docs api javax crypto spec package-summary html

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Here is a sample I made a couple of months ago The class encrypt and decrypt data  import java security    import java security spec     import java io    import javax crypto    import javax crypto spec     public class TestEncryptDecrypt    private final String ALGO    DES   private final String MODE    ECB   private final String PADDING    PKCS5Padding   private static int mode   0   public static void main String args          TestEncryptDecrypt me   new TestEncryptDecrypt        if args length    0  mode   2      else mode   Integer parseInt args 0        switch  mode        case 0          me encrypt            break      case 1          me decrypt            break      default          me encrypt            me decrypt             public void encrypt     try       System out println  Start encryption                Get Input Data        String input   getInputData        System out println  Input data     input           Create Secret Key        KeyGenerator keyGen   KeyGenerator getInstance ALGO       SecureRandom random   SecureRandom getInstance  SHA1PRNG    SUN        keyGen init 56 random         Key sharedKey   keyGen generateKey            Create the Cipher and init it with the secret key        Cipher c   Cipher getInstance ALGO     MODE     PADDING         System out println   n    c getProvider   getInfo         c init Cipher ENCRYPT MODE sharedKey       byte   ciphertext   c doFinal input getBytes         System out println  Input Encrypted     new String ciphertext  UTF8             Save key to a file        save sharedKey getEncoded    shared key            Save encrypted data to a file        save ciphertext  encrypted txt      catch  Exception e        e printStackTrace            public void decrypt     try       System out println  Start decryption                Get encoded shared key from file       byte   encoded   load  shared key          SecretKeyFactory kf   SecretKeyFactory getInstance ALGO       KeySpec ks   new DESKeySpec encoded       SecretKey ky   kf generateSecret ks           Get encoded data        byte   ciphertext   load  encrypted txt        System out println  Encoded data       new String ciphertext  UTF8             Create a Cipher object and initialize it with the secret key        Cipher c   Cipher getInstance ALGO     MODE     PADDING       c init Cipher DECRYPT MODE ky           Update and decrypt        byte   plainText   c doFinal ciphertext       System out println  Plain Text     new String plainText  UTF8       catch  Exception e        e printStackTrace            private String getInputData         String id    owner id           String name    owner name           String contact    owner contact           String tel    owner tel           final String rc   System getProperty  line separator        StringBuffer buf   new StringBuffer        buf append id       buf append rc       buf append name       buf append rc       buf append contact       buf append rc       buf append tel       return buf toString        private void save byte   buf  String file  throws IOException         FileOutputStream fos   new FileOutputStream file         fos write buf         fos close       private byte   load String file  throws FileNotFoundException  IOException       FileInputStream fis   new FileInputStream file       byte   buf   new byte fis available         fis read buf       fis close        return buf

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Here is a solution using the javax crypto library and the apache commons codec library for encoding and decoding in Base64 that I was looking for    import java security spec KeySpec  import javax crypto Cipher  import javax crypto SecretKey  import javax crypto SecretKeyFactory  import javax crypto spec DESedeKeySpec  import org apache commons codec binary Base64   public class TrippleDes        private static final String UNICODE FORMAT    UTF8       public static final String DESEDE ENCRYPTION SCHEME    DESede       private KeySpec ks      private SecretKeyFactory skf      private Cipher cipher      byte   arrayBytes      private String myEncryptionKey      private String myEncryptionScheme      SecretKey key       public TrippleDes   throws Exception           myEncryptionKey    ThisIsSpartaThisIsSparta           myEncryptionScheme   DESEDE ENCRYPTION SCHEME          arrayBytes   myEncryptionKey getBytes UNICODE FORMAT           ks   new DESedeKeySpec arrayBytes           skf   SecretKeyFactory getInstance myEncryptionScheme           cipher   Cipher getInstance myEncryptionScheme           key   skf generateSecret ks               public String encrypt String unencryptedString            String encryptedString   null          try               cipher init Cipher ENCRYPT MODE  key               byte   plainText   unencryptedString getBytes UNICODE FORMAT               byte   encryptedText   cipher doFinal plainText               encryptedString   new String Base64 encodeBase64 encryptedText              catch  Exception e                e printStackTrace                      return encryptedString              public String decrypt String encryptedString            String decryptedText null          try               cipher init Cipher DECRYPT MODE  key               byte   encryptedText   Base64 decodeBase64 encryptedString               byte   plainText   cipher doFinal encryptedText               decryptedText  new String plainText             catch  Exception e                e printStackTrace                      return decryptedText              public static void main String args     throws Exception               TrippleDes td  new TrippleDes             String target  imparator           String encrypted td encrypt target           String decrypted td decrypt encrypted            System out println  String To Encrypt     target           System out println  Encrypted String     encrypted           System out println  Decrypted String     decrypted               Running the above program results with the following output    String To Encrypt  imparator Encrypted String FdBNaYWfjpWN9eYghMpbRA   Decrypted String imparator

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If you use a static key  encrypt and decrypt always give the same result   public static final String CRYPTOR KEY    your static key here   byte   keyByte   Base64 getDecoder   decode CRYPTOR KEY   key   new SecretKeySpec keyByte   AES

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Symmetric Key Cryptography   Symmetric key uses the same key for encryption and decryption  The main challenge with this type of cryptography is the exchange of the secret key between the two parties sender and receiver   Example    The following example uses symmetric key for encryption and decryption algorithm available as part of the Sun s JCE Java Cryptography Extension   Sun JCE is has two layers  the crypto API layer and the provider layer     DES  Data Encryption Standard  was a popular symmetric key algorithm  Presently DES is outdated and  considered insecure  Triple DES and a stronger variant of DES  It is a symmetric-key block cipher  There are other algorithms like Blowfish  Twofish and AES Advanced Encryption Standard   AES is the latest encryption standard over the DES   Steps     Add the Security Provider   We are using the SunJCE Provider that is available with the JDK   Generate Secret Key   Use KeyGenerator and an algorithm to generate a secret key  We are using DESede    Encode Text   For consistency across platform encode the plain text as byte using UTF-8 encoding   Encrypt Text   Instantiate Cipher with ENCRYPT MODE  use the secret key and encrypt the bytes   Decrypt Text   Instantiate Cipher with DECRYPT MODE  use the same secret key and decrypt the bytes      All the above given steps and concept are same  we just replace algorithms     import java util Base64      import javax crypto Cipher    import javax crypto KeyGenerator     import javax crypto SecretKey    public class EncryptionDecryptionAES         static Cipher cipher         public static void main String   args  throws Exception                        create key           If we need to generate a new key use a KeyGenerator          If we have existing plaintext key use a SecretKeyFactory                     KeyGenerator keyGenerator   KeyGenerator getInstance  AES            keyGenerator init 128      block size is 128bits         SecretKey secretKey   keyGenerator generateKey                          Cipher Info           Algorithm   for the encryption of electronic data           mode of operation   to avoid repeated blocks encrypt to the same values            padding  ensuring messages are the proper length necessary for certain ciphers            mode padding are not used with stream cyphers                        cipher   Cipher getInstance  AES      SunJCE provider AES algorithm  mode optional  and padding schema optional             String plainText    AES Symmetric Encryption Decryption           System out println  Plain Text Before Encryption      plainText            String encryptedText   encrypt plainText  secretKey           System out println  Encrypted Text After Encryption      encryptedText            String decryptedText   decrypt encryptedText  secretKey           System out println  Decrypted Text After Decryption      decryptedText              public static String encrypt String plainText  SecretKey secretKey              throws Exception           byte   plainTextByte   plainText getBytes            cipher init Cipher ENCRYPT MODE  secretKey           byte   encryptedByte   cipher doFinal plainTextByte           Base64 Encoder encoder   Base64 getEncoder            String encryptedText   encoder encodeToString encryptedByte           return encryptedText             public static String decrypt String encryptedText  SecretKey secretKey              throws Exception           Base64 Decoder decoder   Base64 getDecoder            byte   encryptedTextByte   decoder decode encryptedText           cipher init Cipher DECRYPT MODE  secretKey           byte   decryptedByte   cipher doFinal encryptedTextByte           String decryptedText   new String decryptedByte           return decryptedText            Output    Plain Text Before Encryption  AES Symmetric Encryption Decryption Encrypted Text After Encryption  sY6vkQrWRg0fvRzbqSAYxepeBIXg4AySj7Xh3x4vDv8TBTkNiTfca7wW dxiMMJl Decrypted Text After Decryption  AES Symmetric Encryption Decryption   Source  Example  Cipher with two modes  they are encrypt and decrypt  we have to start every time after setting mode to encrypt or decrypt a text

[java] Encrypt and Decrypt in Java

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