How to detect an invalid pass phrase?
I used the sample code from Java Developers Almanac to encrypt a file (http://javaalmanac.com/egs/javax.crypto/DesFile.html). I changed a bit of the code so that user can enter a pass phrase.
When it comes to decrypting the file, I found that the file gets "decrypted" and becomes corrupt even when a wrong pass phrase is supplied.
How can I detect if the pass phrase is correct before the program goes on to decrypt the file?
My code (for the constructor) is as below:
public EncryptDecrypt(String passphrase){
byte[] iv =newbyte[]{(byte)0x8E, 0x12, 0x39, (byte)0x9C, 0x07, 0x72, 0x6F, 0x5A};
AlgorithmParameterSpec paramSpec =new IvParameterSpec(iv);
try{
KeySpec keyspec =new DESKeySpec(passphrase.getBytes());
SecretKey key = SecretKeyFactory.getInstance("DES").generateSecret(keyspec);
ecipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
dcipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
}catch(java.security.InvalidAlgorithmParameterException e){
}catch(javax.crypto.NoSuchPaddingException e){
}catch(java.security.NoSuchAlgorithmException e){
}catch(java.security.InvalidKeyException e){
}catch(java.security.spec.InvalidKeySpecException e){
}
}// constructor
