My aim is to write a Java program to encrypt a text file (cipher text
) using AES algorithm
. And then, write another program to decrypt that encrypted file (cipher text
) to get the plain text back. I want to use same key (same key, generate once, save it somewhere, and use it in both encryption and decryption program) for encryption and decryption process. If I generate key and do the encryption and decryption line by line in the same program then it works perfectly. Here is the working code snippet for that:
String strDataToEncrypt = new String();
String strCipherText = new String();
String strDecryptedText = new String();
KeyGenerator keyGen = KeyGenerator.getInstance("AES");
keyGen.init(128);
SecretKey secretKey = keyGen.generateKey();
Cipher aesCipher = Cipher.getInstance("AES");
aesCipher.init(Cipher.ENCRYPT_MODE,secretKey);
strDataToEncrypt = "any text input";
byte[] byteDataToEncrypt = strDataToEncrypt.getBytes();
byte[] byteCipherText = aesCipher.doFinal(byteDataToEncrypt);
strCipherText = new BASE64Encoder().encode(byteCipherText);
System.out.println("cipher text: " +strCipherText);
aesCipher.init(Cipher.DECRYPT_MODE,secretKey,aesCipher.getParameters());
byte[] byteDecryptedText = aesCipher.doFinal(new BASE64Decoder().decodeBuffer(strCipherText));
strDecryptedText = new String(byteDecryptedText);
System.out.println("plain text again: " +strDecryptedText);
But, I need to have two different programs (java files) for encryption and decryption. So, I have to somehow generate a key and save that somewhere. Then use the same key for both encryption and decryption program. How can I do that?
EDIT_1
KeyGenerator keyGen = KeyGenerator.getInstance("AES");
keyGen.init(128);
SecretKey secretKey = keyGen.generateKey();
byte[] encoded = secretKey.getEncoded();
System.out.println("key: "+encoded);// key: [B@52b2a2d8
I can get the encoded key value using the above program. But my question is how to generate the SecretKey using this value in my decryption program?
Forgive me if I misunderstood your question but I believe you wish to reconstruct a SecretKey
object from a existing key encoded in a byte array.
This can be performed simply by using the javax.crypto.spec.SecretKeySpec
's constructor as such:
byte[] encoded = //Key data
SecretKey secretKey = new SecretKeySpec(encoded, "AES");
Since SecretKeySpec
is a subclass of SecretKey
no casting is needed. Should your encryption/decrption algorithm change please make sure to change the string literal used in the constructor AES
to whatever algorithm you decided to use in the future.