Image encryption/decryption using AES256 symmetric block ciphers [closed]

Question

Is there any good example of how to encrypt and decrypt image and other files with AES on Android?

Answer 1

Warning: This answer contains code you should not use as it is insecure (using SHA1PRNG for key derivation and using AES in ECB mode)

Instead (as of 2016), use PBKDF2WithHmacSHA1 for key derivation and AES in CBC or GCM mode (GCM provides both privacy and integrity)

You could use functions like these:

private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {     SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");     Cipher cipher = Cipher.getInstance("AES");     cipher.init(Cipher.ENCRYPT_MODE, skeySpec);     byte[] encrypted = cipher.doFinal(clear);     return encrypted; }  private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {     SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");     Cipher cipher = Cipher.getInstance("AES");     cipher.init(Cipher.DECRYPT_MODE, skeySpec);     byte[] decrypted = cipher.doFinal(encrypted);     return decrypted; } 

And invoke them like this:

ByteArrayOutputStream baos = new ByteArrayOutputStream();   bm.compress(Bitmap.CompressFormat.PNG, 100, baos); // bm is the bitmap object    byte[] b = baos.toByteArray();    byte[] keyStart = "this is a key".getBytes(); KeyGenerator kgen = KeyGenerator.getInstance("AES"); SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); sr.setSeed(keyStart); kgen.init(128, sr); // 192 and 256 bits may not be available SecretKey skey = kgen.generateKey(); byte[] key = skey.getEncoded();      // encrypt byte[] encryptedData = encrypt(key,b); // decrypt byte[] decryptedData = decrypt(key,encryptedData); 

This should work, I use similar code in a project right now.

Answer 2

As mentioned by Nacho.L PBKDF2WithHmacSHA1 derivation is used as it is more secured.

import android.util.Base64;  import java.security.NoSuchAlgorithmException; import java.security.spec.InvalidKeySpecException; import java.security.spec.KeySpec;  import javax.crypto.Cipher; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.PBEKeySpec; import javax.crypto.spec.SecretKeySpec;  public class AESEncyption {      private static final int pswdIterations = 10;     private static final int keySize = 128;     private static final String cypherInstance = "AES/CBC/PKCS5Padding";     private static final String secretKeyInstance = "PBKDF2WithHmacSHA1";     private static final String plainText = "sampleText";     private static final String AESSalt = "exampleSalt";     private static final String initializationVector = "8119745113154120";      public static String encrypt(String textToEncrypt) throws Exception {          SecretKeySpec skeySpec = new SecretKeySpec(getRaw(plainText, AESSalt), "AES");         Cipher cipher = Cipher.getInstance(cypherInstance);         cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(initializationVector.getBytes()));         byte[] encrypted = cipher.doFinal(textToEncrypt.getBytes());         return Base64.encodeToString(encrypted, Base64.DEFAULT);     }      public static String decrypt(String textToDecrypt) throws Exception {          byte[] encryted_bytes = Base64.decode(textToDecrypt, Base64.DEFAULT);         SecretKeySpec skeySpec = new SecretKeySpec(getRaw(plainText, AESSalt), "AES");         Cipher cipher = Cipher.getInstance(cypherInstance);         cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(initializationVector.getBytes()));         byte[] decrypted = cipher.doFinal(encryted_bytes);         return new String(decrypted, "UTF-8");     }      private static byte[] getRaw(String plainText, String salt) {         try {             SecretKeyFactory factory = SecretKeyFactory.getInstance(secretKeyInstance);             KeySpec spec = new PBEKeySpec(plainText.toCharArray(), salt.getBytes(), pswdIterations, keySize);             return factory.generateSecret(spec).getEncoded();         } catch (InvalidKeySpecException e) {             e.printStackTrace();         } catch (NoSuchAlgorithmException e) {             e.printStackTrace();         }         return new byte[0];     }  }