Google's Android Update Alliance Is Already Dead(pcmag.com)

  1234567890ABCDEF\0

  1. Load your previous key, and counter into AES-128/CTR
  2. Increment the counter by the full blocks already used
  3. Update the location into the current block by encrypting a random byte
  4. Provide the rest of your plaintext which will now be correctly encrypted for appending to an already encrypted segment

  1. the AES key, counter for the start of the file
  2. Use CTR to "decrypt" the content from start to finish

  Cipher c = Cipher.getInstance("AES/CTR/NoPadding");
  SecretKeySpec keySpec = new SecretKeySpec(aeskey, "AES");
  IvParameterSpec ivSpec = new IvParameterSpec(iv);
  c.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);

  c.update(new byte[count]);

  CipherOutputStream cipher_out = new CipherOutputStream(output, c);