title: Partial re encryption in AES-GCM mode in Java
body: <p>I want to encrypt and decrypt file with AES. I know how to entirely encrypt and decrypt a file but sometimes I just want to manipulate a part of the file (for example with a RandomAccessFile).</p>
  <p>I found some solutions to decrypt a part of a encrypted file with AES-GCM but my main problem is:</p>
  <p>If I modify just a part of a file, <strong>I need to re encrypt this new part. For performance reason, I don't want to re encrypt the whole file.</strong></p>
  <p><strong>It is possible to just re encrypt the block of bytes where changes has been done in the file?</strong></p>