I have a 10GB `.iso` file with sensitive information.

**How can I fake its format to be a format of my choice (say `.mp4`)**

Is this method valid for any format?

```
$ cat picture.png myiso.iso.gpg > picture2.png

```

where `picture.png` is a random picture, `myiso.iso.gpg`, a gpg encrypted file with sensitive information and `picture2.png` the hidden file with fake format.