Steganography is for hiding the fact that you're hiding something, it's not for protecting the thing that you're hiding. You still need real cryptography to do

Steganography is for hiding the fact that you're hiding something, it's not for protecting the thing that you're hiding. You still need real cryptography to do that. You can encode a real cryptographic key in a relatively short passphrase that's easy to memorize using key-stretching. You can then use this passphrase to strongly encrypt as much data as you want. The only thing you should be hiding are the encrypted blocks. If they manage to find these blocks (which they absolutely might! steganography is nowhere near perfect), they should still be encrypted, and they should still look like uniform random noise. You're not supposed to hide the key!