how to search my keynote files for a word even if password protected

I have 15 Keynote files that I use for studying, and they're saved in a folder. I would like to be able to search the folder for certain keywords, and pull up the correct file which contains that word. However, it looks like the password-protection feature makes it impossible to search the Keynote files for certain words.

Is there any way around this? I would like to keep these Keynote files password-protected, but I'd also like to be able to search the folder for certain words, and find the right file.

thx