Should I Use ByteArray or Something Else?

hello everybody
at the current status of my project i must write an application (With AIR or ZINC) who its job is:

1st-getting some files from user
2nd-modify them with an algorithm (encryption or encoding or changing byteArray) to simply corrupt the file and make it impossible for other applications to read the corrupted file!!
3th-saving corrupted file on disk!!

then i must make another application to:
1st- open the corrupted file
2nd- fix it with the reversed algorithm of above “file corrupter application”
3th- read it in normal way

currently the files that needs to be corrupted with my “file corrupter application” are FLV files and may be something else in the future

I’ve got this thing to work previously with Encryption/Decryption methods in MDM Zinc and/or Crypto for AS3 but both of them was so weak :huh:

maybe i could use ByteArray to corrupt/repair files and i think it might be too fast but i dont know how could i implement it :h:

any advice is really appreciated…

you should excuse me for my poor English…