Encryption check SWIFT

[Alex Lipici]

Hi!

I want to check if a file is already encrypted without decrypting it. I heard about a v4 with those magic bytes at the beginning of file. I tried checking for the first byte to see if it is already encrypted, but i think that the response is the same like another error. So, how can I be sure that the file is encrypted by RNCryptor?

Thanx,

   Alex

[Rob Napier]

The v3 format is not ideal for this in the general case (the v4 format tries to improve this). But the first two bytes will either be 03 00 (key-based) or 03 01 (password-based). 03 01 are not printable characters and are not the signature for any well known format (at least none that I know), so this is a fairly good signature to look for.

-Rob