in php how to find already encrypted file in specific folder - php

Question

I am using PGP (GNU Privacy Guard) for encrypting the file.
while encrypting i removed the '.pgp' extension of encrypted file.
Now some how i want to know which file is already encrypted in the specific folder.
Note :- my goal is that ... do not encrypt any file twice ... so before encrypt any file .. i want to check is the file already encrypted.
in php can we find out which file is already encrypted ?

Answer 1

PGP file all starts with "-----BEGIN PGP MESSAGE-----".
So you can do something like this:
$content = file_get_contents($filename);
$encrypted = strpos($content, '-----BEGIN PGP MESSAGE-----') === 0;

Answer 2

I really don't know much about how it works, or how you could look at the contents of the file to tell if it is encrypted properly, but could you try decrypting them? If you know you're only working with plain text files, you could examine the first 500 bytes of the decrypted data and if there's strange characters (outside the standard a-z A-Z 0-9 + punctuation, etc), then that could be a clue that the file wasn't encrypted.
This really is a half-arsed answer, I know, but it was a bit long to fit into a comment.

Answer 3

You can't unless you understand the algorithm used in the encryption. Once you understand it, you can apply that to check whether a file is already encrypted.
Also check to make sure that there is already a function available in PGP for checking if something is already encrypted. This is usually present in encryption solutions.
Thanks

Answer 4

There are two possible formats for OpenPGP data, binary and ascii armored.
Ascii-armored files are easy to recognize by looking for "-----BEGIN PGP MESSAGE-----" which can also be done using the unix command file:
$ file encrypted
encrypted: PGP message
#ZZ_Coders answer is totally fine if you're only dealing with ascii armored encrypted files.
If it shows something else, it's not an OpenPGP message - or in binary format. This isn't as easy to recognize (at least I don't know which magic packets you could look for), but you can easily use the gpg command to test the file:
$ gpg --list-only --list-packets encrypted
:pubkey enc packet: version 3, algo 1, keyid DEAFBEEFDEADBEEF
data: [2048 bits]
:encrypted data packet:
length: 73
mdc_method: 2
If it isn't encrypted, response will look like this:
$ gpg --list-only --list-packets something_else
gpg: no valid OpenPGP data found.
In PHP, you could use this code to check if a file is OpenPGP-encrypted:
if (strpos(`gpg --list-only --list-packets my_file.txt 2>&1`,
'encrypted data packet'))
echo "encrypted file";