Can I use PHP base64_encode for image duplicate check?

Question

Converting base64_encode gives the binary data into characters like

9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAUDBAQEAwUEBAQFBQUGBwwIBwcHBw8LCwkMEQ8

Can I take some set of character to check duplicate? Can I do it the same for videos?

Answer 1

No, you don't. Use digest for duplicates checking. SHA1 is good enough choice. It has constant and small footprint in comparing to base64. Base64 is good for transmitting or exchanging binary data but that's all. In addition, base64 is about 1/3 greater than binary data.

Verifying that two files are identical using pure PHP?

Answer 2

Like the others have said, don't use Base64 as a means of comparing files, it would be much much less expensive to to use something like SHA1, particularly if you are using this for videos. See the sha1_file function

For example if you already have a SHA1 sum, it is easy to compare:

if ($storedSHA1 == sha1_file($newImage)){
    // ...some rejection code
}

I'd recommend creating a database table that stores the name, size and SHA1 of each file you upload. Then you can run a simple query to check if any of the records match. If you have a match in your database you know you have a duplicate.

See the below MySQL query.

SELECT SHA1_hash FROM Uploads
WHERE SHA1_hash = '<hashOfIncomingImage>';

Answer 3

You want to use hash functions for that, for example, Sha1. It always returns a 40 character wich you can use to compare.