How do you analyze JPEG files for hidden messages?

Answer 1

There are many ways to encrypt a message in an image file.

The way I've seen people do this on YouTube is them just editing the image's hex coding.

Anyway, it depends on how the message is encrypted. If it is just regular text in the image, you have to get a hex editor, such as Hex Workshop, then load the image and parse the hex coding to find the message.

In most cases, it will be located in the first few lines of the hex coding and it will be just a regular string, unencrypted.

In more advanced cases I've seen, it could be located near the middle of the whole hex coding of the image, then encoded again using a method called "Base64". To decrypt this message, I had to open up the hex coding, find the Base64 encoded string (usually ends with two equal signs "=="), then I had to unencrypt the Base64 string, which is really easy. In PHP, it's just a simple command:

echo base64_decode("base64string");

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Once I unencrypted the base64 string, it output the hidden message.

Conclusion:

Just open the image up in Hex Workshop, and read a few lines of the hex coding. Usually the message can be found in the first few lines.