How can you hide information inside a jpg or gif photo?

Question

How can I write some information inside a photo file like jpg or gif without destroying the image? and of course without showing it on the photo since the whole idea is to s

Answer 1

Hey that method is called as Steganography. With that we can hide messages in not just images but also in audio,vedeo and other formats.

Here is an opensouce Steganography software called steganotool This project is an open source steganography tool that can be used to hide and extract text to/ from Bitmap images.

About Steganography Mediums

Steganography in images

This type of steganography is very effective against discovery and can serve a variety of purposes. These purposes can include authentication, concealing of messages, and transmission of encryption keys. The most effective method for this type of steganography is normally the least significant bit method. This simply means that the hidden message will alter the last bit of a byte in a picture. By altering that last bit, there will be relatively no change to the color of that pixel within the carrier image. This keeps the message from being easily detected. The best type of image file to hide information inside of is a 24 bit Bitmap. This is due the large file size and high quality.

Steganography in Audio

In audio files, the most prominent method for concealing information is the low bit encoding method. The low bit encoding method is somewhat similar to the least significant bit method used in image files. The secret information is attached to the end of the file. One of the issues with low bit encoding is that it can be noticeable to the human ear. If someone is trying to hide information, this could be risky, since it is so easily detectable. The spread spectrum method is another method that has been used in the concealment of information in audio files. What this method does, is it adds random noise to the audio broadcast. This method enables for the information to be spread accross the frequency spectrum and remain hiffffden under the random noise. The last method seen in audio steganography is echo hiding data. This method seeks to hide information by using the echos that occur naturally within sound files. Then, extra sound can be added to these echos, extra sound being the concealed message. This is a sufficient way to hide information, expecially since it even improves the sound of the original audio file in some cases.

Steganography In Video

Steganography in Videos is basically hiding of information in each frame of video. Only a small amount of information is hidden inside of video it generally isn’t noticeable at all, however the more information that is hidden the more noticeable it will become. This method is effective as well, but must be done right or else reveal more information instead of hiding.

Steganography In Documents

This is basically adding white space and tabs to the ends of the lines of a document. This type of Steganography is extremely effective, because the use white space and tabs is not visible to the human eye in most text/document editors.

You can also refer to this open source project

This article can be very useful.

Answer 2

compressed data in gif files is in variable sized chunks. each chunk starts with a length byte. Usually these chunks are 255 bytes of data (and the length byte says 255) except for the last two chunks (the last one is 0)

But you could re-code the gif with chunks whose size spells out the message eg using characters for ASCII text or bytes 1 2 3 4 representing 00 01 10 11 binary data,

byte-frequency analysis on the gif would reveal fewer than expected 255 bytes. and the size would be larger than the original, but the image would look exactly the same.