ahhh! i should have realised that compression bit.. now, how dumb do i feel?

As an alternative i could then convert the gif to a jpg, however wouldnt that be reasonably expensive for a web application?..

The reason i'm interested particularly in gifs is i have a CGI that generates a graph as a gif. What i need to be able to do is determine whether the generated graph is authentic (ie a user has not altered it..) As the website generates a reasonable amount of hits, what i cant do is store a digest anywhere..
i figure embedding a 'fingerprint' in the graph is a reasonable method of achieving this.

The next question is, what do i use as a message? i figure a SHA1 or MD5 digest seeded with a combination of the users name and a long, strong password, known only to administrators.

In reply to Re: Re: Gif steganography by Ryszard
in thread Gif steganography by Anonymous Monk

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