search for: steganography

...s/ssh-timing.pdf > > I'm sure this has been addressed (or dismissed) but I'm looking for the > specific section of code that might deal with this. Any pointers? > > Thanks, > > Chris Why would any code "deal with this"? What you're describing is a form of steganography, embedding another subtler, more dangerous message inside the larger, safer, apparent message. Because there are so many ways to hide such data, it's not even theoretically possible to avoid altogether. OpenSSH would be the wrong layer of the stack to manipulate this, especially given the attem...

Hi, Jean-Marc Valin wrote: > Well, you could change the order in the encoder as long as you reverse > it in the decoder as well. Ok, I see that in the split_cb_shape_sign_unquant function, that each coefficient is tied to it's position in the nb_subvect exc coefficients. Honestly, I have problems understanding what exactly the codebook search works like. If you have the time to to

Hello kind developers, I am planning on creating a steganographic extension for speex/CELP. Since speex/CELP is lossy, there should be quite many bits that one can use for hiding data. I'm familiar with the principles of CELP (two filter loops, one for pitch, the other for formants, let the raw speech frame run through those filter loops, take residue signal, map it on a codebook entry,

...represent a 2D array in C: the codebook has > shape_cb_size entries and subvect_size samples per entry. Ok, that helps. Thanks. >> PS: for me personally, I'd like to know how to change the cb id found >> while keeping the error introduced by this low. > > That's for steganography? I'd say you just look at the nbest list and > chose the 2nd, 3rd, ... best entry instead of the first. Yes. I already introduced into the LSP prediction such an nbest list to do that straightforward. My goal is to make sure if nothing is embedded, the altered Speex version still needs to w...

...quite many bits that one > can use for hiding data. Quite the opposite. Speex uses very few bits, so every bit you corrupt is likely to be heard. You would need to use "fractions of bits" at a time. Even then, it may be hard to hide data efficiently (so it's hard to detect whether steganography was applied). > I'm familiar with the principles of CELP (two filter loops, one for > pitch, the other for formants, let the raw speech frame run through > those filter loops, take residue signal, map it on a codebook entry, > transmit the the two filters and the codebook key). Ple...

...ut especially, how the best_ntarget list is being updated, I am a > little clueless. Hard to explain simply. It's a fundamental thing in CELP. > PS: for me personally, I'd like to know how to change the cb id found > while keeping the error introduced by this low. That's for steganography? I'd say you just look at the nbest list and chose the 2nd, 3rd, ... best entry instead of the first. Jean-Marc

...C: the codebook has >> shape_cb_size entries and subvect_size samples per entry. > > Ok, that helps. Thanks. > >>> PS: for me personally, I'd like to know how to change the cb id found >>> while keeping the error introduced by this low. >> That's for steganography? I'd say you just look at the nbest list and >> chose the 2nd, 3rd, ... best entry instead of the first. > > Yes. I already introduced into the LSP prediction such an nbest list to > do that straightforward. My goal is to make sure if nothing is embedded, > the altered Speex...

...ut especially, how the best_ntarget list is being updated, I am a > little clueless. Hard to explain simply. It's a fundamental thing in CELP. > PS: for me personally, I'd like to know how to change the cb id found > while keeping the error introduced by this low. That's for steganography? I'd say you just look at the nbest list and chose the 2nd, 3rd, ... best entry instead of the first. Jean-Marc ------------------------------ Message: 3 Date: Tue, 19 Sep 2006 15:40:59 +0200 From: Bj?rn Thalheim <s9268716@mail.inf.tu-dresden.de> Subject: Re: [Speex-dev] Exc CB Sear...

Howdy all, So, one night over beers I was telling a friend how you could use the timing between key presses on a type writer to extract information. Basically, you make some assumptions about the person typing (touch typing at so many words per second and then fuzzing the parameters until words come out). The I found a paper written back in 2001 talked about using the interpacket timing in

...;>can use for hiding data. > > Quite the opposite. Speex uses very few bits, so every bit you corrupt > is likely to be heard. You would need to use "fractions of bits" at a > time. Even then, it may be hard to hide data efficiently (so it's hard > to detect whether steganography was applied). Of course, I cannot blindly change bits. But everywhere, where truncation is done, one can change things to embed data. Besides, even if I find no good possibility to embed data in the CELP encoding process, that would still be an ok result for this work. At this time, I see the poss...

Dear OpenSSH team, First of all thanks a lot for your good work on developing such a usable peace of software. Nice job. As you may know, we have some issues using OpenSSH in Iran. Recently the government did some packet filtering on some protocols, including SSH. We don't know what exactly they've done but it appears to be some routing rule that prevents SSH protocol to initiate a