Re: quantum computer factors number
Steve Bellovin wrote: A quantum computer has been built that has actually factored a number: 15. It's not a very interesting number from a cryptographic perspective, but it is real. http://www.nature.com/nature/links/011220/011220-2.html Its worth noting that not only is the number not very interesting (15), but various properties of it have been used to make the quantum computer simpler. The quantum computer would not be capable of performing any other calculation. In particular, addition has been substituted for multiplication in one part of the calculation, and the other multiplication has been changed to a completely different operation (bit swapping). Once simplified thus, several operations were omitted because they were known to not actually influence the outcome or because enough of their inputs were known to make them guaranteed to be null operations. These changes are described as optimisations - but since in any real case they would involve performing most of the calculation on a classical computer (AFAICS), its difficult to see how this experiment demonstrates anything other than a remarkable ability to control and measure the quantum state of 7 atoms in a molecule. Which is impressive in itself, but it seems hardly fair to describe it is factorisation. Probably the coolest thing about this experiment is that they have produced what appears to be a very accurate model of the decoherence effects, which should allow quantum computers to be modelled with some certainty in the future. Cheers, Ben. -- http://www.apache-ssl.org/ben.html http://www.thebunker.net/ There is no limit to what a man can do or how far he can go if he doesn't mind who gets the credit. - Robert Woodruff - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
Stegdetect 0.4 released and results from USENET search available
I just released Stegdetect 0.4. It contains the following changes: - Improved detection accuracy for JSteg and JPhide. - JPEG Header Analysis reduces false positives. - JPEG Header Analysis provides rudimentary detection of F5. - Stegbreak uses the file magic utility to improve dictionary attack against OutGuess 0.13b. You can download the UNIX source code or windows binary from http://www.outguess.org/download.php - The results from analyzing one million images from the Internet Archive's USENET archive are available at http://www.citi.umich.edu/u/provos/stego/usenet.php [...] After scanning two million images from eBay without finding any hidden messages, we extended the scope of our analysis. This page provides details about the analysis of one million images from the Internet Archive's USENET archive. Processing the one million images with stegdetect results in about 20,000 suspicious images. We launched a dictionary attack on the JSteg and JPHide positive images. The dictionary has a size of 1,800,000 words and phrases. The disconcert cluster used to distribute the dictionary attack has a peak performance of roughly 87 GFLOPS. However, we have not found a single hidden message. [...] Comments and feedback are welcome. We have an FAQ at http://www.citi.umich.edu/u/provos/stego/faq.html Regards and a merry Christmas, Niels Provos - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
Re: Stegdetect 0.4 released and results from USENET search available
Niels Peter, congratulations on finding no secret messages. This is why computers are getting faster -- so we can spend more and more time searching out the lack of any information being communicated. An obvious step is to extend your detector to handle other formats besides JPEG. That would involve more 'research' than merely running it on other collections of images (e.g. JPEGs pulled from the Web in the Internet Archive collection, or from your own crawler). [Other people can also do the work of running your publicly released software against other collections. It would take more talent to write something that processes other formats.] By the way, I'm interested in what steganographic messages you are finding in the plaintext tags in JPEG files. I've heard that some cameras mark each photo with the serial number of the camera, date, etc. You can probably also detect what model of camera produced the image (based on exactly what tags it puts in the image, whether there's a thumbnail, what the filename is, etc). (Jpegdump provides an easy way to see these tags.) Remember how Microsoft Word documents encode the Ethernet address of the PC on which they were created, and how this has been used in several high-profile cases to track documents to individuals? I am a lot more concerned about popular cameras that spy on their own users, than I am about the occasional subliminal message sent through the Usenet. It would be useful to have a tool that removes all the nonessential tags from a jpeg file, a 'stegremover' to delete any spyware that your camera has left behind, as well as a detector, and a hall of shame page for manufacturers who are building that spyware. John PS: Cypherpunks, where *are* you putting your secret messages? Give us a hint! Surely *somebody* in this crew must be leaving some bread-crumbs around for Niels and NSA to find... :-) - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
Re: Stegdetect 0.4 released and results from USENET search available
On Fri, 21 Dec 2001, John Gilmore wrote: . . . . PS: Cypherpunks, where *are* you putting your secret messages? Give us a hint! Surely *somebody* in this crew must be leaving some bread-crumbs around for Niels and NSA to find... :-) I always assumed newsgroups, like alt.images.binary.*, but perhaps websites that allow users to upload pictures are the preferred channels. Of course there is a big distiction between (intentionally) leaving something around for Niels to find and really trying to hide something -- pj - The Cryptography Mailing List Unsubscribe by sending unsubscribe cryptography to [EMAIL PROTECTED]
