[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Computer-stored encryption keys are not safe from side-channel attacks

If you didn't patent it and you published it publicly, you effectively gave it away for anyone to use.  It is also now prior art, so 
finding a link that proves it was published would be useful.  And you have bragging rights to inventing it if you were first.

So, the $5000 would have been a good deal since you didn't have any value to sell, since everyone already "owns" a license to use it.


On 3/13/15 11:21 AM, jim bell wrote:
> Approximately December 24, perhaps it was 1996, I published an idea on a USENET area (maybe it was SCI.CRYPT) that proposed an 
> idea that clock oscillators used in computers could be frequency-modulated with a long-period pseudo-random (linear feedback shift 
> register) value to smear the output of the signal (and everything that depends on it) over a range of frequencies.
> Curiously, in early 2007 (When I was at United States Penitentiary, Florence Colorado) I received a letter from a law firm 
> offering me $5,000 for ownership of this idea.  (They had apparently figured out who I was, and had traced me down at my 
> then-current address.)  I presumed that around that time, there was probably a lawsuit challenging a patent on this matter, and 
> the law firm was doing 'due diligence' looking for ammunition.  I counter-offered that if they pay me 1/3 of the value of this 
> idea, I would settle for that.  Never heard back from them.
>  Jim Bell
> On Friday, March 13, 2015 3:56 AM, Eugen Leitl <[email protected]> wrote:
> http://www.techrepublic.com/article/computer-stored-encryption-keys-are-not-safe-from-side-channel-attacks/
> Computer-stored encryption keys are not safe from side-channel attacks
> By Michael Kassner March 11, 2015, 1:25 PM PST
> Using side-channel technology, researchers at Tel Aviv University can extract
> decryption keys from RSA and ElGamal implementations without altering or
> having control of a computer.
> Figure A: Tel Aviv University researchers built this self-contained PITA
> receiver.  Image courtesy of Daniel Genkin, Lev Pachmanov, Itamar Pipman,
> Eran Tromer, and Tel Aviv University
> Not that long ago, grabbing information from air-gapped computers required
> sophisticated equipment. In my TechRepublic column Air-gapped computers are
> no longer secure, researchers at Georgia Institute of Technology explain how
> simple it is to capture keystrokes from a computer just using spurious
> electromagnetic side-channel emissions emanating from the computer under
> attack.
> Daniel Genkin, Lev Pachmanov, Itamar Pipman, and Eran Tromer, researchers at
> Tel Aviv University, agree the process is simple. However, the scientists
> have upped the ante, figuring out how to ex-filtrate complex encryption data
> using side-channel technology.
> The process In the paper Stealing Keys from PCs using a Radio: Cheap
> Electromagnetic Attacks on Windowed Exponentiation (PDF), the researchers
> explain how they determine decryption keys for mathematically-secure
> cryptographic schemes by capturing information about secret values inside the
> computation taking place in the computer.
> "We present new side-channel attacks on RSA and ElGamal implementations that
> use the popular sliding-window or fixed-window (m-ary) modular exponentiation
> algorithms," the team writes. "The attacks can extract decryption keys using
> a low measurement bandwidth (a frequency band of less than 100 kHz around a
> carrier under 2 MHz) even when attacking multi-GHz CPUs."
> If that doesn't mean much, this might help: The researchers can extract keys
> from GnuPG in just a few seconds by measuring side-channel emissions from
> computers. "The measurement equipment is cheap, compact, and uses
> readily-available components," add the researchers. Using that philosophy the
> university team developed the following attacks.
> Software Defined Radio (SDR) attack: This comprises of a shielded loop
> antenna to capture the side-channel signal, which is then recorded by an SDR
> program installed on a notebook.
> Portable Instrument for Trace Acquisition (PITA) attack: The researchers,
> using available electronics and food items (who says academics don't have a
> sense of humor?), built the self-contained receiver shown in Figure A. The
> PITA receiver has two modes: online and autonomous.
> Online: PITA connects to a nearby observation station via Wi-Fi, providing
> real-time streaming of the digitized signal. Autonomous: Similar to online
> mode, PITA first measures the digitized signal, then records it on an
> internal microSD card for later retrieval by physical access or via Wi-Fi.
> Consumer radio attack: To make an even cheaper version, the team leveraged
> knowing that side-channel signals modulate at a carrier frequency near 1.7
> MHz, which is within the AM radio frequency band. "We used a plain
> consumer-grade radio receiver to acquire the desired signal, replacing the
> magnetic probe and SDR receiver," the authors explain. "We then recorded the
> signal by connecting it to the microphone input of an HTC EVO 4G smartphone."
> Cryptanalytic approach
> This is where the magic occurs. I must confess that paraphrasing what the
> researchers accomplished would be a disservice; I felt it best to include
> their cryptanalysis description verbatim:
> "Our attack utilizes the fact that, in the sliding-window or fixed window
> exponentiation routine, the values inside the table of ciphertext powers can
> be partially predicted. By crafting a suitable ciphertext, the attacker can
> cause the value at a specific table entry to have a specific structure.
> "This structure, coupled with a subtle control flow difference deep inside
> GnuPG's basic multiplication routine, will cause a noticeable difference in
> the leakage whenever a multiplication by this structured value has occurred.
> This allows the attacker to learn all the locations inside the secret
> exponent where the specific table entry is selected by the bit pattern in the
> sliding window. Repeating this process across all table indices reveals the
> key."
> Figure B is a spectrogram displaying measured power as a function of time and
> frequency for a recording of GnuPG decrypting the same ciphertext using
> different randomly generated RSA keys. The research team's explanation:
> "It is easy to see where each decryption starts and ends (yellow arrow).
> Notice the change in the middle of each decryption operation, spanning
> several frequency bands. This is because, internally, each GnuPG RSA
> decryption first exponentiates modulo the secret prime p and then modulo the
> secret prime q, and we can see the difference between these stages.
> "Each of these pairs looks different because each decryption uses a different
> key. So in this example, by observing electromagnetic emanations during
> decryption operations, using the setup from this figure, we can distinguish
> between different secret keys."
> Figure B: A spectrogram Image courtesy of Daniel Genkin, Lev Pachmanov,
> Itamar Pipman, Eran Tromer, and Tel Aviv University
> Any way to prevent the leakage?
> One solution, albeit unwieldy, is operating the computer in a Faraday cage,
> which prevents any spurious emissions from escaping. "The cryptographic
> software can be changed, and algorithmic techniques used to render the
> emanations less useful to the attacker," mentions the paper. "These
> techniques ensure the behavior of the algorithm is independent of the inputs
> it receives."
> Interestingly, the research paper tackles a question about side-channel
> attacks that TechRepublic readers commented on in my earlier article, "It's a
> hardware problem, so why not fix the equipment?"
> Basically the researchers mention that the emissions are at such a low level,
> prevention is impractical because:
> Any leakage remnants can often be amplified by suitable manipulation as we do
> in our chosen-ciphertext attack; and Leakage is often an inevitable side
> effect of essential performance-enhancing mechanisms.
> Something else of interest: the National Institute of Standards and
> Technology (NIST) considers resistance to side-channel attacks an important
> evaluation consideration in its SHA-3 competition.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://cpunks.org/pipermail/cypherpunks/attachments/20150313/e32d0474/attachment-0001.html>