Editing Acoustic cryptanalysis (section)

== Known attacks ==
In 2004, Dmitri Asonov and Rakesh Agrawal of the [[IBM]] [[Almaden Research Center]] announced that [[computer keyboard]]s and keypads used on [[telephone]]s and [[automated teller machine]]s (ATMs) are vulnerable to attacks based on the sounds produced by different keys. Their attack employed a [[Artificial neural network|neural network]] to recognize the key being pressed. By analyzing recorded sounds, they were able to recover the text of data being entered. These techniques allow an attacker using [[covert listening device]]s to obtain [[password]]s, [[passphrase]]s, [[personal identification number]]s (PINs), and other information entered via keyboards.  In 2005, a group of UC Berkeley researchers performed a number of practical experiments demonstrating the validity of this kind of threat.<ref name="Berkeley">{{cite journal
 | url = http://www.berkeley.edu/news/media/releases/2005/09/14_key.shtml
 | title = Researchers recover typed text using audio recording of keystrokes
 | first = Sarah | last = Yang
 | date = 14 September 2005
 | journal = UC Berkeley News
}}</ref>

Also in 2004, [[Adi Shamir]] and [[Eran Tromer]] demonstrated that it may be possible to conduct [[timing attack]]s against a [[Central processing unit|CPU]] performing cryptographic operations by analyzing variations in acoustic emissions.  Analyzed emissions were [[ultrasound|ultrasonic]] noise emanating from [[capacitor]]s and [[inductor]]s on computer [[motherboard]]s, not [[Electromagnetic radiation|electromagnetic emissions]] or the human-audible humming of a cooling fan.<ref name="Shamir">{{cite web
 | url = http://cs.tau.ac.il/~tromer/acoustic/ec04rump/
 | title = Acoustic cryptanalysis: On nosy people and noisy machines
 | first1 = Adi | last1 = Shamir | first2 =  Eran | last2 = Tromer
 | website = tau.ac.il
}}</ref> Shamir and Tromer, along with new collaborator Daniel Genkin and others, then went on to successfully implement the attack on a laptop running a version of [[GnuPG]] (an [[RSA (algorithm)|RSA]] implementation), using either a mobile phone located close to the laptop, or a laboratory-grade microphone located up to 4&nbsp;m away, and published their experimental results in December 2013.<ref name="Genkin">{{cite web
 | url = http://cs.tau.ac.il/~tromer/acoustic/
 | title = RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis
 | first1 = Daniel | last1 = Genkin | first2 = Adi | last2 = Shamir | first3 =  Eran | last3 = Tromer
 | website = tau.ac.il
}}</ref>

Acoustic emissions occur in coils and capacitors because of small movements when a current surge passes through them.  Capacitors in particular change diameter slightly as their many layers experience electrostatic attraction/repulsion or piezoelectric size change.<ref>{{Cite web |url=http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/118EBDDDFA5D532C852572BF0046B776/$file/2007%20CARTS%20-%20Reduced%20Microphonics%20and%20Sound%20Emissions.pdf |publisher=Electronic Components, Assemblies & Materials Association (ECA) |work=CARTS 2007 Symposium Proceedings, Albuquerque |date=March 2007 |title=Capacitors for Reduced Micro phonics and Sound Emission |access-date=2014-01-24 |archive-date=2019-11-16 |archive-url=https://web.archive.org/web/20191116171801/http://www.kemet.com/Lists/TechnicalArticles/Attachments/62/2007%20CARTS%20-%20Reduced%20Microphonics%20and%20Sound%20Emissions.pdf |url-status=dead }}</ref>  A coil or capacitor which emits acoustic noise will, conversely, also be microphonic, and the high-end audio industry takes steps with coils<ref>{{cite web |url=http://meniscusaudio.com/foilq-50mh-16ga-p-1124.html |title=FoilQ, .50mH 16ga |publisher=Meniscusaudio.com |access-date=2014-01-24 |archive-url=https://web.archive.org/web/20140220190435/http://meniscusaudio.com/foilq-50mh-16ga-p-1124.html |archive-date=2014-02-20 |url-status=dead }}</ref> and capacitors<ref>{{cite web|url=http://www.erseaudio.com/Products/PEx250v/50uF-250-volt-Metallized-Polyester-Mylar-Film-Capacitor |title=50uF 250volt Metallized Polyester Mylar Film Capacitor-ERSE |publisher=Erseaudio.com |access-date=2014-01-24}}</ref> to reduce these microphonics (immissions) because they can muddy a hi-fi amplifier's sound.{{Citation needed|date=September 2023}}

In March 2015, it was made public that some inkjet printers using ultrasonic heads can be read back using high frequency [[MEMS]] microphones to record the unique acoustic signals from each nozzle and using timing reconstruction with known printed data,{{Citation needed|date=August 2015}} that is, "confidential" in 12-point font.{{Clarify|date=March 2015}}  Thermal printers can also be read using similar methods but with less fidelity as the signals from the bursting bubbles are weaker.{{Citation needed|date=August 2015}}  The hack also involved implanting a microphone, chip storage IC and burst transmitter with long-life Li+ battery into doctored cartridges substituted for genuine ones sent by post to the target, typically a bank, then retrieved from the garbage using challenge-response [[RFID]] chip.{{Citation needed|date=March 2015}}  A similar work on reconstructing printouts made by [[dot-matrix printer]]s was publicized in 2011.<ref>{{cite web
 | url = https://spqr.eecs.umich.edu/courses/cs660sp11/papers/printers.pdf
 | title = Acoustic Side-Channel Attacks on Printers
 | date = January 9, 2011 | access-date = March 10, 2015
 | author1 = Michael Backes | author2 = Markus Dürmuth | author3 = Sebastian Gerling
 | author4 = Manfred Pinkal | author5 = Caroline Sporleder
 | website = eecs.umich.edu }}</ref>

A new acoustic cryptanalysis technique discovered by a research team at Israel's [[Ben-Gurion University of the Negev|Ben-Gurion University]] Cybersecurity Research Center allows data to be extracted using a computer's speakers and headphones.{{Citation needed|date=November 2020}} ''[[Forbes]]'' published a report stating that researchers found a way to see information being displayed, by using microphone, with 96.5% accuracy.<ref>{{Cite web|url=https://www.forbes.com/sites/leemathews/2018/08/31/now-hackers-can-spy-on-you-by-listening-to-your-screen/|title=Now Hackers Can Spy On You By Listening To Your Screen|last=Mathews|first=Lee|website=Forbes|language=en|date=2018-08-31|access-date=2019-03-13}}</ref>

In 2016, Genkin, Shamir, and Tromer published another paper that described a key extraction attack that relied on the acoustic emissions from laptop devices during the decryption process. They demonstrated the success of their attack with both a simple mobile phone and a more sensitive microphone.<ref>{{Cite journal|last1=Genkin|first1=Daniel|last2=Shamir|first2=Adi|last3=Tromer|first3=Eran|date=2016-02-08|title=Acoustic Cryptanalysis|url=http://link.springer.com/10.1007/s00145-015-9224-2|journal=Journal of Cryptology|language=en|volume=30|issue=2|pages=392–443|doi=10.1007/s00145-015-9224-2|s2cid=31377774|issn=0933-2790|url-access=subscription}}</ref>