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Chapel Hill Computational Linguists Crack Skype Calls

timothy posted more than 3 years ago | from the hookt-on-fon-iks-indeed dept.

Communications 156

mikejuk writes "You might think of linguistics as being interesting but not really useful. Now computational linguistics [PDF of original paper] has been used to crack Skype encryption and reconstruct what is being said in a VoIP call. What is surprising is that though they are encrypted, the frames that make up a Skype call contain clues about what phonemes are being spoken."

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156 comments

Speach recognition (3, Insightful)

city (1189205) | more than 3 years ago | (#36255540)

My Google Voice voicemail transcription gets about 1 out of 4 words correct. Can Google please buy this company already.

Re:Speach recognition (2, Funny)

Anonymous Coward | more than 3 years ago | (#36255554)

Do you speak as well as you spell?

Re:Speach recognition (2, Funny)

newcastlejon (1483695) | more than 3 years ago | (#36255848)

I hope so; city's spelling was flawless.

You'd best learn what grammar is before you try to be a grammar nazi.

Re:Speach recognition (1)

Eponymous Coward (6097) | more than 3 years ago | (#36255928)

Speach?

Re:Speach recognition (3, Funny)

drb226 (1938360) | more than 3 years ago | (#36255994)

speach [wiktionary.org]

Scottish Gaelic. Noun speach f (genitive speacha, plural speachan)
1. wasp

Like newcastlejon said, his Scottish Gaelic spelling was flawless. I always hate it when Google doesn't recognize my wasps.

Re:Speach recognition (0)

Anonymous Coward | more than 3 years ago | (#36257104)

Like newcastlejon said, his Scottish Gaelic spelling was flawless. I always hate it when Google doesn't recognize my wasps.

Or he's blind and using TTS, you (possibly) insensitive clods!. Not you drb226, that was very amusing.

Could Google [google.com] Speech [google.com] google [google.com] a googol [wikipedia.org] of speach [wiktionary.org] ?

Re:Speach recognition (1)

somersault (912633) | more than 3 years ago | (#36255954)

"Speach"?

Re:Speach recognition (0)

Anonymous Coward | more than 3 years ago | (#36255962)

I hope so; city's spelling was flawless.

I assume you're being sarcastic since we are discussing this in a thread titled "Speach recognition".

Re:Speach recognition (1)

Anonymous Coward | more than 3 years ago | (#36256082)

Moving to the country, I'm gonna eat a lot of speaches.

Speaches come from a can, they were put there by a man, in a factory downtown.

Re:Speach recognition (0)

Anonymous Coward | more than 3 years ago | (#36255990)

Do you consider "speach" to be proper spelling? That's the way city spelled it.

Perhaps YOU'D better learn proper spelling before you falsely call someone else a grammar nazi.

Re:Speach recognition (1)

johanatan (1159309) | more than 3 years ago | (#36257410)

His punctuation left a little to be desired though.

Re:Speach recognition (1)

AK Marc (707885) | more than 3 years ago | (#36257616)

I read his damn post 4 times, slowly, and didn't notice any spelling errors. I never read TFA, and I never read subject lines. I was considering posting something like you did, until I scrolled down and read all the replies that pointed out the error wasn't within the post body...

Re:Speach recognition (1)

jdpars (1480913) | more than 3 years ago | (#36257968)

I applaud your use of the semicolon, good sir!

Re:Speach recognition (0)

Anonymous Coward | more than 3 years ago | (#36255854)

Ze cow goes ... 'Shazzoooouuu'

Re:Speach recognition (1)

bhcompy (1877290) | more than 3 years ago | (#36255556)

Vonage gets about 75%. Not bad. I think, secretly, that they hire people in India to do it.

Re:Speach recognition (1)

fragfoo (2018548) | more than 3 years ago | (#36255680)

Vonage gets about 75%. Not bad. I think, secretly, that they hire people in India to do it.

I should have guessed when the robotic voice sounded like Apoo! Vonaaage!

Re:Speach recognition (1)

city (1189205) | more than 3 years ago | (#36255612)

or hire these researchers I should say.

Linguistics not really useful. The ignorance (3, Insightful)

jmcbain (1233044) | more than 3 years ago | (#36255948)

The ignorance of the statement "You might think of linguistics as being interesting but not really useful" is simply astounding. Linguistics provides the foundation and formal frameworks for grammar, syntax, morphology, phonetics, and semantics that allows us to better understand language. From that basis, computational linguistics is seen simply as an application of linguistics, and computational linguistics of course leads to information retrieval, automatic speech recognition, text classification, and other fields that are among the most important computing topics of the 21st century. Ignorantly saying linguistics is interesting but not useful is like saying physics and chemistry are interesting but not useful.

Re:Linguistics not really useful. The ignorance (2)

moogaloonie (955355) | more than 3 years ago | (#36256668)

Yet it is no less true that someone reading that statement may indeed hold that opinion. I've always found it very interesting... How else might we ever develop human/animal translators?

Re:Linguistics not really useful. The ignorance (1)

sgt scrub (869860) | more than 3 years ago | (#36256836)

Linguistics provides the foundation and formal frameworks for...

Agreed. mikejuk was obviously feeling dyslexic. In point of fact, nobody likes to discuss linguistics. It is boring as hell. :p

Re:Speach recognition (0)

gandhi_2 (1108023) | more than 3 years ago | (#36256054)

Amazing.

This has so little to do with the article, you might as well have said that your cats breath smells like cat food.
Also off topic:
My droid's voice recognition gets Australopithecus afarensis right every time.

Re:Speach recognition (1)

city (1189205) | more than 3 years ago | (#36257034)

Sorry im new here, there are articles?

Side channel attack (5, Informative)

betterunixthanunix (980855) | more than 3 years ago | (#36255566)

The wording in TFS is a little misleading; they did not "crack Skype encryption," they found an exploitable side channel in Skype. The crypto itself has not been cracked, but it was being used in a way that leaked lots of information.

Re:Side channel attack (0)

Anonymous Coward | more than 3 years ago | (#36255796)

It's time for yet another layer of encryption [xkcd.com] .

Re:Side channel attack (2, Interesting)

Anonymous Coward | more than 3 years ago | (#36256154)

The simple description is: By looking at the size of the encrypted data packets you can guess what phonemes were spoken. Yes, that's all there is to it. They are just looking at how much data is sent and guessing what might be said that reasonably fits in that size.

An obvious simple fix would be to vary the length of the packets with random padding (using a cryptographically secure random algorithm to determine the length). It would add overhead but probably not that much considering how small these packets are in the first place (they typically don't use the full allotted bandwidth).

Re:Side channel attack (2)

betterunixthanunix (980855) | more than 3 years ago | (#36256382)

A simpler fix would be to use a different method of compression, which does not vary the length of its output frames.

Re:Side channel attack (3, Informative)

NoSig (1919688) | more than 3 years ago | (#36256774)

If the padding is random you'll decrease the amount of information leaked, but there may still be enough information leaked to reconstruct some conversations. What you really need for total security from this attack is to eliminate the side-channel completely, such as by sending packets of the same size and with the same frequency no matter how much data you've actually got that needs sending. That is a form of padding too, but it is better than random.

Re:Side channel attack (2)

blair1q (305137) | more than 3 years ago | (#36256168)

if your encryption leaves the message where it can be read without decrypting it, then it was never actually encrypted

skype is using a lot more bandwidth than they need to. like single-sideband radio, they can drop at least half the channels they're sending and the information will still be perfectly intelligible on the other end. they've effectively done that by sending superfluous encrypted gibberish on their "main" channel.

the bonus is, their method of sending the message in the side channel is probably patentable.

Re:Side channel attack (1)

betterunixthanunix (980855) | more than 3 years ago | (#36256354)

if your encryption leaves the message where it can be read without decrypting it, then it was never actually encrypted

While you are technically correct, you are not really contradicting what I said.

The encryption algorithm itself does not allow you to obtain the plaintext without decrypting it (as far as we know); the problem is that the protocol requires many encrypted messages to be sent in a particular sequence, and the size and sequence of those messages leaks information about the plaintext. This is a side channel, not a break of the encryption algorithm itself, and the problem is solved without any change to the encryption algorithm: use a different kind of compression (or no compression at all, but there are compression techniques that would not create this sort of side channel).

There is a relevant anecdote: some time ago, an ambassador used an encryption machine to communicate with his home country electronically. The host country was eavesdropping on his communication, and discovered that the plaintext was being transmitted along with the ciphertext (apparently this was due to some wire crosstalk). They had not cracked his encryption algorithm, they simply exploited the fact that the machine he was running the algorithm on was poorly designed.

Re:Side channel attack (4, Interesting)

thePowerOfGrayskull (905905) | more than 3 years ago | (#36256562)

There's a reason that SSH has inserted random padding into its packets since its inception. You would think that the folks at Skype might've done just a a bit more research...

Re:Side channel attack (1)

blair1q (305137) | more than 3 years ago | (#36256822)

The Cone of Silence was never really all that soundproof, either. Nor was it at all cone-like.

Re:Side channel attack (0)

Anonymous Coward | more than 3 years ago | (#36257490)

Here's another anecdote: early digital encrypted mobile phones would have difficulty driving the powerful RF system from the phone's small battery, especially when the battery level was low. And so the power drain from the audio system (powering the speaker) would modulate the RF signal at audio frequencies.

So you might not be able to break the encryption, but that's ok, because you could pick up what was being said using an AM radio!

Oops...

Re:Side channel attack (1)

AK Marc (707885) | more than 3 years ago | (#36257720)

You are right and wrong at the same time. If the encryption still allows information to be accurately pulled from it after encryption, then the encryption is broken. The person that pointed out this flaw and exploited it is termed the person who broke it. So you are correcting someone that was actually correct. And you are correct as well. They aren't unencrypting the encrypted packet and extracting the information. But the encryption is broken because it allows information to be gained from the encrypted packets.

There is a relevant anecdote: some time ago, an ambassador used an encryption machine to communicate with his home country electronically. The host country was eavesdropping on his communication, and discovered that the plaintext was being transmitted along with the ciphertext (apparently this was due to some wire crosstalk). They had not cracked his encryption algorithm, they simply exploited the fact that the machine he was running the algorithm on was poorly designed.

Then to put it in the terms of your anecdote, they were able to compromise his secure communications link, thus the "secure link" was broken. That they didn't ever decrypt the encrypted communications is irrelevant to whether they were able to decode the communications that were encrypted. It doesn't matter if the failure was bad equipment, or, in this case, a poor encryption algorithm. It was broken. Arguing about whether they broke "the encryption" or "the secure channel" or "the encryption machine" is a worthless rhetorical exercise.

Re:Side channel attack (1)

betterunixthanunix (980855) | more than 3 years ago | (#36257840)

Arguing about whether they broke "the encryption" or "the secure channel" or "the encryption machine" is a worthless rhetorical exercise.

Except that it is not just rhetoric. Suppose I use PGP to encrypt all of my email, but then save copies of the plaintext on a "cloud system" and someone comes along and reads the plaintext. What was broken? It was not PGP; PGP, when used correctly is secure.

Yes, if you use a cryptographic algorithm incorrectly, your security may be compromised. That does not mean the cryptographic algorithm was broken, it means your specific way of using it was bad. Just because someone managed to compute Sony's PS3 signing key does not mean that ECDSA has been cracked, and the same method they used would fail against a proper implementation. Likewise, the cipher being used by Skype has not been broken, and if it were used properly there would not be a problem (assuming the cipher itself is secure).

Re:Side channel attack (0)

Anonymous Coward | more than 3 years ago | (#36256590)

I believe that if the original message can be reconstructed, it's fair to say it's cracked. This is not unlike an age- old frequency analysis.

Re:Side channel attack (1)

gatkinso (15975) | more than 3 years ago | (#36256746)

Is that really side channel - by that I mean it seems to me like block cipher mode crypto on a per packet basis is being employed... which would make it akin to a watermarking attack.

Very.... (0)

Anonymous Coward | more than 3 years ago | (#36255604)

cunning!

Re:Very.... (1)

jgtg32a (1173373) | more than 3 years ago | (#36255744)

You might say he's a cunning linguist

Re:Very.... (1)

Nadaka (224565) | more than 3 years ago | (#36256346)

And you sir are a master debater.

Re:Very.... (0)

Anonymous Coward | more than 3 years ago | (#36255754)

You should have said:

Oh! Those cunning linguists.

eww it's not Skype's day... (1)

Azmodan (572615) | more than 3 years ago | (#36255620)

Looks like their karma isnt so good these days!

Ouch.. (0)

SuperCharlie (1068072) | more than 3 years ago | (#36255678)

Seems like the Skype buy wasnt such a good thing for MS... its been what..a week or two and already its been down and compromised?

Re:Ouch.. (1)

Lunix Nutcase (1092239) | more than 3 years ago | (#36256162)

Microsoft hasn't even bought it yet. Secondly, Skype has already had 2 major outages in the last 4 years.

Encrypting a wave (2, Informative)

Anonymous Coward | more than 3 years ago | (#36255692)

Of course, since the data basically represents sound waves, there is a certain level of predictability and pattern on the data unlike normal data which is much more random.

It would have to be a special encryption to get rid of this pattern using a more dynamic algorithm that changes as it progress (which can make it annoying to decrypt or simpler to detect) or disjoint the data over a greater amount of data (making it somewhat harder to find the patterns though still might be possible) of the encryption though that is difficult in a time sensitive app like Skype which encrypts and sends as it receives the data.

Re:Encrypting a wave (2)

betterunixthanunix (980855) | more than 3 years ago | (#36255850)

normal data...is much more random.

Actually, most data used in practice is not uniformly random. Text, images, and even computer programs tend to have significant biases.

It would have to be a special encryption to get rid of this pattern using a more dynamic algorithm that changes as it progress

http://en.wikipedia.org/wiki/Stream_cipher [wikipedia.org]

We know how to get these things right, and the problem with Skype was not the type of data, but rather the way in which that data was compressed.

Re:Encrypting a wave (0)

Anonymous Coward | more than 3 years ago | (#36255956)

What's normal data? If you're encrypting instant messages or text files or pdfs or jpgs or database backups they all have similar amounts of predictability such as file format markers or text containing written language.

In the case of text messages, the length of the ciphertext may leak information, i.e. the fact that a message sent was long or short. Terribly naive text message encrypters might even use ECB mode to encrypt, so the same messages sent multiple times would be obvious to a researcher (e.g. "lol" sent multiple times during a session would have the same ciphertext.)

From the article it looks like the leaked data (message length) exposed possible phonemes, which can be used to recreate phrases that possibly match the original spoken message.

overheard in a private jet hanger (0)

Anonymous Coward | more than 3 years ago | (#36255734)

"8.5 billion USD doesn't buy you as much as it used to"

Re:overheard in a private jet hanger (1)

MightyMartian (840721) | more than 3 years ago | (#36255824)

Indeed. In a few years it will probably buy you a frozen pizza... or Kansas.

Re:overheard in a private jet hanger (1)

blair1q (305137) | more than 3 years ago | (#36256186)

it's a large multiple of what you need to buy a presidential election

Re:overheard in a private jet hanger (1)

BLToday (1777712) | more than 3 years ago | (#36255834)

It's how you spent it not how much you can buy with it. Skype was probably only worth $3B. Microsoft is acting like a newly rich basketball player by overpaying for needless stuff. Just because you can pay for something doesn't mean you should.

Re:overheard in a private jet hanger (2)

somersault (912633) | more than 3 years ago | (#36256022)

It's hardly "newly rich" - it's been rich for quite some time. I'd call this more a "desperate grab for relevance".

Re:overheard in a private jet hanger (1)

NemosomeN (670035) | more than 3 years ago | (#36256896)

You forgot to point out that microsoft isn't. a basketball player, either.

Re:overheard in a private jet hanger (1)

somersault (912633) | more than 3 years ago | (#36257670)

Touche.

plague of any compressed voip conversation (2)

youn (1516637) | more than 3 years ago | (#36255742)

I remember reading something similar with sip over encrypted channel... I guess it is the plague of all compressed communication even if encrypted... the only way to bypass that is use an uncompressed protocol and not blank out the silence. I guess what's new is they've done it with skype.

Re:plague of any compressed voip conversation (2)

afidel (530433) | more than 3 years ago | (#36256000)

I believe if you use a CBR codec like G.711 without VAD or CNG you should be ok.

Re:plague of any compressed voip conversation (1)

19thNervousBreakdown (768619) | more than 3 years ago | (#36256310)

Or make it a constant bitrate.

Re:plague of any compressed voip conversation (1)

NemosomeN (670035) | more than 3 years ago | (#36256914)

Or a constant packet size.

Re:plague of any compressed voip conversation (1)

swalve (1980968) | more than 3 years ago | (#36257020)

Then you can use the variability of the packet rate to deduce [something]. AM versus FM.

Skype's encryption sucks (2)

HBI (604924) | more than 3 years ago | (#36255746)

The reason why is that any serious encryption attempt of IP traffic would make all packets a constant size, significantly below expected MTU size (taking into account tunnels). This attack would not exist in that scenario. They are measuring the payload size of IP packets and matching it to phonemes spoken.

I probably shouldn't blame them for this, but it's barely worth the effort of encrypting the traffic if it is this easy to sniff out the words being spoken.

Re:Skype's encryption sucks (1)

Anonymous Coward | more than 3 years ago | (#36255900)

The reason why is that any serious encryption attempt of IP traffic would make all packets a constant size

From TFA: A solution might be to break the data up into fixed sized frames but this would make it more difficult to reconstruct the data if there was packet loss.

Re:Skype's encryption sucks (1)

HBI (604924) | more than 3 years ago | (#36256038)

Yeah, more difficult but not impossible. You just need a larger window and more buffers.

Re:Skype's encryption sucks (1)

swalve (1980968) | more than 3 years ago | (#36257042)

You don't want buffers in voip. And its UDP, so I don't think there is a window.

Re:Skype's encryption sucks (2)

indeterminator (1829904) | more than 3 years ago | (#36256150)

From TFA: A solution might be to break the data up into fixed sized frames but this would make it more difficult to reconstruct the data if there was packet loss.

And even then, the data rate would leak some information about the content.

The only trivial solution for zero leakage is to either use constant rate encoding, or use some kind of padding to make the data rate constant. Non-trivial solutions would include some random data rate variations to obfuscate the data rate of actual payload content. Unfortunately, all these methods will waste bandwidth.

Re:Skype's encryption sucks (4, Informative)

subreality (157447) | more than 3 years ago | (#36256020)

The reason why is that any serious encryption attempt of IP traffic would make all packets a constant size, significantly below expected MTU size (taking into account tunnels). This attack would not exist in that scenario.

It's actually harder than that. You also have to generate the packets at an even rate as well, or you'll still have some leakage.

Even after you do that, the presence or absence of a stream of packets will at the very least indicate if a call is in progress; to defend against that, you have to *always* transmit the stream.

Even then you're leaking information about the maximum amount of data you could be communicating.

The goalposts keep moving right on down the field when you're talking about side channels. You just have to pick the point where you're comfortable.

Re:Skype's encryption sucks (2)

HBI (604924) | more than 3 years ago | (#36256164)

"Somebody's talking" is information that it'll be hard to conceal without the measures you cite. I'd be ok with that, generally. Having 60% of what I say easily ferreted out is not ok, however.

I read it as... (0)

Anonymous Coward | more than 3 years ago | (#36255756)

Cypress Hill Computational Linguistics

Re:I read it as... (1)

snookerhog (1835110) | more than 3 years ago | (#36255910)

insane in the membrane. so did I.

Re:I read it as... (0)

Anonymous Coward | more than 3 years ago | (#36256124)

Insane in the Skype fraaames

Codec as the weak point (1)

hackertourist (2202674) | more than 3 years ago | (#36255776)

TFA states that this is possible due to the codec that is used:

the best...compression for voice data makes use of the structure of speech

So using a not-optimized-for-speech codec (e.g. mp3 or wav) would defeat this.

Re:Codec as the weak point (1)

blair1q (305137) | more than 3 years ago | (#36256254)

it could have been defeated by encrypting the entire data stream instead of just part of it.

Re:Codec as the weak point (1)

profplump (309017) | more than 3 years ago | (#36256442)

No, it really can't. Essentially this same paper, but as an analysis of SIP-IPSec/SIP-TLS, was published not long ago. Any real-time, size-efficient voice codec leaks a ton of information about the underlying speech just in the rate and size of its packets, so any encryption system that is real-time and length-preserving (i.e. any system that would be considered suitable to be paired with the underlying codec) leaks the same information. You can add padding to hide this, but A) that defeats the purpose of your size-efficient codec and B) while I haven't read any papers specifically analyzing padding techniques in voice comm, the papers analyzing padding in general packet comm suggest it's hard to come up with a padding system that provides an effective screen without adding a significant amount of latency or wasting more bandwidth than you're actually using.

The easiest workaround is really to just use uLaw encoding (or any other CBR codec) so that the packet size and rate doesn't reveal anything about the content of the audio stream. As hacktour suggests, even using a VBR but general-purpose audio codec instead of a voice-specific one would help, though if you're worried about security I wouldn't take the risk (unless you really can't run CBR due to low available throughput).

Re:Codec as the weak point (2)

blair1q (305137) | more than 3 years ago | (#36256794)

Okay, so, then, what are the teachers in the Charlie Brown specials saying?

Huh? Mr. Smarty-pants?

Language? (1)

Kamiza Ikioi (893310) | more than 3 years ago | (#36255828)

TFA was TLDR, but a quick question to those of you with knowledge to understand this... Did a particular language help? Does this work on all languages? Are some languages more secure than others?

IE - Esperanto - Easy to break, but languages with Click Consonants [wikipedia.org] are harder?

Huh? (4, Insightful)

tthomas48 (180798) | more than 3 years ago | (#36255888)

No, I find linguistics pretty useful. Especially since it has some pretty 1:1 relationships with computer programming. And Larry Wall was a linguist. And what kind of lead in is that?

Re:Huh? (1)

blair1q (305137) | more than 3 years ago | (#36256304)

i find linguistics pretty useful, too, since it's how translation of all kinds works (including code compilation). in fact, it's pretty silly to say anyone doesn't find it useful. maybe they meant studying linguistics is pretty useless, if you're not going to work in the construction of translators. but that could be said of any subject, and the continued propagation of that attitude across all subjects and throughout the population, in a nation operating democratically under the principle of majority rule, would result in the ending of public education.

and i'm pretty sure nobody wants that (except those who prefer an ignorant, easily-defrauded public).

Re:Huh? (0)

Anonymous Coward | more than 3 years ago | (#36256682)

"You might think $THING_THAT_ONLY_A_DROOLING_IDIOT_WOULD_THINK but actually, ..."

Speculatively insulting readers is fun, I guess.

Re:Huh? (1)

Trivial Solutions (1724416) | more than 3 years ago | (#36256910)

C:\TEXT\BIBLE.TXT

e
Baruch the scribe and Jeremiah the prophet: but the LORD hid them.

36:27 Then the word of the LORD came to Jeremiah, after that the king
had burned the roll, and the words which Baruch wrote at the mouth of
Jeremiah, saying, 36:28 Take thee again another roll, and write in it
all the former words that were in the first roll, which Jehoiakim the
king of Judah hath burned.

36:29 And thou shalt say to Jehoiakim king of Judah, Thus saith the
LORD; Thou hast burned this roll, saying, Why hast thou

Re:Huh? (0)

Anonymous Coward | more than 3 years ago | (#36257050)

Especially since it has some pretty 1:1 relationships with computer programming.

bullshit

And Larry Wall was a linguist.

would prefer he'd stuck to linguistics.

Similar work in a December 2010 paper (2)

guusbosman (151671) | more than 3 years ago | (#36255898)

A December 2010 paper, "Uncovering Spoken Phrases in Encrypted Voice over IP Conversations", takes a similar approach.

The article was published in ACM Transactions on Information and System Security, PDF version [unc.edu] .

The paper details a gap in the security of VBR compressed encrypted VoIP streams. The authors had earlier found that it is possible to determine the language that is spoken on such a VoIP call, based on packet lengths. Now they have expanded their research and show that itâ(TM)s possible to detect entire spoken phrases during a VoIP call. On average, their method achieved recall of 50% and precision of 51% for a wide variety of phrases spoken by a diverse collection of speakers (some phrases are easier to detect than others; the recall various from 0% to 98%, depending on length of the phrase and the speaker). In other words: they can detect fairly well if a certain phrase is being used in a conversation, even though the VoIP conversation is encrypted.

Encryption... (1)

theamarand (794542) | more than 3 years ago | (#36255908)

Not sure how it works with voice, but I know with text, if you have a part of the message, it's a lot easier to break the encryption method - assuming it's breakable. Security is just a cat and mouse game, anyway. Someone finds a hole, someone plugs the hole, then someone finds another hole...etc. Fun stuff though!

Re:Encryption... (1)

betterunixthanunix (980855) | more than 3 years ago | (#36256036)

with text, if you have a part of the message, it's a lot easier to break the encryption method

This is called a known plaintext attack, and any decent modern cipher should be secure against it (that is, you should learn very little even if I give you plaintext/ciphertext pairs). Modern ciphers are generally designed to be secure against this type of attack, as well as stronger attacks:

  • Chosen plaintext attacks -- the attacker is allowed to request ciphertexts for plaintexts of his choosing.
  • Chosen ciphertext attacks -- the attacker is allowed to request decryptions of ciphertexts of his choosing prior to observing the challenge ciphertext.
  • Adaptive chosen ciphertext attacks -- the attacker is allowed to request decryptions of ciphertexts before and after observing the challenge ciphertexts, but cannot request a decryption of the challenge itself (he can, however, request a decryption of the challenge with a bit flipped or any other modification).

Original Slashdot Story (1)

SJ2000 (1128057) | more than 3 years ago | (#36255916)

Re:Original Slashdot Story (2)

nickersonm (1646933) | more than 3 years ago | (#36256148)

Yes; this is follow-up work to the paper [acm.org] in that earlier article.

Also important to note, neither paper is specific to Skype; their work is on encrypted VoIP in general. But apparently /. prefers things having to do with Skype for some reason.

side channel exploits latency constraint (1)

epine (68316) | more than 3 years ago | (#36255934)

If you can compress the data stream from the packet contents to just the lengths of the packets and still recover the word stream, that suggests two things: A) vocal inflection is worth 100 words per syllable, and B) you're not compressing enough in the first place. Yet there's a reason why compression sucks: the low latency requirement. Compression over 5 minute speech blocks would blow this side channel away.

Were it not for the human tension of a conversation amounting to a group of people mutually waiting to speak (sometimes not so well), this wouldn't be so much of a problem in the first place.

Skeptic: My, what short packets you have!
Skype: All the better to interrupt you with.
Skeptic: What a juicy side-channel that makes.
Skype: Facebook rocks. Shut up and keep talking. I know it's you Alice, under that Hood.

Obligatory XKCD (0)

Anonymous Coward | more than 3 years ago | (#36255940)

http://xkcd.com/114/

Obligatory (1)

Anonymous Coward | more than 3 years ago | (#36255980)

Fuck Computational Linguists!

http://xkcd.com/114/ [xkcd.com]

God encryption (0)

Trivial Solutions (1724416) | more than 3 years ago | (#36256300)

9
4 Be irresolute, stupefied; blind yourselves and stay blind! Be drunk, but not from wine, stagger, but not from strong drink!
10
For the LORD has poured out on you a spirit of deep sleep. He has shut your eyes (the prophets) and covered your heads (the seers).
11
For you the revelation of all this has become like the words of a sealed scroll. When it is handed to one who can read, with the request, "Read this," he replies, "I cannot; it is sealed."
12
When it is handed to one who cannot read, with the request, "Read this," he replies, "I cannot read."
13
The Lord said: Since this people draws near with words only and honors me with their lips alone, though their hearts are far from me, And their reverence for me has become routine observance of the precepts of men,
14
Therefore I will again deal with this people in surprising and wondrous fashion: The wisdom of its wise men shall perish and the understanding of its prudent men be hid.
15
Woe to those who would hide their plans too deep for the LORD! Who work in the dark, saying, "Who sees us, or who knows us?"
16
Your perversity is as though the potter were taken to be the clay: As though what is made should say of its maker, "He made me not!" Or the vessel should say of the potter, "He does not understand."
17

God says, "Gift dispute persevering tamed arrival consequential bridegroom
colours doubtless breath harmonise lost grantest caves
year considereth watchfully king aright styled far shape
based like Hide difference Project's bitter Valentinian
tediousness foamed spokest discontent unstayed unquiet
presides examples soothes ."

And here (1)

MonsterTrimble (1205334) | more than 3 years ago | (#36256390)

I was hoping that Skype had been cracked so we can start using 3rd party messengers!

Fsck You, Slashdot (3, Interesting)

theshibboleth (968645) | more than 3 years ago | (#36256522)

"You might think of linguistics as being interesting but not really useful" Way to go Slashdot, insult one of the most important fields in existence. Do the editors and readers really not realize how closely comp ling is related to AI? I have confidence that eventually computational linguistics will crack speech/language in general and lead to computers that can learn languages as readily as human infants. This will be momentous because it would allow communication between computers and humans. Now it wouldn't solve the consciousness problem, but it would be a step in the right direction.

Re:Fsck You, Slashdot (1)

TeethWhitener (1625259) | more than 3 years ago | (#36257038)

I noticed that too. Replace "linguistics" with "the space program" and watch how many slashdotters go supercritical.

Re:Fsck You, Slashdot (1)

xyourfacekillerx (939258) | more than 3 years ago | (#36257132)

Haha that was about my reaction, and I agree with you entirely. The majority of my off-work hobby time involves something relating to THIS field. 60% of my personal notebooks are dedicated to it.

In particular, I am not so much interested in the models of physical intelligent machines (ANN's and so on) so much as the kind of abstract features of intelligence these capture (language, reasoning, decision making, etc.) I don't think there's a one-to-one mapping between the ability to use, computationally at least, a language - and the physical features of the machine that achieves that "behavior". I mean, I don't think the AI you mentioned depends on those physical details, much like our automobiles do the same things but don't all have internal combustion engines.

I think comp ling, and a few others fields (like those pertaining purely to natural deduction), these are the best approaches to get what you said.

Though let us be responsible as programmers and dispense with the notion of "consciousness" problem. We all know that the machine does what it's told. We will have machines that do very well to understand language in general, but map out its physical implementations, the spaces of RAM the "information" occupies, you see a bunch of disjointed, disconnected, random bits of meaningless data, whose only meaning is determined by the constraints provided by the programmer. This is quite different from the brain, where pieces of matter assert their own relationships. Machines won't be conscious, they need not be.

Do you have Aspergers? (0)

Anonymous Coward | more than 3 years ago | (#36257798)

Or maybe narcissistic personality disorder.
How is 'you might think of linguistics as...' an insult?
That's saying *SOME* people may think that, *NOT ALL* people.

Either you're Dr. Sheldon Cooper or you're trolling.

Crack pipe kills (1)

Anonymous Coward | more than 3 years ago | (#36256552)

First glance: "Computational linguist's crack pipe kills"

First thought: "I guess you would have to smoke crack to want to spend your life as a computational linguist"

What?! (1)

erroneus (253617) | more than 3 years ago | (#36256560)

You mean Skype wasn't smart enough to mix in other sounds while encrypting the original sound?! That is just retarded. Note that I am not a mathematician or any sort of "really smart guy." But I can definitely picture in my mind why this would be somewhat trivial. Vocal sound is primarily frequency modulated which means that the flow of signal will vary in density on a constant carrier. If you mix up the numbers, you will still see a great deal of fidelity in the variations of the frequencies of data regardless of the accuracy of the "decryption" involved. (a decryption of this sort would only need to be approximate to achieve results.)

And from the very beginning, I saw this possibility and presumed everyone else did as well. But if the signal were combined with another sound pattern which the receiving end would know how to properly remove after decryption, there would be a great deal less likelihood that an audio extraction could be made from the encrypted stream.

I have to wonder why this isn't being done. It is simply too obvious to patent.

Re:What?! (1)

Em Adespoton (792954) | more than 3 years ago | (#36256740)

I have to wonder why this isn't being done. It is simply too obvious to patent.

You may have just answered your own question.

Other than that, the only thing I can think of (I had the same assumption you did) is that they were attempting optimal performance and low latency -- Skype actually works amazingly well over some routes that SIP dies on.

It takes a computational linguist... (1)

WaffleMonster (969671) | more than 3 years ago | (#36256622)

To demonstrate the obvious. What do you expect when using high complexity VBR codecs with no blinding of any kind. I sincerely hope this was not news to anyone.

Missed opportunity (1)

essjaytee (141772) | more than 3 years ago | (#36256840)

Surely this was the first ever legitimate use of the phrase "cunning linguist"

School or Town? (1)

methano (519830) | more than 3 years ago | (#36257044)

I found it somewhat surprising that the Town name was used to identify the University. Would you say Ann Arbor or Ithaca or New Haven? You might say Berkeley or Princeton. So, I guess you might say Chapel Hill. OK, never mind.

Can't be that good. (0)

Anonymous Coward | more than 3 years ago | (#36257250)

Voice recognition still sucks, and those guys have UNencrypted data. Neat concept, but reliable enough for what?

Visual example (1)

CODiNE (27417) | more than 3 years ago | (#36257728)

This is not the exact same thing, but it's a great example of how encryption alone is not enough and it must be done right.

Block cipher modes of operation [wikipedia.org]

Scroll down til you see the penguins.

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