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# How secure is AES against brute force attacks?

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re: How secure is AES against brute force attacks?
5/14/2012 6:45:03 AM
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This is quite interesting! This article is talking about a brute force attack, however there can be other kind of attacks. more sophisticated and with higher complexity algorithms. Like the next link http://www.computerworld.com/s/article/9219297/AES_proved_vulnerable_by_Microsoft_researchers belongs to an article in which a pair of scientists doing research in Microsoft facilities discovered a way to crack the AES encryption 3 to 5 times faster. Still this seems to be actually hypothetical since even so, they'd need still billions of years to actually decode the key. However all this makes us realize that is a thing of time and the progress of technology. Today's supercomputer's power will become tomorrow's laptop's power.

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re: How secure is AES against brute force attacks?
3/20/2015 1:03:59 PM
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You are right. Allow me to add a couple of things: Please try to learn from history. Enigma had about 2^76 possibilities. Much more than single DES (!). In a way as users we are always behind: All we use can be broken, exept for 1 method...

Now you might think: "Yes, but Enigma had vulnerabilities", that's right. But each crypto system is designed by humans, so each crypto system is weak in a certain way. While trying to crack systems you have to think equally: Think as a software design engineer. So, let me suggest that by choosing large keys, they are often formed by primes. Well, with a -for example- 128 bit key, let us first test THE LARGEST PRIMES and I will ensure you that you will find the key faster than you think. This is what the 'capable bodies' would do (and probably will do). My thoughts are that this is the way you have to think while working with crypto. So -at least- use a 1024 bit key or even larger. The rest smaller than this already has been lost, it is not safe anymore.

Another annoying thing that most people forget is the following: Key exchange is one thing, but data exchange is another. Most people fuzz about key exchange and how safe this must be. Most fantastic procedures are designed for that. But then... , to be followed by a laughable data exchange format to be cracked by seconds (with some statistics only). Then you don't even *need* the key. Please consider this as well.

The best way to encipher data is with the Vernam principle. Only problem is that your key has to be as large as your message, and you have to distribute your key in a safe way. During the cold war the Washington-Moscow hotline worked with this principle. It contained the Siemens M190 mixer machine with a couple of TELEX machines. Look at the cryptomuseum dot com webpages and search for M190. This website will be an eye-opener for you and it is also good to learn about the history. Vernam is the way to go, anywaym have fun !

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re: How secure is AES against brute force attacks?
5/14/2012 12:46:44 PM
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Thanks. To be able to do anything meaningful, encryption has to be way way faster. Microsoft may doing it to support decryption of past smaller key size AES(i.e 64 bits). May be similar to what NSA came up recently setting up huge facility with army of super-computers to reduce decryption time. http://www.forbes.com/sites/andygreenberg/2012/03/16/nsas-new-data-center-and-ultra-fast-supercomputer-aim-to-crack-worlds-strongest-crypto/ Now what is being suspected is NSA may have been recording past encrypted data since long and now it may help recover data that was previously encrypted by 64 bit AES or less. At the end, i agree it a matter of time...

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re: How secure is AES against brute force attacks?
3/26/2013 12:37:55 AM
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Yup i belive it only a matter of time , i don't know if using big masive grid computing it maybe hapend. And i belive military have huge masive computer can make it. Or it has bean try i don't know

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re: How secure is AES against brute force attacks?
10/29/2012 9:52:00 PM
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That may have been true yesterday, however today the fastest computer in the world is capable of 27 quadrillion operations per second, next year it will be a quintillion, a few years later it will be sextillion... in a decade or two it will take minutes to decrypt AES 128. The real question is how long do you need to protect your information?

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re: How secure is AES against brute force attacks?
1/17/2013 4:39:04 AM
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@ MarkRC - OK, when that happens I will just go to 192, or 256 bit keys. Or, in the same time frame as you so wildly assume, perhaps the AES will also increase its complexity exponentially. One of the many other barriers you are ignoring is the problem of energy. To power such supercomputers as you theorize (and more likely that it will be a group of supercomputers like the NSA now uses) it would require about one-half of the world's current electrical energy production. And that is if you run them at normal room ambient temperatures. How will you meet the needs of the world's population if you feed every other gigawatt to a computer? As you wildly increase the computational limits you forget that everything has a cost. Be it energy, world resources, money, people, or whatever, there are limits to even a global effort. The foresight of youth is so shortsighted.

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re: How secure is AES against brute force attacks?
5/21/2013 7:12:50 PM
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The energy argument is a good point. There are theoretical limits to information storage density, and to the minimum amount of energy for calculations. As far as I know, the theoretical minimum energy for switching one line is kT, where k is the Boltzmann constant and T is the temperature (in K). That's 4e-21 J at room temperature. If we assume that testing an n-bit key takes 1000n switches (an absurdly low estimate), then it takes 5e-16 J per test, and thus 1.75e23 J total to do a brute-force crack of a 128-bit key. The earth's current energy consumption is about 150 PWh per year, or 5.4e17 J per year. That means it would take 300000 years to power the calculation to break the 128-bit key, assuming the same power generation of the earth, assuming absolute theoretical minimal switching energies, and assuming ridiculously small numbers of switches per test. Call me naive, but I don't think the NSA has a secret AES-128 cracking lab...

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re: How secure is AES against brute force attacks?
5/21/2013 7:14:34 PM
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I made a mistake in my calculations - the theoretical minimum switching energy is kT.ln(2). So it would only take 200000 years to power the calculations!

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re: How secure is AES against brute force attacks?
5/5/2013 1:31:54 PM
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I have written an encryption/decryption system which uses Blowfish to generate the DES keys of which there are 4x blocks also I am using AES 256 as the filling to this DES sandwich algorithm which also uses cipher block chaining so would this be a better solution and resistant to hacking.

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re: How secure is AES against brute force attacks?
5/5/2013 1:37:06 PM
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Sorry to have forgotten to add this the way the system would work is to start with DES being used 4 times on the four input blocks then those four input blocks are fed into AES256 and finally into 4 OUTPUT blocks via the DES to complete one cycle of encryption also the system can be used in reverse.

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re: How secure is AES against brute force attacks?
5/20/2013 3:53:26 PM
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Thanks for the great article on data security based on brute force attacks. I am looking at quantum algorithms and the use of quantum computers (D-Wave from Canada). My sense is that quantum is the biggest threat to data security in the medium term. In the short term attacks based on side channel leakage and active attacks are the main problem.

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re: How secure is AES against brute force attacks?
5/20/2013 10:11:36 PM
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People who talk about this stuff often ignore 3 factors that make any code more secure. I was reminded of this by the speed comment. - Symmetric encryption is usually used to securely open a conversation. The initial part of the conversation trades information that is then used to encrypt the rest of the conversation with a much simpler asymmetric encryption. - Because it is primarily a conversation opener, you can say that you have to have 100 msec between attempts. At this point the power of your computer doesn't matter. You can only try 10 times per second no matter how fast your computer is. - The response to the last one is that they don't have to retry. They can try repeatedly to decrypt the same recorded message. However, that only works if they have a way to assess that they have successfully decrypted it. Information exchanges as given above can be in the form of a chain of completely random numbers with no encrypted checksum. That makes it impossible to know if you have cracked it without cracking the whole bloody conversation. What I am saying is that the messages can be designed in such a way that the code breaker has no way of knowing when he got it right. It does him no good to guess the correct key if he doesn't know he got it.

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re: How secure is AES against brute force attacks?
3/20/2015 1:09:15 PM
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@Sparky:  You have the Symmetric and Asymmetric (Public Key) parts switched.  The Public Key algorithms are used to perform the authentication and key handshake, and then the symmetric algorithms such as AES or 3DES are used to encrypt the conversation.  The author was only disussing the cracking of AES here, and with a brute force approach there would be no need to attack the Public Key handshake (although of course that's another attack vector that could be used!)  Regardless, your concluding point at the end is valid regarding the cracker's need to know something about what properly decoded plaintext "should" look like.  But in almost all cases, that is quite reasonable since the wrong decryption key yields statistically random jibberish and the correct key yields something that stands out as being non-random (regardless of what the payload actually is).  Sure, the paranoid can obscure their plaintext in a really good way by performing another encryption layer, but then of course your workload has doubled to protect the traffic!

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re: How secure is AES against brute force attacks?
2/22/2016 12:00:13 PM
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This may be just a "nit", but isn't that 1 billion billion years the time required to evaluate ALL possible keys?

I guess what I'm pointing out is a slight flaw in the calculation/logic that seems to assume a brute force attack must calculate all possible outcomes prior to determining which was the correct one. Granted, It would still come out to about half a billion billion years (on average), which is still essentially "unbreakable"...

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re: How secure is AES against brute force attacks?
5/21/2013 3:41:54 PM
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According to current research on cryptoanalisys strenght of AES-256 is comparable with bruteforce key size about 220-bits. So there is no sense to use pure bruteforce. Of course 2^220 is still very big number, but future technics may still lower number. Beside of that, there are additional tricks that could be used against particular AES implementation (in hardware or software), that may lead to recovering the value of the key. This is the most current problem.

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re: How secure is AES against brute force attacks?
5/21/2013 8:39:40 PM
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It is correct that there are ways to reduce the keyspace you need to search - and that future research may reduce this a little more. And it may turn out that in the future, there will be a breakthrough that reduces the search keyspace significantly - but there is no indication of that at the moment. So even with 128-bit AES, the cheapest and most reliable way to break the key is to use one of the two traditional methods - the three B's technique (bribery, burglary, blackmail) or rubber hose cryptoanalysis. And it looks likely to remain that way for a long time yet.

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re: How secure is AES against brute force attacks?
5/22/2013 3:35:13 PM
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Pentaflops? Good one.

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Demo
11/13/2013 6:14:43 AM
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There is an online demo for AES encryption and decryption

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AES weakness
2/3/2014 1:17:01 PM
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I believe AES weakness is not in the Symmetric algorithm itself.

Rather, IMO, the weakness comes in the randomization of the initialization vector.  We've already heard how NSA underminds the Dual_EC_DRBG.  :)

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security
7/14/2014 8:32:55 AM
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The cryptographic algorithms used in Advanced Encryption Standards are more secure due to 128-bit symmetric keys, if someone sets a password containing both letters and symbols it is very hard for any hacker to find out the code. I use a 128 bit key size password on our workflow management systems and I am sure no one will break it, for a better security I use a random password generator that maximizes the security of the password.