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Why do you think the NSA would like to have a quantum computer?



<< Cracking through everyone's encryption.. >>



use a good algorithm and encrypt at 128 bits and you'll be fine 🙂
 
Basically, they would use it to crack encryption. With current computers, you have to try each possible code in order to crack encryption. Of course, with fast computers that has gotten easier, but it can take a LOOONG time when the encryption code get's really long. With quantum computer you could try every possible combination simultaneously. No matter how long the code is, it would be compromised instantly.
 


<< Basically, they would use it to crack encryption. With current computers, you have to try each possible code in order to crack encryption. Of course, with fast computers that has gotten easier, but it can take a LOOONG time when the encryption code get's really long. With quantum computer you could try every possible combination simultaneously. No matter how long the code is, it would be compromised instantly. >>



that's not true, if you have a flawless 128 bit encryption scheme, it would take a really long time. you can't try every possible combination at the same time, there are still limits as to how many calculations can be performed in a given space of time.
 


<<

<< Basically, they would use it to crack encryption. With current computers, you have to try each possible code in order to crack encryption. Of course, with fast computers that has gotten easier, but it can take a LOOONG time when the encryption code get's really long. With quantum computer you could try every possible combination simultaneously. No matter how long the code is, it would be compromised instantly. >>



that's not true, if you have a flawless 128 bit encryption scheme, it would take a really long time. you can't try every possible combination at the same time, there are still limits as to how many calculations can be performed in a given space of time. >>



That's true for normal computer, but not quantum computers (AFAIK). Quantum computers are fundamentally different when compared to regular computers. You could say that they are bigger revolutionary leap than migration from vacuum-tubes to transistors was. With quantum computer you could try out each possible combination simultaneously.

And 128bit encryption ain't nothing to write home about. I have seen systems with 1024bit encryption.



<< The memory of a classical computer is a string of 0s and 1s, and a classical computer can do calculations on only one set of numbers at once. The memory of a quantum computer is a quantum state which can be in a superposition of many different numbers at once. A classical computer is made up of bits, and a quantum computer is made up of quantum bits, or qubits. A quantum computer can do an arbitrary reversible classical computation on all the numbers simultaneously, and also has some ability to produce interference, constructive or destructive, between various different numbers. By doing a computation on many different numbers at once, then interfering the results to get a single answer, a quantum computer has the potential to be much more powerful than a classical computer of the same size. >>



Source
 


<< that's not true, if you have a flawless 128 bit encryption scheme, it would take a really long time. you can't try every possible combination at the same time, there are still limits as to how many calculations can be performed in a given space of time. >>


128bit encryption is nothing for a Quantum computer. If they existed, it could brute force that in no time...
 
That's true for normal computer, but not quantum computers (AFAIK). Quantum computers are fundamentally different when compared to regular computers. You could say that they are bigger revolutionary leap than migration from vacuum-tubes to transistors was. With quantum computer you could try out each possible combination simultaneously.

no, i am talking about quantum computers. yes, you can perform many more calculations than a normal computer with them. but it is not infinitely many. at least that's what my book says... "Web Security, Privacy, and Commerce" by Simson Garfinkel... according to that book, it would take a quantum computer 108 million years to crack a good 128 bit. *shrug*

And 128bit encryption ain't nothing to write home about. I have seen systems with 1024bit encryption.

yea, but what algorithm? you can crack 128 bits easily if they are poorly implemented.
 


<<

<< Basically, they would use it to crack encryption. With current computers, you have to try each possible code in order to crack encryption. Of course, with fast computers that has gotten easier, but it can take a LOOONG time when the encryption code get's really long. With quantum computer you could try every possible combination simultaneously. No matter how long the code is, it would be compromised instantly. >>



that's not true, if you have a flawless 128 bit encryption scheme, it would take a really long time. you can't try every possible combination at the same time, there are still limits as to how many calculations can be performed in a given space of time. >>

Not true. You're thinking about regular computers. Quantum computers use all kinds of weird quantum physics to break just about any encryption instantly. Even if you had 1024 bit encription it could be broken almost withough effort from a quantum computer. I can't explain it very well myself, but if you head to Slashdot and type quantum into the search box you'll come up with about 500 different articles that have been written, most with links to scientific journals that show exactly how quantum computers work when breaking encryption. I just hope that the NSA doesn't use it on everyday americans until we get quantum computers/quantum encryption on our desks.

Also: As it stands now, quantum computers will not be general purpose machines like a normal desktop is now. A quantum computer will be like an add-in card for todays computers. This may change in the future, but for right now they cannot design a general purpose machine, and specific job machines are still being worked on.
 


<< That's true for normal computer, but not quantum computers (AFAIK). Quantum computers are fundamentally different when compared to regular computers. You could say that they are bigger revolutionary leap than migration from vacuum-tubes to transistors was. With quantum computer you could try out each possible combination simultaneously.

no, i am talking about quantum computers. yes, you can perform many more calculations than a normal computer with them. but it is not infinitely many. at least that's what my book says... "Web Security, Privacy, and Commerce" by Simson Garfinkel... according to that book, it would take a quantum computer 108 million years to crack a good 128 bit. *shrug*

And 128bit encryption ain't nothing to write home about. I have seen systems with 1024bit encryption.

yea, but what algorithm? you can crack 128 bits easily if they are poorly implemented. >>

You're joking right? Throw that book away, the author doesn't know what he's talking about. I've been reading from the very beginning that 128 bit would be as easy as your current computer decoding 2 bit encryption.
 
well, i'm not an expert, i'm just reading my o'reilly book here 😛

but i still say that it would not be simultaneous. if you read up on shor's algorithm, it would still take a quantum computer a few seconds... not instantaneous.
 


<< no, i am talking about quantum computers. yes, you can perform many more calculations than a normal computer with them. but it is not infinitely many. at least that's what my book says... "Web Security, Privacy, and Commerce" by Simson Garfinkel... according to that book, it would take a quantum computer 108 million years to crack a good 128 bit. *shrug* >>



Ummmm.... No. Like others have already said, that's just wrong. Quantum computer would crack 128bit encryption instanteniously. Like I said, quantum computer can try out each possible combination simultaneously, whereas regular computer would try them one after another (naturally it would try them really fast, but it would still take very long time)
 
okay but what i don't get is, if it can do all that stuff simultaneously, how come shor's algorithm is not instantaneous?
 


<< okay but what i don't get is, if it can do all that stuff simultaneously, how come shor's algorithm is not instantaneous? >>



It isn't? To my knowledge, Shor's algorithm is a prime example that demonstrates superiority of quantum computers over regular computers.



<< Calculating this function for an exponential number of a's would take exponential time on a classical computer. Shor's algorithm utilizes quantum parallelism to perform the exponential number of operations in one step. >>



Source

If you are of mathematician-sort, you might want to read the entire paper 🙂. As for me, it went right over my head....
 


<< from the same source

O((log n)^2 * log log n) is fast, but it is not instantaneous! >>



Shor's algorithm might be the exception to the rule 😉. Maybe I should talk with a friend of mine about this, she studies technical physics (quantum physics and the like) and her boyfriend studies mathematics.
 
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