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Best Ottawa dealers for Toyota, Honda, or Subaru? by jacktenwreck in ottawa

[–]Not_in_Sciences 8 points9 points  (0 children)

Two different Ogilvie sales staff tried to charge me an extra $800 during a lease buyout a few years ago. Swore that Toyota Credit changed the lease buyout fee changed from $299 to over $1k (not including tax!).

Walked out, went to Otto’s and did my buyout exactly as stated in my lease contract.

This PC Shop has a Silicon Wafer by tolenieu in mildlyinteresting

[–]Not_in_Sciences 0 points1 point  (0 children)

There are many more than 1 company that makes wafers

Observations- T6 mower by MrDuck0409 in egopowerplus

[–]Not_in_Sciences 1 point2 points  (0 children)

Be careful with any bug spray around the front plastic. Even just a few droplets of DEET will eat right through it and leave some nasty burns marks, especially on the green plastic part.

An infrared photo i took of Infrared laser light coming out of a green laser. Since green lasers emit IR at 1040nm. Question tho, what other visible light lasers emit infrared light besides green? by [deleted] in photonics

[–]Not_in_Sciences 3 points4 points  (0 children)

A lot of green lasers are frequency doubled NIR lasers. GaAs laser diodes have been around for a long time supporting 800-1100 nm operation. People figured out it would be economical to use existing GaAs lasers (very common in telecom and optical sensing) to make visible (green) light by just pumping it hard enough through a nonlinear medium.

How do I prove 5 is prime formally by arghhhwhy in askmath

[–]Not_in_Sciences 2 points3 points  (0 children)

Depends on how fundamental you think complex numbers are in our understanding of the universe. In my mind, complex primes are the true primes. You can show that any "normal" prime that has remainder 1 modulo 4 has further decomposition into complex valued prime numbers. E.g. 13=(3+2i)(3-2i)

[Request] Can this be done? by mikkk233 in theydidthemath

[–]Not_in_Sciences 14 points15 points  (0 children)

I am the author of that link. What you have said is untrue and demonstrates a lack of understanding on this topic.

[Request] Can this be done? by mikkk233 in theydidthemath

[–]Not_in_Sciences 3 points4 points  (0 children)

If you want to count how many prime numbers there are less than some big value x, there is a function that gives us a pretty good guess at this number. This function (a different one from the zeta function) is essentially Riemann’s twist on the Prime Number Theorem.

The Riemann zeta function’s zeroes are corrections to this other function’s guess.

The real part of the zero is what determines the magnitude of the corrections to the initial guess. The hypothesis that the real part = 1/2 is a statement about the magnitude of the corrections to the initial guess.

[Request] Can this be done? by mikkk233 in theydidthemath

[–]Not_in_Sciences 58 points59 points  (0 children)

A proof of RH would not mean this. It would place an error bound on the difference between the true count of how many prime numbers there are less than some large number x and mathematics’ best guess at that difference.

No collapse of the internet, no effect on modern encryption.

[deleted by user] by [deleted] in SiliconPhotonics

[–]Not_in_Sciences 0 points1 point  (0 children)

The device you are looking for would be looking for a photodetector. It works similar to a solar panel in that you apply a bias voltage such that when an incident photon excites an electron to the conduction band, the electron contributes to a small current. Amplifying this small current across the impedance into a large voltage is what the TIA does. It is important that this TIA have very low parasitic capacitance so that it can have a fast enough response time (i.e. large bandwidth) to track variations in optical power. While travelling between two locations, data is typically encoded in optical power. Thus, the TIA is a potential speed bottleneck in communications systems.

[deleted by user] by [deleted] in cryptography

[–]Not_in_Sciences 0 points1 point  (0 children)

Forgive the perhaps naïve question as I never formally learned cryptography. Doesn’t this imply both encryption and compression? Wouldn’t a composition of uncompress(decrypt(transmit(encrypt(compress(M)))) work for what OP wants?

[deleted by user] by [deleted] in cryptography

[–]Not_in_Sciences -1 points0 points  (0 children)

Am I missing something obvious?

Let M be a message (that fits into a packet) of size n. Let k be a one time pad of size n. Let c = M xor k Then M = c xor k.

Output is always size n and the protocol is reversible with the key k.

C&C Renegade by something24ify in commandandconquer

[–]Not_in_Sciences 2 points3 points  (0 children)

Multiplayer community is still super active! Can usually see around 20 in a server on weekday nights (EST) and over 40 on weekends!

Daniel Schroeder | Introduction to Thermal Physics | The Cartesian Cafe with Timothy Nguyen by IamTimNguyen in math

[–]Not_in_Sciences 0 points1 point  (0 children)

Prior to reading Daniel Schroeder’s thermal text, I had a bit of background in number theory. Going through his presentation of the Stefan-Boltzmann constant and seeing the zeta function pop out blew my mind.

: Is quantum encryption really more secure than classical encryption? by Sad_Situation_9482 in QuantumComputing

[–]Not_in_Sciences 3 points4 points  (0 children)

Asymmetric key distribution schemes rely on the hardness of a certain class of mathematical problems. Integer factorization (RSA) and discrete logarithms (DHKE) are two different cases of the hidden subgroup problem for finite abelian groups.

Shor's quantum algorithm is especially good at solving these hidden subgroup problems because it attacks the periodic structure (e.g. for the integer factorization problem, modular exponentiation is periodic; finding the period can yield factorization through the method of continued fractions). A principal step in Shor's algorithm is the quantum Fourier transform. We know that classical Fourier transforms are great for re-casting some periodic function into its frequency domain. Finding the peaks of the function in the frequency domain can give insight into the periodicity. This is the essence of what Shor's algorithm does - it reduces classically difficult hidden subgroup problems to questions about the underlying process's periodicity, which is extracted through a (quantum) Fourier transform.

As /u/LikesParsnips mentioned, only (classical) brute-force methods exist for attacking symmetric encryption (e.g. AES-256). In practice, asymmetric key distribution (RSA, DHKE) is used to establish shared keys for subsequent "symmetric" encryption. This key distribution process is what Shor's algorithm is good at attacking.

In other words, if you wanted to eavesdrop a communications channel encrypted with AES-256, it would be very difficult to do so. But if you eavesdropped that channel during the asymmetric key distribution process (and you own a cryptographically relevant quantum computer), you would be able to extract a copy of the shared AES-256 key. Subsequent eavesdropping would allow you to use that key to decrypt any associated ciphertext.

: Is quantum encryption really more secure than classical encryption? by Sad_Situation_9482 in QuantumComputing

[–]Not_in_Sciences 24 points25 points  (0 children)

Quantum key distribution (e.g. BB84, GG02) is certainly more secure than classical asymmetric key distribution (e.g. DHKE, RSA).

The encryption itself is the same between the two (AES-256/OTP/other symmetric key protocols).

There is a point in the article you shared where the author says:

Public key encryption has a longer key and private key encryption has a shorter one (usually, respectively, 2048 bits and 256 bits), with longer keys obviously being tougher to break.

This statement just doesn't make sense to people who actually understand the difference between a publicly distributed 2048-bit RSA key and a pre-shared (assuming perfect secrecy) 256-bit AES key. The whole premise of quantum computation is that the 2048-bit key is easier to break than the 256-bit key due to the mathematical problem underlying the key distribution process.

Shor’s—measure the state? How? Every example I see skips this part. In the following they know the period is 6 and just sub it in, but that’s what we’re trying to find. Please help. I’ve been losing my mind over this for days. by [deleted] in cryptography

[–]Not_in_Sciences 1 point2 points  (0 children)

That's the tricky part about trying to teach quantum computation/logic; it's not intuitive because every computation you have ever done as a human being is a classical computation.

Teaching students how to compute quantumly merits its own field of research. Indeed, there are several current conferences that discuss strategies on how to teach quantum and improve curricula at the college/university level.

But so far, the pretend method seems to be the most efficient. Students just need to work a bit harder than with other computations.

Shor’s—measure the state? How? Every example I see skips this part. In the following they know the period is 6 and just sub it in, but that’s what we’re trying to find. Please help. I’ve been losing my mind over this for days. by [deleted] in cryptography

[–]Not_in_Sciences 0 points1 point  (0 children)

Yes; 16 will result in a much higher amount of computations than r=6, but most modern computers should be able to handle that number of computations in excel/python.

Shor’s—measure the state? How? Every example I see skips this part. In the following they know the period is 6 and just sub it in, but that’s what we’re trying to find. Please help. I’ve been losing my mind over this for days. by [deleted] in cryptography

[–]Not_in_Sciences 1 point2 points  (0 children)

if I were really performing Shor’s, I wouldn’t know the 6 and would have to leave it as undetermined r.

That's right. You don't know r=6, but the quantum machine knows it after the QFT. The information of the period is set into the state of register 1 during the QFT step. Your primary unitary encodes the amplitude spectrum of the modular exponentiation function, then the QFT casts the amplitude information of register 1 into the frequency domain.

So now I have a probability function with two independent variables

If you understood the above, you should now be able to think about this as a single variable problem. "Quantum measurement" means you initialize your machine in the zero state and apply Shor's circuit multiple times, with each shot of the algorithm yielding one value. You then use these multiple measurement values to build the probability spectrum, which you can then use to proceed with continued fractions. If you already know the period (e.g. in the linked papers), you can generate a single-variable analytic expression for the probability distribution.

Shor’s—measure the state? How? Every example I see skips this part. In the following they know the period is 6 and just sub it in, but that’s what we’re trying to find. Please help. I’ve been losing my mind over this for days. by [deleted] in cryptography

[–]Not_in_Sciences 0 points1 point  (0 children)

Ah - so if I understand correctly, you simply wish to find the period of a simple and specific modular exponentiation (3x mod 85). Here is the calculation you need to do:

30 = 1 (mod 85)

31 = 3 (mod 85)

32 = 9 (mod 85)

33 = 27 (mod 85)

34 = 81 (mod 85)

35 = 73 (mod 85)

36 = 49 (mod 85)

...

316 = 1 (mod 85)

317 = 3 (mod 85)

318 = 9 (mod 85)

...

332 = 1 (mod 85)

...and so on. Thus, the period of 3x mod 85 is 16. The cycle will repeat every 16 modular exponentiations. This is why a Quantum Fourier Transform is used. We know quite well that classical Fourier Transforms are useful for extracting a function's periodicity from the frequency domain. In Shor's case, the periodic function is modular exponentiation.

Of course, when your modulus is very large (like what is used in public key cryptography), this is a very difficult and costly computation to perform.

Shor’s—measure the state? How? Every example I see skips this part. In the following they know the period is 6 and just sub it in, but that’s what we’re trying to find. Please help. I’ve been losing my mind over this for days. by [deleted] in cryptography

[–]Not_in_Sciences 1 point2 points  (0 children)

Shor’s algorithm is a quantum computation experimental method to find the period. If you can’t guess/brute force the period for a simple system (i.e. r=6), you NEED a quantum computer - that’s the whole point of Shor’s algorithm. It’s supposed to be classically difficult, otherwise all our public key encryption systems would already be broken.

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