<p>I have posted a similar question recently, but not this specific.  I have found that a lot may ride on the idea of "point multiplication" yet all explanations I have found lack explanation or are in code that not everyone (especially myself) can decipher.</p>

<p>Supposedly you "add point G to itself k times". Most examples of point addition or point multiplication show multiple x,y coordinates in the same equation but in this situation, I only have an integer to apply to the equation.  Secondarily, many equations that show this also show that you do something such as "Qy - Py" (aka: Q's y-value minus P's y-value).  This is a problem if the only x,y value I'm working with is Q.  If I subtract Q's y-value from Q's y-value I get zero, thereby nullifying the value of the equation.</p>

<p>I think the criteria for the correct answer to this question are as follows:</p>

<ol>
<li><p>It is explained such that anyone who has mathematical experience less than Calculus can at least stumble through it by cutting, pasting, and using a basic calculator that can handle exceedingly large numbers,</p></li>
<li><p>Programming experience/understanding is not needed (code can be used but must not require pre-understanding/experience thereof by anyone reading it),</p></li>
<li><p>Must show or enable people to show themselves how a K value of 18E14A7B6A307F426A94F8114701E7C8E774E7F9A47E2C2035DB29A206321725, and a Gx value of 79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798 and a Gy value of 483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8 equals x and y values of 36422191471907241029883925342251831624200921388586025344128047678873736520530 and 20277110887056303803699431755396003735040374760118964734768299847012543114150.  (Note: whether the answer is in Hex or Decimal is not significant as converters are readily available on many websites), </p></li>
<li><p>Criteria 4 is applicable such that the point multiplication is truly applicable to the question (IE:  that I have asked the proper question in the proper manner).</p></li>
<li><p>Whomever meets criteria 1 through 4 must also post their Bitcoin address to permit a donation.</p></li>
</ol>

<p>I know this seems complicated and perhaps odd (what with me adding actual answer criteria when I'm essentially a beggar) but I want to be clear such that others who read my post and may be wondering the same thing have a better chance of understanding what I'm asking and the answer.  I also want to filter out, as best I can, answers which don't truly answer the question (as I have seen too many of them on this forum and others).  I am not promising any particular amount of bounty but if someone meets all these criteria I will be sufficiently grateful that I would feel guilty if I failed to provide them with some value.  If your answer to my question meets the criteria, please do not hesitate to leave address for alt-coins you may have as well.</p>

CC BY-SA 3.0
2014-05-10T20:54:47.497Z
I think the detail you're missing is that [point doubling](http://en.wikipedia.org/wiki/Elliptic_curve_point_multiplication#Point_doubling) uses a different algorithm than ordinary [point addition](http://en.wikipedia.org/wiki/Elliptic_curve_point_multiplication#Point_addition).
David Schwartz
CC BY-SA 3.0
2014-05-11T00:52:02.247Z
Doh, you're completely right, gotta edit my post to address that part (as I still don't know how to do 3 * (9,8) either)
Mine
CC BY-SA 3.0
2014-05-11T01:43:44.243Z
2 * (4,3) = (56, -419) on what curve? The point (4,3) is not on the "bicoin" curve and the operation is dependent on the curve.
Felipe Voloch
CC BY-SA 3.0
2014-05-11T03:02:59.940Z
`3 * (9,8)` = `[2 * (9,8)] + (9,8)` So if you can do point doubling and you can do addition of two different points, you can do point tripling.
David Schwartz
CC BY-SA 3.0
2014-05-11T05:03:58.173Z
David, I think you may be the one who understands this.  So if we went with your 3 * (9,8) what would the be resulting x,y value?  And is that the same setup/equation for the conversion of the bitcoin private key to public key?
Mine
CC BY-SA 3.0
2014-05-12T01:10:56.683Z
I'm not exactly sure (because I've only scratched the surface of the topic--it's a Calculus 2 topic generally), but I'm pretty sure you need to know the *G* value to calculate it. At least I could calculate it, given the value of *G*.
KJ O
CC BY-SA 3.0
2014-05-14T05:46:51.820Z
KJ O, the "G" value that is mentioned is: 0479BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8 but that is the Gx and Gy I already gave combined and starting with a 04.
Mine
<private-key><ecdsa>
How do you do point multiplication in bitcoin associated with the ecdsa algorithm?
Mine
# How do you do point multiplication in bitcoin associated with the ecdsa algorithm?

(Asked by: username_0 on 2014-05-10)

I have posted a similar question recently, but not this specific. I have found that a lot may ride on the idea of "point multiplication" yet all explanations I have found lack explanation or are in code that not everyone (especially myself) can decipher.

Supposedly you "add point G to itself k times". Most examples of point addition or point multiplication show multiple x,y coordinates in the same equation but in this situation, I only have an integer to apply to the equation. Secondarily, many equations that show this also show that you do something such as "Qy - Py" (aka: Q's y-value minus P's y-value). This is a problem if the only x,y value I'm working with is Q. If I subtract Q's y-value from Q's y-value I get zero, thereby nullifying the value of the equation.

I think the criteria for the correct answer to this question are as follows:

1. It is explained such that anyone who has mathematical experience less than Calculus can at least stumble through it by cutting, pasting, and using a basic calculator that can handle exceedingly large numbers,
2. Programming experience/understanding is not needed (code can be used but must not require pre-understanding/experience thereof by anyone reading it),
3. Must show or enable people to show themselves how a K value of 18E14A7B6A307F426A94F8114701E7C8E774E7F9A47E2C2035DB29A206321725, and a Gx value of 79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798 and a Gy value of 483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8 equals x and y values of 36422191471907241029883925342251831624200921388586025344128047678873736520530 and 20277110887056303803699431755396003735040374760118964734768299847012543114150. (Note: whether the answer is in Hex or Decimal is not significant as converters are readily available on many websites),
4. Criteria 4 is applicable such that the point multiplication is truly applicable to the question (IE: that I have asked the proper question in the proper manner).
5. Whomever meets criteria 1 through 4 must also post their Bitcoin address to permit a donation.

I know this seems complicated and perhaps odd (what with me adding actual answer criteria when I'm essentially a beggar) but I want to be clear such that others who read my post and may be wondering the same thing have a better chance of understanding what I'm asking and the answer. I also want to filter out, as best I can, answers which don't truly answer the question (as I have seen too many of them on this forum and others). I am not promising any particular amount of bounty but if someone meets all these criteria I will be sufficiently grateful that I would feel guilty if I failed to provide them with some value. If your answer to my question meets the criteria, please do not hesitate to leave address for alt-coins you may have as well.

**Tags:** private-key, ecdsa

> **Comments:**
> **username_1**: I think the detail you're missing is that [point doubling](http://en.wikipedia.org/wiki/Elliptic_curve_point_multiplication#Point_doubling) uses a different algorithm than ordinary [point addition](http://en.wikipedia.org/wiki/Elliptic_curve_point_multiplication#Point_addition).  
> **username_0**: Doh, you're completely right, gotta edit my post to address that part (as I still don't know how to do 3 * (9,8) either)  
> **username_2**: 2 * (4,3) = (56, -419) on what curve? The point (4,3) is not on the "bicoin" curve and the operation is dependent on the curve.  
> **username_1**: `3 * (9,8)` = `[2 * (9,8)] + (9,8)` So if you can do point doubling and you can do addition of two different points, you can do point tripling.  
> **username_0**: username_1, I think you may be the one who understands this.  So if we went with your 3 * (9,8) what would the be resulting x,y value?  And is that the same setup/equation for the conversion of the bitcoin private key to public key?  
> **username_3**: I'm not exactly sure (because I've only scratched the surface of the topic--it's a Calculus 2 topic generally), but I'm pretty sure you need to know the *G* value to calculate it. At least I could calculate it, given the value of *G*.  
> **username_0**: username_3, the "G" value that is mentioned is: 0479BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8 but that is the Gx and Gy I already gave combined and starting with a 04.  

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## 0 answers

