Compressed keys, Y from X

[jackjack]

I don't get where those values come from...

See https://github.com/jackjack-jj/jasvet/blob/master/jasvet.py
Line 361

[piotr_n]

I don't get where those values come from...

See https://github.com/jackjack-jj/jasvet/blob/master/jasvet.py
Line 361

Thanks! I will have a look..

I was hoping that it would actually be less complicated than what I see in bitcoind+openssl

[jackjack]

I don't find that as complicated as in bitcoin-qt
Your specific problem is only between lines 361->412. I even left the print's so you can uncomment them to see the values

Just delete everything after line 530 and put this

Code:

verifySignature('mqMmY5Uc6AgWoemdbRsvkpTes5hF6p5d8w','H+HUh1GiTw22BMhqRwbSET/4aYCFIuivSgTyU/A+qH7xZp5gz61zp//WMFTbpNDbiMYoYz7pD88NYg/0DekcMpY=','test')

[piotr_n]

Indeed, it looks cool and simple - and it works!

But can you please tell me what the "R*s" (in line 406) actually does?
I mean, you have (decimals):

Code:

Rx = 102145896445573563625240447116654222837109247557536823325858067433615090286321
Ry = 64919894836278270547560110097107560214300342546989031110129938591497073087260
s = 46415740558353013011708862292271156479711188487571029354677187424581448381078

... and R*s gives you a point having:

Code:

x = 112793881772482502863430761842017408792441979840968192252645857563994847441261
y = 47321320458075246750488099844078925876574705494449064910511016586200529015312

So how do I multiply a point by a number to get such a result? I mean, not using python..

[jackjack]

It's the ECC multiplication
You can look at lines 216->237 for algorithm

To understand:
http://cs.ucsb.edu/~koc/ccs130h/notes/ecdsa.pdf
http://en.wikipedia.org/wiki/Elliptic_curve_cryptography
http://en.wikipedia.org/wiki/Elliptic_curve
etc...

[piotr_n]

It's the ECC multiplication
You can look at lines 216->237 for algorithm

To understand:
http://cs.ucsb.edu/~koc/ccs130h/notes/ecdsa.pdf
http://en.wikipedia.org/wiki/Elliptic_curve_cryptography
http://en.wikipedia.org/wiki/Elliptic_curve

OK - thanks a lot, man!
That's all I needed to know.

[piotr_n]

And so it worked in my language as well.
https://github.com/piotrnar/gocoin/blob/master/tools/versigmsg.go

Thanks again, @jackjack!

[jackjack]

I'm glad that helped!