# Bitcoin Forum

## Bitcoin => Bitcoin Discussion => Topic started by: Delek on April 15, 2015, 02:42:24 PM

 Title: Simple question about Elliptic Curve Cryptography Post by: Delek on April 15, 2015, 02:42:24 PM Hi! :)I was reading about ECC in the mastering bitcoin book and this image is very clear about how the multiplication is done:http://orm-chimera-prod.s3.amazonaws.com/1234000001802/images/msbt_0404.pngHowever, what will happen if a resulting NG exactly hits the most left point in the curve (intersection between the function and X axis)? The tangent line will not find any other point and the multiplication will fail?Thanks a lot for your time. Title: Re: Simple question about Elliptic Curve Cryptography Post by: LiteCoinGuy on April 15, 2015, 04:12:47 PM https://www.youtube.com/watch?v=iB3HcPgm_FI Title: Re: Simple question about Elliptic Curve Cryptography Post by: YarkoL on April 15, 2015, 04:41:18 PM Layman's Guide to Elliptic Curve Digital Signatures (http://www.royalforkblog.com/2014/09/04/ecc/) Title: Re: Simple question about Elliptic Curve Cryptography Post by: carstenh on April 15, 2015, 04:59:47 PM That will never happen for the group used in Bitcoin. That specific point, is not a point on the elliptic curve used by Bitcoin. Such a point, call it Q, would have order 2, i.e. 2Q = O, the point at infinity. However, the points on the elliptic curve Y^2 = X^3 + 7 over Fp form a cyclic group of order a huge prime (almost as large as p). Hence not divisible by 2 and therefore no elements of order 2. Title: Re: Simple question about Elliptic Curve Cryptography Post by: Delek on April 15, 2015, 05:13:13 PM OK, but consider that graph, what will happen if a multiplication reach that point? Title: Re: Simple question about Elliptic Curve Cryptography Post by: sukamasoto on April 15, 2015, 05:26:28 PM more about ECChttp://www.johannes-bauer.com/compsci/ecc/?menuid=4