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Can you tell me why doing scalar multiplication of a point on a Elliptic curve over a finite field gets to a point at infinity?


What is the relationship between p (prime), n (order) and h (cofactor) of an elliptic curve?What is the point at infinity on secp256k1 and how to calculate it?Modulus for elliptic curve point multiplicationGraphically representing points on Elliptic Curve over finite fieldElliptic curve group over a prime finite field $F_p$Scalar Multiplication for Elliptic CurveUsage of parameter “b” of an elliptic curve over GF(p)Elliptic curve scalar point multiplicationElliptic curve point multiplication — who is wrong?Understanding elliptic curve point addition over a finite fieldPoint-at-infinity in the scalar multiplicationelliptic curve infinity point implementation returns exception













2












$begingroup$


I am reading Programming Bitcoin. The author said:




Another property of scalar multiplication is that at a certain multiple, we get to the point at infinity (remember, the point at infinity is the additive identity or $0$). If we imagine a point $G$ and scalar-multiply until we get the point at infinity.




He doesn't explain why. So I don't understand why. I would like you to give me a plain explanation, without a serious mathematical proof, if that could be possible.










share|improve this question









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inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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  • $begingroup$
    If you're interested in elliptic curve cryptography, you should maybe just get a book on elliptic curve cryptography in which the basic concepts of groups, elliptic curves, scalar multiplication, and the point at infinity will appear in the first act. If you're interested in cryptocurrency applications, you probably don't need to worry about elliptic curves in detail, and can just use higher-level ideas like signatures.
    $endgroup$
    – Squeamish Ossifrage
    3 mins ago















2












$begingroup$


I am reading Programming Bitcoin. The author said:




Another property of scalar multiplication is that at a certain multiple, we get to the point at infinity (remember, the point at infinity is the additive identity or $0$). If we imagine a point $G$ and scalar-multiply until we get the point at infinity.




He doesn't explain why. So I don't understand why. I would like you to give me a plain explanation, without a serious mathematical proof, if that could be possible.










share|improve this question









New contributor




inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$











  • $begingroup$
    If you're interested in elliptic curve cryptography, you should maybe just get a book on elliptic curve cryptography in which the basic concepts of groups, elliptic curves, scalar multiplication, and the point at infinity will appear in the first act. If you're interested in cryptocurrency applications, you probably don't need to worry about elliptic curves in detail, and can just use higher-level ideas like signatures.
    $endgroup$
    – Squeamish Ossifrage
    3 mins ago













2












2








2


1



$begingroup$


I am reading Programming Bitcoin. The author said:




Another property of scalar multiplication is that at a certain multiple, we get to the point at infinity (remember, the point at infinity is the additive identity or $0$). If we imagine a point $G$ and scalar-multiply until we get the point at infinity.




He doesn't explain why. So I don't understand why. I would like you to give me a plain explanation, without a serious mathematical proof, if that could be possible.










share|improve this question









New contributor




inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$




I am reading Programming Bitcoin. The author said:




Another property of scalar multiplication is that at a certain multiple, we get to the point at infinity (remember, the point at infinity is the additive identity or $0$). If we imagine a point $G$ and scalar-multiply until we get the point at infinity.




He doesn't explain why. So I don't understand why. I would like you to give me a plain explanation, without a serious mathematical proof, if that could be possible.







elliptic-curves cryptocurrency






share|improve this question









New contributor




inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question









New contributor




inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|improve this question




share|improve this question








edited 9 hours ago









Maarten Bodewes

55.7k679196




55.7k679196






New contributor




inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









asked 18 hours ago









inherithandleinherithandle

1111




1111




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inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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New contributor





inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






inherithandle is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











  • $begingroup$
    If you're interested in elliptic curve cryptography, you should maybe just get a book on elliptic curve cryptography in which the basic concepts of groups, elliptic curves, scalar multiplication, and the point at infinity will appear in the first act. If you're interested in cryptocurrency applications, you probably don't need to worry about elliptic curves in detail, and can just use higher-level ideas like signatures.
    $endgroup$
    – Squeamish Ossifrage
    3 mins ago
















  • $begingroup$
    If you're interested in elliptic curve cryptography, you should maybe just get a book on elliptic curve cryptography in which the basic concepts of groups, elliptic curves, scalar multiplication, and the point at infinity will appear in the first act. If you're interested in cryptocurrency applications, you probably don't need to worry about elliptic curves in detail, and can just use higher-level ideas like signatures.
    $endgroup$
    – Squeamish Ossifrage
    3 mins ago















$begingroup$
If you're interested in elliptic curve cryptography, you should maybe just get a book on elliptic curve cryptography in which the basic concepts of groups, elliptic curves, scalar multiplication, and the point at infinity will appear in the first act. If you're interested in cryptocurrency applications, you probably don't need to worry about elliptic curves in detail, and can just use higher-level ideas like signatures.
$endgroup$
– Squeamish Ossifrage
3 mins ago




$begingroup$
If you're interested in elliptic curve cryptography, you should maybe just get a book on elliptic curve cryptography in which the basic concepts of groups, elliptic curves, scalar multiplication, and the point at infinity will appear in the first act. If you're interested in cryptocurrency applications, you probably don't need to worry about elliptic curves in detail, and can just use higher-level ideas like signatures.
$endgroup$
– Squeamish Ossifrage
3 mins ago










1 Answer
1






active

oldest

votes


















3












$begingroup$

The points on the Elliptic Curves are forming an additive group with the identity $mathcalO$, the point at infinity.



The scalar multiplication $k P$ this actually means adding $P$, $k$-times itself



$$kP=underbraceP+P+cdots+P_text$k$ times.$$



Bitcoin uses Secp256k1 which has characteristic $p$ and it is defined over the prime field $mathbbZ_p$ with the curve equation $y^2=x^3-7$.



Point addition in $mathbbZ_p$ has an interesting property since the number of elements is finite if you add a point $P$ itself many times eventually you will get the identity $mathcalO$.



$$underbraceP+P+cdots+P_text$t$ times = mathcalO$$



The smallest $t$ will be the order of the subgroup generated by the $P$. For security, we want this order huge.



Note 1: a point $P$ may not generate the whole group but it generates a cyclic subgroup.



Note 2: As pointed by SqueamishOssifrage, The Smart showed that if the order of the curve and order of the base field are same then the discrete logarithm on this curves runs in linear time.






share|improve this answer











$endgroup$








  • 1




    $begingroup$
    The order of the scalar ring is not the characteristic or order of the coordinate field. The orders are related, but are not the same except in cases that are trivially breakable as Nigel Smart showed.
    $endgroup$
    – Squeamish Ossifrage
    10 hours ago










  • $begingroup$
    @SqueamishOssifrage thanks and for the links.
    $endgroup$
    – kelalaka
    8 hours ago












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1 Answer
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active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









3












$begingroup$

The points on the Elliptic Curves are forming an additive group with the identity $mathcalO$, the point at infinity.



The scalar multiplication $k P$ this actually means adding $P$, $k$-times itself



$$kP=underbraceP+P+cdots+P_text$k$ times.$$



Bitcoin uses Secp256k1 which has characteristic $p$ and it is defined over the prime field $mathbbZ_p$ with the curve equation $y^2=x^3-7$.



Point addition in $mathbbZ_p$ has an interesting property since the number of elements is finite if you add a point $P$ itself many times eventually you will get the identity $mathcalO$.



$$underbraceP+P+cdots+P_text$t$ times = mathcalO$$



The smallest $t$ will be the order of the subgroup generated by the $P$. For security, we want this order huge.



Note 1: a point $P$ may not generate the whole group but it generates a cyclic subgroup.



Note 2: As pointed by SqueamishOssifrage, The Smart showed that if the order of the curve and order of the base field are same then the discrete logarithm on this curves runs in linear time.






share|improve this answer











$endgroup$








  • 1




    $begingroup$
    The order of the scalar ring is not the characteristic or order of the coordinate field. The orders are related, but are not the same except in cases that are trivially breakable as Nigel Smart showed.
    $endgroup$
    – Squeamish Ossifrage
    10 hours ago










  • $begingroup$
    @SqueamishOssifrage thanks and for the links.
    $endgroup$
    – kelalaka
    8 hours ago
















3












$begingroup$

The points on the Elliptic Curves are forming an additive group with the identity $mathcalO$, the point at infinity.



The scalar multiplication $k P$ this actually means adding $P$, $k$-times itself



$$kP=underbraceP+P+cdots+P_text$k$ times.$$



Bitcoin uses Secp256k1 which has characteristic $p$ and it is defined over the prime field $mathbbZ_p$ with the curve equation $y^2=x^3-7$.



Point addition in $mathbbZ_p$ has an interesting property since the number of elements is finite if you add a point $P$ itself many times eventually you will get the identity $mathcalO$.



$$underbraceP+P+cdots+P_text$t$ times = mathcalO$$



The smallest $t$ will be the order of the subgroup generated by the $P$. For security, we want this order huge.



Note 1: a point $P$ may not generate the whole group but it generates a cyclic subgroup.



Note 2: As pointed by SqueamishOssifrage, The Smart showed that if the order of the curve and order of the base field are same then the discrete logarithm on this curves runs in linear time.






share|improve this answer











$endgroup$








  • 1




    $begingroup$
    The order of the scalar ring is not the characteristic or order of the coordinate field. The orders are related, but are not the same except in cases that are trivially breakable as Nigel Smart showed.
    $endgroup$
    – Squeamish Ossifrage
    10 hours ago










  • $begingroup$
    @SqueamishOssifrage thanks and for the links.
    $endgroup$
    – kelalaka
    8 hours ago














3












3








3





$begingroup$

The points on the Elliptic Curves are forming an additive group with the identity $mathcalO$, the point at infinity.



The scalar multiplication $k P$ this actually means adding $P$, $k$-times itself



$$kP=underbraceP+P+cdots+P_text$k$ times.$$



Bitcoin uses Secp256k1 which has characteristic $p$ and it is defined over the prime field $mathbbZ_p$ with the curve equation $y^2=x^3-7$.



Point addition in $mathbbZ_p$ has an interesting property since the number of elements is finite if you add a point $P$ itself many times eventually you will get the identity $mathcalO$.



$$underbraceP+P+cdots+P_text$t$ times = mathcalO$$



The smallest $t$ will be the order of the subgroup generated by the $P$. For security, we want this order huge.



Note 1: a point $P$ may not generate the whole group but it generates a cyclic subgroup.



Note 2: As pointed by SqueamishOssifrage, The Smart showed that if the order of the curve and order of the base field are same then the discrete logarithm on this curves runs in linear time.






share|improve this answer











$endgroup$



The points on the Elliptic Curves are forming an additive group with the identity $mathcalO$, the point at infinity.



The scalar multiplication $k P$ this actually means adding $P$, $k$-times itself



$$kP=underbraceP+P+cdots+P_text$k$ times.$$



Bitcoin uses Secp256k1 which has characteristic $p$ and it is defined over the prime field $mathbbZ_p$ with the curve equation $y^2=x^3-7$.



Point addition in $mathbbZ_p$ has an interesting property since the number of elements is finite if you add a point $P$ itself many times eventually you will get the identity $mathcalO$.



$$underbraceP+P+cdots+P_text$t$ times = mathcalO$$



The smallest $t$ will be the order of the subgroup generated by the $P$. For security, we want this order huge.



Note 1: a point $P$ may not generate the whole group but it generates a cyclic subgroup.



Note 2: As pointed by SqueamishOssifrage, The Smart showed that if the order of the curve and order of the base field are same then the discrete logarithm on this curves runs in linear time.







share|improve this answer














share|improve this answer



share|improve this answer








edited 8 hours ago

























answered 16 hours ago









kelalakakelalaka

8,75532351




8,75532351







  • 1




    $begingroup$
    The order of the scalar ring is not the characteristic or order of the coordinate field. The orders are related, but are not the same except in cases that are trivially breakable as Nigel Smart showed.
    $endgroup$
    – Squeamish Ossifrage
    10 hours ago










  • $begingroup$
    @SqueamishOssifrage thanks and for the links.
    $endgroup$
    – kelalaka
    8 hours ago













  • 1




    $begingroup$
    The order of the scalar ring is not the characteristic or order of the coordinate field. The orders are related, but are not the same except in cases that are trivially breakable as Nigel Smart showed.
    $endgroup$
    – Squeamish Ossifrage
    10 hours ago










  • $begingroup$
    @SqueamishOssifrage thanks and for the links.
    $endgroup$
    – kelalaka
    8 hours ago








1




1




$begingroup$
The order of the scalar ring is not the characteristic or order of the coordinate field. The orders are related, but are not the same except in cases that are trivially breakable as Nigel Smart showed.
$endgroup$
– Squeamish Ossifrage
10 hours ago




$begingroup$
The order of the scalar ring is not the characteristic or order of the coordinate field. The orders are related, but are not the same except in cases that are trivially breakable as Nigel Smart showed.
$endgroup$
– Squeamish Ossifrage
10 hours ago












$begingroup$
@SqueamishOssifrage thanks and for the links.
$endgroup$
– kelalaka
8 hours ago





$begingroup$
@SqueamishOssifrage thanks and for the links.
$endgroup$
– kelalaka
8 hours ago











inherithandle is a new contributor. Be nice, and check out our Code of Conduct.









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