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miracl / MIRACL

MIRACL Cryptographic SDK: Multiprecision Integer and Rational Arithmetic Cryptographic Library is a C software library that is widely regarded by developers as the gold standard open source SDK for elliptic curve cryptography (ECC).
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some questions about ecn2_add3 method #60

Open kubbydd opened 6 years ago

kubbydd commented 6 years ago

In this method ,if Q == P ,mr_mip->Asize = 0,and if P->marker = MR_EPOINT_NORMALIZED,than P->z = 2P->y,or P->z = 2P->zP->y.Why P->z = 2P->y when the P->z is zero?

mcarrickscott commented 6 years ago

Not sure about the question. But see the explicit formula database at

http://hyperelliptic.org/EFD/g1p/auto-shortw.html

Specifically http://hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#doubling-dbl-2009-l

And http://hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#doubling-mdbl-2007-bl

When the point is normalized, z=1

Mike

On Sun 11 Feb 2018 at 07:40, kubbydd notifications@github.com wrote:

In this method ,if Q == P ,mr_mip->Asize = 0,and if P->marker = MR_EPOINT_NORMALIZED,than P->z = 2P->y,or P->z = 2P->zP->y.Why P->z = 2P->y when the P->z is zero?

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