hello,

I read this post several, several, several times and i can't understand how it is possible to half a point like the first example.
Is it possible without the private key to divide a point by 2 ?

assume i have like the first example a point without the private key for it and divide it by 2

x = 545d2c25b98ec8827f2d9bee22b7a9fb98091b2008bc45b3b806d44624dc038c
y = f1e18224b09ed00841c5407e571829e41876d44522f97e05e405a91ef38d4f00

How get ?

x = 8f870b1693cb408f96a3da9e3623b6d0315a403395d79f412f26044210bcddd2
y = 8a0a3e2399787a1f084d53500bc577ba1cc4e19ab7b2d9a2bd327e5e56e8afa0

I clearly don't understand the concept of multiply by 2^-1 (mod n)
is it possible for someone to clarify this with an real example (not n, N P Q ETC... LOL ..I was the one sleeping in math classroom ^)

Thanks