# Tag Info

## New answers tagged modular-arithmetic

### Is it true that Public keys with even y coordinate correspond to private key that are less than n/2 and vice versa? (Secp256k1)

A little test with Sagemath for the first 10 integers as the private key; ...
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Since this is a past CTF we can provide a guide to solve it. Euler's theorem states that if $\gcd(m,n) =1$ with $m,n \in \mathbb{Z}^+$ then $$m^{\varphi (n)} \equiv 1 \pmod{n} \label{5}\tag{1}$$ and \$\...