Being Smart will mean completely different if you can use special numbers!
Files given:
The challenge requires us to enter values \(a,b,p\) such that \(ab\neq0\), \(p,2p+1\) are prime, then asks us to solve the elliptic curve discrete log problem over \(\mb F_p,\mb F_{2p+1}\) on the curve \(y^2=x^3+ax+b\). However since the check \(ab\neq0\) doesn’t take mod \(p,q\), we can just set \(a=pq,b=pq\) such that we end up solving the discrete log problem on \(y^2=x^3\), which has a map to \(\mb F_\cdot^+\) via \((x,y)\mapsto x/y\).
Solution at solve.sage
Flag:
CCTF{ECC_With_Special_Prime5}