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RCTF 2020 - infantECC
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| from Crypto.Util.number import getStrongPrime, bytes_to_long, long_to_bytes | |
| from hashlib import sha256 | |
| flag = open("flag.txt","rb").read() | |
| p=getStrongPrime(512) | |
| q=getStrongPrime(512) | |
| R=Zmod(p*q) | |
| Mx=R.random_element() | |
| My=R.random_element() | |
| b=My^2-Mx^3 | |
| E=EllipticCurve(R, [0,b]) | |
| Ep=EllipticCurve(GF(p), [0,b]) | |
| Eq=EllipticCurve(GF(q), [0,b]) | |
| Ecard=Ep.cardinality()*Eq.cardinality() | |
| r=random_prime((p^^q)>>100) | |
| s=inverse_mod(r, Ecard) | |
| print((s,b)) | |
| print(s*E(Mx,My)) | |
| print(randint(0,Ecard)*E(Mx,My)) | |
| print(r^^(bytes_to_long(sha256(long_to_bytes(Mx)).digest())^^bytes_to_long(flag))<<256) |
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A lot of weird stuff going on!