TSGCTF

#hakatashi #TSGCTF_2021 require 'openssl' require 'digest' STDOUT.sync = true class OpenSSL::PKey::EC::Point def xy n = to_bn(:uncompressed).to_i mask = (1 << group.degree) - 1 return (n >> group.degree) & mask, n & mask end alias_method :+, :add alias_method :*, :mul end class ECDSA def initialize …

#TSGCTF_2021 from Crypto.Util.number import isPrime from random import randrange from secret import p, q, L, e, d class RSA: def __init__(self, p, q, L, e, d): assert(isPrime(p) and isPrime(q)) self.N = p * q self.L = L self.e = e self.d = d # these are the normal RSA conditions for _ in range(100):…

#TSGCTF_2021 from mpmath import mp, power, ln import json mp.dps = 1000000000 def decode(enc): return int(power(2, enc * ln(2))) s, e = json.load(open('encoded.json')) flag = decode(s << e) print(flag.to_bytes((flag.bit_length() + 7) // 8, 'big')[:74]) 算数 やってることは でめちゃくちゃでかくてどうしようもない テイラー展開すると したがって …

#TSGCTF_2021 #hakatashi require 'openssl' require 'digest' STDOUT.sync = true class OpenSSL::PKey::EC::Point def xy n = to_bn(:uncompressed).to_i mask = (1 << group.degree) - 1 return (n >> group.degree) & mask, n & mask end alias_method :+, :add alias_method :*, :mul end class ECDSA def initialize …

#TSGCTF_2021 #hakatashi # See also https://github.com/tsg-ut/pycryptodome from Crypto.PublicKey import DSA from Crypto.Signature import DSS from Crypto.Hash import SHA256 from Crypto.Util.number import getPrime from Crypto.Random.random import randrange from base64 import b64decode from signal impor…

#TSGCTF_2021 #hakatashi from secret import e from Crypto.Util.number import getStrongPrime, isPrime p = getStrongPrime(1024) q = getStrongPrime(1024) N = p * q phi = (p - 1) * (q - 1) with open('flag.txt', 'rb') as f: flag = int.from_bytes(f.read(), 'big') assert(isPrime(e)) assert(isPrime(e + 2)) a…