HSCTF 8 | Regulus Satrapa

#hsctf8

from Crypto.Util.number import *
import binascii
flag = open('flag.txt','rb').read()
p = getPrime(1024)
q = getPrime(1024)
n = p*q
e = 2**16+1
pt = int(binascii.hexlify(flag).decode(),16)
print(p>>512)
print(q%(2**512))
print(n, e)
print(pow(pt,e,n))

• RSA

• と を上下半分ずつ与えられている

with open("output.txt") as f:
    ph = int(f.readline().strip())
    ql = int(f.readline().strip())
    n = int(f.readline().strip().split(" ")[0])
    c = int(f.readline().strip())


qhigh = n // (ph << 512)
for diff in  range(-10000, 10000):
    qh = (qhigh >> 512) + diff
    q = (qh << 512) | ql
    if n % q == 0:
        break

p = n // q
d = pow(65537, -1, (p-1)*(q-1))
m = pow(c, d, n)

print(bytes.fromhex(hex(m)[2:]))