eHlvl2

Challenge Description :

In the sequel to our cryptography challenge, John embarks on a deeper cryptographic journey as he discovers a second email with an even more intricate code. Unraveling this complex puzzle will lead him closer to unveiling the secrets of his uncle's legacy. Can John decipher the cryptic message to unlock the next chapter of his mysterious inheritance?

source.py

from Crypto.Util.number import*
from gmpy2 import *
from secret import flag,hint,p,q,n,e

m = bytes_to_long(flag)
h = [i^n for i in hint]
print(f"h = {(h)}")
ct = pow(m,e,n)
print("ct = ",ct)
print("p = ",p)
print("q = ",q)

output.txt

h = [94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961521, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961485, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961472, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961541, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961472, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961541, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961560, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961541, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961553, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961555, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961558, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961557, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961554, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961541, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961567, 94679407488132818404660699098842374931489424397235444032237590365827255722083367058700051514705537574410165711179896056841523082769989050948432027496868754650692929646830509011686345739543788335116663878603193093822729085523727432834299509271223474277629700801997533152872965865087117035426980349126297961548]
ct =  67505152689735765883791932740130754794209575051890980602600781674553775583258220666677751769017514328860789798530248480070252409403368045243830780631402335081141998133869158737642149138788268554416336823598505828237139319106610394963826005339971182324217930994374291223950212588510430646278894660497182784293
p =  12183163052748797962152083951276410017023381414297530966097687939312125214962148117236820737625705839607797813446007939630781665285299250570390516148709817
q =  7771332213006128671514628362741773970588675422315769188626146232673657294809145256158466322140793048100178050459366164928658849208228006813771330133382669

Author : im._.a.p

Solution :

• Values of 'p','q','ciphertext','h'(encrypted hint which has the value of e) is given.
• According to the code given, 'hint' is xored with 'n' to get the ciphertext 'h'.
• To find the 'hint', 'h' is xored with 'n' to get 'hint', thus getting the value of 'e'.

n = p*q
hi = [i^n for i in h]
l = []
for i in hi:
    x = chr(i)
    l.append(x)
li = ''.join(l)
print(li)
#The e = 46307 :)

• With the values 'e','n','p','q', the ciphertext 'ct' can be decrypted to get the flag.

e = 46307
n = p*q
phi = (p-1)*(q-1)
d = invert(e,phi)
msg = pow(ct,d,n)
print(long_to_bytes(msg))

Flag : shaktictf{RSA_1s_fun_t0_d0_ri8?}