CTFtime / HSCTF
How i solved the primes challenge!.
In this challenge they provide some text file only, lets download and look at the text file.
fe7l1Owa85YA9g8CELs3F{H11s1o258p6hOo77di7Y0V83M1feBdNeP3QuS9G7LVjd8EZUei9NOi3p3p9jKcbiUYsy4zA6P88Y7NP73jiLFW4nl8m6xN3LcHttxA2ML73J68g2PtR52926v1sDi22KE9VhBT8kgc26581q2pP77_bTZ6XPBR3iRT7Jbo9YvsEUiXE6Lv4y790z5wu145p6W8Mc6l38tCBPfCq30P7fXD2652g1INKDF3EeUnXm6gLUWOZ9NKhFr19gAaVldd7FkjlMuqSaNW3E0BEt4_6y8C35pI6y7IWQoimXQgkIZTR19Z21e33er4YENvt4paILApj4nwPiDpLFJP8UP0wTZNGN2grACDd6h5MfTWlxpdY8iF79uK38Rn7lFzU15Y6gTA2FSz5163C4eWTI80c5o9OANDD6WZ0T8M5SC42t6CANB4rDNJH49J9aQQdE6ylWR23c7337ex7vp4KLI9xYpvBDC0E7VgSZXkE186uDA93lMRNeZ1ynL31hntD9vZQ4V18sd9lWyt433B2jX843A77E8Sl22ds46y640C1q3QthAov3LuB24n9nq3y5f0pJ9E67ECu5g8w29PIuUR2VLhwX1b3IdhykJ8p8mimNxRPYrGEnMeXoWulV0tTtz_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}c1CHsMd05v3Fmo3YeT7EaduRD2Q6eOrKbAWn
this is file i have downloaded from the challenge!. I noticed some clue in the title “Primes”.
Look this text it’s looks like a encrypted text. but actually they hidden a flag inside this text.
for example take the first 20 characters in these text:
fe7l1Owa85YA9g8CELs3
and look the clue. prime its like prime number concept.
The text start with f. but if you closely look the prime number and the text it has one connection.
f e7 l 1Ow a 85YA9 g 8CELs3
2,3,5, remove the prime number characters in the taken text, and the result was
f lag.
so that, we got the result but we can manually remove the prime number in the entire text. let’s make a code to get the flag.
var_out =[]
olvar = “fe7l1Owa85YA9g8CELs3F{H11s1o258p6hOo77di7Y0V83M1feBdNeP3QuS9G7LVjd8EZUei9NOi3p3p9jKcbiUYsy4zA6P88Y7NP73jiLFW4nl8m6xN3LcHttxA2ML73J68g2PtR52926v1sDi22KE9VhBT8kgc26581q2pP77_bTZ6XPBR3iRT7Jbo9YvsEUiXE6Lv4y790z5wu145p6W8Mc6l38tCBPfCq30P7fXD2652g1INKDF3EeUnXm6gLUWOZ9NKhFr19gAaVldd7FkjlMuqSaNW3E0BEt4_6y8C35pI6y7IWQoimXQgkIZTR19Z21e33er4YENvt4paILApj4nwPiDpLFJP8UP0wTZNGN2grACDd6h5MfTWlxpdY8iF79uK38Rn7lFzU15Y6gTA2FSz5163C4eWTI80c5o9OANDD6WZ0T8M5SC42t6CANB4rDNJH49J9aQQdE6ylWR23c7337ex7vp4KLI9xYpvBDC0E7VgSZXkE186uDA93lMRNeZ1ynL31hntD9vZQ4V18sd9lWyt433B2jX843A77E8Sl22ds46y640C1q3QthAov3LuB24n9nq3y5f0pJ9E67ECu5g8w29PIuUR2VLhwX1b3IdhykJ8p8mimNxRPYrGEnMeXoWulV0tTtz_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}c1CHsMd05v3Fmo3YeT7EaduRD2Q6eOrKbAWn”
for num in range(1, 105 + 1):
if num > 1:
for i in range(2, num):
if (num % i) == 0:
break
else:
#print(num)
for j in range(0,num+1):
if(j==0):
var_out.append(olvar[j])
elif j==num:
olvar = olvar[num+1 : : ]
for i in var_out:
print(i,end=’’)
flag{h1din9_1n_pl41n_519ht}
Cool We got the flag.
YouTube Channel : TamilOverflow
