S.H.E.L.L CTF 2021: encoder | szymanski.ninja

encoder

Category: Cryptography

chal

50 points

can you decrypt this text : “ZOLSS{W1GD3HY4_T45R}”

NOTE: do not shift the numbers and the special charecters( ’{’ , ’}’ , ’_’ ).

Solution

The string characters were shifted by 7. I’ve unshifted it as below.

from string import ascii_uppercase

flag = ''
for i in 'ZOLSS{W1G_D3HY_4_T45R}':
    if i in ascii_uppercase:
        i = ascii_uppercase.index(i) - 7
        if i < 0:
            i = i + len(ascii_uppercase)
        flag = flag + ascii_uppercase[i]
    else:
        flag = flag + i

print(flag)

Output:

SHELL{P1Z_W3AR_4_M45K}

Flag

SHELL{P1Z_W3AR_4_M45K}