corCTF - writeup for crypto/fibinary

It is a simple crypto chall. 

It provides below code and encrypted flag:

enc.py

fib = [1, 1]

for i in range(2, 11):

        fib.append(fib[i - 1] + fib[i - 2])

def c2f(c):

        n = ord(c)

        b = ''

        for i in range(10, -1, -1):

                if n >= fib[i]:

                        n -= fib[i]

                        b += '1'

                else:

                        b += '0'

        return b

flag = open('flag.txt', 'r').read()

enc = ''

for c in flag:

        enc += c2f(c) + ' '

with open('flag.enc', 'w') as f:

        f.write(enc.strip()) 

flag.enc

10000100100 10010000010 10010001010 10000100100 10010010010 10001000000 10100000000 10000100010 00101010000 10010010000 00101001010 10000101000 10000010010 00101010000 10010000000 10000101000 10000010010 10001000000 00101000100 10000100010 10010000100 00010101010 00101000100 00101000100 00101001010 10000101000 10100000100 00000100100  

I made simple brute-force code to decrypt the encrypted flag.

dec.py

fib = [1, 1]

for i in range(2, 11):

        fib.append(fib[i - 1] + fib[i - 2])

def c2f(c):

        n = ord(c)

        b = ''

        for i in range(10, -1, -1):

                if n >= fib[i]:

                        n -= fib[i]

                        b += '1'

                else:

                        b += '0'

        return b

flag_enc = open('flag.enc', 'r').read()

dec = ''

for flag_blk in flag_enc.split(' '):

    for c in range(0,127):

        if c2f(chr(c)) == flag_blk:

            dec += chr(c)

print(dec)

Flag:

corctf{b4s3d_4nd_f1bp!113d}