Hardwood Floors

Challenge

Our intelligence tells us that this function was used to encrypt a message. They also managed to capture a spy while in the field. Unfortunately, our interrogators only managed to find the ciphertext of a message on his phone. Can you help us recover the secret message?

function:

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message = "<redacted>"
key = 3
encrypted = ' '.join([str(ord(c)//key) for c in message])
print(encrypted)

ciphertext:

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27 39 33 34 10 36 32 33 35 10 37 34 10 38 35 34 37 38 15 15 15 10 33 32 38 40 33 38 34 41 34 36 16 16 38 31 33 16 39 35 38 35 16 36 41

Solution

All characters were integer-divided by 3 during encryption. So for every ciphertext character, there are threee possible plaintext characters (x3, x3+1 x3+2)

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floors=open("floors.txt").readline().rstrip().split()

for fl in floors:
    val=int(fl)*3
    print chr(val)+"-"+chr(val+1)+"-"+chr(val+2)

output:

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Q-R-S
u-v-w
c-d-e
f-g-h
--
l-m-n
`-a-b
c-d-e
i-j-k
--
o-p-q
f-g-h
--
r-s-t
i-j-k
f-g-h
o-p-q
r-s-t
--.-/
--.-/
--.-/
--
c-d-e
`-a-b
r-s-t
x-y-z
c-d-e
r-s-t
f-g-h
{-|-}
f-g-h
l-m-n
0-1-2
0-1-2
r-s-t
]-^-_
c-d-e
0-1-2
u-v-w
i-j-k
r-s-t
i-j-k
0-1-2
l-m-n
{-|-}

For each position, choose one of the letters to find the flag,

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Such lack of rigor... easyctf{fl00r_d1visi0n}

Flag