Suninatas Game 19

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challenges

Game 19

We have a large block of binary data. Decode it to get an encrypted message:

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0100111001010110010000110101010001000110010001000101
0110001000000100101101000110001000000100101001001100
0100010101011010010001010101001001001011010100100100
1010001000000101001001000101010101010010000001001011
0100011001010101010100100101000000100000010110100100
1010001000000101001000100000010110000100011001000110
0101010100100000010101010101001001010000001000000101
0010010001010101010100100000010100100100110001001011
0101100101000010010101100101000000100000010110100100
1010001000000100011101000011010100100101101001010101
0101010001001011010101110101101001001010010011010101
0110010010010101000001011001010100100100100101010101

Decode as binary to get:

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NVCTFDV KF JLEZERKRJ REU KFURP ZJ R XFFU URP REU RLKYBVP ZJ GCRZUTKWZJMVIPYRIU

The uppercase alphabet is A=0 through Z=25. The retained ciphertext is a Caesar shift, the affine special case a=1, b=17: encryption is C=(P+17) mod 26, so decryption subtracts 17. The following complete decoder preserves spaces and can be run offline as python3 decode.py:

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ciphertext = "NVCTFDV KF JLEZERKRJ REU KFURP ZJ R XFFU URP REU RLKYBVP ZJ GCRZUTKWZJMVIPYRIU"
plaintext = "".join(
    chr((ord(char) - ord("A") - 17) % 26 + ord("A"))
    if "A" <= char <= "Z" else char
    for char in ciphertext
)
print(plaintext)

The decoded message, with the key hidden in this display, is:

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WELCOME TO SUNINATAS AND TODAY IS A GOOD DAY AND AUTHKEY IS **********************
PLAIDCTFISVERYHARD