The Decryption Challenge

Work backwards to decipher the intercepted data, then answer the final exam question.

Mission Brief: You have intercepted a wireless transmission. It is encrypted, but our system has discovered the Key. To decrypt the message, you must reverse the algorithm. If the key is a '+3 shift', you must shift each letter backwards by 3 in the alphabet.
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Transmission 1 of 3

0 / 3 Decrypted
Intercepted Ciphertext
Encryption Key Used: +3 Shift