Brain Teasers
The Code Breaker's Job Interview
Cryptography
In Cryptography teasers, a phrase or expressions has been encoded in some way (frequently by replacing letters with other letters). You need to figure out the encoding method and then decode the message to find the answer.Cryptography
You walk into your interview for a position as a code breaker with a top secret government agency specializing in cryptography. You are met by Agent X and hold out your resume for him to read.
"Don't tell me what you've done", he snorts dismissively. "Show me what you can do."
He leads you into a small sparse room with a black box on a table, a waste basket, and a chair. He says, "That black box is an encryption machine of my own design. It reads special punch cards with input text and spits out slips of paper with the encoded message."
He notes your surprised look and grumbles, "Yes, punch cards. Don't get me started! Anyway, if you are as good as you claim, you should be able to decipher this short message I've encoded with the machine."
Agent X hands you a slip of paper, then leaves the room without another word. The slip reads:
WBNZ DSGL KZU BGA UCH RGI
You know there is no way to decipher such a short message with no information, so you go inspect the black box, but see nothing that can help. Then you notice the waste basket has two punch cards lying on top. Each has a hand written quote with a highlighted section.
One card says, "Our relationships live in the space between us which is sacred" – Martin Buber
The other says, "Our goal should be to understand our differences" – James D. Watson
You feed these two cards through the machine and collect the encoded messages. Matching the highlighted sections to the encoded slips you determine the following.
"THE SPACE BETWEEN US" is encoded as "TBG ZPQTY AFZWBGU PI"
"UNDERSTAND OUR DIFFERENCES" is encoded as "UIMRJCWXLP EZR VEKQVNSGJOH"
With this new information, can you decipher the message on the slip of paper?
"Don't tell me what you've done", he snorts dismissively. "Show me what you can do."
He leads you into a small sparse room with a black box on a table, a waste basket, and a chair. He says, "That black box is an encryption machine of my own design. It reads special punch cards with input text and spits out slips of paper with the encoded message."
He notes your surprised look and grumbles, "Yes, punch cards. Don't get me started! Anyway, if you are as good as you claim, you should be able to decipher this short message I've encoded with the machine."
Agent X hands you a slip of paper, then leaves the room without another word. The slip reads:
WBNZ DSGL KZU BGA UCH RGI
You know there is no way to decipher such a short message with no information, so you go inspect the black box, but see nothing that can help. Then you notice the waste basket has two punch cards lying on top. Each has a hand written quote with a highlighted section.
One card says, "Our relationships live in the space between us which is sacred" – Martin Buber
The other says, "Our goal should be to understand our differences" – James D. Watson
You feed these two cards through the machine and collect the encoded messages. Matching the highlighted sections to the encoded slips you determine the following.
"THE SPACE BETWEEN US" is encoded as "TBG ZPQTY AFZWBGU PI"
"UNDERSTAND OUR DIFFERENCES" is encoded as "UIMRJCWXLP EZR VEKQVNSGJOH"
With this new information, can you decipher the message on the slip of paper?
Hint
The highlighted quote passages encoded on the punchcards are also hints to breaking the encryptionAnswer
The message is WELL DONE YOU GET THE JOBThe encryption machine associates each letter with a number: a=1, b=2, etc. For every letter after the first, it adds the next input letter to the previous encrypted letter, wrapping around from Z to A.
To decrypt the messages, look at the differences between the encrypted letters, adding 26 to avoid negative numbers, and convert the result back into a letter.
For example, WBNZ translates to the word WELL as follows:
W = W
B - W = 2 – 23 (+ 26) = 5 => E
N - B = 14 – 2 = 12 => L
Z – N = 26 – 14 = 12 => L
Enjoy your rewarding and tedious life as a code breaker!
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