Two days ago, on Thanksgiving, the NSA sent encrypted greetings to “every NSA employee across the globe”. Can you break this encryption?

The NSA is very active on Facebook, sometimes publishing several posts a day. Last Thursday, i.e. on Thanksgiving (contrary to Halloween, this festivity has not gained popularity in my home country yet), the NSA spread the following message via its Facebook account:


Apparently, these greetings contain two encrypted lines. According to a few Facebook comments, the solution isn’t very hard to find. Can a reader solve this challenge?


Advent challenges

Readers who (like most Europeans) don’t celebrate Thanksgiving and who (like some Europeans) speak German might be more interested in the advent challenges of the Karlsruher IT-Sicherheitsinitiative. This series of crypto puzzles, titled “Krypto im Advent”, runs from Dezember 1-24. Everybody may participate, but only pupils up to the ninth grade (i.e., up to the age of about 16) can win a prize.


Much to my joy, one of the prizes is a copy of my book Versteckte Botschaften- Die faszinierende Geschichte der Steganografie, which was donated by the Thalia book store in Karlsruhe, Germany. If you happen to live in the Karlsruhe area, please consider this store on your next shopping tour.

Further reading: Revisited: NSA’s unsolved Twitter challenge from 2014


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Kommentare (11)

  1. #1 ok
    24. November 2018


  2. #2 Colin Bierton
    48485 Neuenkirchen
    24. November 2018

    “Happy Thanksgiving!” to you also…

  3. #3 Andy
    24. November 2018

    That riddle qualifies for an encryption? That’s an encoding and there’s even a standard for that ;-).

    And, b.t.w., ok’s solution (#1) is wrong :-P.

  4. #4 Thomas
    24. November 2018

    So the question remains: What does “21” stand for?

  5. #5 TWO
    24. November 2018

    21= !

  6. #6 Jerry McCarthy
    England, Europa
    25. November 2018

    > Readers who (like most Europeans) don’t celebrate Thanksgiving….

    Although I see that the “Black Friday” phenomenon has arrived in Germany:

  7. #7 Thomas
    26. November 2018

    @Jerry Mc Carthy:
    When I heard a German ad on the radio, I first thought of stock market issues, because the “Black Thursday” is called “Schwarzer Freitag” (Black Friday) in Germany. Why is the day after Thanksgiving called “Black” Friday?

    • #8 Jerry McCarthy
      England, Europa
      26. November 2018

      @Thomas. Probably better answered by an American reader, but I believe it has to do with financial books either being “in the red” = loss, negative, or “in the black” = profit, positive. The day after Thanksgiving is the start of the Christmas shopping season, so books will (with luck) switch from being “in the red” to being “in the black”.

  8. #9 Jerry McCarthy
    England, Europa
    26. November 2018

    I guess that I should add that the colours red and black refer to the colour of the ink traditionally used to write negative and positive numbers.

  9. #10 Patric Hausammann
    27. November 2018

    Colin Bierton is right. I hope you all had a fantastic Thanksgiving!

  10. #11 Thore
    17. Juni 2019

    The cypher key is actually the ASCII table in hexadecimal notation.