British cryptographic hacking from WW2 - how well would *you* have done?

Filed Under: Cryptography, Featured

Update: The Naked Security editors have agreed to a modest incentive.
There is now a prize for the challenge we set out below!
The best effort posted in the comments by Thursday 2013-05-09T23:59Z will receive a Naked Security T-shirt. The judges' decision is final, Sophos staff and family may enter but cannot win, and you will need to give us your email address if you want to be considered for the prize.
(Your email address will not appear with your comment, and we will not use it other than to contact you if you win.)

If you were taken prisoner and wanted to send messages home right under your captors' noses, what would you do?

You don't have access to a computer or email, not only because you're a captive, but because they haven't been invented yet.

You know that your captors will only let your letters out if you write convincingly and fluently about largely inconsequential things, and give a positive impression of how they are treating you.

And you know that if your letters too obviously contain a secret subtext, you might be shot, or worse.

You might think there's not a lot worse that being shot, but remember that the enemy might let you carry on writing letters for a while, milking you for intelligence about your countrymen and your fellow captives, and then shoot you and your chums.

→ That's what happened to Mary, Queen of Scots, though she was beheaded, not shot, and her co-conspirator Babington was hanged. Elizabeth's spymaster Walsingham was able not only to read their traitorous correspondence but also to forge messages of his own to extract more information from the conspirators.

If you were a British captive in a Nazi prison camp during the Second World War, like Sub Lieutenant John Pryor of the Royal Navy, you might well have used a code devised by No. 9 Intelligence School.

Selected officers were trained before leaving Britain in what we would today call steganography, the art of hiding one message inside another.

As a trained steganographer, you had a code number, such as 45, which told the decoding staff to skip four words ahead, then five, then four, and so forth, when extracting the hidden text from your letters.

This gave a competent coded letter writer just enough "noise words" to create a fluent and believable narrative to surround the secret message.

It's not as easy as it sounds.

Let's try it out with this fifteen-word bulletin:

To make things a little less obvious to the German censors, the words from the hidden message were written out of order.

You imagined a rectangle made up of sufficiently many imaginary tiles to hold your message, say 5x3 for a 15-word message.

You mentally filled the rectangle diagonally, moving upwards from the bottom right, with the numbers 1 to 15.

Then you inserted the secret words into your letter in the numeric order given by reading the rectangle naturally from top to bottom.

If your code number was 45, your codewords would be inserted as the fourth word, then five words further on, then four, and so on.

So, your cover letter would need to cushion and contain the secret message as follows:

. . . DAILY . . . . SEARCHED . . . DOUBLED . . . . AIR . . . HOUR . . . . BUNGALOWS . . . GUARD . . . . AND . . . 24 . . . . MOVEMENTS . . . COVER . . . . ARTILLERY . . . WITH . . . . RAILWAY . . . INCREASED

Give it a go! By adding just 52 words of your own, see if you can write a convincingly innocent-sounding paragraph about your most recent week at work.

→ If you take on the challenge, why not post your paragraph as a comment below? (You can post anonymously if you like.) But be warned: it's harder than it looks!

What we now call in-band signals were used for four special purposes:

  • You signalled the size of your word-order rectangle by the lengths of the first two words in your letter, such as opening with Every day to signify a 5x3 rectangle and thus a 15-word secret message.
  • You used the codeword the to switch from codeword mode into "spelling" mode, a special but cumbersome system for spelling out words that could never realistically appear in a letter home.

  • You used but as an extra codeword after your secret message as a double-check that the message was complete and thus to reassure the reader he had decoded correctly.
  • You included a telltale mark, such as writing the date in a special way or underlining your signature, to signal to MI9 that the letter contained a hidden message. (This avoided wasting time battling to decode messages that were just plain messages.)

Did the system work?

Apparently, it did, because academics at the University of Plymouth have just decoded a message sent by the abovementioned Lt. Pryor from his captivity at the Marlag und Milag Nord prison camp in Northern Germany.

What we don't know, of course, is whether the secret messages in a cache of letters now kept as a memoir by John Pryor's son, Stephen, were ever successfully decoded by MI9.

That still really is a secret!

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62 Responses to British cryptographic hacking from WW2 - how well would *you* have done?

  1. Paul Ducklin · 443 days ago

    To kick things off I thought I'd better have a go myself :-)

    Here's "my last week at work," by someone who does owner-driver deliveries for a living:

    "I found a DAILY driver for deliveries. I SEARCHED for pickups with DOUBLED rear wheel axles and AIR conditioning hour after HOUR - finally, down at those BUNGALOWS where that security GUARD lives, I found one AND bought it with 24 thousand miles on. For MOVEMENTS of stock I COVER it with an old ARTILLERY tarpaulin. Drove it WITH Johnno to Wembley - the RAILWAY prices have really INCREASED."

    It really *is* harder than you think to create something that sounds even remotely natural...

  2. I thank God DAILY for your patience. I've SEARCHED for many houses, DOUBLED my efforts and the AIR turned blue one HOUR after we were badly gazumped. BUNGALOWS are really rubbish. GUARD houses in barracks are better! AND I am sure 24 hours will show us MOVEMENTS in the market. COVER your ears until then - ARTILLERY Road is expensive WITH no garage and the RAILWAY use is now INCREASED.

    Not very good, I think, but it is much harder than I expected!

    • Paul Ducklin · 443 days ago

      I like it, but you need to lose two words. You can easily drop the "badly" before gazumped (leaving four non-code-words), but "GUARD houses in barracks are better!" needs to drop a word as well. You only get four words at most between successive codewords.

      Let me know how you want to tweak it...other than the glitches I think you've done well. Pretty realistic stuff, and the housing topic was a neat way of dealing with the tricky words BUNGALOW, ARTILLERY and RAILWAY. (A PoW talking about a RAILWAY journey would surely attract interest!)

      I assume in WW2 you'd have spelled out words like A-R-T-I-L-L-E-R-Y (or used circumlocution) but I fancied having something militaristic left in to increase the challenge :-)

      • Ooops! I had so many crossings out and insertions among my scribblings that I lost count. I would fail my attempt to join MI9.

        I'll drop the 'badly' as you suggest and change the sentence following GUARD to.... "GUARD our deposit with care."

        • Paul Ducklin · 443 days ago

          Nice recovery :-)

          Now imagine trying to do this in a single, smooth pass of writing on standardised sheets provided by the prison camp for official letters home (a privilege you had to earn that could easily be taken away).

          It would all have to be done in your head to avoid having to make notes you couldn't risk having around on paper you wouldn't want to waste anyway.

          (If discovered, any practice letters would be a dead giveaway of what was going on, and quite a good crib sheet for Nazi codebreakers to figure out how the scheme worked).

  3. Randy Tayler · 443 days ago

    Great men arrive DAILY disappointed in themselves. I've SEARCHED my soul, and DOUBLED my prayers, and breathe AIR that just an HOUR before felt stale. The BUNGALOWS are chapels, the GUARDS our priests, and food AND drink our sacrament. 24 men gained religion with MOVEMENTS of their hearts. COVER yourself in prayer, with ART, and of course WITH hymns. And please don't RAIL against God. Prayers INCREASED with faith, yours truly.

    • Paul Ducklin · 443 days ago

      I like your thinking...t's probably how many of the new arrivals at a PoW camp would have thought, and thus reads realistically.

      Your cheating with ARTILLERY and RAILWAY is also good thinking - nicely done, in fact - but, as mentioned above, having them in the final letter is part of the challenge in this case.

      All that said, I suspect the censors would have found this letter way too metaphysical for a letter home :-)

  4. Xavier · 443 days ago

    I didn't realise it was supposed to be about a week at work. Mine turned out to be a casual letter to a friend lol.

    I played crosswords DAILY with Jimmy who always SEARCHED the thesaurus for DOUBLED meaning words. Though the AIR was tense, an HOUR went quicker than the BUNGALOWS in California. Anyway, GUARD the old man's car AND land for me. 24 minutes of constant odd MOVEMENTS he does can COVER his brilliance. Retired ARTILLERY captains like him, WITH luck, will ride the RAILWAY without his anxiety INCREASED.

    This was tough but fun =)

  5. Robert · 443 days ago

    Oh, the tedious DAILY word games. Note I SEARCHED for words. I DOUBLED my efforts with an AIR of superiority every HOUR. Using large words like BUNGALOWS in hopes to GUARD my path to victory AND win for another 24 hours. Alas, my opponents MOVEMENTS were but a COVER to play the word ARTILLERY. That followed quickly WITH a clever play using RAILWAY so their score INCREASED, but I still won.

    • Paul Ducklin · 443 days ago

      Ah! What I am calling the "SCRABBLE cover trick" :-)

      Hope you have a homemade Scrabble set in your BUNGALOW, and you've let the GUARDS see you playing DAILY, and told them you got the habit from your parents back home...to build your COVER story nicely.

      (I commited anachronism there...Scrabble was apparently invented in the 1930s, but didn't get that name until after WW2.)

  6. Jen Hall · 443 days ago

    Thanks Paul! Always love the monday morning brain teaser.

    Given our unusually 84 degree weather prediction today, I went with something thematic for our region. Enjoy!

    "Seattle sun calls DAILY for another hike. We SEARCHED through books then DOUBLED attention on water and AIR vistas. Within an HOUR a listing for oceanfront BUNGALOWS was discovered! On GUARD for a golden dud AND yet excited for 24 miles of trekking, our MOVEMENTS escalated. Calling to COVER with large deposit as ARTILLERY, fee negotiations proceeded WITH the owner, a former RAILWAY conductor, whose retirement INCREASED!"

  7. The easiest thing to do to get this correct, is hide the words in the way the letters were written. And while it may be a secret, or at least unconfirmed, that MI9 decoded the letters or not, I for one believe absolutely did they get the message. In my mind, that's unquestioned. Dealing with the team at Bletchley Park, the same team that decoded the Enigma? Of course they got this message IMO.

    The way to write the above message convincingly is of course, to hide the trigger words (artillery and so forth). Not only do the more sensitive words not appear in the clear within the content of the original letters (Elder, for example), given enough length, the actual cipher having to do with these letters might have been able to encode all the secret message with no words in the clear.

    [Post edited for length...this commenter has a writeup here: http://airdisa.tumblr.com/post/49711803990/cipher...

    That way, I don't have to write words like artillery in the clear! Dangerous!!!

    Best wishes,
    disa

  8. Massimo Contaldo · 443 days ago

    My dear,

    "I think you DAILY. Lately i have SEARCHED new stimuli. I DOUBLED my hopes. The fresh AIR of the first HOUR improves lives in our BUNGALOWS. Jokes of the GUARD, which had been allocated, AND a cigarette every 24 hours, raise me. The MOVEMENTS of the soldiers COVER the noide of the ARTILLERY. But, everything changes WITH the unmistakable smell and RAILWAY noise, that cause INCREASE desire to London."

    Your Massimo.

    • Paul Ducklin · 443 days ago

      Close, but strictly speaking you need four words between DAILY and SEARCHED.

  9. tom · 443 days ago

    agent 65 reporting

    day break came at last, daily chores began, sweet memories searched for those tender moments, which doubled that pain of separation -
    bungalows by the sea, angels to guard us, sweet herb-scented air across the dunes, kisses to cover you - time meant nothing and everything: that day seemed an hour: only distant thunder, faint, artillery-like, rumbling dully behind our 24 hour rhapsody, induced conscious movements in our languorous bodies and with a sort of monotonous railway-train like shaking, rhythmic rumble, increased our sense of impending loss.

    what German censor, steeped in Goethe as he would be, could fail to feel the anguish and pain felt by the lonely PoW and so let the magic fly homeward on wings of doves - perhaps.

    • Paul Ducklin · 443 days ago

      Nice idea, but you didn't stick to the word rythym needed to decode it.

      The guys at MI9 needed a reliable pattern to be able to separate the codewords from the cover text - in this case, the code words need to appear in a pattern of 4-5-4-5-etc.

      So where I wrote, in the article:

      . . . DAILY . . . . SEARCHED . . . DOUBLED . . .

      I meant that each dot must be replaced with exactly one word, no more and no less.

      • tom · 443 days ago

        i deliberately changed it to 6-5-6-5 etc
        which you will see when I reported in as agent 65!
        you can go back to sleep now

        oh - and I changed the shape to 3/5, not 5/3

        • Paul Ducklin · 443 days ago

          Hmm. You're not allowed to do that! [*]

          PS. If you are doing it MI9-style, and treating "Day break" as your signal for 3/5, then the message definitely doesn't decode correctly...the MI9 rules are that the part of the message that contains codewords (in your case in a 6-5-6-5- pattern) starts from the beginning of the second line. See where changing the rules in the field gets you...

          [*] By unilaterally changing your field code, you have done two very naughty things. One is that the "45" I specified above would have been agreed in Blighty and was supposed to be a secret, keyed only by your name, rank and force number, which would appear on all correspondence of this sort anyway. You've now revealed it in the clear, which MI9 would not like at all. The other is that 6-5-6-5 is easier than 4-5-4-5 because you have more flexibility with cover words, so you have accorded yourself an advantage. I can't be sure, but I think the judges might take this into account when reaching their decision...I don't think they'd call it cheating, but they might mark you down :-)

  10. Dear mum and dad,

    Where did I leave off? Oh yes, my daily sports activities the gardening has helped with my moods. All year my nights tend to always be spent reading in fiction. I know my bedside night lamp hasn't helped with my eye health. It's like seeing doubled in the daytime open air, plus every additional hour it gets worse. Our bungalows are the respite from that. Does this insight let you down? Sorry that sounds unhappy. It's really very minimal - promise! So, this is why clear and plain reading over 24 hours conflicts with sports movements, and reading from cover to cover at night isn't wise.

    Yesterday we gave chase in football when my goalie forgot his foot on left and on right sides. This was hilarious. Only in football! So very funny. So it is with great delight and trepidation too that I will play with that goalie on my team ever again. I laughed over days because goalies forget their left or right almost never yet this guy who did, got so lost. The other team increased their advantage but we all had fun regardless.

    Best wishes,
    disa

    • Paul Ducklin · 443 days ago

      No multi-paragraph replies and no use of "spelling mode", I'm afraid. You need to fit one word, and only one word, for each dot in the example text:

      . . . DAILY . . . . SEARCHED . . . DOUBLED . . . etc.

      We really are looking for creative cover for words like ARTILLERY and RAILWAY, without spelling out, abbreviation or circumlocution :-)

  11. Kieran Brown · 443 days ago

    David not happy. DAILY temperature 85 degrees, constantly SEARCHED for a fan. DOUBLED the window opening so AIR came in for HOUR after hour. Now painting BUNGALOWS outside, perfectionist on GUARD so we are clean AND eagerly working for 24 hours a day. Moon MOVEMENTS very beautiful, under COVER of night sky. Wish ART was more British WITH poor quality paintings. Wish RAILWAY speed had not INCREASED and killed Mr John But last week.

    Very difficult! I had to cheat with shortening artillery to art... I guess they'd understand what it meant!

    • Paul Ducklin · 443 days ago

      Nice one.

      Though I do have some cynical thoughts...it must be quite an upmarket (and liberal) PoW camp if they let you go searching for a fan and had an art gallery for the prisoners :-)

  12. Mike Czumak · 443 days ago

    My DAILY Google query SEARCHED for “home firewall”. Removing quotes DOUBLED the results and I needed AIR! An HOUR later I changed “home” to “BUNGALOWS”, “firewall” to “GUARD” AND bingo, 24 (irrelevant) results. A few mouse MOVEMENTS later I was still nowhere, with much ground to COVER. I broke out the heavy ARTILLERY WITH an advanced search, navigating the Internet with RAILWAY car speed and INCREASED accuracy.

    :) Mike Czumak @SecuritySift

    • Paul Ducklin · 443 days ago

      See above (response to @tom) - you haven't followed the 4-5-4-5- rythym of cover words and code words.

      So where I wrote, in the article:

      . . . DAILY . . . . SEARCHED . . . DOUBLED . . .

      I meant that each dot must be replaced with exactly one word, no more and no less.

      • Mike Czumak · 443 days ago

        Ah yes, missed that part. Here's my quick rewrite:

        As I do DAILY I opened Google and SEARCHED but response time DOUBLED. Maybe it was my AIR card but an HOUR to search for “American BUNGALOWS”? I reconfigured the GUARD for two way traffic AND within a mere 24 seconds noticed network traffic MOVEMENTS. With much to COVER, I broke out heavy ARTILLERY (Advanced Search), proceeding WITH the speed of a RAILWAY and accuracy greatly INCREASED.

        -MC

  13. Greg · 443 days ago

    Prayed to Jesus DAILY. I eagerly tried and SEARCHED for friends for DOUBLED chance of living. Anyway AIR here is cooler. HOUR here is slow outside BUNGALOWS. Assisted a friendly GUARD here because they're busy AND everyday inside the 24 hour limit I ensure MOVEMENTS for warmth, avoiding COVER. We wiped some of ARTILLERY here as always WITH some of the PoWs. RAILWAY distance it seems, INCREASED

    • Greg · 442 days ago

      Sober version (undrunk ver.)

      Prayed to Jesus DAILY. Already found but still SEARCHED new friends which DOUBLED my will to live. AIR today is freezing. HOUR here is slow outside BUNGALOWS. Assisted a friendly GUARD yesterday because they're busy AND everyday inside the 24 hour limit I ensure MOVEMENTS for warmth, minimizing COVER. We wiped some of ARTILLERY here last week WITH some of the PoWs. RAILWAY distance, I think, INCREASED.

      p.s. CAPS of course are for counting purposes only and should be removed.

  14. joe · 443 days ago

    The repairman comes DAILY now. We have both SEARCHED the manual and DOUBLED our effort but the AIR conditioner fails every HOUR. It's like living in BUNGALOWS in Guam! I GUARD the ice cubes, water AND beer like gold 24 hours a day. Our MOVEMENTS are limited without COVER from the scorching sun. ARTILLERY against these flies WITH fangs: gone. But RAILWAY vacation dreams have INCREASED!

    • Paul Ducklin · 443 days ago

      Good one. Could pass for an email advert from (say) a vacation company, which means it's excellent cover...

  15. Massimo Contaldo · 443 days ago

    (Correct version)

    My dear,

    "I think you DAILY. Here lately i have SEARCHED new stimuli. I DOUBLED my hopes. The fresh AIR of the first HOUR improves lives in our BUNGALOWS. Jokes of the GUARD, which had been allocated, AND a cigarette every 24 hours, raise me. The MOVEMENTS of the soldiers COVER the noide of the ARTILLERY. But, everything changes WITH thejavascript: postComment(0); unmistakable smell and RAILWAY noise, that cause INCREASE desire to London."

    Your Massimo.

  16. Massimo Contaldo · 443 days ago

    (Correct version2)

    My dear,

    "I think you DAILY. Here lately i have SEARCHED new stimuli. I DOUBLED my hopes. The fresh AIR of the first HOUR improves lives in our BUNGALOWS. Jokes of the GUARD, which had been allocated, AND a cigarette every 24 hours, raise me. The MOVEMENTS of the soldiers COVER the noise of the ARTILLERY. But, everything changes WITH the unmistakable smell and RAILWAY noise, that cause INCREASE desire to London."

    Your Massimo.

  17. Victoria · 443 days ago

    I had a DAILY routine where I always SEARCHED interesting topics. This DOUBLED the amount of cellular AIR time used each HOUR. Anyway, Louis has built BUNGALOWS which have a GUARD! They are quite fancy AND residents want security 24 by 7 whereby stranger's MOVEMENTS are monitored. The COVER for the Veteran's Day ARTILLERY monument is stored WITH the locomotive at the RAILWAY, so costs are INCREASED.

  18. Linda · 443 days ago

    Write to me DAILY! I've lost my pen, SEARCHED high and low.DOUBLED up on getting fresh AIR.Up till late HOUR, also looked in the BUNGALOWS.Even the security GUARD helped.Gave up looking AND went for 24 hour nap. Slept without MOVEMENTS under the bed COVER.Had a dream about ARTILLERY.May get bus WITH friend, although I prefer RAILWAY, but fares have INCREASED.

    • Paul Ducklin · 443 days ago

      A nap lasting 24 hours? (OK, you could just change "nap" to "sleep.") But 24 hours? *In a prison camp*? Don't you think there would have been a few rollcalls during that time :-)

      (Only kidding...nice effort.)

  19. Maestro · 443 days ago

    Using words like "Artillery", "Guard" and maybe "Railway", will definetly make the message seem suspicious.

    So I recommend replacing the words as follows:
    Artillery -> rain
    Guard -> coffee
    Railway -> visitors

    • Paul Ducklin · 443 days ago

      As mentioned in the article, MI9 had an "escape mode", signalled by a codeword of "the", by which you could spell out words that couldn't be fitted in any other way.

      Or you could just use circumlocution - finding a way of "talking around it" - that would be obvious to the recipient, like ART for ARTILLERY, or TRAIN (which can be used as a verb unrelated to rail travel) instead of RAILWAY.

      And I don't think that GUARD would be a weird word to have in a letter from a prison camp.

      What you can't do is invent a substitution code in the field. How would you tell MI9 the new codebook? You have to go by the rules. And part of the idea of this code is that it shouldn't require a prodigious memory, so it could be used by regular officers (not trained intelligence agents), perhaps over many years of remote captivity, without being forgotten or mixed up.

  20. Sootie · 443 days ago

    Thinking of you DAILY, my thoughts have been SEARCHED and my longing DOUBLED each moment without you AIR seems bitter, our HOUR spent together cowered in BUNGALOWS, my arms your GUARD against the cold night AND though it was 24 hours those gripping intense MOVEMENTS with you under COVER broke through the hard ARTILLERY of my heart WITH force like a runaway RAILWAY my love has INCREASED

    50 shades of coded message?....

  21. Stephen Malolepszy · 443 days ago

    Hey David. The DAILY updates as follows. I SEARCHED the database, we DOUBLED loan approaches since yesterday!
    AIR quality the last HOUR has been Terrible a/c? BUNGALOWS deal collapsed, the GUARD called in sick tonight
    AND he thinks that 24 hour bug's the cause. MOVEMENTS are restricted until COVER arranged. By the way,
    ARTILLERY crescent sold even WITH its distance from the RAILWAY. The mortgage value INCREASED!

    • Paul Ducklin · 443 days ago

      When I read of the GUARD getting a 24-hour bug, which I assume is a euphemism for food poisoning or similar, I was expecting a different use of the word MOVEMENTS...

  22. Morgan · 443 days ago

    Here are my DAILY tasks. The first, I SEARCHED for information which DOUBLED as research. With no AIR conditioning, every single HOUR seemed long. Looking for BUNGALOWS was second. My GUARD was down, looked hard AND lost another hour. 24 minutes later, lunch stopped MOVEMENTS a while. I COVER my chips like tiny ARTILLERY in a swamp WITH gravy. I realised the RAILWAY line noise had INCREASED.

  23. Adam · 442 days ago

    Still owe that DAILY office pool ante? I SEARCHED who didn't pay, DOUBLED the pot, made paper AIR planes for an HOUR, then went to the BUNGALOWS with the money. GUARD it with your life AND when there are 24 people entered, trash bin MOVEMENTS can help to COVER and conceal our collections. ARTILLERY of paper clips WITH the mail chute as RAILWAY keep our security INCREASED.

  24. Phil · 442 days ago

    Since Jim introduced DAILY safety checks we have SEARCHED for risks together, DOUBLED up. We needed fresh AIR and spent an HOUR or two visiting those BUNGALOWS checking their fire GUARD, smoke alarm, bannisters AND steps. Once every 24 weeks we check land MOVEMENTS and public insurance COVER. Jim farts like an ARTILLERY piece. Really, travelling WITH him in an enclosed RAILWAY carriage has only INCREASED my pain, but there you go.

  25. Warren · 442 days ago

    As we look DAILY through the logs, we SEARCHED for the dreaded DOUBLED quotes. Tension in the AIR increased with each HOUR as executives living in BUNGALOWS with an armed GUARD continuously called for updates AND demanded it fixed 24 HOURS later. With our MOVEMENTS limited, had to COVER our tracks. Executives fired ARTILLERY like word barrages WITH zero results. Position at RAILWAY? Has resume been INCREASED?

  26. As I performed DAILY routine computer checks, I SEARCHED for issues and DOUBLED efforts. Spraying devices with AIR has helped. Another HOUR, they would be like BUNGALOWS In Hawaii. I GUARD all of our systems, AND hope that in 24 hours, all of the MOVEMENTS in our servers, COVER the equipment lifespan. Like ARTILLERY in a war WITH devices now shipping via RAILWAY, productivity indeed is INCREASED

  27. Message Effort · 442 days ago

    This isn't quite "last week at work." It's "last week during our holiday on the subcontinent." (Pun intended.) @Phil above ("Jim farts like an ARTILLERY piece") gave me the idea of how to deal with the word MOVEMENTS. I am afraid it was downhill from there. I also took some extra words to use the end-of-message "BUT". Hope that is allowed.

    "We did our DAILY shopping for supplies, and SEARCHED for roti that's DOUBLED over, puffed up with AIR and fried. An HOUR later, back at the BUNGALOWS, Roger hadn't taken GUARD against dodgy foreign food, AND soon we had 24 uncontrolled toilet filling bowel MOVEMENTS (without removing the COVER, making a mess like ARTILLERY shells), mixed up WITH a sound like a RAILWAY locomotive revving for INCREASED power to start climbing. BUT that was only the start..."

  28. I'm bored of DAILY Facebook privacy warnings. I SEARCHED for advice, and DOUBLED down on security. Hot AIR! Facebook links an HOUR later led to infected BUNGALOWS website. Sure, my GUARD should have been raised, AND yet... for some 24 hours, odd clickjacking mouse MOVEMENTS had me seeking COVER. Brought out the heavy ARTILLERY - Sophos! Fed up WITH the graffiti on Zuckerberg's RAILWAY toilet doors? Adopt INCREASED security by logging off BUT remember to never come back!

  29. Well there is DAILY exercise. We are rarely SEARCHED. We asked for DOUBLING of hours of fresh AIR that we get. HOURs feel like days. The BUNGALOWS could be worse. GUARDs are usually nice, fair AND friendly if all 24 inmates behave. Dream of TRAVELLING back to England. SUPPORTING each other is tough. ARTY says to stick WITH prayer to keep on TRACK and my hopes INCREASED.

    I changed the message a bit to obscure the code words and assumed the decoder could figure things out without grammar and dropping the ing on supporting. If hand written I likely could put a slight space on the ing if I felt the decoder would needed the extra help:

    Increased track travelling with 24 hour arty and air support(ing) guards doubling bungalows searched daily

    Some things I thought about when I wrote this. I included the 4/5 hint in the first two words. I wanted the screener to assume I'm the persona of a slightly depressed prisoner trying to make the best of it. I was worried about the words Guards and stating I was rarely searched but felt if I said something nice about them they might not look too closely. This also depends on 24 inmates being in either my unit / section / bungalow. It was tough but fun to do.

    • Paul Ducklin · 442 days ago

      Hmmmmmmm. I don't think you're allowed to do that :-)

      As for the "45" (4-5-4-5 etc) part of the code: that was a secret agreed back in Blighty and logged with MI9. It wasn't meant to be revealed in the messages. Each person hd his own two-digit "password".

      The first two words of the message in real-world use would actually be 5 and 3 letters long, to indicate a 5x3 word-order rectangle and 15 words of message. (The decoder started counting from the first word of the second line.)

      I guess that since the first two words of the message are irrelevant in this competition version of the code, your choice of "Well there" does no harm...

  30. Again rushing the daily routines, even though I've searched for something that doubled the benefit of the air team and other hour based staff. But the bungalows, the ones without guard dogs, are not cheap and providing cover for 24 hours given the guard movements have to completely cover all the property in artillery lane, especially those with gardens backing into the railway, means costs have increased

  31. joe · 441 days ago

    I made the DAILY cold calls and Jim SEARCHED the MLS. We've DOUBLED our TV infomercials to AIR nightly for an HOUR but we failed. The BUNGALOWS won't sell. To GUARD against another big loss AND limit compensation to 24 investors, monitor all stock MOVEMENTS. Be sure to COVER losses immediately. Our only ARTILLERY now is hyperbole. WITH enough buzzwords to fill RAILWAY cars, survivability is INCREASED!

  32. Here's my tuppence worth. A day in the camps:

    Someone stole my DAILY paper. Even though we SEARCHED almost everywhere and DOUBLED back on ourselves, stale AIR was all an HOUR of trawling thru our BUNGALOWS achieved. A close GUARD is now required.

    John AND I spent nearly 24 hours working out people's MOVEMENTS. So many to COVER, we resolved nothing! Brimstone ARTILLERY from hell be WITH you thief!

    Thinking of RAILWAY days in June INCREASED my cheer temporarily but this sort of thing really gets my goat. Thanks for listening old chap.

  33. Blake · 440 days ago

    Fascinating read... so here's my effort.

    Still job hunting DAILY! My god, how I've SEARCHED. Sick of being DOUBLED up and gasping for AIR - for nearly an HOUR sometimes! What next? Painting BUNGALOWS? Call centre? Security GUARD? Better than waking battered AND bruised. I'm not 24 anymore - now even small MOVEMENTS hurt. Graham can COVER now punters love his "ARTILLERY Man" act. Especially WITH their appetite for shattered RAILWAY sleepers having massively INCREASED.

  34. blake · 440 days ago

    Inspired by Mike Czumak's approach I had to try this one too...

    What a week! DAILY passwords enforced so I SEARCHED for 9-letter words. DOUBLED login times and blue AIR everywhere. Wasted an HOUR thinking. Ended up with "BUNGALOWS" Monday. Difficult to GUARD against bad password choices AND so after another 24 hours changed it to "MOVEMENTS". Wednesday, IT Support COVER guy jokingly suggested using "ARTILLERY". Thursday, got hacked. WITH that, they exposed my RAILWAY enthusiasm. Friday, chose "INCREASED".

    ...I know, it's a bit of a cop out but couldn't resist...

    • Paul Ducklin · 440 days ago

      It IS a bit of a cop-out, but...as far as "last week at work" goes, for a helpdesk guy it couid have happened that way :-)

  35. Nick · 440 days ago

    Mistakes here are DAILY routine now. I have SEARCHED for better people, DOUBLED my efforts, but everyone's AIR heads. One more HOUR... Were they raised in BUNGALOWS? Can't let my GUARD down with Peter especially AND his apparent illiteracy...

    24 people without neurological MOVEMENTS means I gotta COVER our butts from the ARTILLERY that corporate wields WITH such pleasure. And the RAILWAY of crap has INCREASED again just this second. BUT I love you!

  36. Emiliano · 439 days ago

    Sorry for my bad English. Only sexual metaphors can make ARTILLERY and RAILWAY look a bit less suspicious. Hope it's fun.

    I receive spam DAILY at work. I once SEARCHED V i a g r a, discovering the DOUBLED sex duration is hot AIR. Actually a quarter HOUR. Stupids living in isolated BUNGALOWS are so off-GUARD that they bite it. AND spammers promise you 24 hours a day of... "MOVEMENTS" under the bed COVER. Fraud. Nobody had his "ARTILLERY" barely enlarged, ever, WITH enlargers, nor had his "RAILWAY crossing barrier" erection INCREASED.

  37. Gary · 433 days ago

    I know the contest is over, but this was still fun.

    Colonoscopies stack up DAILY. I'll bet that I've SEARCHED miles of gut. DOUBLED the recovery beds! The AIR gets unbreathable an HOUR post-op. Fart tenants: butt BUNGALOWS. Anybody eat fiber? GUARD your wallet around here. AND cranky patients after 24 hours of uncontrolled bowel MOVEMENTS! Better warn housekeeping. COVER yourself. It's either ass ARTILILLERY or butts flapping WITH gas on the turd RAILWAY. Daily "runs" just INCREASED. I need a drink.

  38. Great fun, missed the competition but decided to give it a try anyway

    Have done mine as if I was a POW

    My time for DAILY prayers gives hope. I've SEARCHED deep down and DOUBLED my resolve.
    The night AIR gets unbreathable an HOUR after lockup, very stuffy, the BUNGALOWS are hot.
    Anyway GUARD our love, memories, devotion AND young family .
    Each 24 hours passes slowly but MOVEMENTS in camp help COVER the fact I'm here
    ARTILLERY bombardment exposure along WITH time working on the RAILWAY at home has INCREASED my jitters but I'm Ok

  39. Blake · 429 days ago

    Which one's the winner then?

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About the author

Paul Ducklin is a passionate security proselytiser. (That's like an evangelist, but more so!) He lives and breathes computer security, and would be happy for you to do so, too. Paul won the inaugural AusCERT Director's Award for Individual Excellence in Computer Security in 2009. Follow him on Twitter: @duckblog