Hardware.IO - my tiny bit of a major Virtual Conference! aka 'What are Wall Challenges'?

I was busy during April 2020. Several deadlines all conspired to converge on the same 'month end' delivery date. But one of them was the sort of project that I really like: puzzles!

Antriksh at Hardware.IO asked me if I could reprise the 'Wall Challenges' that I did for the 2017 and 2018 Hardwear.IO conferences in Den Haag (The Hague) in The Netherlands. '21 mysterious A4 pages blu-tacked to the walls with only a brief explanation' is something I've been doing for various events for some time, and it is a low-key, often mostly overlooked facet of the whole event - except for the people who get into it. If you go to one of the big, serious, 'suits' events, then you find teams of people who turn up just for the 'Capture the Flag' penetration or 'Capture the Signal' radio competitions etc., and they are usually pretty totally focussed on that for the whole event.

My 'Wall Challenges' are several opposites at the same time: they are carefully crafted training exercises, just like a 'Capture the Flag' contest; but they are also deliberately abstracted, which isn't a CTF or CTS feature. They are also fun challenges! So I thought that this might be a good time to look at what they are for, and why you might like to consider immersing yourself in one next time you see a sheet of paper stuck on the wall...(physical or virtual!).

Wall Challenges - what are they?

If you've ever wondered how people acquire an assured, casual ease with some technical subjects: 'facility' is one of the words that sometimes gets used, then one way to do it is not to read lots, or watch videos or attend lectures/seminars. Instead, actually doing something is often another good way to build familiarity, explore the limits of what you know (or don't know), and maybe extend your boundaries a bit. This is your cue: keep reading and do some WallChallenges!

Wall Challenges are apparently simple problems that are often harder than they appear, and doing them is good for you! If you ever wanted a Sudoku that was more than just a few numbers in squares, or that required programming to solve, or that went into the mathematics or theory a bit more, then you might find that Wall Challenges are exactly what you are looking for.

What sort of topics are covered? Things like Binary, Hex, Number bases, ASCII, ROT-13, Hashes, Look-up tables, Modulo arithmetic, Pointers, Pictograms, Anagrams, Cryptic clues, Codes, the Periodic Table, Lateral thinking, Critical thinking, and more. Solving them can often be done with just pen and paper, although some require a spreadsheet, and the harder ones can require some programming (Python is what I've used...). In the course of finding solutions, you will also acquire a collection of interesting look-up tables (ASCII, Periodic Table...) that often have interesting histories and are very good things to know for Pub Quizzes or Only Connect (My Team didn't get onto TV, by the way...).

There's a school of thought that making things simple is both a work of genius and a genius-level way of making it look trivial. When Einstein wrote 'E=mc squared' then it looked simple enough, but the ramifications were universe-altering. Now, Wall Challenges aren't quite at that level, but they can change the way that you think...and that's the whole point. These aren't trivial ways to pass time, they are intended to make you think about things that might well be useful in Penetration Testing, Risk Assessments, Threat Modelling, Security Analysis, White and Black-hat Hacking, and so on and so on.

I'm going to show examples, and in each and every case, the answer will be 'Cryptography', and it will be in capitals, which is supposedly how 'real' cryptographers do writing (sometimes). Not the crypto of block-chain currencies, but the 'hidden writing' of encryption, AES, CIA and several other three-letter acronyms (that's Confidentiality, Integrity and Availability), of course...). The Wall Challenges shown here are deliberately simple and easy to solve, plus you already know the answer! Real Wall Challenges are a bit harder, and some, like the ones you find at hardware security conferences like Hardwear.io, are very hard indeed.

Anyway,  here's the first Wall Challenge, which is called 'Bounce':

YCHRPYAPRTGO

Okay, so even though I've given you the answer, you are probably struggling to see how we went from cryptography to that! What you need are some strategies to get you started, and the first of these is:

Strategy 1: Start at the ends and scan across, skipping to see if anything looks interesting.

Well, the first letter is 'Y', reading from left-to-right, and 'Y' is the last letter of CRYPTOGRAPHY, but continuing gives 'YCHRPY' which isn't CRYPTOGRAPHY backwards (which is YHPARGOTPYRC, of course). The other end is 'O', and going right-to-left across gives 'OGTRPA' which isn't helping much either. 

So let's repeat that, but skipping every other letter, and we get 'YHPARG' and 'OTPYRC'. Woah! That's CRYPTOGRAPHY backwards isn't it? So if we start at the C, second letter in from the left, and miss out every other letter, then we get 'CRYPTO' as we go across from left-to-right, and then we need to reverse direction and go right-to-left to get 'GRAPHY'. So at the end of the word, we 'bounce' and reverse direction. Maybe there should be a brick wall graphic on the piece of paper on the right hand-side? 

So, we now know that doing a bit of adjusting of the order of letters can hide a word, but what use is that? Well, one of the basic transformations that encryption algorithms like AES use is shuffling the order of the data bytes...

Here's the second Wall Challenge, which is called 'Inside out':

PARG

HRCO

YYPT

Starting at the 'P' on the left and going across to the right doesn't give anything useful (PARG might be the start of PARGETER, but it is an unusual word, and there aren't any 'E's!), so try right-to-left from the 'G' - which gives 'GRAP' and we know that is in the middle of the word we are looking for... But in a real challenge then we would not know what the hidden word is, and so this wouldn't be that useful. 

What we probably need is a revised strategy:

Strategy 1: Start at the ends and scan across, vertically and diagonally, skipping to see if anything looks interesting.

If we do this from the lower left hand 'Y', then we get 'YHP', and if we turn the corner at the 'P' to go across to the right, then we get 'YHPARG', which is the end half of CRYPTOGRAPHY, but reversed. If we carry on going round then we eventually hit the 'Y' where we started, so let's turn and carry on in a spiral, which takes us all the way to the 'C', giving 'YHPARGOTPYRC', which is CRYPTOGRAPHY backwards again. So this time, the word was written 'inside out', as a spiral from the initial letter 'C'. Here's me trying to make it more obvious by using coloured letters for the first three letters in the spiral:

PARG

HRCO

YYPT

...and then the last letters...

PARG

HRCO

YYPT

What have we learned this time? Well, it seems that people who are used to reading from left-to-right can find it difficult to go from right-to-left, and that turning things into a 4x3 grid and using a spiral is hard to read. So the shuffling that encryption algorithms carry out looks like it can be effective at obfuscating (a fancy way of saying 'concealing') the sequence of letters in a word. Now, I'm not aware of any cryptographic algorithms that use spirals - they tend to just shuffle or rotate rows or columns. But spirals occur all over the place in nature, and people like them, so there may well be a bias in my usage of them.

The third challenge changes tack, and goes for numbers instead of letters, and is called 'Index':

3 18 25 16 20 15 7 18 1 16 8 25

Whenever numbers appear in a Wall Challenge, then you use another strategy:

Strategy 2: Are the numbers in decimal, hex or another base?

In this case, the numbers appear to be decimal. Often the '3' will be shown as '03' to make you think that it might be in hexadecimal or some other base. Notations like 0x8E for indicating hexadecimal numbers are quite rightly used in programming to make it unambiguously perfectly clear that the '8E' is in hex, but in Wall Challenges there are no rules, and so clues like '0x' are rare. In fact, if I did use that notation, then it would probably be mis-direction!

Oh, nearly forgot:

Strategy 0: There are no rules, standard practices or conventions. (The bad guys break them all the time anyway.)

So we have a list of numbers which might be decimal, so what do we do next? A variation of Strategy 1 is a good starting point: look at the ends, and then scan across and find the largest and smallest numbers. In this case, 3 and 25 are the ends, 1 is the smallest value, and 25 is the largest value. This information is full of clues - can you think of something that comes in a set with about 25 different members?

How about the alphabet? 26 letters... So starting on the left, what is the 3rd letter of the alphabet? 'C'. The 18th? Er, and here you get to the first lookup table. Open your favourite spreadsheet of choice and create a table that has the numbers from 1 to 26 in the first column, and then the letters from A-Z in the second column. Voila - you now have a useful Wall Challenge solving aid, and the beginnings of a collection of tables about symbols and numbers that you will be using a lot. Here's what I produced:

Producing lookup tables like this also has a strategy:

Strategy 3: Whenever you need a look-up table, make one, save it, and add a few extra columns so you are better prepared for next time...

For this table, I added the third column, which is a reversed index to the alphabet. This is good preparation for what myself and lots of other security analysts call 'The T-Shirt Effect'. We all wish that we had a T-Shirt that says on it: 'There's no way that would ever happen!', because this occurs  every time in a Risk Assessment or Threat Modelling session - there's always someone who says these words. In fact, governments around the world probably heard the same or similar words when they looked at the risk of a problem with a new virus epidemic at any time in the last decade...

Anyway, the table makes looking up the 18th letter of the alphabet much easier: 'R'. Going across from left to right, converting from the index number to the corresponding letter of the alphabet, we get: 'CRYPTOGRAPHY' just like you knew we would.

The fourth introductory Wall Challenge is a bit different, and is called 'Standard Interchange':

67 82 89 80 84 79

71 82 65 80 72 89

This time, the ends are bigger than the previous example, at which point experienced Wall Challenge solvers use another strategy:

Strategy 4: Is the range of numbers 26, 36, or some other small number that might contain an alphabet and numbers?

The lowest is 65, and the highest is 89 which is a range of 24, so immediately you should be suspecting something based on the alphabet. Now 65 is one of those 'magic' numbers that shouts out for attention, because the capital letter A is 65 in ASCII, the 'American Standard Code for Information Interchange'. 89 is Y, and so it looks like this is the time to get or make an ASCII lookup table for your collection.

If you replace 67 with the ASCII letter equivalent, you get 'C'. 82 is R, 89 is Y, and before you know it, you have: 'CRYPTOGRAPHY'.

There's an interesting thing to note here. The index table for the alphabet is actually a sub-set of part of the ASCII table - if you add 64 to the first column then it decodes CYRPTOGRAPHY perfectly fine, and this could be added as a fourth 'Shifted ASCII column'... But the ASCII table has lots of other characters in it - numbers, lowercase letters and all sorts of symbols, plus characters that control what a printer does (line feed, carriage return and those curious references back to mechanical printers that borrowed terminology and actions from mechanical typewriters...), as well as characters that don't actually print anything. If you go beyond the 127th character, then ASCII changes from something which is pretty consistent everywhere, to something with lots of alternatives. This 'Extended ASCII' is still standard, it's just that there are lots of standards covering all the variations.

So a nefarious puzzle-setter who wanted to hide some text might well make the capital A have the value 65, but that doesn't mean that it is automatically ASCII. Suppose B was 64, and C was 63? The correct reaction at this point is to already have your spreadsheet open and be adding a column, by the way...

That completes this first introduction to Wall Challenges. If you want more examples, then there are a few posts in this blog that contain them, and attending a Hardwear.io or Nullcon conference might get you a view before anyone else...

Resources

My YouTube channel. Go to the 'Playlists' and look for 'Wall Games'. There are quite a few other videos here to look at, covering topics like security, anime and music...

Hardwear.IO Virtual Con 2020 Questions Only - this is the 'Questions Only' version of the Wall Challenges from the Hardwear.IO Virtual Conference 2020 held online on the 30th of April and 1st of May 2020.

Hardwear.IO Virtual Con 2020 Questions and Answers

Hardwear.IO 2018 Questions

Hardwear.IO 2018 Questions and Answers

Hardwear.IO 2017 Questions

Hardwear.IO 2017 Questions and Answers

Hardwear.IO are excellent hardware security conferences! 

Nullcon is a recommended security conference...

The Nullcon 2020 Badge meta-puzzle...

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Nullcon 2020 Conference Badge Answers

The Nullcon Goa 2020 Conference Badge is a meta-puzzle. There is lots of data all over it, and it obviously has some meaning, but it isn't the usual 'little bit of manufacturer metadata in the corner' stuff, or even a Verhoeff checksum. At a security conference, then there is almost no need to have any further instructions - the badge is intrinsically a challenge to people whose modus operandi is to question everything.

Of course, it might all mean nothing. Unless someone published the answers. If you don't want to know what all that data means, then stop reading now and click away ( Try this as a distraction! ). If you carry on reading, then welcome down the rabbit hole!

The badge was laser etched onto clear plastic (Now this is tricky - I'm not sure if that gorgeous green/orange plastic is 'clear' or 'transparent' - language is an impressively imprecise communication medium!) The design was produced as a DXF file, and has two slots for the lanyard, plus three other holes/circles (manufacturing detail!) There are more than twenty interconnected puzzles (hence the word: meta-puzzle) on the badge, and it looks very cool!  

(In the graphics that follow, I have deliberately left room around the central area so that when you print out this blog, there is plenty of room for notes and calculations...)

The first thing that you probably notice is the central 'tile', which looks like an entry in an alternative Periodic Table - or maybe one from a different universe (paywall) in the multiverse (not paywalled), where the elements are slightly different... A Google search for Nullconium doesn't reveal much, and assuming that it is a Latin word is satisfyingly self-referential. 'Nu' isn't an abbreviation for any element, either. ( Link to useful list for puzzle designers )  Atomic numbers as high as 2000 are way beyond current physics, and 2000+ fails as an atomic number because it isn't unique. The mass number of 20.167 is all wrong as well - it should be larger than the atomic number! At this point, it should be clear that this isn't a tile for an element - but an eye-catching device to gab your attention. 

Warning: if you don't want to know, stop reading now!

The Answers!

The 2000+ is a reference to one of the many year numbering systems that are in use around the world. In the Gregorian Calendar, the current year is 2020, the 20th year of the 21st century. So the 2000 is a hint, and the 20.167 is 20 years, plus .167 of a year, which is meant to be the elapsed part of the year to the beginning of March when Nullcon Goa 2020 started. The 1st of March is day 54 out of 365, which is 0.147, so Nullcon obviously started after that... Day 61 is the 8th of March, which is the day after the last day of the conference. Nullconium thus appears to have the unusual property that the mass number of its most stable isotope increases over the course of a year, then resets, increments and continues to rise: two concatenated sawtooth waveforms...

The green holes/circles allow a 20-sided regular icosagon to be drawn, which is unlikely to be very useful in most security-related areas, but it is interesting that it is another occurrence of '20'... This also highlights an interesting security consideration: The green layer has been interpreted by the badge manufacturer as the 'holes/drill layer' and so they have cut or drilled holes at those points (and probably wondered why I didn't put targets instead of circles! But I forgot this, and so added the screen '+' sign to the middle hole as a extra clue (as it says in the diagram above). I should have moved the green cross to another layer so that it got laser-etched and would be visible...

Of course, a security-minded person quickly realises that this is a classic potential vulnerability - the designer made a mistake that is subtle and hard to spot, but which may have consequences that the designer wasn't anticipating. In my case, a clue was missing and the diagram above highlights this! This type of vulnerability is not restricted to DXF files, of course: any place where two things are affected when only one was supposed to be, or when the coder assumes that two things are related when they shouldn't be, crops up in all sorts of coding situations. A bug like this is very hard to spot because people are very good at seeing patterns and associating things as groups - and in this case, this is exactly wrong - the hole and the '+' symbol should definitely be on two different layers. For a security analyst, this gives a clue to how to find this type of potential vulnerability: look for things that are out of context, exceptions or variations, or where multiple similar things happen at once - you can almost guarantee that a copy/paste/modify will have been done wrong, or that one or more references or paths or pointers will be wrong. people are very good at king this type of mistake, and very bad at spotting their mistake. Hiding in plain sight!

On the lowest edge of the badge are what look like books on a book-shelf, with some them falling over. You either see it immediately, or else you suddenly can see it when it is pointed out to you - a binary visual interpretation. once seen, you can't un-see it! These spell 'Nullcon' in a rather arcane way, but serve as a clue to some of the other numbers around the edge... I always try to include hints and pointers to things to get people started...

Having said this about leaving clues: the two holes for the lanyard do not have any significance (and 'lanyard-puzzles' are another related class of meta-puzzle!). This is probably the most difficult challenge on the badge. As in many security-related investigations, the hardest problem to solve is one that is not a problem with an answer!

The 'book-shelf' clue leads nicely into the data around the top edges. From the left, clockwise, these get gradually more difficult. CLLNNOU is just the letters in 'Nullcon' sorted alphabetically, which leads to 3522143, which is just the alphabetical positions in CLLNNOU (1223345) undone by forming NULLCON (3522143) and then reversing the order. Over on the right hand side, the 1876^2 + 2767 gives a result of 3,522,143, which is the non-reversed order of the letters of a sorted Nullcon. 

The long row of two digit numbers at the top of the badge is just Nullcon 2020 in 'ASCII', but using character 00 with its meaning of 'Null' instead of spelling out 'NULL' as 78,  85, 76, 76. So not quite normal ASCII... But the inclusion of 2020 is also a clue for the other two sets of numbers. 04 08 04 00 is meant to look like ASCII, but is actually a number: 4,080,400, which is 2020^2, and 4080400 is the same 2020^2 again, but this time shown without commas. At this point, you are probably thinking that 'Nullcon' and '2020' seem to be the answers to the challenges, but this is not true for all of the challenges... 

Underneath the 'tile', there are four rows of numbers and symbols. In general, the numbers are numbers, whilst the symbols are used to indicate the number base that has been used to express the number. So the top left number of 3744 is to the left of an octagon, and turns out to be 2020 in octal (base 8), even with a typo in the diagram! (The missing '4' - which is not missing for any reason other than a typo!) The 011 111 100 100 to the right is also in octal, but binary octal (which is octal expressed in binary form!): '011' is 3, '111' is 7, etc. 

The next row has what looks like binary again, because it is! The '\' symbol indicates binary just as the octagon indicates base 8. I did consider using Unary (base 1), where no symbol at all indicates zero, a single 1 represents 1, 11 is 2, 111 is 3, 1111 is 4, and so on, but decided that having 2020 1's in a row was going to be difficult to count! By using the '\' symbol as a clue that the base changes, the four pentagons indicate base 20, which is slightly outside most people's experience. Anyway, 510 is 2020 in base 20, which looks like there's some interesting patterning going on, and I'm sure that Numberphile et al on YouTube have covered this... (I'm reasonably sure, but didn't search too hard for it...) 

The next row down has base 5, base 18 (well outside my usual path!) and what looks like it might be an ethernet address... Well, it is, for the Tsinghua University in Beijing, China, but this is base 10: decimal, and those dots are shorthand for 'multiply'. So it means 101 x 5 x 2 x 2 = 2020. I'm very fond of giving you a repeated pattern and then suddenly jumping to something entirely different. Lulling you into a false sense of security, as they say!

Now that the context switch has happened, the final row is in base 10 (decimal), then hex (base 16) and then hex again. 45^2 - 5 = 2020, which is interesting, and 7E4 does look like hex, but it's just a straight conversion from 2020. D^2 - B1 is just hex arithmetic to try and test your agility.  

At this point, you might think you were finished. But there is one final puzzle - the numbers on the right hand side...

26, 20, 9 and 0 aren't ASCII, and they don't seem to be 2020 in any base. So what are they? If you replace the values in the rows with the number bases that are used, then you just get a grid of numbers. But if you add them up (clue is the + in front of the numbers on the right) then you get a very special number: 42. (42 is special in lots of ways !) I didn't use the Catalan 5-significance of 42 in this meta-puzzle - that would be for a maths conference, not a security conference...

Finally, after all of those 'Nullcon's and '2020's, we get to a different special number: '42'. Yay!

(It would have been boring if that was a 2020 as well, wouldn't it? Of course, 48.0952381..... x 42 is 2020, but that's another story.)

I hope you found the 42. If not, you now know how to find it!

And a summary!

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More...

To find the first part of this post on the Nullcon badge, visit this page...

If you want more depth about one of the challenges above, then please visit this page...

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I would like to thank the wonderful people at Payatu Technologies, who organise Nullcon, for great conferences (hardware.io, for example), and for asking me to do this badge design for Nullcon Goa 2020. 

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If you find my writing helpful, informative or entertaining, then please consider visiting this link for my Synthesizerwriter alias (I write several blogs, and it makes sense to only have one donation page!):

Buy me a coffee