Crypto for kids

[Nytro]

1.

Professor Krankenstein was the most influential genetic engineer of his time.

When, in the spring of 2030, he almost incidentally invented the most terrible biological weapon known to humanity it took him about three seconds to realize that should his invention fall into the hands of one of the superpowers -- or into the hands of any common idiot, really -- it could well mean the end of the human race.

He wasted no time. He destroyed all the artifacts in the lab. He burned all the notes and hard disks of all the computers they’ve used in the project. He seeded false information all over the place to lead future investigators off the track.

Now, left with the last remaining copy of the doomsgerm recipe, he was contemplating whether to destroy it.

Yes, destroying it would keep the world safe. But if such a breakthrough in genetic engineering was used in a different way it could have solved the hunger problem by producing enough artificial food to feed the swelling population of Earth. And if global warming went catastrophic, it could have been used to engineer microorganisms super-efficient at sequestering carbon dioxide and methane from atmosphere.
In the end he decided not to destroy but rather to encrypt the recipe, put it into a tungsten box, encase the box in concrete and drop it from a cruise ship into Mariana Trench.

The story would have ended there if it was not for one Hendrik Koppel, a rather simple-minded person whom professor Krankenstein hired to help him to move the tungsten-concrete box around. Professor didn’t even met him before he destroyed all his doomsgerm research. Still, Hendrik somehow realized that the issue was of interest to superpowers (Was professor Krankenstein sleep-talking?) and sold the information about the location of the box to several governments.

By the beginning of October the news hit that an American aircraft carrier is heading in the direction of Mariana Trench.

Apparently, there was also a Russian nuclear submarine on its way to the same location.

Chinese government have sent a fleet of smaller, more versatile, oceanographic vessels.

After the initial bout of despair, professor Krankenstein realised that with his superior knowledge of the position of the box he could possibly get to the location first and destroy the box using an underwater bomb.

He used his life savings to buy a rusty old ship called Amor Patrio, manned it with his closest collaborators and set up for Pacific Ocean.

...

Things haven't gone well. News reported that Americans and Chinese were approaching the area while Amor Patrio's engine broke and the crew was working around the clock to fix it.

Finally, they fixed it and approached Mariana Trench.

It was at that point that the news reached them: The box was found by Russians and transported to Moscow. It was now stored in the vault underneath KGB headquarters. There was a whole division of spetsnaz guarding the building. The building itself was filled with special agents, each trained in twelve ways of silently killing a person.

Professor Krankenstein and his associated held a meeting on board of Amor Patrio, in the middle of Pacific Ocean. People came up with desperate proposals: Let's dig a tunnel underneath Moscow river. Let's blackmail Russians by re-creating the virus and threatening them to disperse it in Russia. Nuke the entire Moskovskaya Oblast! There was no end to wild and desperate proposals.

Once the stream of proposals dried up, everyone looked at professor Krankenstein, awaiting his decision.

The silence is almost palpable.

Professor Krankenstein slowly took out his iconic pipe and lighted it with the paper which had the decryption key written on it.

13.

No full story yet, but let's assume a king is at a quest. At some point he realizes that a small item, say a specific hairpin, is needed to complete the quest. He clearly remembers he used to own the hairpin, but he has no idea whether it's still in his possession and if so, where exactly it is. He sends a messenger home asking his counsellors to look for the hairpin and let him know whether they've found it or not.

King's enemies need that information as well so the next day, when the messager is returning, they ambush him and take the message. Unfortunately, the message is encrypted. The messager himself knows nothing about the pin.

Many experienced cryptographers are working around the clock for days in row to decrypt the message but to no avail.

Finally, a kid wanders into the war room. She asks about what they are doing and after some thinking she says: "I know nothing about the high art of cryptography and in no way I can compare to esteemed savants in this room. What I know, though, is that King's pallace has ten thousand rooms, each full of luxury, pictures and finely carved furniture. To find a hairpin in such a place can take weeks if not months. If there was no hairpin it would take at least that long before they could send the messenger back with negative reply. So, if the messager was captured on his way back on the very next day, it can mean only a single thing: The hairpin was found and your encrypted message says so."

20.

Here Legrand, having re-heated the parchment, submitted It my inspection. The following characters were rudely traced, in a red tint, between the death's-head and the goat:

53++!305))6*;4826)4+.)4+);806*;48!8`60))85;]8*:+*8!83(88)5*!;
46(;88*96*?;8)*+(;485);5*!2:*+(;4956*2(5*-4)8`8*; 4069285);)6
!8)4++;1(+9;48081;8:8+1;48!85;4)485!528806*81(+9;48;(88;4(+?3
4;48)4+;161;:188;+?;

"But," said I, returning him the slip, "I am as much in the dark as ever. Were all the jewels of Golconda awaiting me on my solution of this enigma, I am quite sure that I should be unable to earn them."

"And yet," said Legrand, "the solution is by no means so difficult as you might be led to imagine from the first hasty inspection of the characters. These characters, as any one might readily guess, form a cipher --that is to say, they convey a meaning; but then, from what is known of Kidd, I could not suppose him capable of constructing any of the more abstruse cryptographs. I made up my mind, at once, that this was of a simple species --such, however, as would appear, to the crude intellect of the sailor, absolutely insoluble without the key."

"And you really solved it?"

"Readily; I have solved others of an abstruseness ten thousand times greater. Circumstances, and a certain bias of mind, have led me to take interest in such riddles, and it may well be doubted whether human ingenuity can construct an enigma of the kind which human ingenuity may not, by proper application, resolve. In fact, having once established connected and legible characters, I scarcely gave a thought to the mere difficulty of developing their import.

"In the present case --indeed in all cases of secret writing --the first question regards the language of the cipher; for the principles of solution, so far, especially, as the more simple ciphers are concerned, depend on, and are varied by, the genius of the particular idiom. In general, there is no alternative but experiment (directed by probabilities) of every tongue known to him who attempts the solution, until the true one be attained. But, with the cipher now before us, all difficulty is removed by the signature. The pun on the word 'Kidd' is appreciable in no other language than the English. But for this consideration I should have begun my attempts with the Spanish and French, as the tongues in which a secret of this kind would most naturally have been written by a pirate of the Spanish main. As it was, I assumed the cryptograph to be English.

"You observe there are no divisions between the words. Had there been divisions, the task would have been comparatively easy. In such case I should have commenced with a collation and analysis of the shorter words, and, had a word of a single letter occurred, as is most likely, (a or I, for example,) I should have considered the solution as assured. But, there being no division, my first step was to ascertain the predominant letters, as well as the least frequent. Counting all, I constructed a table, thus:

Of the character 8 there are 33.

   ;     "     26.
   4     "     19.
 + )     "     16.
   *     "     13.
   5     "     12.
   6     "     11.
 ! 1     "      8.
   0     "      6.
 9 2     "      5.
 : 3     "      4.
   ?     "      3.
   `     "      2.
 - .     "      1.

"Now, in English, the letter which most frequently occurs is e. Afterwards, the succession runs thus: a o i d h n r s t u y c f g l m w b k p q x z. E however predominates so remarkably that an individual sentence of any length is rarely seen, in which it is not the prevailing character.

"Here, then, we have, in the very beginning, the groundwork for something more than a mere guess. The general use which may be made of the table is obvious --but, in this particular cipher, we shall only very partially require its aid. As our predominant character is 8, we will commence by assuming it as the e of the natural alphabet. To verify the supposition, let us observe if the 8 be seen often in couples --for e is doubled with great frequency in English --in such words, for example, as 'meet,' 'fleet,' 'speed, 'seen,' 'been,' 'agree,' &c. In the present instance we see it doubled less than five times, although the cryptograph is brief.

"Let us assume 8, then, as e. Now, of all words in the language, 'the' is the most usual; let us see, therefore, whether they are not repetitions of any three characters in the same order of collocation, the last of them being 8. If we discover repetitions of such letters, so arranged, they will most probably represent the word 'the.' On inspection, we find no less than seven such arrangements, the characters being ;48. We may, therefore, assume that the semicolon represents t, that 4 represents h, and that 8 represents e --the last being now well confirmed. Thus a great step has been taken.

"But, having established a single word, we are enabled to establish a vastly important point; that is to say, several commencements and terminations of other words. Let us refer, for example, to the last instance but one, in which the combination ;48 occurs --not far from the end of the cipher. We know that the semicolon immediately ensuing is the commencement of a word, and, of the six characters succeeding this 'the,' we are cognizant of no less than five. Let us set these characters down, thus, by the letters we know them to represent, leaving a space for the unknown--

t eeth.

"Here we are enabled, at once, to discard the 'th,' as forming no portion of the word commencing with the first t; since, by experiment of the entire alphabet for a letter adapted to the vacancy we perceive that no word can be formed of which this th can be a part. We are thus narrowed into

t ee,

and, going through the alphabet, if necessary, as before, we arrive at the word 'tree,' as the sole possible reading. We thus gain another letter, r, represented by (, with the words 'the tree' in juxtaposition.

"Looking beyond these words, for a short distance, we again see the combination ;48, and employ it by way of termination to what immediately precedes. We have thus this arrangement:

the tree ;4(+?34 the,

or substituting the natural letters, where known, it reads thus:

the tree thr+?3h the.

"Now, if, in place of the unknown characters, we leave blank spaces, or substitute dots, we read thus:

the tree thr...h the,

when the word 'through' makes itself evident at once. But this discovery gives us three new letters, o, u and g, represented by + ? and 3.

"Looking now, narrowly, through the cipher for combinations of known characters, we find, not very far from the beginning, this arrangement,
83(88, or egree, which, plainly, is the conclusion of the word 'degree,' and gives us another letter, d, represented by !.

"Four letters beyond the word 'degree,' we perceive the combination

46(;88*.

"Translating the known characters, and representing the unknown by dots, as before, we read thus:

th.rtee.

an arrangement immediately suggestive of the word 'thirteen,' and again furnishing us with two new characters, i and n, represented by 6 and *.

"Referring, now, to the beginning of the cryptograph, we find the combination,

53++!.

"Translating, as before, we obtain

.good,

which assures us that the first letter is A, and that the first two words are 'A good.'

"To avoid confusion, it is now time that we arrange our key, as far as discovered, in a tabular form. It will stand thus:

5 represents a
!    "       d
8    "       e
3    "       g
4    "       h
6    "       i
*    "       n
+    "       o
(    "       r
;    "       t

"We have, therefore, no less than ten of the most important letters represented, and it will be unnecessary to proceed with the details of the solution. I have said enough to convince you that ciphers of this nature are readily soluble, and to give you some insight into the rationale of their development. But be assured that the specimen before us appertains to the very simplest species of cryptograph. It now only remains to give you the full translation of the characters upon the parchment, as unriddled. Here it is:

'A good glass in the bishop's hostel in the devil's seat twenty-one degrees and thirteen minutes northeast and by north main branch seventh limb east side shoot from the left eye of the death's-head a bee line from the tree through the shot fifty feet out.'"

"But," said I, "the enigma seems still in as bad a condition as ever. How is it possible to extort a meaning from all this jargon about 'devil's seats,' 'death's-heads,' and 'bishop's hostel'?"

"I confess," replied Legrand, "that the matter still wears a serious aspect, when regarded with a casual glance. My first endeavor was to divide the sentence into the natural division intended by the cryptographist."

"You mean, to punctuate it?"

"Something of that kind."

"But how was it possible to effect this?"

"I reflected that it had been a point with the writer to run his words together without division, so as to increase the difficulty of solution. Now, a not overacute man, in pursuing such an object, would be nearly certain to overdo the matter. When, in the course of his composition, he arrived at a break in his subject which would naturally require a pause, or a point, he would be exceedingly apt to run his characters, at this place, more than usually close together. If you will observe the MS., in the present instance, you will easily detect five such cases of unusual crowding. Acting on this hint, I made the division thus:

'A good glass in the bishop's hostel in the devil's --twenty-one degrees and thirteen minutes --northeast and by north --main branch seventh limb east side --shoot from the left eye of the death's-head --a bee-line from the tree through the shot fifty feet out.'"

"Even this division," said I, "leaves me still in the dark."

32.

A portal suddenly opened on the starboard ejecting a fleet of imperial pursuit vessels. The propulsion system of my ship got hit before the shield activated. I’ve tried to switch on the backup drive but before it charged to 5% I was already dangling off a dozen tractor beams.

It wasn’t much of a fight. They’ve just came and picked me up as one would pick up a box of frozen strawberries in a supermarket.

I must have passed out because of pressure loss because the next thing I remember is being in a plain white room with my hands cuffed behind my back.

There was a sound of door opening and a person walked into my field of vision.

It took me few seconds to realize who the man was. He was wearing an old-fashioned black suit and a bowler hat, black umbrella in his hand, not the baggy trousers seen on his official portraits. But then he smiled and showed the glistening golden teeth on the left side and his own healthy camel-like teeth on the right and the realization hit me.

It was him. Beylerbey Qgdzzxoglu in person.

“Peace be upon you,” he said. Then he sat down on the other side of a little coffee table, made himself comfortable and put his umbrella on the floor.

“We have a little matter to discuss, you and I,” he said.

He took a paper out of his pocket and put in on the coffee table, spinning it so that I can read it.

“Attack the Phlesmus Pashalik,” said one line.

“Attack the Iconium Cluster,” said the line below it.

The rest of the sheet was empty except for holographic seal of High Command of Proximian Insurgency.

"Comandante Ribeira is no fool," he said, "And this scrap of paper is not going to convince me that he's going to split his forces and attack both those places at the same time. Our strategic machines are vastly more powerful than Proximian ones, they've been running hot for the past week and out lab rats tell us that there's no way to win that way."

"You are right, O leader of men," I said.

I knew that this kind of empty flattery was used at the Sublime Porte but I was not sure whether it wasn't reserved for the sultan alone.

Qgdzzxoglu smiled snarkily but haven't said anything. Maybe I was going to live in the end.

"I have no loyalty for the Proximian cause and before the rebelion I have lived happily and had no thoughts of betrayal. And now, hoping for your mercy, I am going to disclose the true meaning of this message to you."

"It is a code, O you, whose slipper weights heavily upon the neck of nations," I said, "The recepient is supposed to ignore the first sentence and only follow the second one."

I hoped I haven't overdone it. Being honest with the enemy is hard.

"So you are trying to convince me that de Ribeira is going to attack Iconium," he gave me a sharp look, apparently trying to determine whether I was lying or not. "And you know what? We've got our reports. And our reports are saying that rebels will try to trick us into moving all our forces into Iconium and then attack pashalik of Phlesmus while it's undefended. And if that's what you are trying to do bad things are going to happen to your proboscis."

"The Most Holy Cross, John XXIII and Our Lady of Africa have already got a command to move to Iconium cluster. And you should expect at least comparable fire force from elsewhere."

...

The messenger has no intention to suffer to win someone else's war. At the same time it's clear that if he continues to tell truth he will be tortured. So he says that general is right and it's the first sentence that should be taken into account.

The general begins to feel a bit uneasy at this point. He has two contradictory confessions and it's not at all clear which one is correct.

He orders the torture to proceed only to make the messager change his confession once again.

...

“Today, the God, the Compassionate, the Merciful have taught me that there are secrets that cannot be given away. You cannot give them away to save yourself from torture. You cannot give them away to save your kids from being sold to slavery. You cannot give them away to prevent the end of the world. You just cannot give them away and whether you want to or not matters little.”

54.

Here's a simple game for kids that shows how asymmetric encryption works in principle, makes the fact that with only public key at your disposal encryption may be easy while decryption may be so hard as to be basically impossible, intuitive and gives everyone a hands-on experience with a simple asymmetric encryption system.

Here's how it works:

Buy a dictionary of some exotic language. The language being exotic makes it improbable that any of the kids involved in the game would understand it. Also, it makes cheating by using Google Translate impossible.

Let's say you've opted for Eskimo language. The story of the game can be located at the North Pole after all.

You should prefer a dictionary that comes in two bands: English-Eskimo dictionary and Eskimo-English dictionary. The former will play the role of public key and the latter the role of secret key. Obviously, if there's no two-band dictionary available, you'll have to cut a single-band one in two.

To distribute the public key to everyone involved in the game you can either buy multiple copies of English-Eskimo dictionary, which may be expensive, or you can simply place a single copy at a well-known location. In school library, at a local mom-and-pop shop or at a secret place known only to the game participants.

If a kid wants to send an encrypted message to the owner of the secret key, they just use the public key (English-Eskimo dictionary) to translate the message, word-by-word, from English to Eskimo. The owner of the secret key (Eskimo-English dictionary) can then easily decrypt the message by translating it back into English.

However, if the message gets intercepted by any other game participant, decrypting it would be an extremely time consuming activity. Each word of the message would have to be found in English-Eskimo dictionary, which would in turn mean scanning the whole dictionary in a page-by-page and word-by-word manner!

78.

It's a puppet show. There are two hills on the stage with country border between them. Law-abiding citizen is on the right hill. Smuggler enters the stage on the left.

SMUGGLER: Hey, you!

CITIZEN: Who? Me?

SMUGGLER: Do you like booze?

CITIZEN: Sure I do. And who are you?

SMUGGLER: I'm the person who will sell you some booze.

CITIZEN: What about cigarettes?

SMUGGLERS: Sure thing. Cheap Ukrainian variety for $1 a pack. Also Slovenian Mariboro brand.

CITIZEN: Thanks God! I am getting sick of our government trying to make me healthy!

Border patrol emerges from a bush in the middle of the stage.

PATROL: Forget about it, guys! This is a state border. Nothing's gonna pass one way or the other. You better pack your stuff and go home.

SMUGGLER: Ignore him. We'll meet later on at some other place, without border patrol around, and you'll get all the booze and cigarettes you want.

PATROL: Ha! I would like to see that. Both of you are going to end up in jail.

CITIZEN: He's right. If you tell me where to meet, he's going to hear that, go there and arrest us.

...

Smuggler has a list of possible places to meet:

1. Big oak at 57th mile of the border.
2. Lower end of Abe Smith's pasture.
3. ...
4. ...

He obfuscates each entry and shout them to the citizen in no particular order.

Citizen chooses one of the puzzles and de-obfuscates it. It takes him 10 minutes. The de-obfuscates message reads: "18. Behind the old brick factory."

CITIZEN (cries): Eighteen!

SMUGGLER: Ok, got it, let's meet there in an hour!

PATROL: Oh my, oh my. I am much better at de-obfuscation than that moron citizen. I've already got two messages solved. But one has number 56, the other number 110. I have no idea which one is going to be number 18. There's no way I can find the right one in just one hour!

The curtain comes down. Happy gulping sounds can be heard from the backstage.

99.

Mr. X is approached in the subway by a guy who claims to be an alien stranded on Earth and to possess time machine that allows him to know the future. He needs funds to fix his flying saucer but filling in winning numbers for next week's lottery would create a time paradox. Therefore, he's willing to sell next week's winning numbers to Mr. X at a favourable price.

Mr. X, as gullible as he is, feels that this may be a scam and asks for a proof. Alien gives him the next week's winning numbers in encrypted form so that Mr. X can't use them and then decide not to pay for them. After the lottery draw he'll give Mr. X the key to unlock the file and Mr. X can verify that the prediction was correct.

After the draw, Mr. X gets the key and lo and behold, the numbers are correct! To rule out the possibility that it happened by chance, they do the experiment twice. Then thrice.

Finally, Mr. X is persuaded. He pays the alien and gets the set of numbers for the next week's draw.

But the numbers drawn are completely different.

And now the question: How did the scam work?

NOTE: The claim about the time paradox is super weak. To improve the story the alien can ask for something non-monetary (sex, political influence). Or, more generally, positive demonstration of knowledge of the future can be used to make people do what you want. E.g. "I know that an asteroid is going to destroy Earth in one year. Give me all your money to build a starship to save you."

 

 

Sursa: https://sustrik.github.io/crypto-for-kids/