[HN Gopher] The Solution of the Zodiac Killer's 340-Character Ci...
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The Solution of the Zodiac Killer's 340-Character Cipher
Author : 0-_-0
Score : 270 points
Date : 2021-03-24 18:01 UTC (4 hours ago)
(HTM) web link (blog.wolfram.com)
(TXT) w3m dump (blog.wolfram.com)
| liquidify wrote:
| Amazing. It seems possible that the killer would have required a
| fairly advanced education to create a cypher with this
| complexity. Not too many self taught encryption creators exist
| out there.
| barbegal wrote:
| The cipher only uses two fairly simple techniques:
| transposition and homophonic substitution. Both of these are
| covered in any elementary book on codes and ciphers. Combining
| the two makes a cipher which is tough but not impossible to
| crack given a long enough ciphertext as demonstrated here.
| qw3rty01 wrote:
| Nothing really sticks out in the cipher as being inherently
| complex or requiring advanced education, it's more of just a
| puzzle where you're meant to figure out arbitrary rules, which
| in this case weren't even consistent throughout the entire
| cipher (adding some artificial difficulty). It's pretty out of
| scope of encryption because it was meant to be broken.
| dtech wrote:
| This cipher isn't all that difficult, even compared to a simple
| modern cipher like DES. Ciphers are meant to withstand attacks
| if you know the rules (algorithm), this one doesn't, making it
| more of a puzzle than a cipher.
| camjohnson26 wrote:
| So is the only unsolved zodiac cipher the text at the end of
| this? Speculation is that it could just be filler text.
|
| ebeorietemethhpiti
|
| https://www.zodiacciphers.com/chronicle-letter.html
| tibbydudeza wrote:
| And the top Hacker News submission right now is
|
| "Superior IQs are associated with mental and physical disorders,
| research suggests"
| camjohnson26 wrote:
| This news broke a few weeks ago and a few write ups were
| already published.
| DSingularity wrote:
| This cipher is pure security-through obscurity and it held up
| well.
| obilgic wrote:
| so It held up pretty well, because he made several mistakes
| along the way, which made much harder than It is to figure out.
| elliekelly wrote:
| Mistakes? Or misdirection?
| camjohnson26 wrote:
| What does "much harder than it is" mean, it took 51 years to
| decipher it, that's how hard it was.
| kshacker wrote:
| Just curious. If someone were to start today, with today's
| computing power and knowledge of computers, how long would
| it take?
|
| The answer to this can tell how easy it may be to create a
| similar problem today.
| thatwasunusual wrote:
| ...and still the killer is unknown. That's pretty good,
| IMO.
| the_af wrote:
| What's the connection between the killer's identity still
| being unknown and the strength of this cipher? The killer
| lied: the plaintext doesn't contain personal information,
| or if it does, it's a riddle unrelated to the cipher.
| evolve2k wrote:
| The killer sent three cipers, my reading is that maybe
| 1-2 are now solved, they are not all solved yet. Are
| they?
| obilgic wrote:
| He made mistakes using his own cypher.
| buescher wrote:
| It can be fiendishly difficult to break a completely unknown
| cypher, or one that has key elements withheld, even if it's
| quite trivial to break if the encryption algorithm is known.
| thatwasunusual wrote:
| Can confirm.
|
| Did a ROT-13/15 (vowels vs consonants, if it matters) test on
| _smart_ collegues. Turns out they fear the worst and start
| top-down.
| SV_BubbleTime wrote:
| Think one of the most interesting things I learned in
| encryption, was that a random xor sheet the same length as your
| plaintext is perfect encryption.
|
| That the problem only happens when you reuse that sheet.
|
| This doesn't apply here specifically, but if you would have
| told me this previously I would have assumed it was securing
| through obscurity.
| chowells wrote:
| It's worth expanding on that observation a bit.
|
| What makes encryption "perfect"? This is not obvious, so I'll
| just skip ahead to the conclusion: encryption is perfect when
| it's impossible to distinguish which candidate plaintext led
| to a specific ciphertext without knowing the entire key.
|
| It's easy to see that a one-time pad qualifies here. Even
| knowing all but one character of the plaintext doesn't give
| you any cryptographic way to determine what the last
| character is. The list of possible keys associating the known
| plaintext with the current ciphertext allows for every single
| character in the unknown position. This isn't a matter of
| computational power, it's an information-theoretic limit. You
| just don't have enough information (from the cryptography,
| anyway) to prefer any choice over another.
|
| You can apply a pigeonhole principle argument here and see
| that this requires the key to have the same size as the
| message. (Something along the lines of each key specifying a
| permutation between messages of the same length, and you need
| the key size to be big enough to specify every possible
| permutation for that message length.)
|
| That argument can then be used to demonstrate the
| information-theory quality of the encryption is related to
| the ratio between the lengths of the message and the key.
|
| When you look at modern cryptography, you can see that we're
| not depending on information-theoretic security at all. If
| you had all but one characters of the plaintext and all the
| ciphertext, it's quite likely there'd only be one key that
| matches the known permutation. We've gone in a different
| direction: computational security. It should require an
| implausible amount of computation to derive what the key is,
| even when you know matching plaintext and ciphertext.
|
| It's certainly more convenient than moving terabytes of key
| around, and computational limits are actually pretty
| compelling, as long as flaws aren't found in the
| construction.
|
| But it lacks the satisfaction of provably unbreakable.
| ben509 wrote:
| One way to explain OTPs is a proof by induction.
|
| The base step:
|
| Start with one bit. The key is also a bit chosen at random,
| and the cipher text is plain XOR key.
|
| You can then work out that no matter what key is chosen,
| you have no reason to believe 0 or 1 is the original plain
| text.
|
| The inductive step is simply to add a new random bit of key
| that is independent from the prior key, and a new bit of
| plaintext.
|
| What I like about this explanation is that you can actually
| work out the decision trees for a few bits to convince
| yourself that the encryption still holds.
| shishy wrote:
| one time pad! so impractical but so good
| afrodc_ wrote:
| There's an interesting episode of Darknet Diaries where a
| former analyst at the NSA talks about OTPs and how he
| created an automated system for field agents to encipher
| and decipher them who found them exhausting to do manually.
|
| Edit: Forgot the link
| https://darknetdiaries.com/episode/83/
| bsza wrote:
| Then you might also like the fact that it can be implemented
| simply using transparent sheets:
|
| https://www.douglas.stebila.ca/teaching/visual-one-time-pad/
|
| IIRC this is exactly how OTP was used by some spies during
| the Cold War. (My compsci teacher actually showed us an
| 'original' pair of sheets that encoded a Chinese character).
|
| Also shows it very neatly why reusing the sheet is a bad
| idea.
| 2OEH8eoCRo0 wrote:
| Obscurity can be a valid layer in a multilayered defense.
| diarrhea wrote:
| My defenses are multiple layers of obscurity.
| jgalt212 wrote:
| never roll your own crypto, but sometimes maybe ....?
| qw3rty01 wrote:
| A thread on the original solution:
|
| https://news.ycombinator.com/item?id=25390941
| willio58 wrote:
| So there are still spelling errors in the result, is this just
| due to the zodiac killer being bad at encryption initially?
| spacepinball wrote:
| in earlier messages from zodiac he spelled PARADICE too, see
| https://en.wikipedia.org/wiki/File:Zodiac-back.pdf
| Jtsummers wrote:
| Some of the spelling errors were common in his messages,
| especially "paradice".
| bowmessage wrote:
| "Paradice" was a well known misspelling of his, and actually
| aided in validating the solution based on others' accounts of
| breaking this code.
| dyingkneepad wrote:
| These days where kids have school-issued Chrome laptops and
| whatnot, the FBI would simply ask Google to grep for
| "paradice" in the records for every school district and
| within a few hours we'd have pretty good list of suspects.
| Voloskaya wrote:
| Or you wouldn't because every kid using Google Doc would be
| using Smart Compose autocomplete feature and corrector
| making everyone's prose very homogeneous.
| mxcrossb wrote:
| This might be naive but, in the age before spell check, I
| wonder if a lot of people consistently made spelling mistakes
| like this. I mean you wouldn't know you were wrong unless you
| checked in the dictionary.
| nerfhammer wrote:
| there's speculation that he was spelling badly on purpose
| to make it harder to compare to his real-life writing style
| dane-pgp wrote:
| One subjective opinion puts this cipher as one of "Six top
| unsolved codes and ciphers"[0]. The other five also have
| interesting stories behind them, but the one I'm most looking
| forward to seeing solved is the fifth on the list, namely the
| Voynich Manuscript.
|
| [0] https://mysteriouswritings.com/six-top-unsolved-codes-and-
| ci...
| galkk wrote:
| I'm curious - if the same thing, with the same approach to
| encryption would be written in non-English language (Russian, for
| example, or Hungarian) - would it be ever be cracked?
|
| Seems like many tools/approaches used were english-specific, and
| unless some lucky guess/hit, they wouldn't be applicable to other
| languates.
| lastofthemojito wrote:
| I think the English-speaking world kind of has a target on its
| back in terms of cybersecurity because everyone who can use a
| computer (a slight exaggeration) has some knowledge of English,
| but not everyone has knowledge of Farsi or Korean or Icelandic
| or whatever. So if just about any hacker comes across a
| vulnerability in your English-language system, they'll
| recognize it. Meanwhile, if I stumbled upon a link that gave me
| unauthorized access to a Hungarian-language system, I'd have no
| idea.
| johnwheeler wrote:
| The zodiac should've used the plaintext of the first 3 messages
| as a one time pad key for the forth
| wyldfire wrote:
| The author's name is Blake, but AFAICT this has no relationship
| with the crypto hash algo BLAKE/BLAKE2 (by Aumasson, Neves,
| Henzen, et al).
| NetOpWibby wrote:
| What a creepy mystery, glad it's cracked though.
| edem wrote:
| We still don't know who was the killer.
| NetOpWibby wrote:
| Oh right.
|
| Well...we have one asset figured out.
| clivecusslerad wrote:
| Waiting for the Netflix documentary...
| partiallypro wrote:
| There are already so many documentaries on Zodiac. It's
| probably my favorite case because of the ciphers and
| letters. Unfortunately I'm not sure we'll ever catch him. I
| personally believe it was likely Arthur Leigh Allen, but
| it's also possible that he was just a fanboy and loved the
| attention of people thinking he was The Zodiac.
| [deleted]
| ChicagoDave wrote:
| This is awesome. Now I'd like to see someone recreate the
| original hand-written mechanism the killer used to create the
| cypher.
| barbegal wrote:
| It's pretty simple really. First you need to write out your
| plaintext and count the frequency of each of the letters in the
| plaintext.
|
| Now choose a set of 40+ symbols to do the homophonic
| substitution. You randomly assign these to the letters A-Z
| making sure you assign more to the letters that you use the
| most in your plaintext (probably e and t having the most)
|
| Now decide on an arrangement of the plaintext (transposition
| cipher), this may involve writing diagonally or spirally or in
| any pattern that can be conveyed as a key and is easy to write
| out.
|
| Finally, substitute the symbols, where you have a choice of
| more than one symbol pick one randomly. This should be done
| randomly rather than methodically to make the cipher the
| toughest to decrypt, you could use dice to do this.
|
| The decryption key that you pass to anyone wanting to decrypt
| the ciphertext is the set of symbol substitutions and the way
| that you have transposed the symbols. (E.g. spiral going
| clockwise from top right)
| akyu wrote:
| I've seen speculation that his method may have been as simple
| as the ancient Spartan Scytale
| (https://en.wikipedia.org/wiki/Scytale).
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