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Famous cryptographers’ tombstone cryptogram decrypted

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Re: Famous cryptographers’ tombstone cryptogram decrypted

#31

Post by dlubarov »

ChrisSD wrote: post #18
ythn wrote: post #10

Earlier quoted context omitted.

> whereas a good puzzle cannot be impossible to crack. This is a very important distinction. It would be no fun if the cipher on a given cryptographer's tombstone were created with a one-time pad.

Interestingly a one time pad may be crackable. Its theoretical uncrackability is only true if a truly random number generator is used. Most cryptography is fine with urandom but a one time pad requires using something like radioactive decay to generate your pad. This is one reason (among many) why it's impractical for most crypto purposes.

Assuming a flawless CSRNG, 128 bits of entropy is more than enough to withstand current attack power. It's hard to predict the future -- quantum computers employing Grover's algorithm could conceivably have 2x or more attack power per unit energy -- but 256 bits should be adequate for a long time.

It's fine to use low-grade sources of entropy like timestamps as long as we have enough of it. I might only generate a few bits of actual entropy per second when I move my mouse in somewhat predictable arcs, but if I keep at it for a while, I'll generate 256 bits of entropy eventually.

Re: Famous cryptographers’ tombstone cryptogram decrypted

#32

Post by mirimir »

ythn wrote: post #10
logfromblammo wrote: post #7

Earlier quoted context omitted.

It's splitting hairs to make a distinction, but a cipher has an intended recipient and potential eavesdroppers, whereas a puzzle has no known recipient other than the potential eavesdroppers. A good cipher has to be readable by the intended recipient, and not by eavesdroppers, whereas a good puzzle cannot be impossible to crack. In that sense, DRM is a sort of anti-puzzle, as the intended recipients are treated as th…

> whereas a good puzzle cannot be impossible to crack. This is a very important distinction. It would be no fun if the cipher on a given cryptographer's tombstone were created with a one-time pad.

If the one-time pad were public somewhere, how hard would it be to find it? Say, if it were indexed by Google?

Re: Famous cryptographers’ tombstone cryptogram decrypted

#34

Post by netrc »

durkie wrote: post #6

also, a book just came out about Elizebeth Friedman and how a lot of her contributions to cryptology and the birth of sigint in general have been erased from histroy: https://www.amazon.com/Woman-Who-Smashed-Codes-Outwitted-ebo... it's supposed to be very good, but I just started it last night so don't have much of an opinion yet.

It is utterly fantastic, a gripping, fascinating, heart-breaking love story.

According to the author, it's in plans to become a mini-series.

Re: Famous cryptographers’ tombstone cryptogram decrypted

#35

Post by tptacek »

dlubarov wrote: post #31
ChrisSD wrote: post #18

Earlier quoted context omitted.

Interestingly a one time pad may be crackable. Its theoretical uncrackability is only true if a truly random number generator is used. Most cryptography is fine with urandom but a one time pad requires using something like radioactive decay to generate your pad. This is one reason (among many) why it's impractical for most crypto purposes.

Assuming a flawless CSRNG, 128 bits of entropy is more than enough to withstand current attack power. It's hard to predict the future -- quantum computers employing Grover's algorithm could conceivably have 2x or more attack power per unit energy -- but 256 bits should be adequate for a long time. It's fine to use low-grade sources of entropy like timestamps as long as we have enough of it. I might only generate a fe…

Right, but his point is that you're not really talking about an OTP anymore, but rather a stream cipher that's as strong as the RNG. It will situationally be quite secure, but not the theoretical unbreakability of an OTP.

OTPs are silly.

Re: Famous cryptographers’ tombstone cryptogram decrypted

#36

Post by tptacek »

pvg wrote: post #29
tptacek wrote: post #2

My nit here would be that these things aren't "ciphers" so much as they are "puzzles".

'Baconian cipher' is a particular kind of steganography, invented by Francis Bacon - he wrote about it and called it a 'cipher' in 1605. This is really more of an SNL Coffee Talk topic than a nit - 'Bacon ciphers are neither ciphers nor made of bacon, talk amongst yourselves'.

You're the worst.

There is an old Wikipedia grudge behind my nit, unfortunately.

Re: Famous cryptographers’ tombstone cryptogram decrypted

#37

Post by ggg9990 »

excalibur wrote: post #11

At first glance, having no information on this other than a title and an image, I assumed there was some data encoded in the odd pattern on the flags at the top of the tombstone. I then read through the article waiting to learn what was there, and of course it was never mentioned. A google search turned up a higher-resolution photo of the tombstone: http://elonka.com/friedman/Tombstone.JPG The lines on the flags appe…

You don’t have a lot of artistic license for headstones in Arlington National Cemetery.

Re: Famous cryptographers’ tombstone cryptogram decrypted

#38

Post by bg0 »

excalibur wrote: post #11

At first glance, having no information on this other than a title and an image, I assumed there was some data encoded in the odd pattern on the flags at the top of the tombstone. I then read through the article waiting to learn what was there, and of course it was never mentioned. A google search turned up a higher-resolution photo of the tombstone: http://elonka.com/friedman/Tombstone.JPG The lines on the flags appe…

I'm confused, they definitely mentioned the what was decrypted. It was the "Knowledge is Power" using different types of fonts decode his initials.

Thank you for the high res photo, it was cool to actually be able to see the close up lettering.

Re: Famous cryptographers’ tombstone cryptogram decrypted

#39

Post by todd8 »

This discussion of ciphers vs puzzles has reminded me of one of my favorite books growing up. It was Helen Fouché Gaines Elementary Cryptanalysis. I found it in the library in 1962 and treasured the copy my Aunt purchased for me.

This book predates the age of computers so every chapter introduces the common ciphers, including, military and diplomatic ones, in use at the time (I believe the first edition was written in 1943) along with the methods used to attack them.

Over time I worked my way through the exercises that appear at the end of each chapter. Computers make light work of these challenging puzzles now, but it’s still fun to write programs to break these old cipher systems.

Around 1987, I approached a very prominent professor in my CS program about being my Ph.D. dissertation advisor for a research project on Cryptography. He said that I should work in another area because cryptography had all been figured out and it didn’t look like there was anything interesting left in that field!

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