Comments on: 70-year old wartime cipher uncracked http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html Brain candy for Happy Mutants Tue, 21 May 2013 15:00:00 +0000 hourly 1 http://wordpress.org/?v=3.4.1 By: Frank Diekman http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590986 Frank Diekman Sun, 25 Nov 2012 04:36:00 +0000 http://boingboing.net/?p=195825#comment-1590986 Dammit! We'll never beat the Hun at this rate! Dammit! We’ll never beat the Hun at this rate!

]]> By: mkanoap http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590778 mkanoap Sat, 24 Nov 2012 17:27:00 +0000 http://boingboing.net/?p=195825#comment-1590778  The problem is that with a one time pad, effectively EACH letter has it's own cypher.  So when you make guesses and match against valid words, every single possibility will eventually match. Here is an example.  Say my ciphertext is "aaaa".  One possible guess for that is "bake" (+1,+0,+10,+4).   Horray, a match!  But then you keep trying different substitutions for each letter and find that it also matches "kale" (+10,+0,+11,+4) and "make", and "four" and "fork".  Eventually, you find that there is a match for every single four letter word in the dictionary.  The problem is that with a one time pad, effectively EACH letter has it’s own cypher.  So when you make guesses and match against valid words, every single possibility will eventually match.
Here is an example.  Say my ciphertext is “aaaa”.  One possible guess for that is “bake” (+1,+0,+10,+4).   Horray, a match!  But then you keep trying different substitutions for each letter and find that it also matches “kale” (+10,+0,+11,+4) and “make”, and “four” and “fork”.  Eventually, you find that there is a match for every single four letter word in the dictionary.

]]> By: mkanoap http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590770 mkanoap Sat, 24 Nov 2012 17:17:00 +0000 http://boingboing.net/?p=195825#comment-1590770  What you are describing are pseudo random number generators/functions and are the basis for all modern cryptography.  But your output has to be indistinguishable from actual random numbers which can be tricky.  As DrDave points out below, your example would be susceptible to a brute force attack against the seed. Even the tiniest amount of predictable pattern can lead to a code being compromised and information being leaked. When you see key length discussed with things like SSL, it is the length of the key (in bits) that is used with pseudo random functions to generate the pads big enough to encrypt large amounts of data, so you are on the right track.  It's just that you have to take it much further. For example, key lengths for SSL certificates are now considered insecure if they are not at least 1024 bits.  What you are describing are pseudo random number generators/functions and are the basis for all modern cryptography.  But your output has to be indistinguishable from actual random numbers which can be tricky.  As DrDave points out below, your example would be susceptible to a brute force attack against the seed.
Even the tiniest amount of predictable pattern can lead to a code being compromised and information being leaked.
When you see key length discussed with things like SSL, it is the length of the key (in bits) that is used with pseudo random functions to generate the pads big enough to encrypt large amounts of data, so you are on the right track.  It’s just that you have to take it much further.
For example, key lengths for SSL certificates are now considered insecure if they are not at least 1024 bits.

]]> By: DrDave http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590705 DrDave Sat, 24 Nov 2012 12:20:00 +0000 http://boingboing.net/?p=195825#comment-1590705 You'll have only 2^24 possible sequences. I can grind through them all.  You’ll have only 2^24 possible sequences. I can grind through them all. 

]]> By: L_Mariachi http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590690 L_Mariachi Sat, 24 Nov 2012 10:49:00 +0000 http://boingboing.net/?p=195825#comment-1590690 Right, I know how they work, but the key doesn’t have to be there in toto, is what I’m getting at. Any operation that provides a long enough sequence of numbers to cover offsetting the message content would do. Take bytes 2, 12, and 22, raise each one to the power of the next one and you’d have a pad big enough to encode the King James Bible. (Multiple encodings would probably be beyond the capabilities of the era, but with these computers we got nowadays you could probably come up with an alternate false encoding to give up in case of torture that would resolve to a plausible-sounding message.) Right, I know how they work, but the key doesn’t have to be there in toto, is what I’m getting at. Any operation that provides a long enough sequence of numbers to cover offsetting the message content would do. Take bytes 2, 12, and 22, raise each one to the power of the next one and you’d have a pad big enough to encode the King James Bible. (Multiple encodings would probably be beyond the capabilities of the era, but with these computers we got nowadays you could probably come up with an alternate false encoding to give up in case of torture that would resolve to a plausible-sounding message.)

]]> By: DrDave http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590671 DrDave Sat, 24 Nov 2012 08:51:00 +0000 http://boingboing.net/?p=195825#comment-1590671 For a one-time pad, the "key" is as long as the message itself: it's a sequence of offsets applied to the sequence of characters in the message. The strength of a one-time pad is that there is no correlation between the coding for different characters. Lots of interesting info on codes used for SOE agents in Europe in Leo Marks's book "Between Silk and Cyanide": poem ciphers, security checks that an agent omitted if captured and forced to communicate, false traffic, deciphering "indecipherable" messages, codes in one system that were made to look like they are in another system, one-time pads with letters instead of numbers. Most of the one-time "pads" used by the SOE in the field were actually rolls of silk, where the used part of the pad could be cut off and destroyed. Silk was preferred to paper, because silk doesn't crinkle like paper does when you're being patted down. For a one-time pad, the “key” is as long as the message itself: it’s a sequence of offsets applied to the sequence of characters in the message. The strength of a one-time pad is that there is no correlation between the coding for different characters.

Lots of interesting info on codes used for SOE agents in Europe in Leo Marks’s book “Between Silk and Cyanide”: poem ciphers, security checks that an agent omitted if captured and forced to communicate, false traffic, deciphering “indecipherable” messages, codes in one system that were made to look like they are in another system, one-time pads with letters instead of numbers. Most of the one-time “pads” used by the SOE in the field were actually rolls of silk, where the used part of the pad could be cut off and destroyed. Silk was preferred to paper, because silk doesn’t crinkle like paper does when you’re being patted down.

]]> By: Sparg http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590611 Sparg Sat, 24 Nov 2012 04:25:00 +0000 http://boingboing.net/?p=195825#comment-1590611  Love the classic 5-letter groups.  Love the classic 5-letter groups.

]]> By: Dr. Chronobiologist http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590466 Dr. Chronobiologist Fri, 23 Nov 2012 23:16:00 +0000 http://boingboing.net/?p=195825#comment-1590466 Regarding "few-time pads": As long as the attacker isn't aware which messages were encoded with the same pad. https://en.wikipedia.org/wiki/Venona_project#Decryption Regarding “few-time pads”: As long as the attacker isn’t aware which messages were encoded with the same pad.
https://en.wikipedia.org/wiki/Venona_project#Decryption

]]> By: L_Mariachi http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590465 L_Mariachi Fri, 23 Nov 2012 23:14:00 +0000 http://boingboing.net/?p=195825#comment-1590465 Regarding one-time pads: Why not seed the pad into the message itself?  I’m thinking that an arbitrary sequence of “bytes,” known to the recipient (e.g. “second letter of every other line” or somesuch) could be a date code, from which one could derive the key (say, the number of seconds since the stroke of midnight on New Year’s Eve A.D. 1, with each digit being an offset.)  That way the recipient wouldn’t have to carry around a pad which could be compromised, he’d only have to know which bytes were the date code, and what baseline date to count seconds from. If that information is cracked or extracted, headquarters can simply change one or both of those for future messages, communicating the change to recipients in a compact and obscure manner. Regarding one-time pads: Why not seed the pad into the message itself?  I’m thinking that an arbitrary sequence of “bytes,” known to the recipient (e.g. “second letter of every other line” or somesuch) could be a date code, from which one could derive the key (say, the number of seconds since the stroke of midnight on New Year’s Eve A.D. 1, with each digit being an offset.)  That way the recipient wouldn’t have to carry around a pad which could be compromised, he’d only have to know which bytes were the date code, and what baseline date to count seconds from. If that information is cracked or extracted, headquarters can simply change one or both of those for future messages, communicating the change to recipients in a compact and obscure manner.

]]> By: Dr. Chronobiologist http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590401 Dr. Chronobiologist Fri, 23 Nov 2012 21:55:00 +0000 http://boingboing.net/?p=195825#comment-1590401 So here's a basic One Time Pad scheme. Pad=key Creating a key: using a 27 sided dice, roll 10 times and write down each result. Each roll must be unrelated to the previous roll and the dice must be perfectly fair. Encrypting the message: Use a message of length 10 letters and spaces or less. a-z=[1-26], spaces=27 (I'll use underscores to denote spaces) message = "nazis_suck" / "14, 1, 26, 9, 19, 27, 19, 21, 3, 11" key = "abddh_tacl" / "1, 2, 4, 4, 8, 27, 20, 1, 3, 12" add the key to the message: cipher text = "occm__lvfw" / "15, 3, 3, 13, 27, 27, 12, 22, 6, 23" The key must be shared with the receiver ahead of time. The receiver will know to subtract the key from the cipher text to decrypt it. As the name implies, the key must only be used once or else it's attackable as a two-time pad/many-time pad. So here’s a basic One Time Pad scheme. Pad=key

Creating a key: using a 27 sided dice, roll 10 times and write down each result. Each roll must be unrelated to the previous roll and the dice must be perfectly fair.

Encrypting the message: Use a message of length 10 letters and spaces or less.
a-z=[1-26], spaces=27 (I’ll use underscores to denote spaces)

message = “nazis_suck” / “14, 1, 26, 9, 19, 27, 19, 21, 3, 11″
key = “abddh_tacl” / “1, 2, 4, 4, 8, 27, 20, 1, 3, 12″

add the key to the message:
cipher text = “occm__lvfw” / “15, 3, 3, 13, 27, 27, 12, 22, 6, 23″

The key must be shared with the receiver ahead of time. The receiver will know to subtract the key from the cipher text to decrypt it.

As the name implies, the key must only be used once or else it’s attackable as a two-time pad/many-time pad.

]]> By: Paul Turnbull http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590393 Paul Turnbull Fri, 23 Nov 2012 21:48:00 +0000 http://boingboing.net/?p=195825#comment-1590393 No. With a one-time pad each letter or word position could be using a different code. For example my pad could be 254 where each number is the offset to use. So the word 'the' would become 'vmh'. If the pad was 837 then 'the' would be 'bkl'. It's called a one-time pad because an agent would only use it once. Pads are generated randomly so there's no pattern to discern, each letter is random. Letter offsets is just one way to do one-time pads. There are more complex versions but they all have in common is that without the pad they are virtually unbreakable. The downside is that rule applies if you lose the pad as well. No. With a one-time pad each letter or word position could be using a different code.

For example my pad could be 254 where each number is the offset to use. So the word ‘the’ would become ‘vmh’. If the pad was 837 then ‘the’ would be ‘bkl’. It’s called a one-time pad because an agent would only use it once. Pads are generated randomly so there’s no pattern to discern, each letter is random.

Letter offsets is just one way to do one-time pads. There are more complex versions but they all have in common is that without the pad they are virtually unbreakable. The downside is that rule applies if you lose the pad as well.

]]> By: Michael Smith http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590373 Michael Smith Fri, 23 Nov 2012 21:19:00 +0000 http://boingboing.net/?p=195825#comment-1590373 You mean there might be a code inside the code? Fair enough but how far does it go? Maybe you could just calculate the entropy on different possible solutions then attack the solutions with low entropy again. You mean there might be a code inside the code? Fair enough but how far does it go? Maybe you could just calculate the entropy on different possible solutions then attack the solutions with low entropy again.

]]> By: Dr. Chronobiologist http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590366 Dr. Chronobiologist Fri, 23 Nov 2012 21:08:00 +0000 http://boingboing.net/?p=195825#comment-1590366 if each letter is equally likely then the message could be any that you like. With OTP a valid cipher text could be 11111111 and there'd be no way to decipher without having the key. (edit: replaced "message" with "cipher text") if each letter is equally likely then the message could be any that you like. With OTP a valid cipher text could be 11111111 and there’d be no way to decipher without having the key. (edit: replaced “message” with “cipher text”)

]]> By: Michael Smith http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590358 Michael Smith Fri, 23 Nov 2012 21:03:00 +0000 http://boingboing.net/?p=195825#comment-1590358 Surely it could brute forced it and matched against valid words. Surely it could brute forced it and matched against valid words.

]]> By: Warren_Terra http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590343 Warren_Terra Fri, 23 Nov 2012 20:55:00 +0000 http://boingboing.net/?p=195825#comment-1590343 I think we need to immediately investigate the chimney for possible German sympathies. I think we need to immediately investigate the chimney for possible German sympathies.

]]> By: John Vance http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590302 John Vance Fri, 23 Nov 2012 19:44:00 +0000 http://boingboing.net/?p=195825#comment-1590302 I only know this because of Cryptonomicon. I only know this because of Cryptonomicon.

]]> By: theophrastvs http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590268 theophrastvs Fri, 23 Nov 2012 18:32:00 +0000 http://boingboing.net/?p=195825#comment-1590268 a lot of those were published weren't specifically meant for secrecy purposes, but rather to reduce cost per words on telegrams (SXZDQ == "sell all stock holdings of"...)  i always assumed it was mostly for that purely economic notion that Claude Shannon founded information theory (largely unrelated to him being a great expert on cryptology and juggling) a lot of those were published weren’t specifically meant for secrecy purposes, but rather to reduce cost per words on telegrams (SXZDQ == “sell all stock holdings of”…)  i always assumed it was mostly for that purely economic notion that Claude Shannon founded information theory (largely unrelated to him being a great expert on cryptology and juggling)

]]> By: oasisob1 http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590258 oasisob1 Fri, 23 Nov 2012 18:12:00 +0000 http://boingboing.net/?p=195825#comment-1590258 When I was in England I found a codebook in a secondhand bookstore in N. Yorkshire. Five-letter codes were assigned to words. It was a huge book, and not terribly overpriced, but it was just a bit out of my reach at that time. If only... When I was in England I found a codebook in a secondhand bookstore in N. Yorkshire. Five-letter codes were assigned to words. It was a huge book, and not terribly overpriced, but it was just a bit out of my reach at that time. If only…

]]> By: theophrastvs http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590249 theophrastvs Fri, 23 Nov 2012 17:56:00 +0000 http://boingboing.net/?p=195825#comment-1590249 ah <b>the Uriah message</b>.  (cuz y'see king david wanted to do bathsheba without her husband, uriah the hittite, hanging about. so he sent uriah to the war-front with a message to hand to ol' general joab presumably written in some (semitic) language the hittite... well it's an old story) ah the Uriah message.  (cuz y’see king david wanted to do bathsheba without her husband, uriah the hittite, hanging about. so he sent uriah to the war-front with a message to hand to ol’ general joab presumably written in some (semitic) language the hittite… well it’s an old story)

]]> By: Ryan Lenethen http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590210 Ryan Lenethen Fri, 23 Nov 2012 16:53:00 +0000 http://boingboing.net/?p=195825#comment-1590210 "This pigeon is a traitor, kill him immediately!" “This pigeon is a traitor, kill him immediately!”

]]> By: Paul Turnbull http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590194 Paul Turnbull Fri, 23 Nov 2012 16:26:00 +0000 http://boingboing.net/?p=195825#comment-1590194 The strength of using what are in essence, few-time pads. If you don't have the pad, there's little that can be used to decrypt it. The strength of using what are in essence, few-time pads. If you don’t have the pad, there’s little that can be used to decrypt it.

]]> By: Jorpho http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590193 Jorpho Fri, 23 Nov 2012 16:25:00 +0000 http://boingboing.net/?p=195825#comment-1590193 I think the key phrase missing from the story is "one-time pad", which is indeed effectively impossible to crack, "if used correctly". http://en.wikipedia.org/wiki/One-time_pad I think the key phrase missing from the story is “one-time pad”, which is indeed effectively impossible to crack, “if used correctly”.
http://en.wikipedia.org/wiki/One-time_pad

]]> By: welcomeabored http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590188 welcomeabored Fri, 23 Nov 2012 16:16:00 +0000 http://boingboing.net/?p=195825#comment-1590188 Were there no false codes -- complete gibberish that intentionally or unintentionally sucked up hundreds of man hours trying to decipher the code?  I'm assuming every known code has been tried.   'When you eliminate the impossible, whatever remains, however improbable, must be the truth.' - Holmes Were there no false codes — complete gibberish that intentionally or unintentionally sucked up hundreds of man hours trying to decipher the code?  I’m assuming every known code has been tried.  

‘When you eliminate the impossible, whatever remains, however improbable, must be the truth.’ – Holmes

]]> By: dragonfrog http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590177 dragonfrog Fri, 23 Nov 2012 15:55:00 +0000 http://boingboing.net/?p=195825#comment-1590177 Help, I'm stuck in a fireplace. Help, I’m stuck in a fireplace.

]]> By: Rob Beschizza http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590165 Rob Beschizza Fri, 23 Nov 2012 15:43:00 +0000 http://boingboing.net/?p=195825#comment-1590165 Yes. Yes.

]]> By: TheMudshark http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590156 TheMudshark Fri, 23 Nov 2012 15:28:00 +0000 http://boingboing.net/?p=195825#comment-1590156 Have you been googling about pigeons, Rob? Have you been googling about pigeons, Rob?

]]> By: Funk Daddy http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590152 Funk Daddy Fri, 23 Nov 2012 15:21:00 +0000 http://boingboing.net/?p=195825#comment-1590152 Milk, bread, butter, biscuits, shaving cream, marmalade (orange),  http://news.bbcimg.co.uk/media/images/64326000/jpg/_64326639_masons_pigeon_code_07.jpg Milk, bread, butter, biscuits, shaving cream, marmalade (orange), 

http://news.bbcimg.co.uk/media/images/64326000/jpg/_64326639_masons_pigeon_code_07.jpg

]]> By: Shaun Usher http://boingboing.net/2012/11/23/70-year-old-wartime-cipher-unc.html#comment-1590148 Shaun Usher Fri, 23 Nov 2012 15:14:00 +0000 http://boingboing.net/?p=195825#comment-1590148 There's an image of the code in question over at the BBC website:  http://www.bbc.co.uk/news/uk-20456782 There’s an image of the code in question over at the BBC website: 

http://www.bbc.co.uk/news/uk-20456782

]]>