Question on "The Code Book - Simon Singh

[ERD50]

Several people mentioned this in the "What have you read recently" thread. It sounded like it was up my alley, and I did enjoy it.

http://www.amazon.com/Code-Book-Science-Secrecy-Cryptography/dp/0385495323

However, in the very first chapter, before they got into all the 'heavy' stuff - I just missed something. I re-read the chapter and still missed it. Can anyone explain?

Mary Queen of Scots was kept under guard, and Gilbert Gifford started smuggling letters from supporters in to her and her replies back out. Gifford was a double agent, and hoped to intercept incriminating letters between her and her supporters. One of the letters plotting her escape was encrypted by the sender (Babington). Gifford had a copy of the letter sent to be decrypted, and Mary's encrypted reply was also decrypted, providing evidence against her.

Here's what I don't get: How did Mary decrypt the message? It says Gifford read and copied every correspondence in and out. So, if the key was sent to Mary, Gifford would have it and he would not have had to go to the effort of 'breaking' the code. But if the key was not sent to Mary, she couldn't read the message either (or encode her replies). There is a gap here, or I missed it on a 3rd reading also.


This might seem trivial, but a significant portion of the book is dedicated to the problems of transferring and exposing the keys. So it seems important to cover this in the introductory story.

I had an easier time with their quantum computing, dual state, polarized photon examples!

BTW, this is the 1st edition, maybe this was re-written in the second?

-ERD50

 

[Gumby]

The 2d edition offers no clarification. I assumed that that the nomenclator (key) had been conveyed to her through a means other than Gifford. Otherwise, as you point out, she could not decrypt the message.

 

[donheff]

There is a full description of the plot in Wikipedia. It doesn't directly address how Mary got the key but I would guess she already had it and was using it when she was imprisoned. The article describes the plot as arising from plots motion for decades involving among others Mary and her "chief cipher clerk for all her French correspondence." Gifford was arrested and enrolled as a double agent far into the plotting.

 

[GregLee]

There was no key other than the cipher itself, but I have also failed to find how Mary, or her cipher clerk, first obtained the cipher:

 

[ERD50]

Thanks all for the input (and the original recc).

This just really had me going - the author seemed to be very complete, and if I read carefully and applied myself, I could eventually understand everything he described, without making assumptions (well, at least I felt it was understandable, even if I didn't always take the time to dig all the way through it).

I even forced myself (something that does not come naturally in ER!) to understand the quantum stuff. I guess 'understand' is too strong a word, but at least comprehend how the strategy/algorithms could work, even if I don't understand the quantum stuff behind how it works.

So it just seemed really odd to me that he would skip explaining how Mary got the key. If she had it far ahead of time, then how did Babington get access to it? Did the whole 'underground' have it?


Hmmm, maybe I'll write the author - I wonder if he knows!

-ERD50

 

[GregLee]

Negative info from a blog:

Scott said... Does anyone know how the encoding scheme was communicated to Mary if she was under lock and key at the time of the plot's formation?
February 14, 2008 10:53 PM
Hamlet D'Arcy said... I've tried to search for details about how they performed their key exchange but haven't found anything. Perhaps a book on the subject might contain details... or perhaps the answer is lost to history.
----------behind the times: Mary Queen of Scot's Guide to Information Security

Edit: The following seems to be saying that keys were passed in preceding ciphered correspondence:

Be this as it may, Phelippes comes before us as a past-
master in all branches of letter stealing, and a man with
a real genius for deciphering. Yet even here exaggerations
have been made. In point of fact, the deciphering of
Mary's correspondence was easy work in the present case,
because at its recommencement all the old ciphers had
been changed, and a new alphabet sent to each corre-
spondent. Phelippes took copies of all these keys as they
passed, and after that his work was relatively simple.
Full text of "Mary Queen of Scots and the Babington plot. Edited from the original documents in the Public Record Office, the Yelverton MSS., and elsewhere"

 

[ERD50]

Well, i just wrote the author, and included the link that GregLee posted (Thanks!) to show I'm not alone in wondering this.

Contact

He states he can't answer every email, so I'm not expecting a reply, but you never know.

-ERD50

 

[Gumby]

There is a full description of the plot in Wikipedia. It doesn't directly address how Mary got the key but I would guess she already had it and was using it when she was imprisoned. The article describes the plot as arising from plots motion for decades involving among others Mary and her "chief cipher clerk for all her French correspondence." Gifford was arrested and enrolled as a double agent far into the plotting.

To my mind, a pre-existing key is certainly a possibility. I was thinking about my best friend. He and I know the same series of numbers and certain very long, mostly nonsensical passages that could be used as a running key in a Vigenere cipher. We learned them together over 30 years ago, it is very unlikely either of us will ever forget them, and each potential number or passage can be called to mind with a word or phrase which is not itself part of the key.

 

[ERD50]

To mind mind, a pre-existing key is certainly a possibility. I was thinking about my best friend. He and I know the same series of numbers and certain very long, mostly nonsensical passages that could be used as a running key in a Vigenere cipher. We learned them together over 30 years ago, it is very unlikely either of us will ever forget them, and each potential number or passage can be called to mind with a word or phrase which is not itself part of the key.

That would be fairly easy between two people, but if it was widespread enough for Babington to know about it, I would think the English spies could have found out about it.

And all those symbols (see GregLee's post) would not be easy to remember. Not impossible, but very improbable, IMO.

Or should I say: wrg;lk qtqeroih-2 bkjguhuiqhgugwtr]whouh g1tr6rw3hwkjgbqepigg4wrthgnjqenrgqpgq egneoqrngngoqerg


-ERD50

 

[ERD50]

Update - a response!

I had kind of given up expecting a response on this, but I got one this AM.

Thanks for your kind words.

I think the assumption is that the key was one that was already being used
in Catholic circles prior to Mary's arrest, and that someone in her circle
was aware of the key.

Simon.

So I guess that's it - but like I said before, it seems to me it would be a difficult cipher to remember, a symbol for each letter (see GregLee's prior post with a picture of the cipher). And if it was widespread enough to be used this way, that spies would have got hold of it. But that is the info we have. It was nice of him to respond.

-ERD50

Well, i just wrote the author, and included the link that GregLee posted (Thanks!) to show I'm not alone in wondering this.

Contact

He states he can't answer every email, so I'm not expecting a reply, but you never know.

-ERD50

 

[GregLee]

And if it was widespread enough to be used this way, that spies would have got hold of it. But that is the info we have.

But the quote I gave in post #6 clearly implies that the key had been passed in preceding enciphered correspondence. The writer, John Hungerford Pollen (a Jesuit), further, says in his 1922 account that he found the deciphered messages which were delivered by Phelippes (and were used to convict Mary) to be accurate decipherments, implying that Pollen examined the documents himself, in detail.

 

[ERD50]

But the quote I gave in post #6 clearly implies that the key had been passed in preceding enciphered correspondence. The writer, John Hungerford Pollen (a Jesuit), further, says in his 1922 account that he found the deciphered messages which were delivered by Phelippes (and were used to convict Mary) to be accurate decipherments, implying that Pollen examined the documents himself, in detail.

I guess I missed the edit. Interesting, thanks.

I then took out "Enigma - The Battle for the Code" by Hugh Sebag-Montefiore, but I just couldn't get into it. Gave up about 60% of the way in and started going through the Appendix code examples for a bit, and gave up.

Maybe it's me, but it seemed that there were things I understood from Singh's book, but when I read them in this book, I couldn't follow it. Even knowing what I learned previously, the explanations just didn't seem to follow from A to B. It was like it presented a bunch of information, but that info was not logically linked.

I sometimes get the feeling that, since there is a finite amount of information available, that authors feel the need to throw it all in the book, just to 'prove' they did this research. But that doesn't always lead to a compelling story.

But I did skim the section on the U-505, since that has been on display in Chicago my whole life. I was kind of surprised that the Officer who captured the U-505 was being threatened with a court-marshal. Rather than being seen as a hero, it was considered a bad risk to capture the boat - if the Germans were to see it, they would probably assume the code books were obtained, the Germans would then change the coding scheme, and this would set the decoding operations back to the beginning.

-ERD50