Ciphers of Elizabeth I

[Peter Fairbrother]

> Ben Laurie at ben@algroup.co.uk wrote:

> John Young wrote:
>> My question is whether these documents have been examined
>> by persons here and/or whether the Elizabethan era ciphers
>> described in them have been written about in contemporary
>> works.
> 
> My son (aged 11) had Elizabeth's cipher for homework (I believe there
> was only one). It was pretty simple minded - a symbolic substitution
> cipher.
> 
> It was cracked while she was using it, and used to incriminate her.
 
The Mary Queen of Scots cypher was cracked and used to incriminate Mary, not
Elizabeth. Mary got her head chopped off because of it. It's a simple
symbolic susbtitution cypher with a few tweaks (symbols to double a letter,
ignore-this symbols, ignore-last-letter symbols).

Elizabeth (in reality Walsingham's codemasters) used and broke many
different cyphers. There was a flourishing of crypto and double-dealing in
those days. IIRC only a few of hers were broken (by the French), generally
to little consequence.

Known broken cyphers were used for disinformation. Forged letters were given
credibility by being "broken" by the forgers. This accusation was made about
the Mary Queen of Scots letter, probably falsely in this case. The broken
Mary Queen of Scots cypher was also used to entrap. Mesages were altered by
knowing the code. The conspirators were lulled into trusting the broken
code. Etc, etc, vanity, vanity, nothin' new,


-- Peter