Re: VMS List post from 1994

[reeds@xxxxxxxxxxxxxxxxxxxx (Jim Reeds)]

Brian Farnell dredged up an old post of mine, naming the
"progeressive" cipher and giving an imprecise 1600s date for
it:

reeds@xxxxxxxxxxxxxxxx wrote:
> 
> The other day I dropped in to the Bancroft library in Berkeley and looked
> at their Schott and Selenus, which date from roughly the same era as the
> Heidel book.  In one of them (I forget which, but I think it was Selenus)
> there is an explanation of a progressive key cipher, according to which
> this paragraph would be enciphered "Ujh synlz..."

In fact this cipher is described in Trithemius's "Clavis 
Polygraphiae" printed in 1518 with his "Polygraphiae Libri Sex":
(in the section headed "Explantio in quintum librum polygraphiae
nostrae brevis", fol. [B iv] = about p.531.)

> Verum ut ordinem uideas, ponamus exe[m]plu[m]. Hxpf gfbmcz
> fueib gmbt gxhsr ege rbd qopma uwu, wfxegk ak,
> tnr qxyx. Huius mystici sermonis sententia est. Hunc caueto
> uiru[m], quia malus est, fur, deceptor, me[n]dax & iniquus. 


approx. trans:
To show you the correct order, we give an example.  Hxpf ...
...  The sense of this mysterious writing is: "Hunc caueto ... "

Here Hunc gets enciphered as Hxpf because H+0=H, u+1=x (in the
Latin alphabet without v or w), n+2=p, c+3=f, and so on.


-- 
Jim Reeds, AT&T Labs - Research
Shannon Laboratory, Room C229, Building 103
180 Park Avenue, Florham Park, NJ 07932-0971, USA

reeds@xxxxxxxxxxxxxxxx, phone: +1 973 360 8414, fax: +1 973 360 8178