quote

acer — Tue, 04 Nov 2008 01:44:04 Z

The string was not transcribed correctly, in the OP's post. It should probably be something more like,

S:="#fM2{Sz{\
&fg{Z22 &{,_32zU{&Y2{r~_%_92{%u$z?TT+{_& 2%{92{f?{J{Y_%{%2yf`Y2z2%{3\
Y2{9_F@&yzf`3{ZYfyY{Y_%{3Y2{3z_F&9@3_3fSF{`zSy2%@z2o{J{3S,%{Y2z{3Y_3{J{\
Y_%o{n>f3YS@3{3Y2{ 2tU{&fzU{2gy@&2{92{f?{J{l2,f2M2{3Y2{3YfFL{f9`S&&fl,2o{n\
jS{tS@{Zf&Y{92{3S{F_92{tS@z{ 2tU{9_%_92){nJ?{tS@{`,2_&2on{J{3Y2F{3S,%{Y2z{\
3Y2{ 2tbZSz%U{ZYfyY{l2,SFL&{3S{FS{,_FL@_L2U{_F%{J{&_Z{Y2z{&@z`zf&2o{kY2{\
3S,%{92{3Y_3{f3{Z_&{f9`S&&fl,2U{?Sz{&Y2{l2,f2M2%{Y2z&2,?{3Y2{SF,t{`S&&2\
&&Sz{S?{3Y_3{ZSz%{ZYfyY{&Y2{ 2`3{fF{Y2z{929Szt{_F%{ZYfyY{&Y2{Y_%{F2M2z{Z\
zf332F{%SZFo{J{yS@,%{Y_M2{3S,%{Y2z{3Y2{3z@3Y{bb{3Y_3{3Y2{&_92{y_,y@,_3f\
SF{ZYfyY{Y_%{&2zM2%{92{?Sz{%2yf`Y2zfFL{3Y2{9_F@&yzf`3{Y_%{2F_l,2%{92{3S\
{,2_zF{3Y2{ZSz%{bb{l@3{SF{_{y_`zfy2{f3{&3z@y {92{3S{32,,{Y2z{3Y_3{_{L2Ff\
2{Y_%{z2M2_,2%{f3{3S{92o{xYf&{?_,&2{%f&y,S&@z2{?2332z2%{~_%_92{%u$z?TT{\
3S{92o{xY_3{%_t{J{l2y_92{3Y2{9_&32z{S?{Y2z{&S@,U{_F%{J{_l@&2%{9t{`SZ2zo\
{wM2zt{3f92{J{3YfF {S?{f3U{J{_9{%f&3z2&&2%{_F%{_&Y_92%U{_F%{J{%S{`2F_Fy2\
{FSZ{fF{3Y2{Sl,fL_3fSF{@F%2z{ZYfyY{J{`,_y2{9t&2,?{S?{32,,fFL{3Y2{3z@3Y{\
fF{Zzf3fFL{9t{929Sfz&o":

It looks like a fragment by Giacomo Casanova (which would be fitting, for a cipher). I don't see how it's helpful to consider it as an affine cipher, without knowing the alphabet in use. The character set of the enciphered message is not the usual alphabet (as claimed by the OP).

Five or six weeks later, she [Madame D'Urfe'] asked me if I had
deciphered the manuscript which had the transmutation procedure.
I told her that I had.

"Without the key, sir, excuse me if I believe the thing
impossible."

"Do you wish me to name your key, madame?"

"If you please."

I then told her the word, which belongs to no language, and I
saw her surprise. She told me that it was impossible, for she
believed herself the only possessor of that word which she kept
in her memory and which she had never written down.

I could have told her the truth -- that the same calculation
which had served me for deciphering the manuscript had enabled
me to learn the word -- but on a caprice it struck me to tell
her that a genie had revealed it to me. This false disclosure
fettered Madame d'Urfe' to me. That day I became the master of
her soul, and I abused my power. Every time I think of it, I am 
distressed and ashamed, and I do penance now in the obligation
under which I place myself of telling the truth in writing my
memoirs.

acer

public key crypt.

me85 — Fri, 07 Nov 2008 20:27:02 Z

Is the plaintext refering to Public Key Crypography?

polyalphabetic

acer — Fri, 07 Nov 2008 20:52:41 Z

I believe that it refers to Madam d'Urfe's use of a polyalphabetic (or Vignere) cipher, used to encrypt her document which explained the secret of transmuting base metals into gold.

Supposedly, the key was NABUCODONOSOR. That is Italian for Nebuchadnezzar, a name that I did not expect to write on mapleprimes.

acer

MaplePrimes - answers and comments on Question, _%{F2M2z.....

quote

public key crypt.

polyalphabetic