LaTeX Uglifier / obfuscator

Question

For JavaScript you have e.g. js uglifier, which obfuscates the javascript so that it is infeasible for humans to read the javascript code. Also, judging by @DavidCarlisle's xii.tex (see below), obfuscations is definitely possible in TeX.

\let~\catcode~`76~`A13~`F1~`j00~`P2jdefA71F~`7113jdefPALLF
PA''FwPA;;FPAZZFLaLPA//71F71iPAHHFLPAzzFenPASSFthP;A$$FevP
A@@FfPARR717273F737271P;ADDFRgniPAWW71FPATTFvePA**FstRsamP
AGGFRruoPAqq71.72.F717271PAYY7172F727171PA??Fi*LmPA&&71jfi
Fjfi71PAVVFjbigskipRPWGAUU71727374 75,76Fjpar71727375Djifx
:76jelse&U76jfiPLAKK7172F71l7271PAXX71FVLnOSeL71SLRyadR@oL
RrhC?yLRurtKFeLPFovPgaTLtReRomL;PABB71 72,73:Fjif.73.jelse
B73:jfiXF71PU71 72,73:PWs;AMM71F71diPAJJFRdriPAQQFRsreLPAI
I71Fo71dPA!!FRgiePBt'el@ lTLqdrYmu.Q.,Ke;vz vzLqpip.Q.,tz;
;Lql.IrsZ.eap,qn.i. i.eLlMaesLdRcna,;!;h htLqm.MRasZ.ilk,%
s$;z zLqs'.ansZ.Ymi,/sx ;LYegseZRyal,@i;@ TLRlogdLrDsW,@;G
LcYlaDLbJsW,SWXJW ree @rzchLhzsW,;WERcesInW qt.'oL.Rtrul;e
doTsW,Wk;Rri@stW aHAHHFndZPpqar.tridgeLinZpe.LtYer.W,:jbye

Is there any such software that would obfuscate a .tex-file, so that it is fairly hard to make sense of?

Possibly related and helpful files:

• Obfuscating TeX
• Can I see a plain TeX source file please?
• Can you explain how this code works?

Answer 1

Using the new tokcycle package (https://www.ctan.org/pkg/tokcycle), we can map tokens from the input into gibberish and write them to an external file. Then, in a second document, as long as the mapping is known from the 1st document, we can unmap the externally input gibberish back into LaTeX code:

MAPPING

This maps a block of input and writes it to the file xform.tex. Any characters not mapped (e.g., capital letters, numerals, etc.) are presented in the clear. Obviously, the mapping must be one-to-one, or the unmapping will be ambiguous.

EDITED to avoid using the \expanded option of \addcytoks, for those users who still have an older LaTeX installation.

After mapping, I also show a detokenized form of the gibberish:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{tokcycle}
\newwrite\xfile
\long\def\remaptext#1#2\endremaptext{\tokcycle
  {\addcytoks[4]{\tcremap{##1}}}
  {\processtoks{##1}}
  {\addcytoks{##1}}
  {\addcytoks{##1}}{#2}%
  \immediate\openout\xfile=#1
  \immediate\write\xfile{\the\cytoks}
}
\newcommand*\tcmapto[2]{\expandafter\def\csname tcmapto#1\endcsname{#2}%
  \tcmapfrom{#1}{#2}}
\newcommand*\tcmapfrom[2]{\expandafter\def\csname tcmapfrom#2\endcsname{#1}}
\newcommand*\tcremap[1]{\ifcsname tcmapto#1\endcsname
\csname tcmapto#1\expandafter\endcsname\else\expandafter#1\fi}
\tcmapto am \tcmapto bf \tcmapto cz \tcmapto de \tcmapto ey
\tcmapto fl \tcmapto gx \tcmapto hb \tcmapto ic \tcmapto jn
\tcmapto ki \tcmapto lr \tcmapto mh \tcmapto nt \tcmapto ok
\tcmapto ps \tcmapto qa \tcmapto ro \tcmapto sq \tcmapto tw
\tcmapto uj \tcmapto vp \tcmapto wd \tcmapto xg \tcmapto yu
\tcmapto zv \tcmapto ^& \tcmapto &^ \tcmapto +- \tcmapto -+
\begin{document}
\remaptext{xform.tex}%
\section{We can map sectioning, as well}

What can't we \textit{accomplish} if we try?
\begin{equation}
y = f(x) = \frac{1 + x^a}{47b}
\end{equation}
Let us be of good spirit and put our minds to it!
\endremaptext
Encoded input (detokenized):\\
\detokenize\expandafter{\the\cytoks}
\end{document}

An examination of the file xform.tex shows the same (line breaks added by me):

\section {Wy zmt hms qyzwcktctx, mq dyrr} \par Wbmw zmt'w dy 
\textit {mzzkhsrcqb} cl dy wou? \begin {yajmwckt} u = l(g) = 
\frac {1 - g&m}{47f} \end {yajmwckt} Lyw jq fy kl xkke qscocw 
mte sjw kjo hcteq wk cw! 

UNMAPPING

Now, we run the unmap of the gibberish (contained in the external file xform.tex), using the mappings from the original encode:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{tokcycle,etoolbox}
\tokcycleenvironment\unmaptext
  {\addcytoks[4]{\tcunmap{##1}}}
  {\processtoks{##1}}
  {\addcytoks{##1}}
  {\addcytoks{##1}}
\newcommand*\tcmapto[2]{\expandafter\def\csname tcmapto#1\endcsname{#2}%
  \tcmapfrom{#1}{#2}}
\newcommand*\tcmapfrom[2]{\expandafter\def\csname tcmapfrom#2\endcsname{#1}}
\newcommand*\tcunmap[1]{\ifcsname tcmapfrom#1\endcsname
\csname tcmapfrom#1\expandafter\endcsname\else\expandafter#1\fi}
\tcmapto am \tcmapto bf \tcmapto cz \tcmapto de \tcmapto ey
\tcmapto fl \tcmapto gx \tcmapto hb \tcmapto ic \tcmapto jn
\tcmapto ki \tcmapto lr \tcmapto mh \tcmapto nt \tcmapto ok
\tcmapto ps \tcmapto qa \tcmapto ro \tcmapto sq \tcmapto tw
\tcmapto uj \tcmapto vp \tcmapto wd \tcmapto xg \tcmapto yu
\tcmapto zv \tcmapto ^& \tcmapto &^ \tcmapto +- \tcmapto -+

\newread\infile
\makeatletter
\newcommand\unmapfile[1]{%
\def\fcont{}
\openin\infile=#1
{\endlinechar=-1
 \everyeof{}%
 \loop\unless\ifeof\infile
  \read\infile to \temp
  \ifx\temp\empty\else
\expandafter\g@addto@macro\expandafter\fcont\expandafter{\temp}%
  \fi
 \repeat
}%
\closein\infile
\expandafter\unmaptext\fcont\endunmaptext
}
\makeatother
\begin{document}
\unmapfile{xform.tex}
\end{document}

which provides the desired output:

So, if you have possession of the original mapping function and the file containing the mapped text, you can reconstitute the original!