gpg -o doc.gpg --symmetric doc
gpg -o doc -d doc.gpg # if you don't specify '-o ...' it will go to stdout

Makefile

.PHONY: test.pdf test.dvi fonts

test.pdf: test.dvi
	dvipdfmx $<
	mv $@ /tex_tmp/
	rm $< test.log
	evince /tex_tmp/$@

test.dvi: test.tex
	tex \\let\\pdf+ \\input $<

fonts:
	echo cmtt10 | tex \\input testfont \\table \\end
	dvipdfmx testfont.dvi
	mv testfont.pdf /tex_tmp/cmtt.pdf
	echo cmr10 | tex \\input testfont \\table \\end
	dvipdfmx testfont.dvi
	rm testfont.dvi testfont.log
	mv testfont.pdf /tex_tmp/cmr.pdf
	evince /tex_tmp/cmr.pdf /tex_tmp/cmtt.pdf

TeX example

Understand how this works:
\vbox{
\def\1{\vrule height 0pt depth 2pt}
\def\2{\vrule height 0pt depth 4pt}
\def\3{\vrule height 0pt depth 6pt}
\def\4{\vrule height 0pt depth 8pt}
\def\ruler#1#2#3{\leftline{$\vcenter{\hrule\hbox{\4#1}}\,\,\rm#2\,{#3}$}}
\def\\#1{\hbox to .125in{\hfil#1}}
\def\8{\\\1\\\2\\\1\\\3\\\1\\\2\\\1\\\4}
\ruler{\8\8\8\8}4{in}}
\end

Set theory axioms.
Construct models for set theory.
Don't work with sentences, work with models.
Read Paul Cohen - Set Theory and the Continuum Hypothesis.

For explanation of LANG vs. LC_ALL vs. LC_CTYPE see https://www.tug.org/TUGboat/tb19-3/tb60bzyl.pdf