Updates to 2020/ferguson2

Added testing procedure (markdown, html: testing-procedure.{md,html}).
Updated the recode.{md,html} and README.md for this as well.

Updated the hidden message file (enigma.html) for a bit more fun.

Updated manifest, rebuilt index.html and .entry.json.

2020/ferguson2/testing-procedure.md

@@ -0,0 +1,126 @@
+# Testing procedure
+
+Because of the significant amount of possible combinations of settings and the
+fact that based on each setting if the text does not have the same sequence -
+even one letter off - then you cannot get the same output - I had to come up
+with a way to test the entry. Here's the problem with just the default settings:
+the same number of characters, the same starting, but the moment a letter
+differs the rest of the message will change even if the rest of the message is
+the same:
+
+``` <!---sh-->
+    $ echo A man and his dog walked in the park...|./prog
+    G spy ige lqk eav ptccpu di clm erkh...
+
+    $ echo A dog and his man walked in the park...|./prog
+    G luq ige lqk jou ptccpu di clm erkh...
+
+    $ echo A man and his dog and its dog walked in the park...|./prog
+    G spy ige lqk eav mbt bwz iwb jsojus pe hnt imny...
+```
+
+As can be seen as soon as a letter is different in the sequence it changes the
+result! So what could be done? First of all I had to make sure that the
+invocations I gave could be properly duplicated. To do this I had key files that
+I could use via `recode` and also I did input some manually. This includes the
+cake recipe key file that originally was in this entry but is now only in
+[2020/ferguson1](../ferguson1/index.html). Now, though, I have a simple
+html file with a fun message for you to decipher, if you wish to find the right
+key, to explore the entry. The script which I will include below can be modified
+to try and find the right key.
+
+## General script format
+
+``` <!---sh-->
+    STR="$(echo ABC | ./prog|tail -n1)"
+
+    if [ "${STR}" != "GYM" ]; then
+    echo "Failed 'ABC' test"
+    exit 1
+    fi
+    STR="$(echo "${STR}" | ./prog|tail -n1)"
+    if [ "${STR}" != "ABC" ]; then
+    echo "Failed 'GYM' test"
+    exit 1
+    fi
+
+    # a simpler way to check that it works:
+    ./recode -Renigma.dat -fenigma.deciphered.html | ./prog - 2>/dev/null > enigma.html
+    ./recode -Renigma.dat -fenigma.html | ./prog - 2>/dev/null | diff -s - enigma.deciphered.html
+
+    ./recode -Robfuscation.key -fobfuscation.txt | ./prog - 2>/dev/null >  out
+    diff out obfuscation.md || echo "Obfuscation test 0.5 failed"
+
+    ./recode -Robfuscation.key -fout | ./prog - 2>/dev/null > out2
+    diff out2 obfuscation.txt || echo "Obfuscation test 1.0 failed"
+
+    ./prog < prog.c > out
+    ./prog < out > out2
+    diff out2 prog.c || echo "Self obfuscation test 1.0 failed"
+
+    mkdir -p tests || exit 1
+    cd tests || exit 1
+
+    let n=0
+    while [ "${n}" -lt 100 ]; do
+
+    for f in ../input.txt ../prog.c ../README.md ../recode.md ../recode.1 ../enigma.1; do
+    	../recode -r -oconfig -f"${f}" | ../prog - 2>/dev/null > out
+    	../recode -Rconfig -fout | ../prog - 2>/dev/null > out2
+    	diff out2 "${f}" || echo "Failed randomised test for file: ${f}"
+    done
+    let n=n+1
+    done
+    rm -f out out2
+    cd ..
+    rm -f out out2
+```
+
+Please don't expect the above script to work without a bit of modification as
+it's not been tested recently and I did make some adjustments when putting this
+document in the website. Still that should give you the idea.
+
+### Historical note:
+
+At the time of development the server was CentOS but as Red Hat decided to axe
+it it is now Rocky Linux. The above script was only tested in macOS but it
+should work fine in linux too. Also, the enigma.html part was added in June 2024
+which expects output so below when I say if I got any output there was a problem
+this is no longer true.
+
+
+## Back to the testing:
+
+Anyway, If I got any output I knew there was a problem. I did not get any output and since
+this tested the default settings, two customised settings as well as 100
+randomised runs for each of the files listed in the script I believed this
+works well. Tests run under Fedora, CentOS and macOS with the same results.
+
+I believe this entry can be used with EBCDIC as it appears that the characters
+used are in contiguous sequence but I do not know for certain. Neither do I know
+about big endian: I don't believe it matters but I have no way to test this
+either.
+
+If there are any discrepancies in the recode.html or any other thing I
+pasted it's probably because of the way I changed the display (or else the
+random option in `recode`!).
+
+If there are any inconsistencies in input/output one also has to be certain that
+input was put in correctly (as I discussed earlier). The results of the script
+are the same under Fedora, CentOS and macOS but I have put the main testing
+platform as macOS because these days I mostly use my laptop (I tend to ssh into
+the other two boxes more and as for the CentOS it's only console anyway. Since
+it's just text I/O it an terminal emulator shouldn't matter either.).
+
+## Command that might be used to decipher the `enigma.html` file:
+
+The following command can be used to decipher the file except that you must
+provide the key file (or the key as a string) with the correct key (see
+[recode.html](recode.html) for a list of keys to try) in order to get correct
+output:
+
+``` <!---sh-->
+	./recode -Renigma.dat -fenigma.html | ./prog - 2>/dev/null > enigma.deciphered.html
+```
+
+Enjoy!