Landon Curt Noll
7712db4a17
Given how problematic leading tabs in markdown files can be,
we have expanded all leading tabs in markdown files by:
```sh
find * -type f -name '*.md' -print |
while read -r file; do
rm -f "$file.tmp" ;
expand < "$file" > "$file.tmp" ;
mv -f -v "$file.tmp" "$file" ;
done
```
Given the previous changes to `bin/pandoc-wrapper.sh` and other recent
commits and recent pull requests, the were were **NO** changes to
any HTML files. This is a **good thing** as the expression goes.
No there are no leading tabs in any markdown files.
A check to catch any re-introduction of leading tabs
into any markdown file is on the way.
BTW: We do not have anything against leading tabs in files,
even though we have had to deal with their impact on forming
HTML from markdown files (as well as the calc source code).
It is just that this is one of those cases where tabs conflict
(sometimes caused by people wanting to change the classic
8-space tab model) with a desired outcome.
Perform `make www` to perform the above and test under macOS.
151 lines
4.6 KiB
Markdown
151 lines
4.6 KiB
Markdown
## To build:
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``` <!---sh-->
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make
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```
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## To use:
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To create a shared secret shared among `M` people with `N+1` needed to reconstruct:
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``` <!---sh-->
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./grothe -secret 1-/dev/urandom 2-/dev/urandom ... \
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N-/dev/urandom 1+shared1 2+shared2 ... M+sharedM
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```
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To reconstruct the original (an arbitrary combination of `N+1` or
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more shared files with their proper numbers):
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``` <!---sh-->
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./grothe I-sharedI J-sharedJ K-sharedK ... +reconstructed
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```
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## Try:
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``` <!---sh-->
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./try.sh
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```
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## Judges' remarks:
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Also known as 'Best abuse of the judging process'.
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The IOCCC 2012 submission page didn't enforce the 2048 meaningful character
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limit. This entry, as submitted, weighed in at 2222 chars but lucky for it, it
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was extremely easy to bring down below the limit. There were a number of
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strings that when concatenated allowed the program to slide under the limit.
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It was clear to the judges that the extra size was an entry beautification step.
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Had it not been, this entry would have been rejected in round 0.
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The judges also took some liberty obfuscating this entry a little more.
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How does this entry work? The only place multiplication is used is
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to perform the `atoi(3)` conversion.
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## Author's remarks:
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### Description
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This program implements a version of [Shamir's Secret
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Sharing](http://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing). Shamir's Secret
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Sharing allows you to encrypt a file into `N` parts where it will take `M` parts to
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recreate the original file. E.g. you can split the secret recipe for Crystal Pepsi
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into 3 parts and require two of them be available to extract the original recipe.
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Actually surprisingly useful for an IOCCC entry :-)
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### Usage
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To share a secret. For example:
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- File to share: [cookie_recipe.txt](cookie_recipe.txt).
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- Number of pieces: 2 + file to be shared
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- Total number of pieces created by program: 4
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- Pieces needed to reassemble recipe: 3 or greater
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### Example usage
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To split a secret into 4 pieces of which at least 3 will be needed to get it (in
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this case the cookie recipe) back:
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``` <!---sh-->
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./grothe \
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-cookie_recipe.txt\
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1-/dev/urandom 2-/dev/urandom\
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1+cookie_piece1.dat 2+cookie_piece2.dat 3+cookie_piece3.dat 4+cookie_piece4.dat
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```
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To put the recipe back together using the first, second and fourth pieces:
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``` <!---sh-->
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./grothe \
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1-cookie_piece1.dat 2-cookie_piece2.dat 4-cookie_piece4.dat
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+cookie_recipe_restore.txt
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```
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### Limitations
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The program is limited to 256 input and output files and will slow down
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dramatically when you get past 20-50 inputs and outputs.
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### Obfuscations
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* Nothing is done consistently throughout the program E.g `i+=1`, `i=i+1`, `i++`
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and `++i` are all used in the program. The mark of true code buggery: "A
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foolish consistency is the hobgoblin of little minds." - [Ralph Waldo
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Emerson](https://en.wikipedia.org/wiki/Ralph_Waldo_Emerson)
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* Uses the most powerful obfuscation of all "Math". "Any sufficiently advanced
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cryptography is indistinguishable from magic." - Apologies to [Arthur C.
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Clarke](https://en.wikipedia.org/wiki/Arthur_C._Clarke)
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* Shadows variables by using brackets in main program to create local copies of
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variables that are the same as global scope variables. `-Wshadow` should
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probably be a part of `-Wall` in gcc.
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* Uses `array_index[array_name]` instead of `array_name[array_index]` in several
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places. Still don't know why C continues to allow this (error strings are
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encoded with offsets that are also used to select them in the case statement.
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All strings are located in one function for easy localization).
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* Liberal use of octal numbers, hexadecimal numbers and regular decimal numbers
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throughout the program.
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* Variables and function names are semi-random and upper and lower case
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characters are used.
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* Use of `#define`s from `stdio.h`, `stdlib.h` for values `_STDIO_H` and
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`EXIT_SUCCESS` used to represent 1 and 0 respectively in the program.
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* Arrays only need to be 256x256 but most are set to greater values than they
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need to be so trying to figure it out can be a bit tough.
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### References
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* David Madore's implementation of Shamir's Secret Sharing - <http://www.madore.org/~david/programs/programs-1.36.html>
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* Steve's Recipe Database - source for the $25k Cookie Recipe - <https://www.mealsteps.com>
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<!--
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Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
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You are free to share and adapt this file under the terms of this license:
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Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
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For more information, see:
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https://creativecommons.org/licenses/by-sa/4.0/
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-->
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