Cody Boone Ferguson
9e456b4750
In particular the following diff for each README.md (with all the
index.html files rebuilt):
-Watch the following [Our Favorite Universe](https://www.youtube.com/@OurFavoriteUniverse) YouTube show:
+Watch the [Our Favorite Universe](https://www.youtube.com/@OurFavoriteUniverse)
+YouTube show for this entry:
139 lines
3.9 KiB
Markdown
139 lines
3.9 KiB
Markdown
## Award presentation:
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Watch the [Our Favorite Universe](https://www.youtube.com/@OurFavoriteUniverse)
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YouTube show for this entry:
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> [IOCCC28 - 2024/tompng - Prize in quasi bijection](https://www.youtube.com/watch?v=9C4PpNCst8Y)
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## To build:
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``` <!---sh-->
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make all
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```
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## To use:
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### Encryption
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``` <!---sh-->
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prog < file.txt > file.enc.txt
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```
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### Decryption
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``` <!---sh-->
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prog < file.enc.txt > file.txt
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```
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### Command line arguments
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You can also specify SIZE of the text-stirring area and a PASSWORD.
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``` <!---sh-->
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./prog 30 < input > output
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./prog PASSWORD < input > output
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./prog 40 PASSWORD < input > output
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```
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You need to specify the same SIZE and PASSWORD to decrypt correctly.
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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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It is well-known that the Enigma cipher was broken due to the fact that a letter could never map to itself.
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Is this algorithm susceptible to a similar cryptanalysis?
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## Author's remarks:
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### Vortex Encryptor/Decryptor
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Secure encryption/decryption is a black box. It's highly based on difficult mathematics. We just blindly TRUST when using it.
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This entry is a visual vortex encryptor/decryptor for a text file.
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You can visually see how this program stirs the text to encrypt/decrypt. It's not a black box at all.
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### Easter Eggs
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#### Random Encryptor/Decryptor
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Some might dislike vortex-encryption algorithm. Alternately, there is one more visual text mixing algorithm.
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``` <!---sh-->
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./prog < prog.c > rand.c
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```
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This program `rand.c` is NOT A VORTEX encryptor/deryptor. You can see the text `N O /,T ,A` somewhere in the code. It randomly swaps characters instead of stirring with vortex.
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To check the randomness, compile it as an executable `rand` and try `./rand < prog.c` or `./rand < rand.c`.
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You can find that the encrypted text claims to be really RAND/rand-om.
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#### Important Passwords
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"password" is the 1st most used alphabet password in the world. Wait, what's the 0th used password? It might be "ioccc" or "IOCCC".
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Let's encrypt prog.c with these passwords.
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``` <!---sh-->
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./prog ioccc < prog.c > prog1.enc.c
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./prog IOCCC < prog.c > prog2.enc.c
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```
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Imagine if you accidentally hit your head hard, forgot the password, lost everything except prog executable and the encrypted prog.c file.
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There's nothing to worry about. Just like important passwords often written on sticky notes, you can find this password in the encrypted text.
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### Internal
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#### Encryption/Decryption
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This program internally have forward-text-stir and backward-text-stir operation.
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It tries both operation and select the one that makes the output have less entropy.
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This is why this program doesn't need a command line argument such as `--encrypt` or `--decrypt`.
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#### Seed and Hash
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For security reason, vortex used to encrypt/decrypt varies over input text.
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Seed is calculated with vortex-stir-stable hash algorithm. This hash doesn't change over encryption/decryption.
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This is making hard to embed easter eggs into this program.
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#### Vortex stirring algorithm
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Character should not disappear by vortex stirring operation, so the velocity field of the vortex is required to be no divergence.
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Velocity field that has no divergence can be created from a [stream function](https://en.wikipedia.org/wiki/Stream_function).
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In this program, stream function which is a scalar field is made of horizontal, vertical and diagonal periodic waves.
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With a simple mathematics, this vortex stirring operation can be decomposed into horizontal, vertical, and diagonal array rotation which is a reversible operation.
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<!--
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Copyright © 1984-2025 by Landon Curt Noll and Leonid A. Broukhis. 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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