A command-line utility to encrypt and decrypt textfiles using a Caesar cipher
1. Get .NET Core 2.1 or later:
This is best done by following the instructions found here.
2. Clone cx-dotnet-assignment:
Assuming you have git installed, navigate to your favorite folder and run:
git clone https://github.com/teodoran/cx-dotnet-assignment.git
3. Try out CaesarCipher!
Navigate to the /CaesarCipher folder and try it out!
$> cd CaesarCipher
$> dotnet run 7 plaintext.txt
lawlyplujlgpzgæolgælhjolygvmghssgæopunz
...
Encryption using a Caesar cipher, works by shifting all letters in the plaintext (the text you want to encrypt) a fixed number of letters (usually called a Caesar shift) down the alphabet.
To make CaesarCipher encrypt your file, you pass it the number of letters you want to shift (in this example 7), and a file or a path to a file containing the text you want to encrypt (plaintext.txt in the example below).
$> dotnet run 7 plaintext.txt
lawlyplujlgpzgæolgælhjolygvmghssgæopunz
uvgvulgpzgzvgiyhålgæohægolgpzguvægkpzæøyilkgibgzvtlæopungøulawljælk
pgohkgyhæolygilgmpyzægpughgåpsshnlgæohugzljvukghægyvtl
tlugmyllsbgilsplålgæohæg opjogæolbgklzpyl
pgjhtlgpgzh gpgjvuxølylk
Remember to make a note of the Caesar shift! This is your encryption key, and if you don't know the shift, you'll have a hard time decrypting the text.
Tip: If you want to save your encrypted text, you can pipe it to another file using $> dotnet run 7 plaintext.txt > ciphertext-shift-7.txt.
To decrypt text encrypted with CaesarCipher, you give CaesarCipher the Caesar shift the text was originally encrypted with, a file or a path to a file containing the encrypted text (usually called ciphertext), and the parameter -d or --decrypt.
$> dotnet run 7 ciphertext-shift-7.txt -d
experience is the teacher of all things
no one is so brave that he is not disturbed by something unexpected
i had rather be first in a village than second at rome
men freely believe that which they desire
i came i saw i conquered
If given no arguments (or wrong arguments!) CaesarCipher will print information about all available options.
$> dotnet run
CaesarCipher 1.0.0.0
Copyright (C) 2018 Computas AS
ERROR(S):
A required value not bound to option name is missing.
-d, --decrypt (Default: false) Decrypt the input file. If not set, the program will default
to encrypt the input file.
--help Display this help screen.
--version Display version information.
caesar shift (pos. 0) Required. The number of letters each letter should be shifted down the
alphabet when encoding or decoding.
input file (pos. 1) Required. Input file with plaintext to encode or ciphertext to decode.