AsymmetricCrypt

Simple .NET asymmetric encryption implementation

Purpose:

data encryption on the systems, where storing password or key in cleartext is not desirable option.

Usage:

Tool will use standard io streams where possible, or files could be specified on command line

Generate private key:

AsymmetricCrypt --genkey private.key
AsymmetricCrypt --genkey >private.key

Extract public key component from private key:

AsymmetricCrypt --publickey private.key public.key
AsymmetricCrypt --publickey <private.key >public.key

Encrypt file using public key:

AsymmetricCrypt --encrypt public.key plaintext.txt encrypted.ascr
AsymmetricCrypt --encrypt public.key <plaintext.txt >encrypted.ascr

Decrypt file using private key:

AsymmetricCrypt --decrypt private.key encrypted.ascr plaintext.txt
AsymmetricCrypt --decrypt private.key <encrypted.ascr >plaintext.txt

Internals:

Each file is encrypted using AES256 with randomly generated key. AES256 key is encrypted using 4096 bit RSA and stored with the file.

File structure:

4 bytes:    signature  "ASCR"
16 bytes:   AES IV
512 bytes:  RSA 4096-encrypted AES key
rest:       encrypted file contents

Installing on Ubuntu:

Install using following commands:

sudo apt-get install mono-runtime libmono-system2.0-cil wget
sudo mkdir -p /usr/lib/ascry
sudo wget https://raw.github.com/galets/AsymmetricCrypt/master/Binary/AsymmetricCrypt.exe \
          -O /usr/lib/ascry/AsymmetricCrypt.exe
sudo chmod +x /usr/lib/ascry/AsymmetricCrypt.exe
sudo ln -s /usr/lib/ascry/AsymmetricCrypt.exe /usr/bin/ascry