asymmetriccrypto

A demo of asymmetric cryptography in C# 9.0, NET 6.0

This is a unit-test driven project.

References

• https://docs.github.com/en/authentication/managing-commit-signature-verification/generating-a-new-gpg-key

• https://www.gnupg.org/documentation/manuals/gnupg/Unattended-GPG-key-generation.html

• https://www.gnupg.org/documentation/manuals/gnupg/Ephemeral-home-directories.html

• https://github.com/mattosaurus/PgpCore

How to use

The PowerShell command Make-RsaFiles.ps1 generates two matched files:

• private.pgp.txt - Which we actually use
• public.pgp.txt - Which matches the private key and could be given to anyone to help encypher files

The unit tests

The unit test start up loads the private key for use in tests.

Notice that this format only allows input text strings of length of AsymmetricCrypto.MaxCharsSupported (250)

The tests exercise this class by encrypting and decrypting strings.

AsymmetricCrypto.cs

1. There is a bit of indirection to this. 1st the openssl library makes a private key but with --- header and footers, split into lines w. CR/LF so we have to clean that up using KeyConverter() to turn this into one long base64 string without line splits or headers and footers.

2. For compatibility we use UnicodeEncoding to turn the strings into byte arrays.

3. Then we call rsa.Encrypt() on the byte array, and turn the resulting byte array into base64 string.

4. The reverse is done on decryption

The class is IDisposable to get rid of the rsa object which is large and holds resources.