You can utilize the library without signing up for a user account and an API key. That user registration part is not live yet. You can download the C# SDK from Nuget here https://www.nuget.org/packages/cas-dotnet-sdk#readme-body-tab or you can download the Typescript SDK from NPM here https://www.npmjs.com/package/cas-typescript-sdk. All documentation for the libraries is on the GitHub README pages.
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I am building open-source cryptographic libraries that utilizes RustCrypto suite of algorithms for C# and Typescript. User's will have the ability to tie their API key to their account and see benchmarks related to their usage of the library.