# noscrypt
*A compact, C90 cross-platform, cryptography library built specifically for nostr*

## What is noscrypt?
A high-level C utility library built specifically for nostr cryptography operations such as those defined in NIP-01 and the new NIP-44. It was designed to simplify the operations that the secp256k1 library was used for, along with data encryption for the new sepc. It is also being built embedded in mind.  

API Example:
```C
NCValidateSecretKey()
NCGetPublicKey()
NCSignData()
NCVerifyData()
NCEncrypt()
NCDecrypt()
NCComputeMac()
NCVerifyMac()
... extended functions
```

There are no functions that handle key generation, because secp256k1 simply requires a 32byte random number that needs to only be validated. I assume most applications will prefer and or have better random number generators than I can assume. Use your preferred or platform CSRNG.  

## Motivation
At the time of building this project I have not come across any C-only libraries that exposed functionality for nostr specific cryptography. IMO it is easy to use the secp256k1 library incorrectly. In the process of building [NVault](https://github.com/VnUgE/NVault) NIP-44 came out in December and I realized my libraries were falling short for my needs for proper and safe nostr cryptographic operations, and I needed to start over and start with a good base that has all the basic  functionality built with trusted and tested libraries.  

I wanted a compact and efficient utility library that was portable across systems and runtimes. I will primarily be using this library in a .NET environment, but would like to make a hardware signer sometime. 

### Testing
Testing is an will be important to a cryptography library, I take that responsibility seriously. There are some basic api validation and correctness tests that can be built into an executable called nctest. Full automated testing suite is done in C# interop as part of my [NVault](https://github.com/vnuge/nvault) package. This includes testing against the official nip44 [vector file](https://github.com/paulmillr/nip44/blob/main/nip44.vectors.json). I'm very dependency adverse so native C90 testing using only stdlibs can get gross in a hurry. It will likely happen in the future but not right now. 

### Hardness
- Time sensitive verification always uses fixed time comparison
- No explicit/dynamic memory allocations
- Public API function input validation is on by default
- All stack allocated structures are securely zeroed before return
- Stack protection is enabled by default for GCC and MSVC compilers (also for deps)
- Schnorr signatures are validated before the signing function returns
- Carefully selected, widley used, tested, and audited dependencies


## Platform Support
| Arch | Support | Notes | Tested |
| ----- | ---------- | ------- | ------- |
| Windows | OpenSSL, Mbed-TLS, BCrypt | NT 6.1 + | ✅ |
| Linux   | OpenSSL, Mbed-TLS         | GCC only | ✅ |
| FreeBSD | OpenSSL, Mbed-TLS         | GCC Only |    |

### Configuring libraries
Noscrypt now supports linking to multiple cryptographic libraries and expanded platform support. At built-time you may choose 

## Packages and Docs
GitHub is simply a mirror for my projects. Extended documentation, pre-compiled binaries and source code bundles are always available on my website, along with PGP signatures and checksums.    

[Docs and Articles](https://www.vaughnnugent.com/resources/software/articles?tags=docs,_noscrypt)  
[Builds and Source](https://www.vaughnnugent.com/resources/software/modules/noscrypt)  

### Getting the package
There are 3 ways to get the source code to build this project.  
1. Download the package from my website above  (recommended)
2. Clone the GitHub repo `git clone https://github.com/VnUgE/noscrypt.git`  
3. Download a github archive or release when they are available  

## Building
This project was built from the start using cmake as the build generator so it is easily cross platform. Builds produce a shared library and a static library so you can choose how to link it with your project.  

*Extended documentation includes more exhaustive build conditions and supported platforms*

### Prerequisites
Before building this library you must install the following dependencies 
- [task](https://taskfile.dev/installation/) - build exec tool
- git
- [cmake](https://cmake.org)
- Your preferred C compiler. Currently supports GCC and MSVC

>[!NOTE]
>The build process will install dependencies locally (in a deps/ dir) and verify the file hashes. Read extended documentation for installing dependencies manually/globally.

### Instructions
After Task is installed you can run the following commands to execute the build steps. I test build steps against Debian, Ubuntu, Fedora, Windows 10 and Windows Server 2019 targets. If you have a platform that is having issues please get in touch. 

>[!TIP]
> Run `task --list-all` to see all available build commands

#### Normal build
The following command will install dependencies and build the libraries in release mode  
``` shell
task #or task build
```

#### Build tests in debug mode
>[!WARNING]
> You may want to clean the entire project before rebuilding in debug mode to cleanup caches
``` shell
task build-tests
```

#### Cleanup
You can delete all build related data (including dependencies) and start over
``` shell
task clean
```
The task file is configured to cache your dependencies once they are built. If you have issues with a download and need to re-run a command, try using `task <cmd> --force` to override the build caching.

#### All done
Once building is complete, your library files should be located under `build/libnoscrypt` or `build/Release/noscrypt.dll` on Windows 

## Notes
#### Builds
Build packages on my website are "manual" I use an internal tool called *vnbuild* that just does the work of preparing a package, but I have to run it myself.  

#### Branches
There are currently 2 branches I use because of my build process. `develop` and `master`. All changes happen in develop, then are merged to master when I feel like they are stable enough. After some testing and time, a tag and release will become available.   

#### Windows Dlls
You may notice that I have msvc pre-compiled packages available for download. I have not compatibility tested them yet so they should only support Windows 10/Server version 1904 running amd64 processors. 

## License
The software in this repository is licensed to you under the GNU Lesser GPL v2.1 or later. `SPDX-License-Identifier: LGPL-2.1-or-later` see the [LICENSE](LICENSE) file for more details.    

## Donations
If you feel so inclined to support me an this project, donations are welcome and much appreciated.   

BTC On-Chain: ``bc1qgj4fk6gdu8lnhd4zqzgxgcts0vlwcv3rqznxn9``