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:

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 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 package. This includes testing against the official nip44 vector file. 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
Schnorr signatures are validated before the signing function returns
Carefully selected, widley used, tested, and audited dependencies

Platform Support

The following table lists the supported platforms and cryptography libraries that noscrypt supports. This will expand in the future. You are free to choose and specify the location of these libraries if you desire during build time, otherwise safe defaults are attempted on your platform.

Arch	Support	Notes	Tested
Windows	OpenSSL (3.0), Mbed-TLS, BCrypt	NT 6.1 +	✅
Linux	OpenSSL (3.0), Mbed-TLS	GCC only	✅
FreeBSD	OpenSSL (3.0), Mbed-TLS	GCC Only

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
Builds and Source

Getting the package

There are 3 ways to get the source code to build this project.
1. Download the signed noscrypt-src.tgz 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

Please see extended documentation for all custom build configurations and tips. For now, here is enough to get most developers going.

CMake

cmake -S . -Bbuild/ -DCMAKE_BUILD_TYPE=Release

Enable built-in tets and debug mode

cmake -S . -Bbuild/test -DCMAKE_BUILD_TYPE=Debug -DNC_BUILD_TESTS=ON

Specify the crypto library

cmake -S . -Bbuild/ -DCMAKE_BUILD_TYPE=Release -DCRYPTO_LIB=<openssl | mbedtls | bcrypt>

Easy mode

A Taskfile file is included for easy building if you wish to build in easy mode! Use the task --list-all to see all available commands. The default command task will build the library in release mode using defaults. You may specify extra cmake build variables using the USER_ARGS variable on the command line.

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.