xpTURN.Atropos 0.1.1

xpTURN.Atropos

Dependency-free, Zero-GC-oriented pure C# Ed25519 (RFC 8032, plain PureEdDSA) sign/verify primitive for Unity (IL2CPP/AOT-safe) and Godot. No native libs, no DLLs, no Klotho dependency — designed to be split out as a standalone project.

Public API

Ed25519 is the only public type — plain Ed25519 (no context, no prehash), RFC 8032 deterministic (signatures byte-identical across any conformant implementation). Every operation allocates zero heap after a one-time per-thread warm-up, is thread-safe, and Verify rejects non-canonical signatures (non-malleable). All I/O is Span<byte>; sizes: SeedSize 32, PublicKeySize 32, SignatureSize 64.

Derive a public key from a 32-byte private seed:

using xpTURN.Atropos;

Span<byte> publicKey = stackalloc byte[Ed25519.PublicKeySize];   // 32
Ed25519.DerivePublicKey(seed /* 32 B */, publicKey);

Sign a message with the seed (writes a 64-byte signature):

Span<byte> signature = stackalloc byte[Ed25519.SignatureSize];   // 64
Ed25519.Sign(seed /* 32 B */, message, signature);

Verify a signature against the public key:

bool ok = Ed25519.Verify(publicKey, message, signature);

Installation

Unity (UPM)

1. Open Window > Package Manager
2. Click + > Add package from git URL...
3. Enter:

https://github.com/xpTURN/Atropos.git?path=com.xpturn.atropos

Assembly Definition usage

If your project uses Assembly Definition (.asmdef), add a reference to this package's runtime assembly in any asmdef that calls the API.

1. Select your Assembly Definition (.asmdef) file and open it in the Inspector.
2. Under References, click + and add xpTURN.Atropos.

NuGet (.NET / Godot)

dotnet add package xpTURN.Atropos

Ships netstandard2.1 + net8.0.

From source

ProjectReference the Server~/xpTURN.Atropos/xpTURN.Atropos.csproj mirror, or <Compile Include> Runtime/**/*.cs.

Third-party

Ed25519 ref10 math + SHA-512 are vendored from Chaos.NaCl (public domain). See Runtime/ThirdParty/Ed25519/LICENSE.txt and PROVENANCE.md for the pinned source commit and the local-modification log.

Performance

Zero allocation on every operation, with latency competitive with BouncyCastle. Measured (net8 Release, Apple-silicon desktop; a comparison against BouncyCastle 2.5.1 as a reference — machine-dependent, relative):

• Latency ×vs BC = BouncyCastle µs ÷ Atropos µs; >1 means Atropos is faster. Derive/Sign run ~1.1× faster; Verify trails by ~12% on this host, offset by 0 allocation.
• 0 bytes/op vs 1.8–6.2 KB/op, and a ~28× smaller code footprint with no dependency.
• Field arithmetic uses an even/odd (radix-2⁵¹) Karatsuba fe_mul/fe_sq with the hot small ops inlined.
• Numbers are machine-dependent (an x86 host enables BouncyCastle's SIMD paths); treat as relative.

Reproduce:

dotnet run -c Release --project Server~/xpTURN.Atropos.Bench

License

Apache-2.0 (see LICENSE.md) for the Atropos wrapper/facade code. Vendored ThirdParty/ retains its upstream public-domain dedication.