QuantumC: Post-Quantum Networking Support Library for C

1. Overview

QuantumC is a portable C library that provides post-quantum secure session establishment for networked applications on GNU/Linux and other POSIX systems.

The library is designed to integrate with existing C networking code using standard sockets and event loops. It does not replace TCP, UDP, or application protocols. Instead, it provides a cryptographic session layer that can be embedded into current designs with minimal disruption.

QuantumC targets developers who need post-quantum readiness while maintaining compatibility with existing infrastructure.

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2. Design Goals

• Post-quantum secure key establishment.
• Clean C API with explicit state management.
• Transport-agnostic design.
• No hidden I/O or threading.
• Suitable for long-lived daemons and constrained environments.
• Easy to audit and reason about.

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3. Non-Goals

• Defining a new network protocol.
• Implementing routing or packet forwarding.
• Replacing TLS, IP, or socket APIs.
• Acting as a cryptographic research sandbox.

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4. Architecture

QuantumC is structured as three layers:

4.1 Core Session Layer

Responsible for:

• Session lifecycle management.
• Handshake state machines.
• Key derivation orchestration.
• Error handling.

4.2 Cryptographic Provider Layer

Responsible for:

• Post-quantum KEM implementations.
• Hybrid classical and post-quantum key exchange.
• Algorithm dispatch via abstract interfaces.

No application code depends directly on algorithm-specific details.

4.3 Transport Binding Layer

Provides optional helpers for POSIX sockets. All I/O remains under user control. The library consumes and produces byte buffers only.

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5. Public API Overview

All public interfaces are exposed under include/quantumc/.

Key headers include:

• qc_context.h; global library configuration.
• qc_session.h; session creation and state transitions.
• qc_crypto.h; cryptographic configuration.
• qc_kem.h; post-quantum KEM abstraction.
• qc_transport.h; optional socket helpers.
• qc_errors.h; error codes and diagnostics.

The API is designed to be usable in select(), poll(), and epoll() driven applications.

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6. Cryptographic Model

QuantumC supports post-quantum key establishment through a pluggable KEM interface.

6.1 Supported Concepts

• Lattice-based KEMs.
• Hybrid classical plus post-quantum handshakes.
• Explicit key material handling.

6.2 Algorithm Policy

Algorithms are selected at build or runtime via configuration. No algorithm is hardcoded into the session logic.

This allows users to:

• Track evolving standards.
• Swap implementations without rewriting application code.
• Meet regulatory or organizational requirements.

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7. Build and Integration

7.1 Requirements

• C99-compatible compiler.
• POSIX environment.
• Make or compatible build system.

7.2 Build

make
make install

The library builds as a static or shared object depending on configuration.

7.3 Integration

QuantumC is intended to be linked directly into applications or system services. No background services or kernel modules are required.

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8. Security Model

• No implicit trust assumptions.
• Explicit handshake transcripts.
• No silent algorithm downgrade.
• Fail-closed behavior.

See docs/threat_model.md for details.

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9. Status

This project is under active development. API stability is a priority, but breaking changes may occur prior to the first stable release.

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10. License

GPLv3. See LICENSE for details.