Proudly developed in
Montreal,
Quebec,
Canada
Proudly open source.
Layer 01Foundation Layer
Foundation Layer
Citadel Base
The minimal, immutable core that provides only essential services: kernel, init system, and graphics. No user applications, no persistent data, no configuration drift. Protected by cryptographic integrity verification.
Layer 02Isolation Layer
Isolation Layer
Hypervisor or Container Engine
Container-based realms offer near-native performance for trusted workloads. Hypervisor-based realms provide hardware-level isolation for high-risk activities such as malware analysis.
Layer 03Application Layer
Application Layer
User Realms
Completely isolated computing environments where your actual work happens. Each realm can only access its own data. Applications are read-only by default; only user data persists across reboots.
System Administrators
Secure endpoints for privileged users at risk of targeted attacks.
Software Developers
Isolated development environments without cross-contamination.
Security Researchers
Safe analysis environments for malware and vulnerability research.
Financial Services
Secure workstations for executing sensitive financial transactions.
Government
Compartmentalized computing for classified and sensitive operations.
Embedded Systems
Secure computing for vehicles, kiosks, and specialized hardware.
0
Persistent
Base Data
Base Data
100%
Reproducible
Builds
Builds
∞
Isolated
Realms
Realms
Technical Specifications
Base System
Distribution Base
Custom Linux build (not derivative)
Package Sources
Official upstream repositories
Init System
systemd
Display Server
Wayland
Desktop Environment
GNOME Shell
Filesystem Protection
dm-verity integrity verification
Update Mechanism
Atomic signed binary blobs
Realm Isolation
Container Engine
Linux namespaces + cgroups
Hypervisor
Custom Rust implementation
Guest Kernels
Modified Linux with reduced attack surface
Syscall Filtering
seccomp-bpf
Network Isolation
Per-realm virtual networks
Filesystem Isolation
Separate mount namespaces
Process Isolation
PID namespaces + user namespaces
Build System
Build Reproducibility
100% reproducible from sources
Source Verification
Cryptographic signature checking
Build Environment
Isolated, deterministic containers
Toolchain
GCC/Clang with hardening flags
Binary Verification
Independent verification possible
Supply Chain
Direct from upstream repositories
Security Features
Boot Security
UEFI Secure Boot
Kernel Hardening
KASLR, SMEP, SMAP, Control Flow Integrity
Memory Protection
ASLR, stack canaries, heap protection
Compiler Security
Stack protector, fortify source, PIE
Runtime Protection
SELinux/AppArmor integration
Cryptography
Hardware crypto acceleration support
Minimum Requirements
Processor
x86_64 with virtualization
Intel VT-x or AMD-V
2+ cores recommended
Intel VT-x or AMD-V
2+ cores recommended
Memory
8 GB minimum
16 GB recommended
32 GB for multiple realms
16 GB recommended
32 GB for multiple realms
Storage
32 GB minimum
128 GB recommended
NVMe for best performance
128 GB recommended
NVMe for best performance
Feature
Container
Hypervisor
Intel VT-x
✓
Required
AMD-V
✓
Required
IOMMU
Optional
Recommended
TPM 2.0
N/A
✓
UEFI Secure Boot
Required
Required
Graphics Acceleration
Native
Limited
✓ supported in this mode; Required = mandatory; Recommended = expected; Optional = possible; Limited = partial; N/A = does not apply
Security Features
Filesystem Integrity
dm-verity provides cryptographic verification of every block in the base filesystem. Any tampering prevents boot, ensuring a pristine starting state.
Realm Sandboxing
Complete process, network, and filesystem isolation between realms using kernel namespaces or hardware virtualization.
Immutable Base
The core Citadel system is mounted read-only. No configuration drift, no persistent malware, no accumulated security debt.
Verified Boot Chain
UEFI Secure Boot through kernel loading ensures only cryptographically signed code executes during system startup.
Reproducible Builds
Every binary can be independently verified to match the claimed source code, eliminating supply-chain compromise.
Hardware Security
TPM integration for cryptographic key storage and attestation, plus hardware random-number generation for strong entropy.
Montreal,
Not yet available
Subgraph OS is in active development, and no public download is available yet. When the download channel opens, every binary will be published with reproducible-build checksums and a signed manifest so you can verify exactly what you are running, and to build it yourself from source.
Auditing Tools for Human Rights Defenders: Our Methodology
A behind-the-scenes look at how we run security audits for the Open Technology Fund Security Lab and why methodology matters.
Read more →Reproducible Builds: Why You Shouldn't Have to Trust Our Binaries
If you can recompile the same binary from the same source twice, you stop needing to trust anyone’s servers. The checksums speak for themselves.
Read more →Introducing Citadel: Secure Computing for a Hostile Internet
Citadel is the read-only computing base inside Subgraph OS: the immutable layer on which isolated realms run.
Read more →