Subgraph

Subgraph is a Canadian software company that develops Subgraph OS, a security-focused Linux-based operating system designed for users who require strong isolation and resistance to sophisticated adversaries. Their flagship product, Citadel, is a custom Linux distribution built around the principle of adversary-resistant computing. Citadel's architecture centers on several core security mechanisms: - Immutable base system: The OS base is mounted read-only and protected by dm-verity, a Linux filesystem integrity mechanism that prevents booting if any data is tampered with. - Partitioned Workspaces ("Realms"): Users can create isolated computing environments for different projects or security contexts, each with its own applications and data. Isolation is achieved via Linux kernel namespaces, cgroups, and optionally a custom Rust-based hypervisor for hardware-level separation. - Reproducible Builds: Every component of the OS builds deterministically from source, allowing independent verification and eliminating supply chain attacks. - Verified Boot Chain: UEFI Secure Boot ensures only cryptographically signed code runs at startup. - Atomic Updates: OS updates are applied as signed binary blobs with full rollback support. The system targets system administrators, software developers, security researchers, financial services professionals, government users handling sensitive operations, and embedded systems deployments. It supports both container-based and hypervisor-based realm isolation, with additional kernel hardening features including KASLR, SMEP, SMAP, Control Flow Integrity, SELinux/AppArmor, and seccomp-bpf syscall filtering. Subgraph is open source and based in Montreal, Quebec, Canada, offering commercial licensing alongside open-source access.