A hardware architecture for memory safety, developed at the University of Cambridge and SRI International (with DARPA funding from ~2010). CHERI makes every pointer a hardware-enforced capability: a fat pointer carrying bounds and permissions, validated in silicon on every memory access, with an unforgeable tag bit. The result is deterministic, hardware-enforced spatial and temporal memory safety for C/C++ code, plus fine-grained software compartmentalisation, without rewriting the code.
CHERIoT is Microsoft Research’s variant for tiny embedded cores (built on the lowRISC Ibex RV32E core), adding compartmentalisation primitives and an open-source RTOS. It is the lineage SCI Semiconductor commercialises in its ICENI microcontrollers.
Why it matters
Roughly 70% of serious security vulnerabilities are memory-safety bugs (Microsoft / Google / US ONCD data). The policy world’s primary fix is memory-safe languages (Rust); CHERI is the hardware path, valuable for the trillions of lines of legacy C/C++ firmware that will never be rewritten. It is a different primitive from confidential computing / TEEs (which protect data in use from a privileged host), and the two are sibling hardware-security mechanisms — see Hardware Memory Safety and Confidential Computing.
How it differs from the alternatives
- vs Rust / software: protects existing C/C++ binaries (recompiled), not only newly written safe code.
- vs ASLR: deterministic, not probabilistic.
- vs Arm MTE (Memory Tagging Extension): finer-grained and stronger (full bounds + permissions per pointer) vs MTE’s coarser, statistical tag-matching.
The adoption tax: it requires new silicon and a recompiled toolchain, which is the central reason its commercialisation is slow.
Ecosystem
- SCI Semiconductor — first commercial CHERIoT silicon (ICENI).
- Microsoft Research — authored CHERIoT; open-sourced CHERIoT-Ibex + RTOS.
- Arm — built the Morello CHERI prototype board, then shelved it (“no roadmap”).
- Codasip — ships CHERI-enabled RISC-V cores; donated a CHERI SDK to the CHERI Alliance (Oct 2024).
- lowRISC — owns the Ibex / Sonata open cores.
- UK Digital Security by Design (DSbD) — ~GBP170M government programme funding the CHERI ecosystem.