Definition
Ledger is a manufacturer of hardware wallets, including the Nano and Stax model lines, that store private keys offline and sign transactions on-device. Ledger's design centers on a certified secure element chip (with Common Criteria certifications such as EAL5+ or EAL6+ across its devices) that isolates cryptographic operations from the host computer and from the device's own general-purpose microcontroller.
Operating system and architecture
Ledger devices run a custom operating system called BOLOS (Blockchain Open Ledger Operating System) on the secure element. Each coin application runs in an isolated environment so that one app cannot read another's data. This architecture lets a single device support many different assets through installable apps managed via Ledger Live.
Open-source status
Ledger's position on openness is mixed and worth stating plainly. The company open-sources much of its application-layer and SDK code and many of its companion apps, but the low-level firmware running on the secure element is closed source and covered by manufacturer non-disclosure agreements. Ledger states this is because the secure element's internals are the chip vendor's protected intellectual property. As a result, the core device firmware cannot be independently audited or reproducibly built in the way fully open-source wallets allow.
For related concepts, see hardware wallet and cold storage.
In Simple Terms
Ledger is a manufacturer of hardware wallets, including the Nano and Stax model lines, that store private keys offline and sign transactions on-device. Ledger’s design…