Cubist, a San Diego company founded in 2022, was built on the premise that this is a false choice, and that the reason everyone accepts it is that they have not read enough security papers. The four founders have read a great many. Between them they have published more than 80 peer-reviewed papers in applied cryptography, systems security, and formal verification; found high-severity bugs in Chrome and Firefox; shipped the sandboxing that protects millions of Firefox users; and designed cryptographic primitives that sit underneath Ethereum and Avalanche. This is a company where the founders wrote parts of the standards their own product depends on.
The product is called CubeSigner, and the trick it pulls is conceptually simple even if the engineering is not. Instead of handing an application the raw private key - the digital equivalent of mailing someone your house key so they can water the plants - CubeSigner keeps the key sealed inside secure hardware: hardware security modules and AWS Nitro Enclaves. The application never sees the key. It asks, politely, over an API, for a signature. The hardware signs. The key never leaves.
What makes this more than a fancy HSM is the word "milliseconds." Traditional hardware-backed signing is slow and clunky, which is why people reach for hot wallets that keep keys in memory where an attacker can grab them. Cubist's bet is that if hardware signing is fast and convenient enough - a few lines of code, a revocable session, an answer back before you notice the wait - nobody has a reason to keep a raw key lying around anymore. Cold-wallet security, hot-wallet speed, is the tagline, and for once the tagline is also the technical claim.
Around the signer sits a programmable policy engine, which is the part that turns "don't lose the key" into "the key will refuse to sign anything that breaks these rules." You can require multiple approvals for a large transfer, enforce spending limits, block the conditions that get an Ethereum validator slashed, or gate access by role. The policies are code, and the hardware enforces them before a signature ever happens. This is a meaningfully different pitch from most custody products, which ask you to trust a black box. Cubist's version is closer to: here is the box, here is the code, and here is the cryptographic attestation that the code is what ran.
The customers are the people for whom a lost key is not an inconvenience but a headline: staking providers, DeFi protocols, cross-chain bridges, and wallet builders. Bridges are a special case of misery in crypto - they have been drained for hundreds of millions of dollars - and Cubist ships a product called Bascule Drawbridge that watches on-chain and off-chain state in real time and attests that a withdrawal actually matches a deposit before funds move. It is the security equivalent of checking that the money you are handing out was actually put in.
There is also a more forward-looking line of work: Confidential Cloud Functions, which run private, verifiable code inside trusted execution environments. The pitch there is off-chain smart contracts and on-chain AI agents that can hold secrets and prove they behaved - a bet that the next set of blockchain applications will need somewhere private but accountable to do their computing.
