Custody model Cold by default, hot by exception
The design goal is simple to state and expensive to build: there should be no single
machine, no single site and no single person whose compromise moves customer funds.
- Cold storage share
- 95% of customer crypto, measured daily against total customer balances rather than quoted as a target.
- Key material
- Generated and held inside FIPS 140-2 Level 3 hardware security modules. Key shares never leave an HSM in plaintext, including during backup.
- Geographic split
- Five HSM sites across three legal jurisdictions. No single site, and no single jurisdiction, holds enough shares to sign anything.
- Signing method
- Multi-party computation. The complete private key is never assembled in memory on any machine, at any point, including at signing time.
- Withdrawal authorization
- A 3-of-5 quorum of custody officers on separate hardware in separate locations. No one person can move funds, and no two can either.
- Hot wallet ceiling
- A hard 5% cap, enforced in code, with an absolute dollar ceiling that overrides the percentage when balances grow.
- Replenishment
- Cold-to-hot top-ups run on a fixed schedule with a mandatory delay window, so an attacker cannot drain the hot wallet and trigger an instant refill.
Why multi-party computation instead of multisig
In a conventional setup, a private key exists somewhere in full, at least for the instant it
signs. Multi-party computation removes that instant. The key is generated as mathematical
shares that are distributed across our HSM sites at creation, and a signature is produced
through a protocol run between those shares. The complete key is never reconstructed, not in
memory, not on disk, not during backup, not during signing. An attacker who takes total
control of one site gets a share, which on its own is useless.
On top of that sits the quorum. Every withdrawal above the automated threshold requires three
of five custody officers to approve on separate hardware, in separate locations, against a
request they can inspect. The officers are drawn from teams that do not report to one
another, so pressuring one person is not a path to anything. If this sounds slow for large
withdrawals, it is. That is the trade we chose, and we would rather explain a delay than a
loss.
The hot wallet, and why it exists at all
A platform that held 100% of assets offline could not process a withdrawal in under a day.
The hot wallet is what makes same-hour withdrawals possible, and it is the honest weak point
of every exchange including this one. Ours is capped at 5% of customer assets, enforced in
code rather than policy, with an absolute dollar ceiling that takes over when the percentage
would allow too large a float. Replenishment from cold storage runs on a fixed schedule with
a mandatory delay, which means an attacker who empties the hot wallet cannot trigger an
immediate automatic refill and do it again.
Balances that back activity on the trading terminal sit inside that
float, which is one reason the terminal settles internally against your ledger balance rather
than moving coins on chain for every fill. It is faster, and it keeps on-chain exposure
small. Withdrawals leave the float; deposits sweep into cold storage on a schedule.