Multisig: money that cannot be stolen
Buyer, vendor and arbiter each generate a pubkey; the software derives a 2-of-3 address. The buyer funds it. The vendor sees "funded" but cannot spend. Release needs buyer + vendor signatures after delivery; disputes add the arbiter as the deciding second key. Nexus never holds two keys — even full server compromise leaks no funds, because funds live on-chain, not in a database. No address reuse: one address, one order, no graph linkability.
Monero (XMR): the default
Ring signatures, stealth addresses and confidential transactions hide sender, receiver and amount. Practical rules: churn once after exchange withdrawal, never reuse a subaddress across identities, and wait for 10+ confirmations during congestion before treating a deposit as final.
Bitcoin (BTC): legacy support
Bitcoin stays for buyers without Monero access, but it is transparent by design. Never send directly from a KYC exchange to escrow — swap to XMR or CoinJoin first, use a fresh address per order, and assume every hop is permanently recorded.