XUSD (BabelFish) wallet

What is XUSD (BabelFish) (XUSD)?

XUSD is a dollar-denominated token issued by BabelFish on Rootstock, the Bitcoin sidechain. Its purpose is aggregation: stablecoins arriving on Rootstock from elsewhere are pooled as backing, and XUSD is the single dollar unit that circulates on top of them, so applications on the chain deal with one stablecoin instead of half a dozen bridged ones.

Holding it means living with Rootstock's habits. The chain runs an EVM, so addresses look like Ethereum addresses, but gas is paid in RBTC - bitcoin pegged onto the sidechain - and not in BTC on the Bitcoin network or in ETH. Sending bitcoin straight to a Rootstock address does not work; RBTC has to come across the peg first. Rootstock also uses a chain-specific address checksum, so an address copied from one tool may be rejected by another that only knows the Ethereum form, even though the underlying characters match. Blocks are merge-mined with Bitcoin, which makes confirmations slower than on fast EVM chains.

Supported networks in Tangem (1): Rootstock RSK.

Tangem generates the private key inside the card's secure element, where it stays; a second identical card, kept somewhere else, restores the same wallet if the first is lost, and a seed phrase is there only if you want one. A dollar unit parked on a quiet sidechain may go untouched for a long stretch, and this is a sensible shape of custody for something you are content to leave alone.