How renbridge turned Bitcoin into renBTC for DeFi

Renbridge turned Bitcoin into renBTC by locking BTC under RenVM’s control and minting an Ethereum token backed by it. That let Bitcoin holders use DeFi services, such as lending and trading, without selling their BTC. Ren’s own account of the process describes the route as a mint on Ethereum followed by a burn to redeem Bitcoin.

In Ren’s design, a network of Darknodes managed the Bitcoin through secure multi-party computation, a way for several parties to use a key without any one party holding the whole key. The name renbridge came to describe this path between Bitcoin and Ethereum. Ren’s account says a Bitcoin deposit address was generated for the user, then the network waited for six Bitcoin confirmations before minting renBTC, minus a fee.

How did renbridge mint renBTC?

After the Bitcoin deposit was confirmed, RenVM produced a signature used to mint renBTC to the user’s Ethereum wallet. Ren described the token as an ERC-20, the common token format used by Ethereum apps. Each renBTC was intended to represent one BTC held by RenVM; it was not a new Bitcoin or a claim based on Bitcoin’s market price.

That Ethereum token could then work with compatible DeFi contracts. For example, someone could supply renBTC to a lending market or trade it through a decentralised exchange. The Bitcoin stayed on its own chain while the token representing it moved on Ethereum.

How did you get Bitcoin back from renBTC?

To return to Bitcoin, the holder burned renBTC in an Ethereum transaction and named a Bitcoin address. Ren’s description says the network then released the corresponding BTC to that address, less a fee. The two directions worked as a pair:

• Send BTC to a deposit address created for the transfer.
• Wait for Bitcoin confirmations, then receive renBTC on Ethereum.
• Burn renBTC and provide a Bitcoin address to request BTC back.

This made renbridge useful for putting Bitcoin value into Ethereum apps, but the token depended on more than Bitcoin’s own network. Users also relied on RenVM’s key management, Ethereum’s contracts and enough network operation to process deposits and redemptions. They paid Bitcoin transaction fees when sending BTC and Ethereum gas for Ethereum transactions.

What were renbridge’s limits?

Ren’s one-to-one backing model did not remove bridge risk. If the network stopped processing redemptions, renBTC could remain on Ethereum without a working route back to Bitcoin. In November 2022, Ren said Alameda’s collapse put funding for RenVM at risk and urged holders to return assets. The Block reported the following month that RenVM could stop functioning, potentially leaving tokens stuck.

That history is central to understanding renbridge: it made Bitcoin usable in Ethereum DeFi by adding a separate custody and software layer. The trade-off was access to Ethereum applications in exchange for reliance on that layer to keep minting and redemption working.