"Multisig," short for "Multisignature," is a form of digital key management that splits a private key into multiple parts, with a minimum required portion of the keys required for spending.
Casa's more advanced multisig function is 3 of 5. This creates a 5-part bitcoin private key, with 3 parts required to spend funds. Advanced multisig is included in all Platinum and Diamond memberships.
We recommend 3 of 5 multisig for individuals holding large amounts of BTC (in excess of $100,000 worth).
With 3 of 5 Multisig, you’ll have five (5) keys protecting your Bitcoin:
1) Mobile Key (held by you and secured by your phone’s secure enclave)
2) Hardware Device Key
3) Hardware Device Key
4) Hardware Device Key
5) Casa Recovery Key (held by Casa, for recoveries only)
For each transaction you send, you’ll need to approve it from any combination of 3 keys.
This provides significantly more security than a single signature keyset or even a 2 of 3 multisig keyset. You can even keep your hardware keys in different locations than your phone (such as a bank safety deposit box or office safe), which helps protect you against in-person attackers trying to steal your bitcoin.
Our more basic level memberships use a more basic 2 of 3 multisig solution. You can check out our membership options here.