"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 basic multisig setup is 2 of 3. This creates a 3-part bitcoin private key, with 2 parts required to spend funds. Basic multisig is included in all Gold memberships.
We recommend basic multisig for individuals holding small to medium amounts of BTC. For a full rundown of the product, read our blog post on Basic Mutisig 2-of-3's release.
With Basic Multisig, you’ll have three keys protecting your Bitcoin:
1) Mobile Key (held by you and secured by your phone’s secure enclave)
2) Hardware Device Key (held by you on either a Trezor or Ledger)
3) Casa Recovery Key (held by Casa, for recoveries only)
Note: You optionally replace the mobile key and use a second hardware device key instead.
For each transaction you send, you’ll need to approve it from your phone and your hardware key (or two hardware keys, depending on your setup).
This provides significantly more security than a single signature keyset. You can even keep your hardware key in a different location 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 higher level memberships use a more advanced 3 of 5 multisig solution. You can check out our membership options here.