The concept of multi-signature has gained some popularity; it involves multiple people (such as 3 to 5 people) approving transactions. Therefore, this limits the threat of theft, as a single controller or server cannot perform transactions (ie, send bitcoin to an address or withdraw bitcoin). The people who can transact are determined at the beginning of the transaction, and when one of them wants to spend or send bitcoins, they ask the others in the group to approve the transaction.
