Multi-sig is an important step towards making Bitcoin both convenient and secure to use. Before multi-sig, Bitcoins were stored in a “hot” wallet for ease of use, and “cold” storage for security. A hot wallet is one where the private keys are stored on a computer connected to the Internet. This makes it easy to use your Bitcoins. However, as we all know, computers connected to the Internet can and are hacked. Many businesses, exchanges, and people have lost their Bitcoins due to being hacked.
Cold storage is where the private keys are not stored on anything not connected to the Internet. It could be an offline computer or printed on a piece of paper. Since the private keys do not exist on the Internet, it is impossible for hackers to get to them. While cold storage is secure, it’s extremely inconvenient to use. In order to spend them, these coins must first be transferred to a hot wallet. Also, you must maintain physical security of the device storing the private keys. That’s difficult to do over a number of years for a typical user. Hard drives crash and paper can be lost, stolen, or destroyed. Private keys are usually also encrypted with a password and can be easily forgotten especially if they haven’t be used in several years. People have also lost their Bitcoins due to forgotten passwords and lost keys.
Multi-sig addresses are a solution to this problem. A multi-sig address is a Bitcoin address that requires 2 or more signatures to initiate a transaction. A typical setup is a 2 of 3 address. To initiate any transaction, 2 out of the 3 private keys must be used. One key is stored with a 3rd party service provider. Another key is stored on the user’s computer. The third is kept in cold storage, as described above. The 3rd party does not control the Bitcoins because they only have 1 out of the 3 keys. But they can provide services such as fraud protection and enabling the user to recover their Bitcoins if they lose 1 of their 2 keys using their key. In normal day to day use, the user spends their Bitcoins like any normal address. The 3rd party signs every transaction they see by the user. However, if a suspicious transaction occurs, the 3rd party can stop the transaction by not signing it. They can then contact the user for further verification. Also, if the user loses his key or his computer is hacked, he has a backup key. If the 3rd party is compromised, the user still has 2 of the 3 keys to get to his Bitcoins. This makes Bitcoin far more convenient and easy to use while maintaining security, and not requiring to trust a 3rd party to secure your Bitcoins.
There are 2 multi-sig wallet providers online
GreenAddress.it and
Bitgo.com. I’m going to give both of them a try. Multi-sig addresses are far superior than the normal Bitcoin addresses. I believe they will become the standard way of using Bitcoins in the future.