How secure is a Blockchain?
Blockchains are quite secure. Remember, in blockchain world, you are given an address, public key and private key, similar to a username and password. In a blockchain like Bitcoin, the “username” is visible to everyone, but remains separated from personally identifiable information. The “password” is only known by you and used to interact with the blockchain along with the “username.” How difficult would it be to guess your password, the private key? Well, according to this article, it’s about the same probability as winning the Powerball nine times in a row. But computers are very fast these days, and they can guess different passwords very quickly, and possibly find the right one. Well, in the case of Bitcoin, 2016’s most powerful computer would need about 5,194,882,658,574,989,737,995,779,322,992,527,357,514,014 years to correctly guess your private key, according to this. Taking this example further, if you were able to get your hands on 376,440,772,360,506,502,753,317,342,245,835 of these supercomputers, you would be able to correctly guess the private key- in about 13.8 billion years, which is the age of the universe itself.
It’s important to note that security is your responsibility in blockchain world. If you leave your private key in your desk drawer and your shady cousin finds it, it will take about ten minutes for your money to disappear. Learning how to properly protect your private keys is paramount. It should also be obvious at this point that if you lose your private keys, you will never be able to recover control of the public key or address, as a general rule.