# How secure is 256 bit security?

In the previous cryptocurrency video I mentioned this situation twice In seek to break a security system You have to guess a 256 bit string The first time it was mentioned in the electronic signature segment The second time was mentioned in the section on password hash gatherings For instance, if you want to find a content Let its SHA2 56 hash cost equal to a certain 256 -bit cord Then there is nothing other good way, you can only guess randomly and check the result On average, this requires 2^ 256 struggles This quantity is much larger than what we often encounter So its hard to appreciate its scale But we might as well try 2^ 256 is 2^ 32 proliferated by itself 8 seasons The advantage of conceiving this course is that 2^ 32 is about 4 billion We can at least imagine this count Is the number that appears in the news headline So what we have to do Is to experience the concept of multiplying 4 billion 8 durations in a row Most people know The GPU in the computer can quickly perform a large number of parallel plannings So if you specific make the GPU calculate the password hash gathering frequently A GPU with good recital may be able to calculate close to 1 billion hashes per second If you take a bunch of such GPUs All into the computer Let your computer calculate 4 billion hashes per second So the initial 4 billion represents The number of hash evaluates calculated by each computer per second Imagine 4 billion computers full of GPUs like this For comparison, although Google has not announced the number of their servers But some reckons say there are various million In actuality, the computing influence of most of their servers Not as good as our computers full of GPUs But lets assume that Google ousts thousand of servers with such computers Then 4 billion computers are about 1,000 such a brutal Google Lets request this computing superpower “Thousand Googles” The natures person is approximately 7.3 billion Next we assume that more than half of people have their own thousand Google Then imagine 4 billion such planets For comparing, the Milky way has about 100 to 400 billion adepts Although we are not sure, the estimate is roughly in this range So this is equivalent to 1% of the stars in the Milky Way will have an Earth And half of the population on this planet has its own thousand Google Then imagine 4 billion such galaxies We call it “Billions of Galaxy Supercomputers” Can guess 2^ 160 durations per second 4 billion seconds is about 126.8 years 4 billion times it is 507 billion years Almost 37 periods persons under the age of the universe So even if you have Full of GPUs, thousands of Googles, planets, billions of galaxy computers Keep guessing the time of 37 periods the age of the universe There is only one in 4 billion probability to get the correct guess By the space, the current hash power of Bitcoin Add up all the miners Can predict and check 50 billion hashes per second This is equivalent to one-third of the thousand Googles I has already mentioned This is not because there are really billions of computers with full GPUs But because the miners use machines that are about 1,000 times better than GPUs Called “Application Specific Integrated Circuit”( ASIC) These hardware are tailor-made for Bitcoin mining Otherwise, it will calculate the SHA2 56 hash ethic I want to get greatly increase efficiency We can give up general computing needs And to design integrated circuits for a single enterprise There is another topic that I find a bit difficult to turn around: when it comes to the power of two The number of dues to this Youtube channel recently surpassed 2^ 18 In order to better interact with some of these 2^ 18 people I will start a question and answer affair I will post the Reddit link to the video introduction You can ask questions or put on the top of the question you want to know the answer Maybe in the next video or Twitter or something I announced today the form of answering questions see you then!