Asymmetric cryptography generally takes more time and requires more computer power, therefore it is not used most of the time. Instead, it is often used for computer signatures, when a computer must know that some data (like a file or a website) was sent from a certain sender. For example, computer software companies that release updates for their software can sign those updates to prove that the update was made by them, so that hackers cannot make their own updates that would cause harm. Websites that use HTTPS use an popular algorithm named RSA to create certificates, that show they own the website and that it is secure. Computers can also use asymmetric ciphers to give each other the keys for symmetric ciphers.