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Digital encryption

There are two main types of encryption. Symmetric encryption requires a sender and a receiver to have identical digital keys to encrypt and decrypt data, whereas asymmetric—or public-key—encryption uses a publicly available key to let people encrypt messages for a recipient who is the sole holder of the private key needed to unscramble them.

Sometimes these two approaches are used together. In the case of HTTPS, for instance, web browsers use public-key cryptography to check websites’ validity and then establish a symmetric key to encrypt communications.

The goal is to stop hackers from using massive amounts of computing power to try to guess the keys being used. To do this, popular cryptography methods, including one known as RSA and another called elliptical curve cryptography, typically use so-called trapdoor functions—mathematical constructs that are relatively easy to compute in one direction to create keys, but are very hard for an adversary to reverse-engineer.

Source : technologyreview