What is Cryptography?

Bitcoin is called a cryptocurrency because of its heavy use of cryptography. Here we'll take a quick look at symmetric and asymmetric encryption, as well as the two cryptographic functions that Bitcoin uses: digital signatures and hashing.

Cryptography

Cryptography is a branch of math that is used to secure communications, to hide them from adversaries. The word "cryptography", or "crypto" is a Greek word that literally means "hidden", or "secret". And we are very used to thinking of cryptography as a tool for securing private data. Cryptography is what is used to create that green lock that you see in your browser when visiting a website with sensitive data. It's what is used to hide your credit card number when you are shopping online. But the branch of math that is cryptography includes a wide variety of functions that serve many purposes besides just the hiding of data. In fact, Bitcoin doesn't encrypt any data at all. All of the data on the network is public. However, Bitcoin makes heavy use of other cryptographic functions. 

Let's take a quick look at some of those functions. We'll start with symmetric cryptography, then asymmetric, or public and private key cryptography, and then introduce two cryptographic functions that are used heavily in Bitcoin, hashing and digital signatures.

Source: Saylor Academy
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