Signing transactions

In this video, Andreas Antonopoulos helps us understand the concepts of public addresses and private keys by using an analogy involving public lockboxes.

Creator	Time	URL
3Blue1Brown	4min	Full source

Takeaway Private keys are inexpressibly secure from brute force attacks, and they are used to proof ownership of public addresses by signing a transaction. This is done in a way that does not require revealing the private key itself.