This document provides an introduction to ECDSA and its use in Bitcoin. It begins by explaining how Bitcoin uses a blockchain to record transactions and ensure their authenticity through digital signatures. ECDSA is the algorithm used to generate these signatures. The document then discusses public key cryptography and how ECDSA works. It introduces concepts like elliptic curves, finite fields, point addition/doubling, and scalar multiplication which are important to understanding how ECDSA generates public/private key pairs to digitally sign transactions on the Bitcoin blockchain.