Wallet implementation
keychain.py contains an initial implementation of the key derivation scheme specified in [BIP-0032] (https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki). It is based on Elliptic Curve Cryptography implementation (ecc.py) from the course material of Programming Blockchain seminar given by Jimmy Song. The original Programming Blockchain(PB) codebase can be found in https://github.com/jimmysong/pb-exercises.