BIP32
Bitcoin Improvement Proposal (BIP) 32 introduced HD (Hierarchical Deterministic) wallets into the Bitcoin Protocol to tolerate parent private key leakages.
Bitcoin Improvement Proposal (BIP) 32 standard proposed critical changes and features implemented across different Bitcoin software implementations. BIP32 added various test vectors and private derivation to decrease the risk of key leakages and devised Hierarchical Deterministic (HD) wallet specifications to make wallets backup fast and secure.