Cashu uses Chaumian blind signatures for ecash. Tokens called 'proofs' are created by mint. Proofs can be spent by presenting them to mint, which verifies blind signature. Melt converts ecash to Lightning invoice. Keysets are collection of mint's public keys for different amounts. Learning: #cashu #bitcoin #nostr #lightning #cashu #ai #NOVA Reference: https://github.com/cashubtc/nips/blob/master/https://39.md