Invoice-based payments is a protocol for communication between a payment host (usually either a merchant, a payment processor, or simply the recipient’s wallet) and their customer (the sender of the funds).
The SPV Envelope is a data structure that encapsulates a transaction along with Merkle Proofs and full transactions of confirmed ancestors.
The Merkle proof is fundamental to the Simplified Payment Verification (SPV) model that underpins bitcoin scaling.
Paymail standardises a communication protocol that offers global user-memorable handles backed by service discovery, feature negotiation, and an extension mechanism for communication between Bitcoin wallets and applications.
The Envelope Specification scope is to provide a common system for identifying the protocol used to encode data, encrypting and decrypting that data, and identifying MetaNet hierarchy and ownership of the data in an unspendable output script.