The research encompassed Hash Time Locked Contracts (HTLC), Chaumian eCash, and Hawala systems, with valuable insights drawn from an eCash without custodial risk documentation by @moonsettler and a tweet thread by @ZmnSCPxj.

A solution was devised where a user named Alice mints eCash tokens and establishes HTLCs with multiple redeemers. Unique segments of a preimage secret are shared with each redeemer. Alice then funds the HTLC address with bitcoin and uses the eCash to pay another user, Eve, providing her with sha256 hashes and a segment of the preimage secret for validation. Eve verifies the eCash has not expired and can re-issue it by creating a new HTLC and following similar steps with different redeemers.

The process includes Bob spending the HTLC created by Alice, generating transactions with outputs for transaction fees and further HTLC creation. A failure to coordinate and complete the preimage by the redeemers leads to invalidation of the eCash, with the locked bitcoin returned after 2016 blocks.

This protocol, which incorporates Python code snippets for implementing the transactions, aims to provide a decentralized and non-custodial method of using eCash. However, it acknowledges potential tradeoffs and the scope for further improvements. The conclusion also suggests that participants in the minting and redeeming processes maintain anonymity and invites commentary for refinements or identification of any inaccuracies in the solution.