“The problem is if they see the token when they sign it, then they will know who they signed it for and can know who made a payment when someone else comes to them to redeem it. To address this, a second random value, a blinding factor, is generated by the user before having the mint notarize a token. The binding factor is essentially multiplying the token value by the blinding value.”
quotingCASHU: A VISION FOR A BITCOIN POWERED ECASH ECOSYSTEM – BITCOIN MAGAZINE
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A look at the long term vision for an ecosystem of Cashu powered ecash mints, and how this can evolve to meet end users' needs balanced with security and functionality.
https://bitcoinmagazine.com/technical/cashu-a-vision-for-a-bitcoin-powered-ecash-ecosystem