When a hot stablecoin project like Rain bets on privacy, you know it’s a signal.
Rain processes more than $3 billion in annual payment volume across 150+ countries, and as a Visa Principal Member, it's not some fluffy crypto-native experiment. It’s already mainstream financial infrastructure.
Last week, Rain announced that it was teaming up with Payy Network, a zero-knowledge blockchain where transactions are private by default. The integration lets Rain clients choose Payy as a settlement layer when enhanced confidentiality is required, without changing anything about the cardholder experience. Privacy operates at the settlement layer. The card still works at any Visa terminal anywhere on earth.
This matters because it puts ZK-based privacy in contact with real commercial volume. Stablecoin payment volumes hit $33 trillion in 2025 according to Artemis Analytics — and as that number grows, so does the business case for keeping transaction details out of public view. Rain recently raised $250 million at a $1.95 billion valuation, signaling that investors see stablecoin card infrastructure as a serious long-term bet. Payy's integration puts privacy at the heart of that bet.
The architecture here is worth noting: configurable confidentiality, selective disclosure, full regulatory auditability. Sound familiar? This is the direction the whole industry is heading, led by one of its most credible stablecoin card issuers.
Privacy Roundup
Miden launched Guardian, an institutional backend offering account backup and compliance enforcement without taking custody of private keys.
Optimism unveiled PrivacyBoost, a confidential computing module built by Sunnyside Labs for OP Stack chains — combining zero-knowledge proofs and TEEs with selective disclosure via viewing keys for regulators.
Payy Network partnered with Rain to offer onchain privacy as a settlement option for enterprise card programs while preserving regulatory auditability.
Starknet v0.14.2 went live on mainnet, activating the STRK20 framework that allows any ERC-20 token to operate with encrypted balances and private transfers.
Paul Brody on Privacy Podcast
This week's episode of Privacy Podcast features Paul Brody, formerly Ernst & Young's global head of blockchain — and now founder of Nightfall Networks, a company built around the privacy technology he developed inside one of the world's largest professional services firms.
The full conversation is out now. In different ways Paul Brody and Rain/Payy are evidence of how central privacy is to the future of decentralized networks. It’s the thing institutions need before they can fully commit to onchain finance.
That, of course, is exactly what we're building at Miden.
Latest on Miden
Last week, we introduced Guardian, an infrastructure layer that makes privacy-first finance usable in the real world. It resolves the central tension of private blockchains: once you remove surveillance, you also remove the readable public ledger that everyone was coordinating through. Guardian is what replaces that coordination surface in private blockchains.
For users, that means genuine financial privacy alongside the safety net of institutional recovery and fraud protection.
For institutions, it opens a new service category; one that delivers trust without absorbing liability.
For regulators, it offers verifiable compliance without invasive surveillance.
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Till next time.