How Blockchain Wallet Developers Are Adopting Async Payjoin to Transform Bitcoin Privacy

Bitcoin’s privacy challenge has found an unexpected answer: Async Payjoin, an open-source toolkit that treats privacy like HTTPS treats web security. Just as Let’s Encrypt revolutionized the web in the 2010s by making encryption accessible to everyone, the Payjoin Foundation is quietly democratizing privacy across the blockchain wallet ecosystem. Unlike specialized privacy-focused wallets, Async Payjoin functions as a universal library that any blockchain wallet application can integrate, creating a privacy standard that strengthens the entire network rather than protecting isolated users.

The elegance of this approach mirrors HTTPS’s success: instead of requiring users to choose between privacy and convenience, Async Payjoin embeds privacy into the infrastructure itself. Built on cryptographic primitives already embedded in Bitcoin core and designed specifically for mass adoption, this technology addresses the fundamental vulnerability affecting blockchain users—the ability to track money flows with forensic precision.

The Core Mechanism: Defeating UTXO Heuristics and Blockchain Surveillance

The privacy problem Async Payjoin solves is deceptively simple yet profoundly important. When blockchain users receive payments, they often control multiple UTXOs—think of them as separate coin pockets, each containing different amounts. When a transaction requires funds from multiple pockets, it links them together on the public ledger, allowing blockchain surveillance companies to assume these UTXOs belong to the same entity.

Chain Analysis and similar firms exploit this assumption ruthlessly. By monitoring wallet histories, they can see exactly who you’ve transferred money to in the past and future, your total holdings, and even your income patterns. This surveillance becomes a tool for both corporate tracking and government oversight.

Async Payjoin dissolves this vulnerability through a deceptively elegant coordination mechanism. The receiver actively participates in transaction creation alongside the sender. Instead of a typical single-input, two-output transaction, Payjoin produces transactions with two inputs and two outputs—with one input originating from the receiver. Both parties coordinate on amounts, co-create the transaction atomically, and maintain full control. The result: what appears to blockchain analysis as a standard transaction now becomes indistinguishable from countless other multi-input transactions.

The power emerges at scale. As more blockchain wallet implementations adopt Payjoin, the single-input heuristic—the foundational assumption of on-chain surveillance—crumbles. The more Payjoin transactions that exist in the network, the less reliable blockchain surveillance becomes for everyone. This is collective privacy: individual adoption strengthens universal protection.

Critically, this mechanism remains completely non-custodial and atomic. Both parties retain control over their amounts. If either party disagrees with the transaction, it simply doesn’t execute. And unlike privacy coins like Zcash or Monero—which encrypt transfer amounts to achieve privacy but create complications for supply validation and introduce theoretical inflation risks—Payjoin preserves Bitcoin’s transparency and scarcity while enhancing fungibility.

Wallet Ecosystem Response: Current Adoption and Integration Strategies

The blockchain wallet ecosystem has begun integrating Payjoin V1 and V2 standards at an accelerating pace. Present implementations span the full wallet spectrum:

Payjoin V1 Support (requiring simultaneous user participation):

• BTCPay Server
• Blue Wallet
• Wasabi Wallet
• Bitmask
• JoinMarket
• Sparrow Wallet

Payjoin V2 Support (Async Payjoin for asynchronous coordination):

• Bull Bitcoin Mobile
• Cake Wallet

The Foundation’s critical design choice ensures backward compatibility—users with non-Payjoin wallets can still send payments to Payjoin addresses and QR codes without experiencing friction. This reduces adoption barriers significantly, allowing the blockchain wallet ecosystem to migrate to stronger privacy gradually rather than requiring simultaneous upgrades.

For blockchain wallet developers, integration has been simplified through open-source tooling. Technical specifications exist in BIP 77, while a plug-and-play developer kit is available on GitHub. The Foundation explicitly modeled this on Let’s Encrypt’s strategy: free, open-source software tooling that removes economic barriers to implementation. Similar to how Lightning dev kits achieved popularity among wallet developers, Async Payjoin’s accessibility invites ecosystem-wide adoption.

Payjoin Foundation: Building Privacy as Open Infrastructure

Founded in August 2025, the Payjoin Foundation operates as a nonprofit precisely because Bitcoin privacy cannot sustain a for-profit model. Foundation Executive Director Dan Gould articulated this clearly: “Bitcoin privacy—for-profits have basically been killed.” The distinction matters profoundly.

For-profit companies monetize privacy tools by selling solutions, but profit incentives create misalignment. If a company profits from each sale, they lack motivation to guarantee actual privacy—they’ve earned their revenue regardless. Phil Zimmerman discovered this when founding Pretty Good Privacy (PGP) as a company; the internet ultimately adopted privacy through nonprofit efforts like Tor, not commercial ventures.

The Payjoin Foundation brings together developers who’ve shaped Bitcoin privacy for decades. Dan Gould pioneered privacy tools during the TumbleBit era, forked Wasabi for mobile deployment, and co-authored BIP 77. Yuval Kogman serves as advisory board member and Spiral Bitcoin Wizard, bringing two decades of programming expertise. Kogman developed WabiSabi DoS protections and identified vulnerabilities across multiple CoinJoin implementations. Armin Sabouri joined as R&D lead, having served as CTO at Botanix and engineer at Casa—the latter co-winning the 2021 MIT Bitcoin Hackathon by implementing BIP 78 CoinJoin functionality on Mac OS via Tor—and co-authored BIP 347 (OP_CAT).

Funding arrives from OpenSats and Cake Wallet, with additional support from Spiral, Human Rights Foundation, Maelstrom, and Btrust. GitHub records 37 contributors to the Rust implementation of Async Payjoin alone. The Foundation has applied for 501©(3) nonprofit status, pending approval, and continuously fundraises. Gould emphasized that “none of this work is possible without the funders,” indicating ongoing resource needs to sustain privacy development as an open infrastructure commons.

The Async Layer: Network Privacy Through Oblivious HTTP

Payjoin V1 required both sender and receiver to remain online simultaneously—a significant practical constraint. Async Payjoin (Payjoin V2) solved this through a blinded directory server architecture using Oblivious HTTP (OHTTP).

The innovation centers on network privacy. The directory server itself never sees user IP addresses or transaction details. All communication routes through OHTTP, which forces proxy encryption—essentially mandatory obfuscation. The payload (pre-signed transaction) remains end-to-end encrypted between sender and receiver. From the directory server’s perspective, it receives only an 8-kilobyte uniform encrypted blob, revealing nothing.

Gould compared this to Tor but noted crucial differences: “OHTTP is the minimal viable product of Tor. Tor layers encryption and does multiple hops; this is the most minimal version—one hop, one layer of encryption.” Yet OHTTP carries significant weight: it’s an Internet Engineering Task Force (IETF) web standard that’s undergone rigorous review, embedded in iOS, and used across browsers. This standardization enables wider adoption compared to purpose-built privacy protocols.

The directory servers themselves offer no financial reward to operators—similar to Tor exit nodes, which volunteers have sustained for decades. This volunteer infrastructure model proves sustainability for privacy networks, removing the necessity for either commercial subsidies or protocol-level incentives.

Privacy-by-Default vs. Compliance: Reconciling Perceived Tensions

Regulators and blockchain wallet exchange operators frequently voice concerns that privacy technologies conflict with compliance requirements. Gould directly contradicted this assumption: “A compliance regime is totally independent from the nature of the chain.”

The misunderstanding runs deep. Regulatory compliance doesn’t require total wallet transparency. Exchanges can enforce Know Your Customer (KYC) procedures, collect identifying information, verify sources of funds—all without blockchain-level surveillance. Payjoin privacy doesn’t prevent these practices; it simply removes the advantage of unrestricted wallet tracking.

As Gould explained: “Having privacy by default doesn’t stop them from asking for identifying information in order to do business. It just doesn’t give them complete insight into your whole wallet, past, present, and future. It puts the power to consent to reveal the information about your money in your own hands.”

This distinction proves critical for Bitcoin’s long-term viability. Fungibility—the principle that all coins are equally valued regardless of history—requires privacy protection. Coins tainted by previous transactions shouldn’t lose purchasing power; privacy ensures this fundamental property of sound money.

Why Open Standards Matter for Blockchain Wallet Evolution

The Payjoin Foundation’s core insight remains this: privacy cannot succeed as boutique software. When privacy lives only in specialized blockchain wallets used by privacy enthusiasts, it signals suspicion and becomes easier to regulate or stigmatize. When privacy becomes the default infrastructure layer embedded in mainstream blockchain wallets—just as HTTPS became the default for the web—it transforms from niche to essential.

Developers interested in strengthening their blockchain wallet implementations should review BIP 77 specifications and evaluate the developer kit on GitHub. The Foundation’s vision extends beyond technology: they’re building an ecosystem where privacy emerges not from paranoid isolation but from technological default. That transformation begins with widespread blockchain wallet adoption.