The two gates — ASP + facilitator policy

TL;DR — a common reviewer question is "if there's a stealth address per call, why do we still need an ASP?" They solve opposite problems and sit at different lifecycle points (ASP at deposit time, stealth at payment time). zBase needs both.

Different parties, different problems

Layer	Protects against	Stops what
ASP (Gate 1, deposit-time)	The prosecutor asking "did you handle sanctioned funds?"	Sanctioned wallet deposits → privately withdraws → laundering. Without ASP, zBase becomes Tornado-Cash-shaped and gets sanctioned.
Facilitator policy (Gate 2, payment-time)	The operator's own bad behavior (or a compromised key)	Approved funds paid to bad destinations. "Approval ≠ unlimited spend."
Stealth address (per-call, settle-time)	The competitor / chain analyst watching the network	"Wallet X paid Nansen $0.50 every 60s — they're running an arbitrage bot using Nansen's premium feed." Provider correlation breaks the pattern.

The four-quadrant truth table

Two independent gates → four positions. Columns = ASP (off → on); rows = stealth address (off → on). Only zBase has both (bottom-right, green).

flowchart TB
    subgraph R1["No stealth address"]
        direction LR
        T["Blind mixer<br/>no ASP → sanctioned"]
        V["Compliance-only pool<br/>ASP only → leaks recipient"]
    end
    subgraph R2["With stealth address"]
        direction LR
        M["Stealth-only mix<br/>no ASP → laundering risk"]
        Z["zBase<br/>ASP + stealth → defensible"]
    end
    R1 ~~~ R2
    style T fill:#f6e6e6,stroke:#b06b6b,color:#18191b
    style V fill:#eef1f4,stroke:#9aa0a6,color:#18191b
    style M fill:#eef1f4,stroke:#9aa0a6,color:#18191b
    style Z fill:#e4f0e6,stroke:#4a7a52,color:#18191b

Why you can't merge them

ASP must operate at deposit time, not payment time. If you screened every payment against a sanctions list, you'd need to know who's paying — which destroys privacy. The ASP design trades a one-time deposit-time check (when the depositor is still publicly identifiable) for permanent payment-time anonymity.

Stealth address must operate at payment time, not deposit time. You don't know at deposit time which providers the operator will pay. The stealth address is derived per call from the provider's meta-address — it has nothing to do with who deposited.

The honest investor framing

"Stealth address defeats the attacker. ASP defeats the prosecutor. Privacy alone gets us delisted; compliance alone gets us out-competed."

This is also why zBase looks structurally different from both a blind mixer (no ASP) and a KYC-at-deposit pool (which links identity to funds instead of screening post-deposit). See the Trust Model for the full comparison.

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