# Private OTC Swaps: Illustrated Primer Published: 2026-06-25 ยท Post Fiat Research A click-through visual primer for the shielding, private swap, certification, private egress, redemption, and transparent control steps behind the Private OTC Swaps post. Canonical: https://postfiat.org/research/private-otc-swaps/primer/ Markdown source of the page above. Other formats and the research blog index: https://postfiat.org/blog/ --- This primer is the visual companion to [Private OTC Swaps](/research/private-otc-swaps/). It walks through the user-visible flow one step at a time: counted cash, shielded ingress, private swap, PFTL certification, private egress, public redemption, and the transparent control path.

Click through the swap

Seven panels, from counted cash to a private NAVCoin swap and back to a public exit.

Public accounting

Start with cash the chain can count.

The input is USDC, but Post Fiat does not treat every dollar-shaped token as the same asset. In the demo, USDC is bridged into PFTL as pfUSDC, a canonical stablecoin representation that can be counted by the NAV and settlement logic.

PublicSource, amount, bridge receipt.
Why it mattersThe NAV system sees reserve-quality cash, not a vague wallet balance.
USDCEthereum, Arbitrum, Base, or another source venue.
bridge attestation
pfUSDC on PFTLA chain-native receipt the swap circuit can consume.

Shielded ingress

Turn public pfUSDC into an Orchard note.

The wallet creates a private note commitment. The chain can verify that value entered the shielded pool, while the note opening and ownership stay wallet-side.

PublicA valid shielded action and commitment.
PrivateNote opening, owner keys, and wallet path.
pfUSDC balanceVisible before shielding.
commit
pfUSDC Orchard notePrivate spendable input for the swap.

Private exchange

Swap pfUSDC into a651 inside the circuit.

The Asset-Orchard proof consumes a pfUSDC note and emits an a651 note. It enforces the permitted asset exchange and conservation rules without publishing the user's note details.

InputPrivate pfUSDC note.
OutputPrivate a651 NAVCoin note.
pfUSDC noteSpent once; its nullifier prevents reuse.
zk proof
a651 noteNAVCoin output remains private until egress.

PFTL finality

Validators certify the batch.

PFTL validators verify the proof, execute the state transition, and sign a block certificate. In the latest shielded execution, the swap certified with five validator votes at height 437.

PublicBatch id, height, certificate, proof validity.
MeasuredProof creation 6.06s; transport/certification 4.90s after prewarm.
ProposerBuilds the shielded batch.
verify and vote
CertificateConsensus accepts the state transition.

Private egress

Exit the private note without revealing its opening.

When the user needs a public asset again, private egress proves the right to exit the a651 note and creates public exit fields. The egress is public; the internal note opening is not.

PublicExit artifact and verification result.
PrivateHow the wallet owned and routed the note.
a651 Orchard notePrivate asset ownership.
private egress proof
Public a651 exitVisible handoff for redemption.

Public exit

Redeem and withdraw on the visible rail.

After egress, the user is back in the public NAV and bridge-out world. The demo uses the public a651 exit to create the redemption path and settle the withdrawal.

PublicRedemption artifact, withdrawal, final balances.
BoundaryPrivacy protects the shielded path, not the final public claim.
Public a651Exit artifact from the shielded pool.
redeem and withdraw
USDC claimPublic settlement leg.

Transparent control

Run the same NAV mechanics without Orchard.

The transparent demo is the control path: a651 trustline, primary mint, NAV money-in, NAV exit, and summary, all on PFTL without shielded notes. It proves the accounting path works before privacy is layered on.

Useful forDebugging, audit traces, and repeatable operator demos.
Not privateIt intentionally exposes the state transitions.
Public pfUSDCTransparent input.
primary mint and NAV exit
Public summaryReceipts, timing, and balances are visible.
Return to [Private OTC Swaps](/research/private-otc-swaps/).