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In plain English: TCAP (Transfer Confidential Asset Protocol) is the private balance layer. It advances commitment-backed tips per TIN, anchors encrypted balance snapshots off-chain, and gates confidential debit and exit behind a proof verifier. Balances are never public; the chain only stores opaque commitments and sequence values.

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What TCAP owns

  • Global config and per-asset governed reserves and vaults.
  • The TIN-TIP tip commitment root and monotonic sequence.
  • The nullifier registry.
  • The liability account per governed asset.
  • The credit, debit, and exit statements (only credit is enabled today).

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Credit

Status: Live on Devnet.
The credit instruction advances the tip commitment from previous_commitment to new_commitment under a GPRU-scoped authorization. It carries:
  • authorization_digest
  • validity window
  • previous_commitment, new_commitment
  • sequence, token_id
  • policy_commitment, gpru_scope_commitment
  • one-time nullifier
No per-transfer PDA. No intent, epoch, receipt, or nullifier account. The credit is authorized by a PDA-signed CPI from the approved TSN program.

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Debit

Status: In development. Not enabled on Devnet.The debit instruction validates structural fields and returns ProofSystemNotEnabled. A GPRU signature, hash-only payload, or placeholder proof cannot mutate a tip.
The debit statement, when enabled, must prove for a private witness (old_balance, debit_amount, new_balance):
The proof must:
  • open the predecessor commitment
  • bind the successor to new_balance, the predecessor, and sequence + 1
  • prove a one-time nullifier
  • satisfy the policy commitment, registered rate version, expiry window, and layer-zero conditions
Enabling debit requires an audited proof verifier, registered rate/version rules, commitment opening and successor checks, nullifier consumption, and protocol liquidity invariants. None of these are turned on today.

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Exit

Status: In development. Not enabled on Devnet.The exit instruction validates structural fields and returns ProofSystemNotEnabled.
Exit uses the same conservation equations as debit, plus a destination binding and pool invariants:
The liquidity pool is protocol and governance controlled. It is not cranker custody. The skeleton account is intentionally not mutated by the disabled instruction.

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Deposit

Status: Live on Devnet.
Two deposit paths exist:
  • Direct deposit. Public deposit into a governed reserve vault; increases reserve balance directly.
  • Deposit with funding commitment. Binds a FundingClaim and FundingRoot, producing a funding_commitment used later by confidential settlement.

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Asset governance

Status: Live on Devnet.
TCAP governance instructions manage which SPL mints are approved and what they can do:
  • Register a governed asset
  • Approve or revoke an asset
  • Set settlement policy (settlements, public exit, confidential settlement)
  • Set operational status (pause or resume)
  • Initialize the governed reserve and vault
  • Sync asset infrastructure
  • Toggle deposit policy
  • Raise the minimum instruction version

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Encrypted snapshots

Private balance state lives off-chain in encrypted snapshots. The owner device verifies the tip commitment and sequence, then decrypts a single commitment-keyed snapshot. Plaintext balances never leave the owner.

TSN

Settlement coordination and epoch treasury.

TIN

Payment identity and route discovery.

GPRU

Non-custodial authorization and routing.

Architecture

End-to-end sequence diagram.