Privacy (FHE) Instructions

Veil’s privacy layer uses Fully Homomorphic Encryption (FHE) via Encrypt . Privacy is opt-in per position. The plaintext UserPosition is never removed — it remains the authoritative source for health factor enforcement.

Implementation status: The Encrypt SDK (encrypt-pinocchio) currently targets pinocchio 0.10.x. Veil’s program uses 0.11.x. All five private instructions are fully implemented and routed. The FHE graph execution CPI (execute_graph) is stubbed and will activate when the SDK ships the version update.

Encrypt program ID (devnet): 4ebfzWdKnrnGseuQpezXdG8yCdHqwQ1SSBHD3bWArND8

EncryptedPosition Account

Discriminator: VEILENC! · Size: 144 bytes

Offset	Size	Field	Description
0	8	`discriminator`	`VEILENC!`
8	32	`owner`	User wallet
40	32	`pool`	Associated lending pool
72	32	`enc_deposit`	Pubkey of the EUint64 ciphertext for deposit balance
104	32	`enc_debt`	Pubkey of the EUint64 ciphertext for debt balance
136	1	`bump`	PDA bump
137	7	`_pad`	—

PDA: seeds ["enc_pos", user, pool]

The ciphertext account pubkeys are opaque 32-byte handles. To any RPC observer the position reveals nothing about the amounts. Only the position owner (with their FHE secret key) can decrypt.

EnablePrivacy

Discriminator: 0x08 (8)

Create an EncryptedPosition for an existing UserPosition. Initialises two ciphertext accounts (enc_deposit, enc_debt) seeded with the current plaintext values.

Accounts

#	Name	Flags	Description
0	`user`	signer, writable	—
1	`user_position`	readonly	Must already exist
2	`encrypted_position`	writable	New PDA — seeds: `["enc_pos", user, pool]`
3	`enc_deposit_ct`	writable	New EUint64 ciphertext account (Encrypt program)
4	`enc_debt_ct`	writable	New EUint64 ciphertext account (Encrypt program)
5	`pool`	readonly	—
6	`encrypt_program`	readonly	Encrypt program

Instruction Data

Offset	Size	Field
0	1	discriminator `0x08`
1	1	`enc_position_bump`

PrivateDeposit

Discriminator: 0x09 (9)

Identical to Deposit plus an FHE add_deposit computation on enc_deposit.

Accounts

#	Name	Flags	Description
0	`user`	signer, writable	—
1	`user_token`	writable	Source token account
2	`vault`	writable	Pool vault
3	`pool`	writable	—
4	`user_position`	writable	Plaintext position (updated)
5	`encrypted_position`	writable	—
6	`enc_deposit_ct`	writable	EUint64 deposit ciphertext (updated)
7	`amount_ct`	writable	Fresh EUint64 holding the plaintext amount
8	`system_program`	readonly	—
9	`token_program`	readonly	—
10	`encrypt_program`	readonly	—

Instruction Data

Offset	Size	Field
0	1	discriminator `0x09`
1	8	`amount` (u64 LE)
9	1	`position_bump`

PrivateBorrow

Discriminator: 0x0A (10)

Borrow tokens (same checks as Borrow) plus FHE add_debt on enc_debt.

Instruction Data

Offset	Size	Field
0	1	discriminator `0x0A`
1	8	`amount` (u64 LE)

PrivateRepay

Discriminator: 0x0B (11)

Repay debt (same as Repay) plus FHE sub_debt on enc_debt.

Instruction Data

Offset	Size	Field
0	1	discriminator `0x0B`
1	8	`amount` (u64 LE)

PrivateWithdraw

Discriminator: 0x0C (12)

Withdraw deposit (same as Withdraw) plus FHE sub_deposit on enc_deposit.

Instruction Data

Offset	Size	Field
0	1	discriminator `0x0C`
1	8	`shares` (u64 LE)

Privacy Model


┌──────────────────────────────────────────────────────────┐
│                  What is on-chain                        │
│                                                          │
│  UserPosition.deposit_shares  ← plaintext (authoritative)│
│  UserPosition.borrow_principal← plaintext (authoritative)│
│                                                          │
│  EncryptedPosition.enc_deposit ← opaque 32-byte pubkey  │
│  EncryptedPosition.enc_debt    ← opaque 32-byte pubkey  │
│                                                          │
│  ciphertext account (Encrypt)  ← FHE-encrypted amount   │
└──────────────────────────────────────────────────────────┘

Health factor checks always use the plaintext UserPosition. The encrypted ciphertexts provide observer confidentiality — an RPC caller cannot infer position size from on-chain data. The protocol itself never operates on encrypted values for solvency decisions.