# Security

> How Senddy keeps your funds and data safe.

Source: https://www.senddy.com/docs/security
Last modified: 2026-08-01T23:49:54.000Z

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## Architecture

Senddy is designed as a non-custodial system. Your funds are held in audited smart contracts — not in a company bank account. No one at Senddy can move, freeze, or access your money.

### Smart contract security

- **Audited** by independent security researchers
- **Upgradeable and access-controlled** — admin functions are restricted to the contract owner (production deployments should use a timelock or multisig; that delay is an ops control, not currently enforced inside the pool itself)
- **Open source** — all contract code is publicly verifiable
- **On-chain Merkle tip checks** — spends must cite a root the pool already knows (`isKnownRoot`), so a poisoned off-chain tree alone cannot invent a payable note

### Zero-knowledge proofs

- Proofs are generated on your device — no server ever sees your transaction details
- The proving system (UltraHonk) is based on well-studied cryptographic primitives and uses a **universal trusted setup**
- Circuits are written in Noir and have been reviewed for correctness

### Attestor security

- Runs in a **hardware-isolated trusted execution environment (TEE)** — isolated from the host, no persistent storage, no shell access
- Signing key managed by a **hardware security module (HSM)** with an enclave-restricted key policy
- The attestor can only verify proofs — it cannot access funds or user data
- Enclave measurements are publicly verifiable

### Key management

- Your **spend key** is derived from an EIP-712 signature and never leaves your device
- Your **view key** allows read access but cannot spend funds
- No seed phrases — keys are deterministically derived from your wallet signature

## What data does Senddy collect?

| Data | Stored? | Details |
|---|---|---|
| Email address | Optional | Only if you sign in with email |
| Username | Yes | Public, chosen by you |
| Transaction history | No | Encrypted on-chain, only you can decrypt |
| Balance | No | Computed client-side from encrypted notes |
| IP address | Temporarily | Standard server logs, not linked to activity |
| On-chain activity | No | ZK proofs ensure transaction details are hidden |

## What risks exist?

### Smart contract risk

If a critical vulnerability is found in the pool contract, funds could potentially be at risk. This risk is mitigated by audits, bug bounties, and the upgrade mechanism.

### Attestor compromise

If the **attestor signing key or enclave** is compromised, invalid proofs could be attested and funds remain at risk. The pool still enforces nullifier uniqueness, share accounting, and `isKnownRoot` against tips advanced in prior leaf-producing transactions — which stops a *gateway-only* tree poison from creating a newly known fake root, but does **not** fully protect against a compromised attestor.

### Regulatory risk

Privacy-preserving financial technology operates in an evolving regulatory landscape. Senddy takes a proactive, layered approach to compliance:

- **Deposit screening** — All deposits are checked against the [Chainalysis sanctions oracle](https://go.chainalysis.com/chainalysis-oracle-docs.html), blocking OFAC-sanctioned addresses at the contract level
- **Association proofs** — Users can voluntarily prove their funds trace back to approved deposit sources using zero-knowledge proofs, without revealing transaction details
- **View key sharing** — Users can grant read-only access to auditors without giving up control of funds

See [Compliance](/docs/technical/compliance) for full details.

## Bug bounty

We maintain a bug bounty program for responsible disclosure of security vulnerabilities. If you discover a security issue, please contact:

**security@senddy.com**

We take all reports seriously and will work with you to resolve issues promptly.