ZORB Cash vs. Umbra Privacy

Both ZORB Cash and Umbra Privacy are building financial privacy infrastructure on Solana. They share the same goal—making private transactions accessible—but take fundamentally different architectural approaches to get there.

This document breaks down the key differences to help you understand which protocol fits your needs.

The Core Difference

ZORB Cash generates all cryptographic proofs locally in your browser using Groth16 ZK-SNARKs. Your private keys and transaction data never leave your device. It's fully self-sovereign.

Umbra Privacy takes a different approach. It uses Arcium's Multi-Party Computation (MPC) network to handle encrypted operations. This enables features like Encrypted Token Accounts, but introduces dependency on an external network.

Neither approach is inherently "better"—they represent different tradeoffs between self-sovereignty, features, and composability.

How Each Protocol Works

ZORB Cash

ZORB Cash uses a pure UTXO shielded pool model. When you deposit tokens, they become encrypted "notes" stored in a Merkle tree with 67 million note capacity. To spend, your browser generates a zero-knowledge proof demonstrating ownership without revealing which notes are yours.

Key characteristics:

4-in-4-out circuit — each transaction can consume up to four input notes and create up to four outputs
Multi-token support — move SOL and USDC in a single proof
Client-side proving — 10-30 seconds depending on your device
On-chain footprint — only the final proof gets submitted

Umbra Privacy

Umbra Privacy implements a hybrid two-layer architecture that combines UTXOs with account-based privacy.

Layer 1: Unified Mixer Pool

Conceptually similar to ZORB Cash's shielded pool. It's an append-only Merkle tree (depth 20, roughly 1 million leaves per tree) where UTXO commitments live alongside a nullifier set preventing double-spends.

Layer 2: Encrypted Token Accounts (ETAs)

This is where Umbra diverges. ETAs are on-chain accounts with encrypted balances, using Rescue cipher optimized for MPC operations. Think of them as private bank accounts rather than discrete notes.

Users can move funds between layers based on their needs—UTXOs for maximum anonymity, ETAs for DeFi composability.

Proof Generation

This is the most significant architectural difference between the two protocols.

ZORB Cash: Fully Client-Side

ZORB Cash proofs are generated entirely in your browser. There's no external party involved in the cryptographic operations.

Your spending keys stay on your device
Your viewing keys stay on your device
Your transaction details stay on your device
Zero network dependencies

Umbra Privacy: MPC Network

Umbra Privacy relies on Arcium's Cerberus MPC network. The protocol uses what they call a "dishonest majority" security model—computation is distributed across MPC nodes rather than happening locally.

Enables ETA operations that require MPC
Depends on Arcium network availability
Requires trusting the MPC network to behave correctly

For users who prioritize complete self-sovereignty, this distinction matters. For users who prioritize features and are comfortable with MPC trust assumptions, it may not.

The Balance Model

Both protocols encrypt balances—your amounts are hidden from public view. The difference is how those balances are structured.

ZORB Cash: Encrypted Notes

All value is stored as encrypted notes in the shielded pool. Each note is a discrete encrypted value that gets combined or split during transactions. It's a pure UTXO model, conceptually similar to how Bitcoin works but with encryption.

Umbra Privacy: Notes + Accounts

Umbra offers two options:

Encrypted notes in their mixer pool (similar to ZORB Cash)
Encrypted Token Accounts that function like private bank accounts

The ETA model may offer advantages for DeFi integration since Solana's ecosystem is built around accounts rather than UTXOs. Key ETA features:

Aggregate multiple UTXOs into a single encrypted balance
Threshold decryption for DAOs and multisigs
Better integration with account-based DeFi protocols

Viewing Keys and Auditability

Both protocols support viewing keys that enable read-only access to your transaction history. This matters for compliance, tax reporting, and institutional adoption.

ZORB Cash: Simple and Effective

ZORB Cash implements a single incoming viewing key (ivk):

Share with auditors, accountants, or institutions
They see your full transaction history
They gain zero spending authority
One key to manage

Umbra Privacy: Granular Control

Umbra takes a more complex approach with two separate viewing systems.

For the Mixer Pool:

Master Viewing Key (MVK) with hierarchical derivation
Time-scoped Transaction Viewing Keys (yearly → monthly → daily → hourly)
One-way derivation — child keys can't derive parent keys

For ETAs:

On-chain viewing grants tied to specific nonces
Each grant works for one encrypted value only
Semi-revocable — delete unused grants before they're used

The tradeoff is complexity versus control. ZORB Cash is simpler. Umbra offers finer-grained permissions.

Yield on Private Funds

ZORB Cash lets you earn yield while maintaining privacy. Your shielded tokens automatically accumulate rewards based on how long you hold them.

How it works:

Each note tracks its creation time
Each note tracks its reward accumulator
Proportional yield distribution when you withdraw
Deposit 100 SOL → hold privately → withdraw 100 SOL + rewards

Umbra Privacy doesn't currently offer native yield on shielded funds. Tokens in the mixer pool or ETAs sit idle.

This is a significant differentiator for users who want privacy without opportunity cost.

Multi-Token Transactions

ZORB Cash's 4-in-4-out circuit supports multiple token types in a single transaction:

Spend SOL notes and USDC notes together
Create outputs in multiple tokens atomically
Single proof covers the entire operation

Umbra Privacy's documentation focuses on single-token operations. Whether they support multi-token atomicity isn't clear from their current materials.

Capital Efficiency and Relayers

Both protocols use tree-based storage to minimize on-chain footprint, and both support gasless transactions through relayer networks.

ZORB Cash:

Relayer submits transactions on your behalf
Fees deducted from your shielded balance
No need to fund addresses with SOL

Umbra Privacy:

Integrated relayer network
Automatic fee reimbursement from transferred funds
Single-click transfer experience

Key Architecture

The protocols structure their key hierarchies differently.

ZORB Cash: Single Seed Derivation

Everything derives from one seed phrase:

Spending key → spend authorization key + nullifier derivation key
From these → incoming viewing key
From viewing key → payment address

One backup. Simple recovery.

Umbra Privacy: Four Independent Keys

Can be generated randomly (no mathematical relationship) or derived from a master seed:

L1 Interaction Key — chain interaction and ETA ownership
X25519 Keypair — ETA visibility and MPC communication
Shielded Spending Key — ZK proofs for UTXO operations
Master Viewing Key — auditability without spending authority

Random generation offers stronger security (compromise of one key doesn't affect others) but requires managing four separate backups.

Current Status

ZORB Cash is live today. You can use it right now.

Umbra Privacy is launching alongside Arcium's mainnet. It's not yet operational.

Technical Specifications

Aspect	ZORB Cash	Umbra Privacy
Proof system	Groth16 (BN254)	Arcium Cerberus MPC
Proof generation	Client-side	MPC network
Hash function	Poseidon	Poseidon + Rescue
Account model	Pure UTXO	Hybrid UTXO + ETA
Merkle tree capacity	~67M notes	~1M per tree
Inputs/outputs per tx	4-in-4-out	Variable
Multi-token support	Yes	Unclear
Yield earning	Yes	No
Status	Live	Pre-launch

Which Should You Choose?

Choose ZORB Cash if you value:

Self-sovereignty — every proof generates locally with no external network dependencies
Yield — earn rewards on shielded funds without sacrificing privacy
Simplicity — a pure UTXO model that's battle-tested and operational today
Multi-token flexibility — move different assets atomically in single transactions

Choose Umbra Privacy if you value:

Account-based privacy — ETAs may integrate more naturally with Solana's DeFi ecosystem
Granular access control — time-scoped viewing keys and per-nonce grants
The Arcium ecosystem — if you're already building on Arcium infrastructure

Summary

ZORB Cash and Umbra Privacy represent two legitimate approaches to Solana privacy with different tradeoffs.

ZORB Cash prioritizes self-sovereignty and simplicity:

Client-side Groth16 proofs mean zero external dependencies
Pure UTXO model is proven and operational
Yield earning means privacy doesn't cost you DeFi opportunities
Live and usable today

Umbra Privacy prioritizes flexibility and composability:

Hybrid UTXO + ETA architecture may enable better DeFi integration
Granular viewing keys offer precise access control
MPC-based operations enable features that pure client-side proving can't easily support
Launching with Arcium mainnet

For users who want privacy today with yield earning and complete self-sovereignty, ZORB Cash is the clear choice.

vs. Umbra Privacy