Ethereum in SSP

Ethereum is the second-largest blockchain by value and the home of most of crypto's smart-contract activity — tokens, DeFi, NFTs, and the account-abstraction tooling that SSP itself builds on. If you already keep Bitcoin in SSP, holding ETH feels familiar on the surface: two keys, one in your browser extension and one on your phone, co-signing every move. Underneath, though, Ethereum works on a different model, and a good ethereum self-custody setup means understanding what changes.

This article is the foundation of SSP's EVM series. It explains what Ethereum is for someone holding their own keys, how SSP turns ETH into a true 2-of-2 multisig, and how the account model differs from Bitcoin's. By the end you'll know what's the same, what's new, and where to read next.

What Ethereum is in a self-custody context

At its core, Ethereum is a global, programmable ledger. Where Bitcoin is built primarily to move value, Ethereum is built to run code: small programs called smart contracts that live at on-chain addresses and execute exactly as written. ETH, the native coin, pays for that computation.

For a self-custody user, the headline is that you are the only party who can authorize a transaction. No exchange, no custodian, no support desk can move your ETH or freeze it. That power comes with responsibility — losing your keys means losing access — which is exactly the problem multisig is designed to soften. If you're new to the basics of holding your own keys, setting up your first SSP wallet is the place to start. For the deeper "what is Ethereum" picture, the Ethereum Foundation's own overview is the canonical primary source.

How SSP holds ETH: an ethereum multisig wallet via ERC-4337

SSP's defining feature is 2-of-2 multisig. Key 1 lives in the SSP Wallet browser extension; key 2 lives in the SSP Key mobile app. Every transaction is built and signed in the extension, then sent to your phone for a co-signing approval. Neither device alone can move funds — that's the whole point. If this model is new to you, read what is 2-of-2 multisig first.

On Bitcoin and the other UTXO chains, SSP achieves this with native BIP-48 multisig: the two public keys form a script, and a valid spend needs both signatures. Ethereum has no native multisig of that kind. Instead, SSP implements the same 2-of-2 guarantee as an ethereum multisig wallet built on ERC-4337 account abstraction.

Here's the idea. Your ETH lives in a smart-contract account rather than a plain key-controlled address. That contract is programmed to accept a transaction only when it sees one combined Schnorr signature produced from both of your keys. Behind the scenes the two devices run a MuSig2-style protocol so their separate signatures aggregate into a single on-chain signature — the chain sees one clean signature, but it could only have been created with both keys present. The smart contracts that make this work were audited by Halborn in 2025. To go deeper on the mechanism, see EVM multisig: the account-abstraction way and the broader explainer on account abstraction (ERC-4337).

The practical upshot: you get the same two-device security on Ethereum that you have on Bitcoin, with an on-chain footprint and a user experience that stay clean.

The account model vs UTXO: balances and nonce, not coins

The biggest conceptual shift from Bitcoin is how the ledger tracks your money.

Bitcoin uses the UTXO model. Your wallet doesn't hold a single balance; it holds a collection of discrete "coins" (unspent transaction outputs). Spending means consuming whole coins and creating new ones, much like paying with cash and getting change. SSP's Bitcoin in SSP guide walks through that in detail.

Ethereum uses the account model instead. Your account simply has a balance number that goes up and down, like a bank-style ledger entry. There are no coins to select and no change to manage. Each account also carries a nonce — a counter that increments with every transaction you send. The nonce guarantees ordering and stops the same transaction from being replayed. You rarely think about it directly, but it's why transactions from one account must confirm in sequence.

For day-to-day use the difference is mostly invisible: SSP handles coin selection on Bitcoin and nonce management on Ethereum for you. But it explains why some things behave differently — for example, why a stuck Ethereum transaction can block the ones behind it until it clears.

What's different from Bitcoin for a self-custody user

Beyond the ledger model, a few things will feel new if Bitcoin was your starting point:

• Gas. Every Ethereum action costs gas — a fee paid in ETH for the computation and storage it uses. Simple transfers are cheap to compute; interacting with contracts costs more. Fees rise and fall with network demand, and the EIP-1559 fee mechanism splits them into a base fee plus a priority tip. Always keep a little ETH on hand to cover gas, even if your main holding is a token.
• Smart contracts. On Ethereum you don't just send value — you can interact with on-chain programs: swaps, lending, staking, and more. Every interaction is still a transaction your two keys must co-sign, so the multisig protection extends to DeFi, not just simple sends.
• ERC-20 tokens. Most assets on Ethereum aren't ETH; they're tokens that follow the ERC-20 standard (stablecoins, governance tokens, and so on). These live in the same account as your ETH, but you still need ETH to pay the gas to move them. A common beginner surprise is having tokens but no ETH to send them with.
• One address, many uses. Unlike Bitcoin wallets that often rotate through many addresses, your Ethereum account is typically a single, reusable address that holds ETH and every token together.

Why "EVM" matters: one key set, many chains

EVM stands for Ethereum Virtual Machine — the runtime that executes Ethereum's smart contracts. Its importance is that many other chains run the exact same machine. Networks like Polygon, Base, BNB Smart Chain, and Avalanche C-Chain are all EVM-compatible, which means the same account model, the same address format, and the same kind of smart-contract account all carry over.

For SSP this is powerful: the same two-key multisig design works across every supported EVM chain. You don't need a separate wallet or a new key set for each one — your SSP setup reaches them all, with gas paid in each chain's native coin. That's why learning Ethereum first pays off: once you understand it, the other EVM chains are mostly the same story with different names and fees.

What the rest of this series covers

This post is the entry point. The rest of the EVM series builds on it:

• Sending and receiving — the hands-on flow for moving ETH in and out of SSP, including addresses and confirmations.
• Other EVM chains — using SSP on Polygon, Base, and beyond, and what to watch for when switching networks.
• Gas fees explained — how Ethereum fees really work and how to think about them as a self-custody user.
• EVM multisig deep dive — the account-abstraction mechanics behind SSP's 2-of-2 on Ethereum.
• Bridging between chains — moving assets across EVM networks from SSP, and the trade-offs involved.

Where to go next

If you're ready to put ETH into practice, continue with sending and receiving Ethereum with SSP. If you'd rather understand the security model first, the account abstraction (ERC-4337) explainer pairs naturally with this one. Either way, the same principle holds across every chain SSP supports: two keys, two devices, one signature — and you in control.