> For the complete documentation index, see [llms.txt](https://docs.zipwire.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zipwire.io/fundamentals/security/crypto-and-blockchain-basics.md).

# Crypto & Blockchain Basics

## What Is a Wallet?

A wallet is best thought of as a **key ring plus a signer**. It holds your cryptographic keys, and when an action needs to go to the blockchain — sending a transaction, or attesting to something — the wallet uses those keys to **sign** the instruction, proving it came from you without ever exposing the key itself.

Zipwire doesn't use wallets to hold or move money; here, a wallet's job is purely to sign attestations and prove identity. See [Sign-in with Ethereum](/fundamentals/security/sign-in-with-ethereum.md) for how signing is used to prove wallet ownership when logging in, and [Wallet Connections](/fundamentals/security/wallet-connections.md) for a deeper look at wallet types.

## Public Key, Private Key, and Wallet Address

* **Private key**: a secret known only to the wallet owner, used to sign things. Never shared.
* **Public key**: derived from the private key, used by others to verify a signature. Safe to share.
* **Wallet address**: a shorter, derived form of the public key — the "account number" others use to refer to your wallet.

You sign with the private key; everyone else verifies with the public key or address. Losing the private key means losing the wallet; leaking it means anyone can sign as you.

## On-Chain vs. Off-Chain

* **On-chain**: written to the blockchain itself — permanent, public, and the same for everyone who looks it up. Zipwire writes attestation roots on-chain so they can't later be disputed or altered.
* **Off-chain**: everything else — the actual documents, Merkle trees, and proofs, held privately by each party rather than published to the blockchain. Off-chain data can be verified against an on-chain root without ever being uploaded anywhere.

Zipwire deliberately keeps as little as possible on-chain (just root hashes), and everything sensitive off-chain, in each party's own protected storage.

## What Is Base?

Base is the specific blockchain Zipwire writes attestations to. It's a Layer 2 (L2) network built on top of Ethereum: transactions are cheaper and faster than on Ethereum itself, while still inheriting Ethereum's security. You don't need to interact with Base directly — Zipwire and its wallet integrations handle that — but it's the network you'd look attestations up on (e.g. via [EAS Scan for Base](https://base.easscan.org/)).

## Read More

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[Sign-in with Ethereum](/fundamentals/security/sign-in-with-ethereum.md)
{% endcontent-ref %}

{% content-ref url="/pages/K4BLwRNETrUKpdJuaJRC" %}
[Understanding Merkle Trees and Proofs](/fundamentals/security/understanding-merkle-trees-and-proofs.md)
{% endcontent-ref %}

{% content-ref url="/pages/TfrUK5pGnJhSthL5TLjm" %}
[Attestations](/fundamentals/security/attestations.md)
{% endcontent-ref %}