Crypto Wallets Explained: Custody, Private Keys and Seed Phrases

Addresses, public keys and private keys

Every wallet is built on pairs of keys. The private key is a secret number that proves ownership and signs transactions. From it, the wallet calculates a public key, and from that, an address.

An address is like an account number: you can share it so people can send you crypto. The private key is like a password and a signature combined, and anyone who has it can move your funds. Share your address freely, but never share your private key with anyone, including people who claim to be support staff.

Custodial vs self-custody

With a custodial wallet, a company such as an exchange holds the keys for you. You log in with a password, and if you forget it, the company can help you recover access. The trade-off is trust: if the company is hacked, freezes withdrawals or goes bankrupt, you may not get your coins back.

With a self-custody wallet (also called non-custodial), you hold the keys yourself. Nobody can freeze your funds or lose them on your behalf, but nobody can rescue you either. If you lose your keys and your recovery phrase, the coins are gone.

Many beginners start with a custodial account because it feels familiar, then move larger amounts to self-custody once they are comfortable with the responsibility.

Hot vs cold wallets

• Hot wallets are connected to the internet: phone apps, browser extensions and desktop programs. They are convenient for everyday use and for connecting to crypto apps, but being online leaves them more exposed to malware and phishing.
• Cold wallets keep the private keys offline. The most common type is a hardware wallet, a small device that signs transactions inside itself so the key never touches your computer. It is safer for long-term savings but less convenient.

A common approach is to keep a small spending balance in a hot wallet and the rest in cold storage, much like carrying some cash in your pocket while keeping savings in a safe.

Seed phrase basics

When you create a self-custody wallet, it usually shows you a seed phrase, also called a recovery phrase. It is most often 12 or 24 ordinary words in a set order. These words can recreate all the private keys in your wallet on any compatible app or device.

That makes the seed phrase the master key to everything. Write it on paper or stamp it into metal, check every word, and store it somewhere safe from fire, water and curious visitors. Do not photograph it, save it in cloud notes, email it to yourself or type it into any website.

A genuine wallet company, exchange or support agent will never ask for your seed phrase. Anyone who does is trying to steal from you.

Choosing a wallet safely

• Download wallet apps only from the official website or the official app store listing, and check the name and developer carefully, since fake copies are common.
• Buy hardware wallets directly from the maker or an authorised seller, never second-hand, and treat any device that arrives with a seed phrase already provided as compromised.
• Make sure the wallet supports the coins and networks you plan to use.
• Prefer wallets that are widely used and actively maintained, and keep the software up to date.
• Send a small test amount first, then the rest once it arrives safely.

Common mistakes to avoid

• Keeping the seed phrase as a phone screenshot or in a cloud folder.
• Sending coins on the wrong network or to a mistyped address. Check at least the first and last few characters, and beware of malware that swaps addresses you copy and paste.
• Approving unknown requests from websites, which can let attackers drain tokens from your wallet.
• Leaving a large balance in a hot wallet or on an exchange just for convenience.
• Having no plan for a lost or broken device, or for how your family could reach your funds in an emergency.