Cashu, NIP-60 and Nutzaps
Cashu brings bearer-style ecash into the Nostr wallet conversation: mints, proofs, encrypted wallet state, P2PK-locked tokens and payments where the token can become the receipt.
Ecash feels simple because the hard part is hidden
Cashu feels almost too easy when you first use it. Someone sends a token. You paste it into a wallet. The balance appears. That cash-like feel is the point. Cashu is a Chaumian ecash protocol for Bitcoin: users hold digital bearer tokens, mints issue and redeem them, and Lightning can move value in and out of the mint ecosystem.
The simplicity hides real structure. A Cashu system has wallets, mints, keysets, proofs, token formats, mint trust and Lightning settlement. The wallet can feel accountless, but the mint still matters. The mint can fail, censor redemption or disappear. A token can be lost if you lose the wallet state. Privacy improves in important ways, but it is not the same as self-custody on-chain Bitcoin.
That is why Cashu belongs in the Wallets hub instead of only in a protocol archive. It changes how small payments can work in social products. It also changes the warning labels you need to read.
What Cashu gives Nostr
Cashu gives Nostr a way to move small amounts with a cash-like feel. A token can be handed over in a message, QR code, link or app flow. A mint can support instant, nearly free payments inside a community. Wallets such as Cashu.me, Minibits and Boardwalk Cash make the experience approachable enough for people who do not want to run a Lightning node.
The Cashu documentation describes ecash as digital bearer tokens stored on your device and notes that mints do not keep a traditional account database of user activity. Blind signatures are the privacy engine: the mint can issue and redeem without seeing the full relationship between issuance and later spend in the same way a normal custodial account would.
For Nostr, the interesting part is that identity and storage are separate. Nostr can carry wallet state pointers, trusted mint lists, payment events and social context. Cashu carries the token logic. Lightning carries settlement between the mint world and the broader Bitcoin network.
NIP-60: wallet state on relays
NIP-60 defines operations for a Cashu-based wallet whose information is stored in relays so it can be accessible across applications. The purpose is ease of use and interoperability: a new user can receive funds without creating a separate account, and the wallet can follow the user across apps.
The NIP describes a replaceable wallet event, `kind:17375`, and token events, `kind:7375`, for unspent proofs. It also describes optional spending-history events. Important content is encrypted. The wallet event can include mints and a private key used for receiving Nutzaps, but that private key is not the user's main Nostr private key.
That separation matters. You do not want a Cashu receiving key to be your whole Nostr identity. You also do not want wallet state to become a public ledger. NIP-60 is trying to make a wallet portable without publishing its private guts in plain text.
NIP-61: when the payment itself is the receipt
NIP-61 defines Nutzaps. A Nutzap is a P2PK Cashu token where the payment itself is the receipt. The flow is different from a Lightning zap. Alice fetches Bob's `kind:10019` event to see the mints and relays Bob accepts. She mints or swaps a token at one of those mints, locks it to Bob's listed P2PK public key and publishes a `kind:9321` event tagging Bob with the proofs.
Bob's client later fetches those events from his relays and swaps the token into his wallet. That sounds technical, but the product implication is clear: instead of asking a Lightning server to publish a zap receipt after invoice payment, the Cashu token is the payment object. The receipt and the value are closer together.
NIP-61 also includes sharp safety language. Clients should not send money to mints the recipient did not list, because that can burn money. Implementations must not use the target user's main Nostr public key as the P2PK receiving key. These are not decorative details. They are the difference between an elegant ecash zap and a very small disaster repeated many times.
The privacy tradeoff
Cashu can improve privacy because blind signatures and bearer tokens reduce the account-style trail that ordinary custodial wallets create. The mint does not need a named database of every user account and every social action. A token can circulate more like cash.
But you should not turn that into mythology. A mint is still a trust point. Network metadata still exists. Wallet backups still matter. A badly designed app can leak identifiers around the token. A small mint can be operationally fragile. A token that lives only in one browser profile can disappear with that profile. Privacy is strongest when the product explains what is hidden, what is not and what depends on the mint.
Nostr adds another layer of caution. Relays can store encrypted wallet events. That helps portability. It also creates a durable place where ciphertext, timing and tags may remain. Encryption is necessary, but UX has to make recovery, backup and mint choice understandable.
Products worth reading side by side
Cashu.me is useful because it shows the web-wallet path: tokens, mints, Lightning in and out, and Nostr-adjacent experiments in one place. Minibits is useful because it shows the mobile path, including Nostr and Lightning integration around ecash. Boardwalk Cash is useful because it puts Cashu in a simple browser surface. Bankify is useful because it experiments with Cashu and NWC bridges.
None of these products should be judged only by how fast the first token appears. Judge them by mint transparency, backup story, receive flow, spend flow, support for NIP-60 or NIP-61 ideas, warning labels and how honestly they explain the relationship between ecash privacy and mint trust.
For Crays, Cashu becomes interesting around fan rewards, small vouchers, event access, paid rooms and creator experiments where tiny payments should feel lighter than a full checkout. The product promise is strong only if the custody story stays plain.
What to remember
Cashu is not Lightning with a different logo. Lightning is the payment network. Cashu is ecash that can use Lightning for mint deposits and redemptions. NIP-60 is wallet state and interoperability. NIP-61 is Nutzaps. The Cashu NUTs are the Cashu protocol specifications.
When you see a Cashu wallet in Nostr, ask four questions: which mint, where are proofs stored, how are backups handled, and what happens if the mint or relay disappears? If the page answers those questions clearly, you are looking at a serious wallet surface. If it hides them, slow down.
Sources worth opening
Open these when you want the specification, product documentation or implementation trail behind the article.
