NIP-19

bech32-encoded entities

draft optional author:jb55 author:fiatjaf author:Semisol

This NIP standardizes bech32-formatted strings that can be used to display keys, ids and other information in clients. These formats are not meant to be used anywhere in the core protocol, they are only meant for displaying to users, copy-pasting, sharing, rendering QR codes and inputting data.

It is recommended that ids and keys are stored in either hex or binary format, since these formats are closer to what must actually be used the core protocol.

Bare keys and ids

To prevent confusion and mixing between private keys, public keys and event ids, which are all 32 byte strings. bech32-(not-m) encoding with different prefixes can be used for each of these entities.

These are the possible bech32 prefixes:

npub: public keys
nsec: private keys
note: note ids

Example: the hex public key 3bf0c63fcb93463407af97a5e5ee64fa883d107ef9e558472c4eb9aaaefa459d translates to npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6.

The bech32 encodings of keys and ids are not meant to be used inside the standard NIP-01 event formats or inside the filters, they're meant for human-friendlier display and input only. Clients should still accept keys in both hex and npub format for now, and convert internally.

Shareable identifiers with extra metadata

When sharing a profile or an event, an app may decide to include relay information and other metadata such that other apps can locate and display these entities more easily.

For these events, the contents are a binary-encoded list of TLV (type-length-value), with T and L being 1 byte each (uint8, i.e. a number in the range of 0-255), and V being a sequence of bytes of the size indicated by L.

These are the possible bech32 prefixes with TLV:

nprofile: a nostr profile
nevent: a nostr event
nrelay: a nostr relay
naddr: a nostr parameterized replaceable event coordinate (NIP-33)

These possible standardized TLV types are indicated here:

0: special
- depends on the bech32 prefix:
  - for nprofile it will be the 32 bytes of the profile public key
  - for nevent it will be the 32 bytes of the event id
  - for nrelay, this is the relay URL
  - for naddr, it is the identifier (the "d" tag) of the event being referenced
1: relay
- for nprofile, nevent and naddr, optionally, a relay in which the entity (profile or event) is more likely to be found, encoded as ascii
- this may be included multiple times
2: author
- for naddr, the 32 bytes of the pubkey of the event
- for nevent, optionally, the 32 bytes of the pubkey of the event
3: kind
- for naddr, the 32-bit unsigned integer of the kind, big-endian
- for nevent, optionally, the 32-bit unsigned integer of the kind, big-endian

Examples

npub10elfcs4fr0l0r8af98jlmgdh9c8tcxjvz9qkw038js35mp4dma8qzvjptg should decode into the public key hex 7e7e9c42a91bfef19fa929e5fda1b72e0ebc1a4c1141673e2794234d86addf4e and vice-versa
nsec1vl029mgpspedva04g90vltkh6fvh240zqtv9k0t9af8935ke9laqsnlfe5 should decode into the private key hex 67dea2ed018072d675f5415ecfaed7d2597555e202d85b3d65ea4e58d2d92ffa and vice-versa
nprofile1qqsrhuxx8l9ex335q7he0f09aej04zpazpl0ne2cgukyawd24mayt8gpp4mhxue69uhhytnc9e3k7mgpz4mhxue69uhkg6nzv9ejuumpv34kytnrdaksjlyr9p should decode into a profile with the following TLV items:
- pubkey: 3bf0c63fcb93463407af97a5e5ee64fa883d107ef9e558472c4eb9aaaefa459d
- relay: wss://r.x.com
- relay: wss://djbas.sadkb.com

Notes

npub keys MUST NOT be used in NIP-01 events or in NIP-05 JSON responses, only the hex format is supported there.
When decoding a bech32-formatted string, TLVs that are not recognized or supported should be ignored, rather than causing an error.

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