# BUD-12

## Chunked blobs

`draft` `optional`

Breaking large blobs into smaller chunks for distribution

### Chunking

The client MAY break large blobs into any number or size of chunks. although its recommended to use the size `1Mb` or `4Mb` for small and large chunks

Clients MUST NOT pad the remaining chunk, If clients need privacy they should use random chunk sizes and optionally encrypt the large blob

### Publishing

Clients should publish a `2001` kind event after chunking the file in order to store the list of chunks

The events MUST contain an ordered list of `chunk` tags with the sha256 hashes of the chunks

The `content` field MUST be a human readable description of the chunked file

```json
{
  "tags": [
    [ "chunk", "7e668b56a58c7891e0cf263ea3f093b75eebade23d663a45aa9920f347b3d671"],
    [ "chunk", "9b9c44a91396f19fd8700986eb0586dff2dcccf96c75bc2caefef302bcd78da1"],
    [ "chunk", "7a281548f1223664b855b10b08e59e84389ccabeb742517f6cd75eda2724a798"],
    [ "chunk", "fadeccee86b123088bbc452df10e8fbc99d4c2f22a70ef7a35605ec8e439c345"],
    [ "chunk", "5d62398419e6d136771541f3d2215e0ce31b1be45e99dbc64b43a4b734b447ca"],
  ]
}
```

### Metadata

The `2001` event MAY include additional metadata tags to help other clients know the filename, mime type or servers to download from

Metadata tags:
  - `name` Filename
  - `mime` Mime type of file
  - `size` Total size in bytes of the file
  - `server` (multiple) Recommended servers to download chunks from

### Examples

Example `2001` event
```json
{
  "pubkey": "5328e6c743a50271745e16476590ba7ea3dc591c65f3a5e2b03430814c1dabc0",
  "created_at": 1731405194,
  "kind": 2001,
  "content": "Large zip archive of documents",
  "tags": [
    [ "chunk", "7e668b56a58c7891e0cf263ea3f093b75eebade23d663a45aa9920f347b3d671"],
    [ "chunk", "9b9c44a91396f19fd8700986eb0586dff2dcccf96c75bc2caefef302bcd78da1"],
    [ "chunk", "7a281548f1223664b855b10b08e59e84389ccabeb742517f6cd75eda2724a798"],
    [ "chunk", "fadeccee86b123088bbc452df10e8fbc99d4c2f22a70ef7a35605ec8e439c345"],
    [ "chunk", "5d62398419e6d136771541f3d2215e0ce31b1be45e99dbc64b43a4b734b447ca"],
    [ "name", "example.mp4" ],
    [ "mime", "video/mp4" ],
    [ "size", "4823449" ],
    [ "server", "https://cdn.example.com" ],
    [ "server", "https://nostr.download" ]
  ]
}
```