1NIP-172======34Private Direct Messages5-----------------------67`draft` `optional` `relay`89This NIP defines an encrypted chat scheme which uses [NIP-44](44.md) encryption and [NIP-59](59.md) gift-wrapping.1011By convention, `kind 14` direct messages, `kind 15` file messages, and [`kind 7` reactions](./25.md) may be sent to an encrypted chat. See [Message Rumor Definitions](#message-rumor-definitions) below.1213## Chat Rooms1415The most common use case is a room with only two peers, but more than one person per room is supported.1617The set of `pubkey` + `p` tags defines a chat room. If a new `p` tag is added or a current one is removed, a new room is created with a clean message history.1819An optional `subject` tag defines the current name/topic of the conversation. Any member can change the topic by simply submitting a new `subject` to an existing `pubkey` + `p` tags room. There is no need to send `subject` in every message. The newest `subject` in the chat room is the subject of the conversation.2021## Encrypting2223Following [NIP-59](59.md), the **unsigned** chat messages must be sealed (`kind:13`) and then gift-wrapped (`kind:1059`) to each receiver and the sender individually.2425```js26{27 "id": "<usual hash>",28 "pubkey": wrapperPublicKey,29 "created_at": randomTimeUpTo2DaysInThePast,30 "kind": 1059, // gift wrap31 "tags": [32 ["p", receiverPublicKey, "<relay-url>"] // receiver33 ],34 "content": nip44.encrypt(35 {36 "id": "<usual hash>",37 "pubkey": senderPublicKey,38 "created_at": randomTimeUpTo2DaysInThePast,39 "kind": 13, // seal40 "tags": [], // no tags41 "content": nip44.encrypt(42 unsignedMessageRumor,43 nip44.compute_conversation_key(senderPrivateKey, receiverPublicKey)44 ),45 "sig": "<signed by senderPrivateKey>"46 },47 nip44.compute_conversation_key(wrapperPrivateKey, receiverPublicKey)48 ),49 "sig": "<signed by randomPrivateKey>"50}51```5253`unsignedMessageRumor` is a rumor (an unsigned event, as per [NIP-59](59.md)), usually a `kind:14`, but could also be a different kind, see [Message Rumor Definitions](#message-rumor-definitions) below.5455`wrapperPrivateKey` and `wrappedPublicKey` are a new keypair, generated randomly anew for each message sent.5657Clients MUST verify if pubkey of the `kind:13` is the same pubkey as that of the `unsignedMessageRumor`, otherwise any sender can impersonate any other by simply changing the pubkey on the rumor.5859Clients SHOULD randomize `created_at` in up to two days in the past in both the seal and the gift wrap to make sure grouping by `created_at` doesn't reveal any metadata.6061## Publishing6263Kind `10050` indicates the user's preferred relays to receive DMs. The event MUST include a list of `relay` tags with relay URIs.6465```yaml66{67 "kind": 10050,68 "tags": [69 ["relay", "wss://inbox.nostr.wine"],70 ["relay", "wss://myrelay.nostr1.com"],71 ],72 "content": "",73 // other fields...74}75```7677Clients MUST only publish events to the relays listed in the recipient’s kind 10050 event. If such a list is not found that indicates the user is not ready to receive messages and clients shouldn't try.7879## Relays8081Relays SHOULD protect message metadata by only serving `kind:1059` events to users p-tagged on the event (enforced using [NIP-42 AUTH](./42.md)).8283Clients SHOULD guide users to keep `kind:10050` lists small (1-3 relays) and SHOULD spread them to as many relays as viable.8485## Delete, edit and disappearing messages8687In addition to the deletion behavior specified in [NIP 59](59.md), in which gift wraps can be deleted by the `p`-tagged recipient, clients MAY also allow users to delete messages by wrapping a `kind:5` delete event in a `kind:1059` gift wrap and sending it to the recipient as part of the conversation. Clients SHOULD remove deleted messages from the conversation, or indicate whether a message has been deleted.8889Clients MAY implement edit by deleting an event and publishing another one with the same timestamp.9091Clients MAY offer disappearing messages by setting an `expiration` tag in the gift wrap of each receiver or by not generating a gift wrap to the sender's public key. This tag SHOULD be included on the `kind:13` seal as well, in case it leaks.9293## Benefits & Limitations9495This NIP offers the following privacy and security features:96971. **No Metadata Leak**: Participant identities, each message's real date and time, event kinds, and other event tags are all hidden from the public. Senders and receivers cannot be linked with public information alone.982. **No Public Group Identifiers**: There is no public central queue, channel or otherwise converging identifier to correlate or count all messages in the same group.993. **No Moderation**: There are no group admins: no invitations or bans.1004. **No Shared Secrets**: No secret must be known to all members that can leak or be mistakenly shared1015. **Fully Recoverable**: Messages can be fully recoverable by any client with the user's private key1026. **Optional Forward Secrecy**: Users and clients can opt-in for "disappearing messages".1037. **Uses Public Relays**: Messages can flow through public relays without loss of privacy. Private relays can increase privacy further, but they are not required.1048. **Cold Storage**: Users can unilaterally opt-in to sharing their messages with a separate key that is exclusive for DM backup and recovery.105106The main limitation of this approach is having to send a separate encrypted event to each receiver. Group chats with more than 10 participants should find a more suitable messaging scheme.107108## Spam109110Since the wrapper events use random keys, relays cannot apply traditional anti-spam based on pubkey reputation, WoT, etc, therefore a naïve implementation of this NIP is an spam target. The recommended approach for spam mitigation is described in the [Spam Protection section of NIP-59](59.md#spam-protection).111112## Message Rumor Definitions113114### Chat Message115116Kind `14` is a chat message. `p` tags identify one or more receivers of the message.117118```yaml119{120 "pubkey": "<sender-pubkey>",121 "created_at": "<current-time>",122 "kind": 14,123 "tags": [124 ["p", "<receiver-1-pubkey>", "<relay-url>"],125 ["p", "<receiver-2-pubkey>", "<relay-url>"],126 ["e", "<kind-14-id>", "<relay-url>"] // if this is a reply127 ["subject", "<conversation-title>"],128 // rest of tags...129 ],130 "content": "<message-in-plain-text>",131}132```133134`.content` MUST be plain text. Fields `id` and `created_at` are required.135136An `e` tag denotes the direct parent message this post is replying to.137138`q` tags MAY be used when citing events in the `.content` with [NIP-21](21.md).139140```json141["q", "<event-id> or <event-address>", "<relay-url>", "<pubkey-if-a-regular-event>"]142```143144## File Message145146```yaml147{148 "pubkey": "<sender-pubkey>",149 "created_at": "<current-time>",150 "kind": 15,151 "tags": [152 ["p", "<receiver-1-pubkey>", "<relay-url>"],153 ["p", "<receiver-2-pubkey>", "<relay-url>"],154 ["e", "<kind-14-id>", "<relay-url>", "reply"], // if this is a reply155 ["subject", "<conversation-title>"],156 ["file-type", "<file-mime-type>"],157 ["encryption-algorithm", "<encryption-algorithm>"],158 ["decryption-key", "<decryption-key>"],159 ["decryption-nonce", "<decryption-nonce>"],160 ["x", "<the SHA-256 hexencoded string of the file>"],161 // rest of tags...162 ],163 "content": "<file-url>"164}165```166167Kind `15` is used for sending encrypted file event messages:168169- `file-type`: Specifies the MIME type of the attached file (e.g., `image/jpeg`, `audio/mpeg`, etc.) before encryption.170- `encryption-algorithm`: Indicates the encryption algorithm used for encrypting the file. Supported algorithms: `aes-gcm`.171- `decryption-key`: The decryption key that will be used by the recipient to decrypt the file.172- `decryption-nonce`: The decryption nonce that will be used by the recipient to decrypt the file.173- `content`: The URL of the file (`<file-url>`).174- `x` containing the SHA-256 hexencoded string of the encrypted file.175- `ox` containing the SHA-256 hexencoded string of the file before encryption.176- `size` (optional) size of the encrypted file in bytes177- `dim` (optional) size in pixels in the form `<width>x<height>`178- `thumbhash`(optional) the [thumbhash](https://evanw.github.io/thumbhash/) to show while the client is loading the file179- `blurhash`(optional) the [blurhash](https://github.com/woltapp/blurhash) to show while the client is loading the file180- `thumb` (optional) URL of thumbnail with same aspect ratio (encrypted with the same key, nonce)181- `fallback` (optional) zero or more fallback file sources in case `url` fails (encrypted with the same key, nonce)182183184## Examples185186This example sends the message `Hola, que tal?` from `nsec1w8udu59ydjvedgs3yv5qccshcj8k05fh3l60k9x57asjrqdpa00qkmr89m` to `nsec12ywtkplvyq5t6twdqwwygavp5lm4fhuang89c943nf2z92eez43szvn4dt`.187188The two final GiftWraps, one to the receiver and the other to the sender, respectively, are:189190```json191{192 "id":"2886780f7349afc1344047524540ee716f7bdc1b64191699855662330bf235d8",193 "pubkey":"8f8a7ec43b77d25799281207e1a47f7a654755055788f7482653f9c9661c6d51",194 "created_at":1703128320,195 "kind":1059,196 "tags":[197 ["p", "918e2da906df4ccd12c8ac672d8335add131a4cf9d27ce42b3bb3625755f0788"]198 ],199 "content":"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",200 "sig":"a3c6ce632b145c0869423c1afaff4a6d764a9b64dedaf15f170b944ead67227518a72e455567ca1c2a0d187832cecbde7ed478395ec4c95dd3e71749ed66c480"201}202```203204```json205{206 "id":"162b0611a1911cfcb30f8a5502792b346e535a45658b3a31ae5c178465509721",207 "pubkey":"626be2af274b29ea4816ad672ee452b7cf96bbb4836815a55699ae402183f512",208 "created_at":1702711587,209 "kind":1059,210 "tags":[211 ["p", "44900586091b284416a0c001f677f9c49f7639a55c3f1e2ec130a8e1a7998e1b"]212 ],213 "content":"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",214 "sig":"c94e74533b482aa8eeeb54ae72a5303e0b21f62909ca43c8ef06b0357412d6f8a92f96e1a205102753777fd25321a58fba3fb384eee114bd53ce6c06a1c22bab"215}216```