add examples to README.

closes https://github.com/fiatjaf/nak/issues/84

README.md

@@ -324,6 +324,21 @@ echo "#surely you're joking, mr npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn6
 ffmpeg -f alsa -i default -f webm -t 00:00:03 pipe:1 | nak blossom --server blossom.primal.net upload | jq -rc '{content: .url}' | nak event -k 1222 --sec 'bunker://urlgoeshere' pyramid.fiatjaf.com nostr.wine
 ```
 
+### gift-wrap an event to a recipient and publish it somewhere
+```shell
+~> nak event -c 'secret message' | nak gift wrap --sec <my-secret-key> -p <recipient-public-key> | nak event wss://dmrelay.com
+```
+
+### download a gift-wrap event and unwrap it
+```shell
+~> nak req -p <my-public-key> -k 1059 relay.com | nak gift unwrap --sec <my-secret-key> --from <sender-public-key>
+```
+
+### sync events between two relays using negentropy
+```shell
+~> nak sync relay1.com relay2.com
+```
+
 ### from a file with events get only those that have kind 1111 and were created by a given pubkey
 ```shell
 ~> cat all.jsonl | nak filter -k 1111 -a 117673e191b10fe1aedf1736ee74de4cffd4c132ca701960b70a5abad5870faa > filtered.jsonl

encrypt_decrypt.go

@@ -17,7 +17,7 @@ var encrypt = &cli.Command{
 		defaultKeyFlags,
 		&PubKeyFlag{
 			Name:     "recipient-pubkey",
-			Aliases:  []string{"p", "tgt", "target", "pubkey"},
+			Aliases:  []string{"p", "tgt", "target", "pubkey", "to"},
 			Required: true,
 		},
 		&cli.BoolFlag{
@@ -79,7 +79,7 @@ var decrypt = &cli.Command{
 		defaultKeyFlags,
 		&PubKeyFlag{
 			Name:     "sender-pubkey",
-			Aliases:  []string{"p", "src", "source", "pubkey"},
+			Aliases:  []string{"p", "src", "source", "pubkey", "from"},
 			Required: true,
 		},
 		&cli.BoolFlag{

gift.go

@@ -0,0 +1,192 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"time"
+
+	"fiatjaf.com/nostr"
+	"fiatjaf.com/nostr/nip44"
+	"github.com/mailru/easyjson"
+	"github.com/urfave/cli/v3"
+)
+
+var gift = &cli.Command{
+	Name:  "gift",
+	Usage: "gift-wraps (or unwraps) an event according to NIP-59",
+	Description: `example:
+  nak event | nak gift wrap --sec <sec-a> -p <sec-b> | nak gift unwrap --sec <sec-b> --from <pub-a>`,
+	DisableSliceFlagSeparator: true,
+	Commands: []*cli.Command{
+		{
+			Name: "wrap",
+			Flags: append(
+				defaultKeyFlags,
+				&PubKeyFlag{
+					Name:     "recipient-pubkey",
+					Aliases:  []string{"p", "tgt", "target", "pubkey", "to"},
+					Required: true,
+				},
+			),
+			Usage: "turns an event into a rumor (unsigned) then gift-wraps it to the recipient",
+			Description: `example:
+  nak event -c 'hello' | nak gift wrap --sec <my-secret-key> -p <target-public-key>`,
+			Action: func(ctx context.Context, c *cli.Command) error {
+				kr, _, err := gatherKeyerFromArguments(ctx, c)
+				if err != nil {
+					return err
+				}
+
+				recipient := getPubKey(c, "recipient-pubkey")
+
+				// get sender pubkey
+				sender, err := kr.GetPublicKey(ctx)
+				if err != nil {
+					return fmt.Errorf("failed to get sender pubkey: %w", err)
+				}
+
+				// read event from stdin
+				for eventJSON := range getJsonsOrBlank() {
+					if eventJSON == "{}" {
+						continue
+					}
+
+					var originalEvent nostr.Event
+					if err := easyjson.Unmarshal([]byte(eventJSON), &originalEvent); err != nil {
+						return fmt.Errorf("invalid event JSON: %w", err)
+					}
+
+					// turn into rumor (unsigned event)
+					rumor := originalEvent
+					rumor.Sig = [64]byte{} // remove signature
+					rumor.PubKey = sender
+					rumor.ID = rumor.GetID() // compute ID
+
+					// create seal
+					rumorJSON, _ := easyjson.Marshal(rumor)
+					encryptedRumor, err := kr.Encrypt(ctx, string(rumorJSON), recipient)
+					if err != nil {
+						return fmt.Errorf("failed to encrypt rumor: %w", err)
+					}
+					seal := &nostr.Event{
+						Kind:      13,
+						Content:   encryptedRumor,
+						PubKey:    sender,
+						CreatedAt: randomNow(),
+						Tags:      nostr.Tags{},
+					}
+					if err := kr.SignEvent(ctx, seal); err != nil {
+						return fmt.Errorf("failed to sign seal: %w", err)
+					}
+
+					// create gift wrap
+					ephemeral := nostr.Generate()
+					sealJSON, _ := easyjson.Marshal(seal)
+					convkey, err := nip44.GenerateConversationKey(recipient, ephemeral)
+					if err != nil {
+						return fmt.Errorf("failed to generate conversation key: %w", err)
+					}
+					encryptedSeal, err := nip44.Encrypt(string(sealJSON), convkey)
+					if err != nil {
+						return fmt.Errorf("failed to encrypt seal: %w", err)
+					}
+					wrap := &nostr.Event{
+						Kind:      1059,
+						Content:   encryptedSeal,
+						CreatedAt: randomNow(),
+						Tags:      nostr.Tags{{"p", recipient.Hex()}},
+					}
+					wrap.Sign(ephemeral)
+
+					// print the gift-wrap
+					wrapJSON, err := easyjson.Marshal(wrap)
+					if err != nil {
+						return fmt.Errorf("failed to marshal gift wrap: %w", err)
+					}
+					stdout(string(wrapJSON))
+				}
+
+				return nil
+			},
+		},
+		{
+			Name:  "unwrap",
+			Usage: "decrypts a gift-wrap event sent by the sender to us and exposes its internal rumor (unsigned event).",
+			Description: `example:
+  nak req -p <my-public-key> -k 1059 dmrelay.com | nak gift unwrap --sec <my-secret-key> --from <sender-public-key>`,
+			Flags: append(
+				defaultKeyFlags,
+				&PubKeyFlag{
+					Name:     "sender-pubkey",
+					Aliases:  []string{"p", "src", "source", "pubkey", "from"},
+					Required: true,
+				},
+			),
+			Action: func(ctx context.Context, c *cli.Command) error {
+				kr, _, err := gatherKeyerFromArguments(ctx, c)
+				if err != nil {
+					return err
+				}
+
+				sender := getPubKey(c, "sender-pubkey")
+
+				// read gift-wrapped event from stdin
+				for wrapJSON := range getJsonsOrBlank() {
+					if wrapJSON == "{}" {
+						continue
+					}
+
+					var wrap nostr.Event
+					if err := easyjson.Unmarshal([]byte(wrapJSON), &wrap); err != nil {
+						return fmt.Errorf("invalid gift wrap JSON: %w", err)
+					}
+
+					if wrap.Kind != 1059 {
+						return fmt.Errorf("not a gift wrap event (kind %d)", wrap.Kind)
+					}
+
+					ephemeralPubkey := wrap.PubKey
+
+					// decrypt seal
+					sealJSON, err := kr.Decrypt(ctx, wrap.Content, ephemeralPubkey)
+					if err != nil {
+						return fmt.Errorf("failed to decrypt seal: %w", err)
+					}
+
+					var seal nostr.Event
+					if err := easyjson.Unmarshal([]byte(sealJSON), &seal); err != nil {
+						return fmt.Errorf("invalid seal JSON: %w", err)
+					}
+
+					if seal.Kind != 13 {
+						return fmt.Errorf("not a seal event (kind %d)", seal.Kind)
+					}
+
+					// decrypt rumor
+					rumorJSON, err := kr.Decrypt(ctx, seal.Content, sender)
+					if err != nil {
+						return fmt.Errorf("failed to decrypt rumor: %w", err)
+					}
+
+					var rumor nostr.Event
+					if err := easyjson.Unmarshal([]byte(rumorJSON), &rumor); err != nil {
+						return fmt.Errorf("invalid rumor JSON: %w", err)
+					}
+
+					// output the unwrapped event (rumor)
+					stdout(rumorJSON)
+				}
+
+				return nil
+			},
+		},
+	},
+}
+
+func randomNow() nostr.Timestamp {
+	const twoDays = 2 * 24 * 60 * 60
+	now := time.Now().Unix()
+	randomOffset := rand.Int63n(twoDays)
+	return nostr.Timestamp(now - randomOffset)
+}

go.mod

@@ -4,10 +4,11 @@ go 1.25
 
 require (
 	fiatjaf.com/lib v0.3.1
-	fiatjaf.com/nostr v0.0.0-20251126101225-44130595c606
+	fiatjaf.com/nostr v0.0.0-20251201232830-91548fa0a157
 	github.com/AlecAivazis/survey/v2 v2.3.7
 	github.com/bep/debounce v1.2.1
 	github.com/btcsuite/btcd/btcec/v2 v2.3.6
+	github.com/charmbracelet/glamour v0.10.0
 	github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.0
 	github.com/fatih/color v1.16.0
@@ -41,7 +42,6 @@ require (
 	github.com/btcsuite/btcd/chaincfg/chainhash v1.1.0 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc // indirect
-	github.com/charmbracelet/glamour v0.10.0 // indirect
 	github.com/charmbracelet/lipgloss v1.1.1-0.20250404203927-76690c660834 // indirect
 	github.com/charmbracelet/x/ansi v0.8.0 // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.13 // indirect

go.sum

@@ -1,7 +1,7 @@
 fiatjaf.com/lib v0.3.1 h1:/oFQwNtFRfV+ukmOCxfBEAuayoLwXp4wu2/fz5iHpwA=
 fiatjaf.com/lib v0.3.1/go.mod h1:Ycqq3+mJ9jAWu7XjbQI1cVr+OFgnHn79dQR5oTII47g=
-fiatjaf.com/nostr v0.0.0-20251126101225-44130595c606 h1:wQHJ0TFA0Fuq92p/6u6AbsBFq6ZVToSdxV6puXVIruI=
+fiatjaf.com/nostr v0.0.0-20251201232830-91548fa0a157 h1:14yLsO2HwpS2CLIKFvLMDp8tVEDahwdC8OeG6NGaL+M=
-fiatjaf.com/nostr v0.0.0-20251126101225-44130595c606/go.mod h1:ue7yw0zHfZj23Ml2kVSdBx0ENEaZiuvGxs/8VEN93FU=
+fiatjaf.com/nostr v0.0.0-20251201232830-91548fa0a157/go.mod h1:ue7yw0zHfZj23Ml2kVSdBx0ENEaZiuvGxs/8VEN93FU=
 github.com/AlecAivazis/survey/v2 v2.3.7 h1:6I/u8FvytdGsgonrYsVn2t8t4QiRnh6QSTqkkhIiSjQ=
 github.com/AlecAivazis/survey/v2 v2.3.7/go.mod h1:xUTIdE4KCOIjsBAE1JYsUPoCqYdZ1reCfTwbto0Fduo=
 github.com/FastFilter/xorfilter v0.2.1 h1:lbdeLG9BdpquK64ZsleBS8B4xO/QW1IM0gMzF7KaBKc=
@@ -13,12 +13,18 @@ github.com/Netflix/go-expect v0.0.0-20220104043353-73e0943537d2/go.mod h1:HBCaDe
 github.com/PowerDNS/lmdb-go v1.9.3 h1:AUMY2pZT8WRpkEv39I9Id3MuoHd+NZbTVpNhruVkPTg=
 github.com/PowerDNS/lmdb-go v1.9.3/go.mod h1:TE0l+EZK8Z1B4dx070ZxkWTlp8RG1mjN0/+FkFRQMtU=
 github.com/aead/siphash v1.0.1/go.mod h1:Nywa3cDsYNNK3gaciGTWPwHt0wlpNV15vwmswBAUSII=
+github.com/alecthomas/assert/v2 v2.7.0 h1:QtqSACNS3tF7oasA8CU6A6sXZSBDqnm7RfpLl9bZqbE=
+github.com/alecthomas/assert/v2 v2.7.0/go.mod h1:Bze95FyfUr7x34QZrjL+XP+0qgp/zg8yS+TtBj1WA3k=
 github.com/alecthomas/chroma/v2 v2.14.0 h1:R3+wzpnUArGcQz7fCETQBzO5n9IMNi13iIs46aU4V9E=
 github.com/alecthomas/chroma/v2 v2.14.0/go.mod h1:QolEbTfmUHIMVpBqxeDnNBj2uoeI4EbYP4i6n68SG4I=
+github.com/alecthomas/repr v0.4.0 h1:GhI2A8MACjfegCPVq9f1FLvIBS+DrQ2KQBFZP1iFzXc=
+github.com/alecthomas/repr v0.4.0/go.mod h1:Fr0507jx4eOXV7AlPV6AVZLYrLIuIeSOWtW57eE/O/4=
 github.com/andybalholm/brotli v1.1.1 h1:PR2pgnyFznKEugtsUo0xLdDop5SKXd5Qf5ysW+7XdTA=
 github.com/andybalholm/brotli v1.1.1/go.mod h1:05ib4cKhjx3OQYUY22hTVd34Bc8upXjOLL2rKwwZBoA=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
+github.com/aymanbagabas/go-udiff v0.2.0 h1:TK0fH4MteXUDspT88n8CKzvK0X9O2xu9yQjWpi6yML8=
+github.com/aymanbagabas/go-udiff v0.2.0/go.mod h1:RE4Ex0qsGkTAJoQdQQCA0uG+nAzJO/pI/QwceO5fgrA=
 github.com/aymerick/douceur v0.2.0 h1:Mv+mAeH1Q+n9Fr+oyamOlAkUNPWPlA8PPGR0QAaYuPk=
 github.com/aymerick/douceur v0.2.0/go.mod h1:wlT5vV2O3h55X9m7iVYN0TBM0NH/MmbLnd30/FjWUq4=
 github.com/bep/debounce v1.2.1 h1:v67fRdBA9UQu2NhLFXrSg0Brw7CexQekrBwDMM8bzeY=
@@ -65,6 +71,8 @@ github.com/charmbracelet/x/ansi v0.8.0 h1:9GTq3xq9caJW8ZrBTe0LIe2fvfLR/bYXKTx2ll
 github.com/charmbracelet/x/ansi v0.8.0/go.mod h1:wdYl/ONOLHLIVmQaxbIYEC/cRKOQyjTkowiI4blgS9Q=
 github.com/charmbracelet/x/cellbuf v0.0.13 h1:/KBBKHuVRbq1lYx5BzEHBAFBP8VcQzJejZ/IA3iR28k=
 github.com/charmbracelet/x/cellbuf v0.0.13/go.mod h1:xe0nKWGd3eJgtqZRaN9RjMtK7xUYchjzPr7q6kcvCCs=
+github.com/charmbracelet/x/exp/golden v0.0.0-20240806155701-69247e0abc2a h1:G99klV19u0QnhiizODirwVksQB91TJKV/UaTnACcG30=
+github.com/charmbracelet/x/exp/golden v0.0.0-20240806155701-69247e0abc2a/go.mod h1:wDlXFlCrmJ8J+swcL/MnGUuYnqgQdW9rhSD61oNMb6U=
 github.com/charmbracelet/x/exp/slice v0.0.0-20250327172914-2fdc97757edf h1:rLG0Yb6MQSDKdB52aGX55JT1oi0P0Kuaj7wi1bLUpnI=
 github.com/charmbracelet/x/exp/slice v0.0.0-20250327172914-2fdc97757edf/go.mod h1:B3UgsnsBZS/eX42BlaNiJkD1pPOUa+oF1IYC6Yd2CEU=
 github.com/charmbracelet/x/term v0.2.1 h1:AQeHeLZ1OqSXhrAWpYUtZyX1T3zVxfpZuEQMIQaGIAQ=
@@ -138,6 +146,8 @@ github.com/hablullah/go-juliandays v1.0.0 h1:A8YM7wIj16SzlKT0SRJc9CD29iiaUzpBLzh
 github.com/hablullah/go-juliandays v1.0.0/go.mod h1:0JOYq4oFOuDja+oospuc61YoX+uNEn7Z6uHYTbBzdGc=
 github.com/hanwen/go-fuse/v2 v2.7.2 h1:SbJP1sUP+n1UF8NXBA14BuojmTez+mDgOk0bC057HQw=
 github.com/hanwen/go-fuse/v2 v2.7.2/go.mod h1:ugNaD/iv5JYyS1Rcvi57Wz7/vrLQJo10mmketmoef48=
+github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
+github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
 github.com/hinshun/vt10x v0.0.0-20220119200601-820417d04eec h1:qv2VnGeEQHchGaZ/u7lxST/RaJw+cv273q79D81Xbog=
 github.com/hinshun/vt10x v0.0.0-20220119200601-820417d04eec/go.mod h1:Q48J4R4DvxnHolD5P8pOtXigYlRuPLGl6moFx3ulM68=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=

main.go

@@ -42,6 +42,7 @@ var app = &cli.Command{
 		blossomCmd,
 		encrypt,
 		decrypt,
+		gift,
 		outbox,
 		wallet,
 		mcpServer,
@@ -50,6 +51,7 @@ var app = &cli.Command{
 		publish,
 		git,
 		nip,
+		syncCmd,
 	},
 	Version: version,
 	Flags: []cli.Flag{

sync.go

@@ -0,0 +1,464 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+
+	"fiatjaf.com/nostr"
+	"fiatjaf.com/nostr/nip77"
+	"fiatjaf.com/nostr/nip77/negentropy"
+	"fiatjaf.com/nostr/nip77/negentropy/storage"
+	"github.com/urfave/cli/v3"
+)
+
+var syncCmd = &cli.Command{
+	Name:        "sync",
+	Usage:       "sync events between two relays using negentropy",
+	Description: `uses nip77 negentropy to sync events between two relays`,
+	ArgsUsage:   "<relay1> <relay2>",
+	Flags:       reqFilterFlags,
+	Action: func(ctx context.Context, c *cli.Command) error {
+		args := c.Args().Slice()
+		if len(args) != 2 {
+			return fmt.Errorf("need exactly two relay URLs: source and target")
+		}
+
+		filter := nostr.Filter{}
+		if err := applyFlagsToFilter(c, &filter); err != nil {
+			return err
+		}
+
+		peerA, err := NewRelayThirdPartyRemote(ctx, args[0])
+		if err != nil {
+			return fmt.Errorf("error setting up %s: %w", args[0], err)
+		}
+
+		peerB, err := NewRelayThirdPartyRemote(ctx, args[1])
+		if err != nil {
+			return fmt.Errorf("error setting up %s: %w", args[1], err)
+		}
+
+		tpn := NewThirdPartyNegentropy(
+			peerA,
+			peerB,
+			filter,
+		)
+
+		wg := sync.WaitGroup{}
+
+		wg.Go(func() {
+			err = tpn.Run(ctx)
+		})
+
+		wg.Go(func() {
+			type op struct {
+				src *nostr.Relay
+				dst *nostr.Relay
+				ids []nostr.ID
+			}
+
+			pending := []op{
+				{peerA.relay, peerB.relay, make([]nostr.ID, 0, 30)},
+				{peerB.relay, peerA.relay, make([]nostr.ID, 0, 30)},
+			}
+
+			for delta := range tpn.Deltas {
+				have := delta.Have.relay
+				havenot := delta.HaveNot.relay
+				logverbose("%s has %s, %s doesn't.\n", have.URL, delta.ID.Hex(), havenot.URL)
+
+				idx := 0 // peerA
+				if have == peerB.relay {
+					idx = 1 // peerB
+				}
+				pending[idx].ids = append(pending[idx].ids, delta.ID)
+
+				// every 30 ids do a fetch-and-publish
+				if len(pending[idx].ids) == 30 {
+					for evt := range pending[idx].src.QueryEvents(nostr.Filter{IDs: pending[idx].ids}) {
+						pending[idx].dst.Publish(ctx, evt)
+					}
+					pending[idx].ids = pending[idx].ids[:0]
+				}
+			}
+
+			// do it for the remaining ids
+			for _, op := range pending {
+				if len(op.ids) > 0 {
+					for evt := range op.src.QueryEvents(nostr.Filter{IDs: op.ids}) {
+						op.dst.Publish(ctx, evt)
+					}
+				}
+			}
+		})
+
+		wg.Wait()
+
+		return err
+	},
+}
+
+type ThirdPartyNegentropy struct {
+	PeerA  *RelayThirdPartyRemote
+	PeerB  *RelayThirdPartyRemote
+	Filter nostr.Filter
+
+	Deltas chan Delta
+}
+
+type Delta struct {
+	ID      nostr.ID
+	Have    *RelayThirdPartyRemote
+	HaveNot *RelayThirdPartyRemote
+}
+
+type boundKey string
+
+func getBoundKey(b negentropy.Bound) boundKey {
+	return boundKey(fmt.Sprintf("%d:%x", b.Timestamp, b.IDPrefix))
+}
+
+type RelayThirdPartyRemote struct {
+	relay    *nostr.Relay
+	messages chan string
+	err      error
+}
+
+func NewRelayThirdPartyRemote(ctx context.Context, url string) (*RelayThirdPartyRemote, error) {
+	rtpr := &RelayThirdPartyRemote{
+		messages: make(chan string, 3),
+	}
+
+	var err error
+	rtpr.relay, err = nostr.RelayConnect(ctx, url, nostr.RelayOptions{
+		CustomHandler: func(data string) {
+			envelope := nip77.ParseNegMessage(data)
+			if envelope == nil {
+				return
+			}
+			switch env := envelope.(type) {
+			case *nip77.OpenEnvelope, *nip77.CloseEnvelope:
+				rtpr.err = fmt.Errorf("unexpected %s received from relay", env.Label())
+				return
+			case *nip77.ErrorEnvelope:
+				rtpr.err = fmt.Errorf("relay returned a %s: %s", env.Label(), env.Reason)
+				return
+			case *nip77.MessageEnvelope:
+				rtpr.messages <- env.Message
+			}
+		},
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return rtpr, nil
+}
+
+func (rtpr *RelayThirdPartyRemote) SendInitialMessage(filter nostr.Filter, msg string) error {
+	msgj, _ := json.Marshal(nip77.OpenEnvelope{
+		SubscriptionID: "sync3",
+		Filter:         filter,
+		Message:        msg,
+	})
+	return rtpr.relay.WriteWithError(msgj)
+}
+
+func (rtpr *RelayThirdPartyRemote) SendMessage(msg string) error {
+	msgj, _ := json.Marshal(nip77.MessageEnvelope{
+		SubscriptionID: "sync3",
+		Message:        msg,
+	})
+	return rtpr.relay.WriteWithError(msgj)
+}
+
+func (rtpr *RelayThirdPartyRemote) SendClose() error {
+	msgj, _ := json.Marshal(nip77.CloseEnvelope{
+		SubscriptionID: "sync3",
+	})
+	return rtpr.relay.WriteWithError(msgj)
+}
+
+var thirdPartyRemoteEndOfMessages = errors.New("the-end")
+
+func (rtpr *RelayThirdPartyRemote) Receive() (string, error) {
+	if rtpr.err != nil {
+		return "", rtpr.err
+	}
+	if msg, ok := <-rtpr.messages; ok {
+		return msg, nil
+	}
+	return "", thirdPartyRemoteEndOfMessages
+}
+
+func NewThirdPartyNegentropy(peerA, peerB *RelayThirdPartyRemote, filter nostr.Filter) *ThirdPartyNegentropy {
+	return &ThirdPartyNegentropy{
+		PeerA:  peerA,
+		PeerB:  peerB,
+		Filter: filter,
+		Deltas: make(chan Delta, 100),
+	}
+}
+
+func (n *ThirdPartyNegentropy) Run(ctx context.Context) error {
+	peerAIds := make(map[nostr.ID]struct{})
+	peerBIds := make(map[nostr.ID]struct{})
+	peerASkippedBounds := make(map[boundKey]struct{})
+	peerBSkippedBounds := make(map[boundKey]struct{})
+
+	// send an empty message to A to start things up
+	initialMsg := createInitialMessage()
+	err := n.PeerA.SendInitialMessage(n.Filter, initialMsg)
+	if err != nil {
+		return err
+	}
+
+	hasSentInitialMessageToB := false
+
+	for {
+		// receive message from A
+		msgA, err := n.PeerA.Receive()
+		if err != nil {
+			return err
+		}
+		msgAb, _ := nostr.HexDecodeString(msgA)
+		if len(msgAb) == 1 {
+			break
+		}
+
+		msgToB, err := parseMessageBuildNext(
+			msgA,
+			peerBSkippedBounds,
+			func(id nostr.ID) {
+				if _, exists := peerBIds[id]; exists {
+					delete(peerBIds, id)
+				} else {
+					peerAIds[id] = struct{}{}
+				}
+			},
+			func(boundKey boundKey) {
+				peerASkippedBounds[boundKey] = struct{}{}
+			},
+		)
+		if err != nil {
+			return err
+		}
+
+		// emit deltas from B after receiving message from A
+		for id := range peerBIds {
+			select {
+			case n.Deltas <- Delta{ID: id, Have: n.PeerB, HaveNot: n.PeerA}:
+			case <-ctx.Done():
+				return context.Cause(ctx)
+			}
+			delete(peerBIds, id)
+		}
+
+		if len(msgToB) == 2 {
+			// exit condition (no more messages to send)
+			break
+		}
+
+		// send message to B
+		if hasSentInitialMessageToB {
+			err = n.PeerB.SendMessage(msgToB)
+		} else {
+			err = n.PeerB.SendInitialMessage(n.Filter, msgToB)
+			hasSentInitialMessageToB = true
+		}
+		if err != nil {
+			return err
+		}
+
+		// receive message from B
+		msgB, err := n.PeerB.Receive()
+		if err != nil {
+			return err
+		}
+		msgBb, _ := nostr.HexDecodeString(msgB)
+		if len(msgBb) == 1 {
+			break
+		}
+
+		msgToA, err := parseMessageBuildNext(
+			msgB,
+			peerASkippedBounds,
+			func(id nostr.ID) {
+				if _, exists := peerAIds[id]; exists {
+					delete(peerAIds, id)
+				} else {
+					peerBIds[id] = struct{}{}
+				}
+			},
+			func(boundKey boundKey) {
+				peerBSkippedBounds[boundKey] = struct{}{}
+			},
+		)
+		if err != nil {
+			return err
+		}
+
+		// emit deltas from A after receiving message from B
+		for id := range peerAIds {
+			select {
+			case n.Deltas <- Delta{ID: id, Have: n.PeerA, HaveNot: n.PeerB}:
+			case <-ctx.Done():
+				return context.Cause(ctx)
+			}
+			delete(peerAIds, id)
+		}
+
+		if len(msgToA) == 2 {
+			// exit condition (no more messages to send)
+			break
+		}
+
+		// send message to A
+		err = n.PeerA.SendMessage(msgToA)
+		if err != nil {
+			return err
+		}
+	}
+
+	// emit remaining deltas before exit
+	for id := range peerAIds {
+		select {
+		case n.Deltas <- Delta{ID: id, Have: n.PeerA, HaveNot: n.PeerB}:
+		case <-ctx.Done():
+			return context.Cause(ctx)
+		}
+	}
+	for id := range peerBIds {
+		select {
+		case n.Deltas <- Delta{ID: id, Have: n.PeerB, HaveNot: n.PeerA}:
+		case <-ctx.Done():
+			return context.Cause(ctx)
+		}
+	}
+
+	n.PeerA.SendClose()
+	n.PeerB.SendClose()
+	close(n.Deltas)
+
+	return nil
+}
+
+func createInitialMessage() string {
+	output := bytes.NewBuffer(make([]byte, 0, 64))
+	output.WriteByte(negentropy.ProtocolVersion)
+
+	dummy := negentropy.BoundWriter{}
+	dummy.WriteBound(output, negentropy.InfiniteBound)
+	output.WriteByte(byte(negentropy.FingerprintMode))
+
+	// hardcoded random fingerprint
+	fingerprint := [negentropy.FingerprintSize]byte{
+		0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
+		0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
+	}
+	output.Write(fingerprint[:])
+
+	return nostr.HexEncodeToString(output.Bytes())
+}
+
+func parseMessageBuildNext(
+	msg string,
+	skippedBounds map[boundKey]struct{},
+	idCallback func(id nostr.ID),
+	skipCallback func(boundKey boundKey),
+) (string, error) {
+	msgb, err := nostr.HexDecodeString(msg)
+	if err != nil {
+		return "", err
+	}
+
+	br := &negentropy.BoundReader{}
+	bw := &negentropy.BoundWriter{}
+
+	nextMsg := bytes.NewBuffer(make([]byte, 0, len(msgb)))
+	acc := &storage.Accumulator{} // this will be used for building our own fingerprints and also as a placeholder
+
+	reader := bytes.NewReader(msgb)
+	pv, err := reader.ReadByte()
+	if err != nil {
+		return "", err
+	}
+	if pv != negentropy.ProtocolVersion {
+		return "", fmt.Errorf("unsupported protocol version %v", pv)
+	}
+
+	nextMsg.WriteByte(pv)
+
+	for reader.Len() > 0 {
+		bound, err := br.ReadBound(reader)
+		if err != nil {
+			return "", err
+		}
+
+		modeVal, err := negentropy.ReadVarInt(reader)
+		if err != nil {
+			return "", err
+		}
+		mode := negentropy.Mode(modeVal)
+
+		switch mode {
+		case negentropy.SkipMode:
+			skipCallback(getBoundKey(bound))
+			if _, skipped := skippedBounds[getBoundKey(bound)]; !skipped {
+				bw.WriteBound(nextMsg, bound)
+				negentropy.WriteVarInt(nextMsg, int(negentropy.SkipMode))
+			}
+
+		case negentropy.FingerprintMode:
+			_, err = reader.Read(acc.Buf[0:negentropy.FingerprintSize] /* use this buffer as a dummy */)
+			if err != nil {
+				return "", err
+			}
+
+			if _, skipped := skippedBounds[getBoundKey(bound)]; !skipped {
+				bw.WriteBound(nextMsg, bound)
+				negentropy.WriteVarInt(nextMsg, int(negentropy.FingerprintMode))
+				nextMsg.Write(acc.Buf[0:negentropy.FingerprintSize] /* idem */)
+			}
+		case negentropy.IdListMode:
+			// when receiving an idlist we will never send this bound again to this peer
+			skipCallback(getBoundKey(bound))
+
+			// and instead of sending these ids to the other peer we'll send a fingerprint
+			acc.Reset()
+
+			numIds, err := negentropy.ReadVarInt(reader)
+			if err != nil {
+				return "", err
+			}
+
+			for range numIds {
+				id := nostr.ID{}
+
+				_, err = reader.Read(id[:])
+				if err != nil {
+					return "", err
+				}
+
+				idCallback(id)
+
+				acc.AddBytes(id[:])
+			}
+
+			if _, skipped := skippedBounds[getBoundKey(bound)]; !skipped {
+				fingerprint := acc.GetFingerprint(numIds)
+
+				bw.WriteBound(nextMsg, bound)
+				negentropy.WriteVarInt(nextMsg, int(negentropy.FingerprintMode))
+				nextMsg.Write(fingerprint[:])
+			}
+		default:
+			return "", fmt.Errorf("unknown mode %v", mode)
+		}
+	}
+
+	return nostr.HexEncodeToString(nextMsg.Bytes()), nil
+}