diff --git a/.deadcode-out b/.deadcode-out
index 0f1b12c257..b5c043e8fd 100644
--- a/.deadcode-out
+++ b/.deadcode-out
@@ -43,6 +43,10 @@ package "code.gitea.io/gitea/models/dbfs"
 	func Create
 	func Rename
 
+package "code.gitea.io/gitea/models/forgefed"
+	func GetFederationHost
+	func UpdateFederationHost
+
 package "code.gitea.io/gitea/models/forgejo/semver"
 	func GetVersion
 	func SetVersionString
@@ -134,12 +138,7 @@ package "code.gitea.io/gitea/models/user"
 	func GetUserNamesByIDs
 
 package "code.gitea.io/gitea/modules/activitypub"
-	func CurrentTime
-	func containsRequiredHTTPHeaders
-	func NewClient
-	func (*Client).NewRequest
 	func (*Client).Post
-	func GetPrivateKey
 
 package "code.gitea.io/gitea/modules/assetfs"
 	func Bindata
@@ -170,6 +169,16 @@ package "code.gitea.io/gitea/modules/eventsource"
 
 package "code.gitea.io/gitea/modules/forgefed"
 	func NewForgeLike
+	func NewPersonID
+	func (PersonID).AsWebfinger
+	func (PersonID).AsLoginName
+	func (PersonID).HostSuffix
+	func (PersonID).Validate
+	func NewRepositoryID
+	func (RepositoryID).Validate
+	func (ForgePerson).MarshalJSON
+	func (*ForgePerson).UnmarshalJSON
+	func (ForgePerson).Validate
 	func GetItemByType
 	func JSONUnmarshalerFn
 	func NotEmpty
@@ -310,7 +319,7 @@ package "code.gitea.io/gitea/modules/util/filebuffer"
 	func CreateFromReader
 
 package "code.gitea.io/gitea/modules/validation"
-	func ValidateMaxLen
+	func IsErrNotValid
 
 package "code.gitea.io/gitea/modules/web"
 	func RouteMock
diff --git a/models/forgefed/federationhost.go b/models/forgefed/federationhost.go
new file mode 100644
index 0000000000..b60c0c39cf
--- /dev/null
+++ b/models/forgefed/federationhost.go
@@ -0,0 +1,52 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"code.gitea.io/gitea/modules/timeutil"
+	"code.gitea.io/gitea/modules/validation"
+)
+
+// FederationHost data type
+// swagger:model
+type FederationHost struct {
+	ID             int64              `xorm:"pk autoincr"`
+	HostFqdn       string             `xorm:"host_fqdn UNIQUE INDEX VARCHAR(255) NOT NULL"`
+	NodeInfo       NodeInfo           `xorm:"extends NOT NULL"`
+	LatestActivity time.Time          `xorm:"NOT NULL"`
+	Created        timeutil.TimeStamp `xorm:"created"`
+	Updated        timeutil.TimeStamp `xorm:"updated"`
+}
+
+// Factory function for FederationHost. Created struct is asserted to be valid.
+func NewFederationHost(nodeInfo NodeInfo, hostFqdn string) (FederationHost, error) {
+	result := FederationHost{
+		HostFqdn: strings.ToLower(hostFqdn),
+		NodeInfo: nodeInfo,
+	}
+	if valid, err := validation.IsValid(result); !valid {
+		return FederationHost{}, err
+	}
+	return result, nil
+}
+
+// Validate collects error strings in a slice and returns this
+func (host FederationHost) Validate() []string {
+	var result []string
+	result = append(result, validation.ValidateNotEmpty(host.HostFqdn, "HostFqdn")...)
+	result = append(result, validation.ValidateMaxLen(host.HostFqdn, 255, "HostFqdn")...)
+	result = append(result, host.NodeInfo.Validate()...)
+	if host.HostFqdn != strings.ToLower(host.HostFqdn) {
+		result = append(result, fmt.Sprintf("HostFqdn has to be lower case but was: %v", host.HostFqdn))
+	}
+	if !host.LatestActivity.IsZero() && host.LatestActivity.After(time.Now().Add(10*time.Minute)) {
+		result = append(result, fmt.Sprintf("Latest Activity cannot be in the far future: %v", host.LatestActivity))
+	}
+
+	return result
+}
diff --git a/models/forgefed/federationhost_repository.go b/models/forgefed/federationhost_repository.go
new file mode 100644
index 0000000000..03d8741c58
--- /dev/null
+++ b/models/forgefed/federationhost_repository.go
@@ -0,0 +1,61 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/validation"
+)
+
+func init() {
+	db.RegisterModel(new(FederationHost))
+}
+
+func GetFederationHost(ctx context.Context, ID int64) (*FederationHost, error) {
+	host := new(FederationHost)
+	has, err := db.GetEngine(ctx).Where("id=?", ID).Get(host)
+	if err != nil {
+		return nil, err
+	} else if !has {
+		return nil, fmt.Errorf("FederationInfo record %v does not exist", ID)
+	}
+	if res, err := validation.IsValid(host); !res {
+		return nil, err
+	}
+	return host, nil
+}
+
+func FindFederationHostByFqdn(ctx context.Context, fqdn string) (*FederationHost, error) {
+	host := new(FederationHost)
+	has, err := db.GetEngine(ctx).Where("host_fqdn=?", strings.ToLower(fqdn)).Get(host)
+	if err != nil {
+		return nil, err
+	} else if !has {
+		return nil, nil
+	}
+	if res, err := validation.IsValid(host); !res {
+		return nil, err
+	}
+	return host, nil
+}
+
+func CreateFederationHost(ctx context.Context, host *FederationHost) error {
+	if res, err := validation.IsValid(host); !res {
+		return err
+	}
+	_, err := db.GetEngine(ctx).Insert(host)
+	return err
+}
+
+func UpdateFederationHost(ctx context.Context, host *FederationHost) error {
+	if res, err := validation.IsValid(host); !res {
+		return err
+	}
+	_, err := db.GetEngine(ctx).ID(host.ID).Update(host)
+	return err
+}
diff --git a/models/forgefed/federationhost_test.go b/models/forgefed/federationhost_test.go
new file mode 100644
index 0000000000..ea5494c6e9
--- /dev/null
+++ b/models/forgefed/federationhost_test.go
@@ -0,0 +1,78 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"code.gitea.io/gitea/modules/validation"
+)
+
+func Test_FederationHostValidation(t *testing.T) {
+	sut := FederationHost{
+		HostFqdn: "host.do.main",
+		NodeInfo: NodeInfo{
+			SoftwareName: "forgejo",
+		},
+		LatestActivity: time.Now(),
+	}
+	if res, err := validation.IsValid(sut); !res {
+		t.Errorf("sut should be valid but was %q", err)
+	}
+
+	sut = FederationHost{
+		HostFqdn: "",
+		NodeInfo: NodeInfo{
+			SoftwareName: "forgejo",
+		},
+		LatestActivity: time.Now(),
+	}
+	if res, _ := validation.IsValid(sut); res {
+		t.Errorf("sut should be invalid: HostFqdn empty")
+	}
+
+	sut = FederationHost{
+		HostFqdn: strings.Repeat("fill", 64),
+		NodeInfo: NodeInfo{
+			SoftwareName: "forgejo",
+		},
+		LatestActivity: time.Now(),
+	}
+	if res, _ := validation.IsValid(sut); res {
+		t.Errorf("sut should be invalid: HostFqdn too long (len=256)")
+	}
+
+	sut = FederationHost{
+		HostFqdn:       "host.do.main",
+		NodeInfo:       NodeInfo{},
+		LatestActivity: time.Now(),
+	}
+	if res, _ := validation.IsValid(sut); res {
+		t.Errorf("sut should be invalid: NodeInfo invalid")
+	}
+
+	sut = FederationHost{
+		HostFqdn: "host.do.main",
+		NodeInfo: NodeInfo{
+			SoftwareName: "forgejo",
+		},
+		LatestActivity: time.Now().Add(1 * time.Hour),
+	}
+	if res, _ := validation.IsValid(sut); res {
+		t.Errorf("sut should be invalid: Future timestamp")
+	}
+
+	sut = FederationHost{
+		HostFqdn: "hOst.do.main",
+		NodeInfo: NodeInfo{
+			SoftwareName: "forgejo",
+		},
+		LatestActivity: time.Now(),
+	}
+	if res, _ := validation.IsValid(sut); res {
+		t.Errorf("sut should be invalid: HostFqdn lower case")
+	}
+}
diff --git a/models/forgefed/nodeinfo.go b/models/forgefed/nodeinfo.go
new file mode 100644
index 0000000000..66d2eca7aa
--- /dev/null
+++ b/models/forgefed/nodeinfo.go
@@ -0,0 +1,123 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"net/url"
+
+	"code.gitea.io/gitea/modules/validation"
+
+	"github.com/valyala/fastjson"
+)
+
+// ToDo: Search for full text SourceType and Source, also in .md files
+type (
+	SoftwareNameType string
+)
+
+const (
+	ForgejoSourceType SoftwareNameType = "forgejo"
+	GiteaSourceType   SoftwareNameType = "gitea"
+)
+
+var KnownSourceTypes = []any{
+	ForgejoSourceType, GiteaSourceType,
+}
+
+// ------------------------------------------------ NodeInfoWellKnown ------------------------------------------------
+
+// NodeInfo data type
+// swagger:model
+type NodeInfoWellKnown struct {
+	Href string
+}
+
+// Factory function for NodeInfoWellKnown. Created struct is asserted to be valid.
+func NewNodeInfoWellKnown(body []byte) (NodeInfoWellKnown, error) {
+	result, err := NodeInfoWellKnownUnmarshalJSON(body)
+	if err != nil {
+		return NodeInfoWellKnown{}, err
+	}
+
+	if valid, err := validation.IsValid(result); !valid {
+		return NodeInfoWellKnown{}, err
+	}
+
+	return result, nil
+}
+
+func NodeInfoWellKnownUnmarshalJSON(data []byte) (NodeInfoWellKnown, error) {
+	p := fastjson.Parser{}
+	val, err := p.ParseBytes(data)
+	if err != nil {
+		return NodeInfoWellKnown{}, err
+	}
+	href := string(val.GetStringBytes("links", "0", "href"))
+	return NodeInfoWellKnown{Href: href}, nil
+}
+
+// Validate collects error strings in a slice and returns this
+func (node NodeInfoWellKnown) Validate() []string {
+	var result []string
+	result = append(result, validation.ValidateNotEmpty(node.Href, "Href")...)
+
+	parsedURL, err := url.Parse(node.Href)
+	if err != nil {
+		result = append(result, err.Error())
+		return result
+	}
+
+	if parsedURL.Host == "" {
+		result = append(result, "Href has to be absolute")
+	}
+
+	result = append(result, validation.ValidateOneOf(parsedURL.Scheme, []any{"http", "https"}, "parsedURL.Scheme")...)
+
+	if parsedURL.RawQuery != "" {
+		result = append(result, "Href may not contain query")
+	}
+
+	return result
+}
+
+// ------------------------------------------------ NodeInfo ------------------------------------------------
+
+// NodeInfo data type
+// swagger:model
+type NodeInfo struct {
+	SoftwareName SoftwareNameType
+}
+
+func NodeInfoUnmarshalJSON(data []byte) (NodeInfo, error) {
+	p := fastjson.Parser{}
+	val, err := p.ParseBytes(data)
+	if err != nil {
+		return NodeInfo{}, err
+	}
+	source := string(val.GetStringBytes("software", "name"))
+	result := NodeInfo{}
+	result.SoftwareName = SoftwareNameType(source)
+	return result, nil
+}
+
+func NewNodeInfo(body []byte) (NodeInfo, error) {
+	result, err := NodeInfoUnmarshalJSON(body)
+	if err != nil {
+		return NodeInfo{}, err
+	}
+
+	if valid, err := validation.IsValid(result); !valid {
+		return NodeInfo{}, err
+	}
+	return result, nil
+}
+
+// Validate collects error strings in a slice and returns this
+func (node NodeInfo) Validate() []string {
+	var result []string
+	result = append(result, validation.ValidateNotEmpty(string(node.SoftwareName), "node.SoftwareName")...)
+	result = append(result, validation.ValidateOneOf(node.SoftwareName, KnownSourceTypes, "node.SoftwareName")...)
+
+	return result
+}
diff --git a/models/forgefed/nodeinfo_test.go b/models/forgefed/nodeinfo_test.go
new file mode 100644
index 0000000000..4c73bb44d8
--- /dev/null
+++ b/models/forgefed/nodeinfo_test.go
@@ -0,0 +1,92 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+
+	"code.gitea.io/gitea/modules/validation"
+)
+
+func Test_NodeInfoWellKnownUnmarshalJSON(t *testing.T) {
+	type testPair struct {
+		item    []byte
+		want    NodeInfoWellKnown
+		wantErr error
+	}
+
+	tests := map[string]testPair{
+		"with href": {
+			item: []byte(`{"links":[{"href":"https://federated-repo.prod.meissa.de/api/v1/nodeinfo","rel":"http://nodeinfo.diaspora.software/ns/schema/2.1"}]}`),
+			want: NodeInfoWellKnown{
+				Href: "https://federated-repo.prod.meissa.de/api/v1/nodeinfo",
+			},
+		},
+		"empty": {
+			item:    []byte(``),
+			wantErr: fmt.Errorf("cannot parse JSON: cannot parse empty string; unparsed tail: \"\""),
+		},
+	}
+
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			got, err := NodeInfoWellKnownUnmarshalJSON(tt.item)
+			if (err != nil || tt.wantErr != nil) && tt.wantErr.Error() != err.Error() {
+				t.Errorf("UnmarshalJSON() error = \"%v\", wantErr \"%v\"", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("UnmarshalJSON() got = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_NodeInfoWellKnownValidate(t *testing.T) {
+	sut := NodeInfoWellKnown{Href: "https://federated-repo.prod.meissa.de/api/v1/nodeinfo"}
+	if b, err := validation.IsValid(sut); !b {
+		t.Errorf("sut should be valid, %v, %v", sut, err)
+	}
+
+	sut = NodeInfoWellKnown{Href: "./federated-repo.prod.meissa.de/api/v1/nodeinfo"}
+	_, err := validation.IsValid(sut)
+	if !validation.IsErrNotValid(err) && strings.Contains(err.Error(), "Href has to be absolute\nValue  is not contained in allowed values [http https]") {
+		t.Errorf("validation error expected but was: %v\n", err)
+	}
+
+	sut = NodeInfoWellKnown{Href: "https://federated-repo.prod.meissa.de/api/v1/nodeinfo?alert=1"}
+	_, err = validation.IsValid(sut)
+	if !validation.IsErrNotValid(err) && strings.Contains(err.Error(), "Href has to be absolute\nValue  is not contained in allowed values [http https]") {
+		t.Errorf("sut should be valid, %v, %v", sut, err)
+	}
+}
+
+func Test_NewNodeInfoWellKnown(t *testing.T) {
+	sut, _ := NewNodeInfoWellKnown([]byte(`{"links":[{"href":"https://federated-repo.prod.meissa.de/api/v1/nodeinfo","rel":"http://nodeinfo.diaspora.software/ns/schema/2.1"}]}`))
+	expected := NodeInfoWellKnown{Href: "https://federated-repo.prod.meissa.de/api/v1/nodeinfo"}
+	if sut != expected {
+		t.Errorf("expected was: %v but was: %v", expected, sut)
+	}
+
+	_, err := NewNodeInfoWellKnown([]byte(`invalid`))
+	if err == nil {
+		t.Errorf("error was expected here")
+	}
+}
+
+func Test_NewNodeInfo(t *testing.T) {
+	sut, _ := NewNodeInfo([]byte(`{"version":"2.1","software":{"name":"gitea","version":"1.20.0+dev-2539-g5840cc6d3","repository":"https://github.com/go-gitea/gitea.git","homepage":"https://gitea.io/"},"protocols":["activitypub"],"services":{"inbound":[],"outbound":["rss2.0"]},"openRegistrations":true,"usage":{"users":{"total":13,"activeHalfyear":1,"activeMonth":1}},"metadata":{}}`))
+	expected := NodeInfo{SoftwareName: "gitea"}
+	if sut != expected {
+		t.Errorf("expected was: %v but was: %v", expected, sut)
+	}
+
+	_, err := NewNodeInfo([]byte(`invalid`))
+	if err == nil {
+		t.Errorf("error was expected here")
+	}
+}
diff --git a/models/forgejo_migrations/migrate.go b/models/forgejo_migrations/migrate.go
index 3b6da74149..fc5a460163 100644
--- a/models/forgejo_migrations/migrate.go
+++ b/models/forgejo_migrations/migrate.go
@@ -66,6 +66,8 @@ var migrations = []*Migration{
 	NewMigration("Add `hide_archive_links` column to `release` table", AddHideArchiveLinksToRelease),
 	// v14 -> v15
 	NewMigration("Remove Gitea-specific columns from the repository and badge tables", RemoveGiteaSpecificColumnsFromRepositoryAndBadge),
+	// v15 -> v16
+	NewMigration("Create the `federation_host` table", CreateFederationHostTable),
 }
 
 // GetCurrentDBVersion returns the current Forgejo database version.
diff --git a/models/forgejo_migrations/v15.go b/models/forgejo_migrations/v15.go
new file mode 100644
index 0000000000..d7ed19ca7c
--- /dev/null
+++ b/models/forgejo_migrations/v15.go
@@ -0,0 +1,33 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgejo_migrations //nolint:revive
+
+import (
+	"time"
+
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+type (
+	SoftwareNameType string
+)
+
+type NodeInfo struct {
+	SoftwareName SoftwareNameType
+}
+
+type FederationHost struct {
+	ID             int64              `xorm:"pk autoincr"`
+	HostFqdn       string             `xorm:"host_fqdn UNIQUE INDEX VARCHAR(255) NOT NULL"`
+	NodeInfo       NodeInfo           `xorm:"extends NOT NULL"`
+	LatestActivity time.Time          `xorm:"NOT NULL"`
+	Created        timeutil.TimeStamp `xorm:"created"`
+	Updated        timeutil.TimeStamp `xorm:"updated"`
+}
+
+func CreateFederationHostTable(x *xorm.Engine) error {
+	return x.Sync(new(FederationHost))
+}
diff --git a/modules/activitypub/client.go b/modules/activitypub/client.go
index 66b977c01f..d47990430d 100644
--- a/modules/activitypub/client.go
+++ b/modules/activitypub/client.go
@@ -1,6 +1,8 @@
 // Copyright 2022 The Gitea Authors. All rights reserved.
+// Copyright 2024 The Forgejo Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
+// TODO: Think about whether this should be moved to services/activitypub (compare to exosy/services/activitypub/client.go)
 package activitypub
 
 import (
@@ -10,11 +12,13 @@ import (
 	"crypto/x509"
 	"encoding/pem"
 	"fmt"
+	"io"
 	"net/http"
 	"strings"
 	"time"
 
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/proxy"
 	"code.gitea.io/gitea/modules/setting"
 
@@ -84,6 +88,7 @@ func NewClient(ctx context.Context, user *user_model.User, pubID string) (c *Cli
 			Transport: &http.Transport{
 				Proxy: proxy.Proxy(),
 			},
+			Timeout: 5 * time.Second,
 		},
 		algs:        setting.HttpsigAlgs,
 		digestAlg:   httpsig.DigestAlgorithm(setting.Federation.DigestAlgorithm),
@@ -96,9 +101,9 @@ func NewClient(ctx context.Context, user *user_model.User, pubID string) (c *Cli
 }
 
 // NewRequest function
-func (c *Client) NewRequest(b []byte, to string) (req *http.Request, err error) {
+func (c *Client) NewRequest(method string, b []byte, to string) (req *http.Request, err error) {
 	buf := bytes.NewBuffer(b)
-	req, err = http.NewRequest(http.MethodPost, to, buf)
+	req, err = http.NewRequest(method, to, buf)
 	if err != nil {
 		return nil, err
 	}
@@ -116,9 +121,52 @@ func (c *Client) NewRequest(b []byte, to string) (req *http.Request, err error)
 // Post function
 func (c *Client) Post(b []byte, to string) (resp *http.Response, err error) {
 	var req *http.Request
-	if req, err = c.NewRequest(b, to); err != nil {
+	if req, err = c.NewRequest(http.MethodPost, b, to); err != nil {
 		return nil, err
 	}
 	resp, err = c.client.Do(req)
 	return resp, err
 }
+
+// Create an http GET request with forgejo/gitea specific headers
+func (c *Client) Get(to string) (resp *http.Response, err error) {
+	var req *http.Request
+	emptyBody := []byte{0}
+	if req, err = c.NewRequest(http.MethodGet, emptyBody, to); err != nil {
+		return nil, err
+	}
+	resp, err = c.client.Do(req)
+	return resp, err
+}
+
+// Create an http GET request with forgejo/gitea specific headers
+func (c *Client) GetBody(uri string) ([]byte, error) {
+	response, err := c.Get(uri)
+	if err != nil {
+		return nil, err
+	}
+	log.Debug("Client: got status: %v", response.Status)
+	if response.StatusCode != 200 {
+		err = fmt.Errorf("got non 200 status code for id: %v", uri)
+		return nil, err
+	}
+	defer response.Body.Close()
+	body, err := io.ReadAll(response.Body)
+	if err != nil {
+		return nil, err
+	}
+	log.Debug("Client: got body: %v", charLimiter(string(body), 120))
+	return body, nil
+}
+
+// Limit number of characters in a string (useful to prevent log injection attacks and overly long log outputs)
+// Thanks to https://www.socketloop.com/tutorials/golang-characters-limiter-example
+func charLimiter(s string, limit int) string {
+	reader := strings.NewReader(s)
+	buff := make([]byte, limit)
+	n, _ := io.ReadAtLeast(reader, buff, limit)
+	if n != 0 {
+		return fmt.Sprint(string(buff), "...")
+	}
+	return s
+}
diff --git a/modules/activitypub/client_test.go b/modules/activitypub/client_test.go
index 65ea8d4d5b..2ef16fcdf5 100644
--- a/modules/activitypub/client_test.go
+++ b/modules/activitypub/client_test.go
@@ -1,4 +1,5 @@
 // Copyright 2022 The Gitea Authors. All rights reserved.
+// Copyright 2023 The Forgejo Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
 package activitypub
@@ -14,11 +15,87 @@ import (
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 
 	"github.com/stretchr/testify/assert"
+
+	_ "github.com/mattn/go-sqlite3"
 )
 
+/* ToDo: Set Up tests for http get requests
+
+Set up an expected response for GET on api with user-id = 1:
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    "https://w3id.org/security/v1"
+  ],
+  "id": "http://localhost:3000/api/v1/activitypub/user-id/1",
+  "type": "Person",
+  "icon": {
+    "type": "Image",
+    "mediaType": "image/png",
+    "url": "http://localhost:3000/avatar/3120fd0edc57d5d41230013ad88232e2"
+  },
+  "url": "http://localhost:3000/me",
+  "inbox": "http://localhost:3000/api/v1/activitypub/user-id/1/inbox",
+  "outbox": "http://localhost:3000/api/v1/activitypub/user-id/1/outbox",
+  "preferredUsername": "me",
+  "publicKey": {
+    "id": "http://localhost:3000/api/v1/activitypub/user-id/1#main-key",
+    "owner": "http://localhost:3000/api/v1/activitypub/user-id/1",
+    "publicKeyPem": "-----BEGIN PUBLIC KEY-----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\nVuJ4A3mcti2QLS9j0fSwSJdlfolgW6xaPgjdvuSQsgX1AgMBAAE=\n-----END PUBLIC KEY-----\n"
+  }
+}
+
+Set up a user called "me" for all tests
+
+
+
+*/
+
+func TestNewClientReturnsClient(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})
+	pubID := "myGpgId"
+	c, err := NewClient(db.DefaultContext, user, pubID)
+
+	log.Debug("Client: %v\nError: %v", c, err)
+	assert.NoError(t, err)
+}
+
+/* TODO: bring this test to work or delete
+func TestActivityPubSignedGet(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1, Name: "me"})
+	pubID := "myGpgId"
+	c, err := NewClient(db.DefaultContext, user, pubID)
+	assert.NoError(t, err)
+
+	expected := "TestActivityPubSignedGet"
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Regexp(t, regexp.MustCompile("^"+setting.Federation.DigestAlgorithm), r.Header.Get("Digest"))
+		assert.Contains(t, r.Header.Get("Signature"), pubID)
+		assert.Equal(t, r.Header.Get("Content-Type"), ActivityStreamsContentType)
+		body, err := io.ReadAll(r.Body)
+		assert.NoError(t, err)
+		assert.Equal(t, expected, string(body))
+		fmt.Fprint(w, expected)
+	}))
+	defer srv.Close()
+
+	r, err := c.Get(srv.URL)
+	assert.NoError(t, err)
+	defer r.Body.Close()
+	body, err := io.ReadAll(r.Body)
+	assert.NoError(t, err)
+	assert.Equal(t, expected, string(body))
+
+}
+*/
+
 func TestActivityPubSignedPost(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})
diff --git a/modules/forgefed/actor.go b/modules/forgefed/actor.go
new file mode 100644
index 0000000000..d3cae20dec
--- /dev/null
+++ b/modules/forgefed/actor.go
@@ -0,0 +1,226 @@
+// Copyright 2023, 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"fmt"
+	"net/url"
+	"strings"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/validation"
+
+	ap "github.com/go-ap/activitypub"
+)
+
+// ----------------------------- ActorID --------------------------------------------
+type ActorID struct {
+	ID               string
+	Source           string
+	Schema           string
+	Path             string
+	Host             string
+	Port             string
+	UnvalidatedInput string
+}
+
+// Factory function for ActorID. Created struct is asserted to be valid
+func NewActorID(uri string) (ActorID, error) {
+	result, err := newActorID(uri)
+	if err != nil {
+		return ActorID{}, err
+	}
+
+	if valid, err := validation.IsValid(result); !valid {
+		return ActorID{}, err
+	}
+
+	return result, nil
+}
+
+func (id ActorID) AsURI() string {
+	var result string
+	if id.Port == "" {
+		result = fmt.Sprintf("%s://%s/%s/%s", id.Schema, id.Host, id.Path, id.ID)
+	} else {
+		result = fmt.Sprintf("%s://%s:%s/%s/%s", id.Schema, id.Host, id.Port, id.Path, id.ID)
+	}
+	return result
+}
+
+func (id ActorID) Validate() []string {
+	var result []string
+	result = append(result, validation.ValidateNotEmpty(id.ID, "userId")...)
+	result = append(result, validation.ValidateNotEmpty(id.Schema, "schema")...)
+	result = append(result, validation.ValidateNotEmpty(id.Path, "path")...)
+	result = append(result, validation.ValidateNotEmpty(id.Host, "host")...)
+	result = append(result, validation.ValidateNotEmpty(id.UnvalidatedInput, "unvalidatedInput")...)
+
+	if id.UnvalidatedInput != id.AsURI() {
+		result = append(result, fmt.Sprintf("not all input was parsed, \nUnvalidated Input:%q \nParsed URI: %q", id.UnvalidatedInput, id.AsURI()))
+	}
+
+	return result
+}
+
+// ----------------------------- PersonID --------------------------------------------
+type PersonID struct {
+	ActorID
+}
+
+// Factory function for PersonID. Created struct is asserted to be valid
+func NewPersonID(uri, source string) (PersonID, error) {
+	// TODO: remove after test
+	//if !validation.IsValidExternalURL(uri) {
+	//	return PersonId{}, fmt.Errorf("uri %s is not a valid external url", uri)
+	//}
+	result, err := newActorID(uri)
+	if err != nil {
+		return PersonID{}, err
+	}
+	result.Source = source
+
+	// validate Person specific path
+	personID := PersonID{result}
+	if valid, err := validation.IsValid(personID); !valid {
+		return PersonID{}, err
+	}
+
+	return personID, nil
+}
+
+func (id PersonID) AsWebfinger() string {
+	result := fmt.Sprintf("@%s@%s", strings.ToLower(id.ID), strings.ToLower(id.Host))
+	return result
+}
+
+func (id PersonID) AsLoginName() string {
+	result := fmt.Sprintf("%s%s", strings.ToLower(id.ID), id.HostSuffix())
+	return result
+}
+
+func (id PersonID) HostSuffix() string {
+	result := fmt.Sprintf("-%s", strings.ToLower(id.Host))
+	return result
+}
+
+func (id PersonID) Validate() []string {
+	result := id.ActorID.Validate()
+	result = append(result, validation.ValidateNotEmpty(id.Source, "source")...)
+	result = append(result, validation.ValidateOneOf(id.Source, []any{"forgejo", "gitea"}, "Source")...)
+	switch id.Source {
+	case "forgejo", "gitea":
+		if strings.ToLower(id.Path) != "api/v1/activitypub/user-id" && strings.ToLower(id.Path) != "api/activitypub/user-id" {
+			result = append(result, fmt.Sprintf("path: %q has to be a person specific api path", id.Path))
+		}
+	}
+	return result
+}
+
+// ----------------------------- RepositoryID --------------------------------------------
+
+type RepositoryID struct {
+	ActorID
+}
+
+// Factory function for RepositoryID. Created struct is asserted to be valid.
+func NewRepositoryID(uri, source string) (RepositoryID, error) {
+	if !validation.IsAPIURL(uri) {
+		return RepositoryID{}, fmt.Errorf("uri %s is not a valid repo url on this host %s", uri, setting.AppURL+"api")
+	}
+	result, err := newActorID(uri)
+	if err != nil {
+		return RepositoryID{}, err
+	}
+	result.Source = source
+
+	// validate Person specific path
+	repoID := RepositoryID{result}
+	if valid, err := validation.IsValid(repoID); !valid {
+		return RepositoryID{}, err
+	}
+
+	return repoID, nil
+}
+
+func (id RepositoryID) Validate() []string {
+	result := id.ActorID.Validate()
+	result = append(result, validation.ValidateNotEmpty(id.Source, "source")...)
+	result = append(result, validation.ValidateOneOf(id.Source, []any{"forgejo", "gitea"}, "Source")...)
+	switch id.Source {
+	case "forgejo", "gitea":
+		if strings.ToLower(id.Path) != "api/v1/activitypub/repository-id" && strings.ToLower(id.Path) != "api/activitypub/repository-id" {
+			result = append(result, fmt.Sprintf("path: %q has to be a repo specific api path", id.Path))
+		}
+	}
+	return result
+}
+
+func containsEmptyString(ar []string) bool {
+	for _, elem := range ar {
+		if elem == "" {
+			return true
+		}
+	}
+	return false
+}
+
+func removeEmptyStrings(ls []string) []string {
+	var rs []string
+	for _, str := range ls {
+		if str != "" {
+			rs = append(rs, str)
+		}
+	}
+	return rs
+}
+
+func newActorID(uri string) (ActorID, error) {
+	validatedURI, err := url.ParseRequestURI(uri)
+	if err != nil {
+		return ActorID{}, err
+	}
+	pathWithActorID := strings.Split(validatedURI.Path, "/")
+	if containsEmptyString(pathWithActorID) {
+		pathWithActorID = removeEmptyStrings(pathWithActorID)
+	}
+	length := len(pathWithActorID)
+	pathWithoutActorID := strings.Join(pathWithActorID[0:length-1], "/")
+	id := pathWithActorID[length-1]
+
+	result := ActorID{}
+	result.ID = id
+	result.Schema = validatedURI.Scheme
+	result.Host = validatedURI.Hostname()
+	result.Path = pathWithoutActorID
+	result.Port = validatedURI.Port()
+	result.UnvalidatedInput = uri
+	return result, nil
+}
+
+// ----------------------------- ForgePerson -------------------------------------
+
+// ForgePerson activity data type
+// swagger:model
+type ForgePerson struct {
+	// swagger:ignore
+	ap.Actor
+}
+
+func (s ForgePerson) MarshalJSON() ([]byte, error) {
+	return s.Actor.MarshalJSON()
+}
+
+func (s *ForgePerson) UnmarshalJSON(data []byte) error {
+	return s.Actor.UnmarshalJSON(data)
+}
+
+func (s ForgePerson) Validate() []string {
+	var result []string
+	result = append(result, validation.ValidateNotEmpty(string(s.Type), "Type")...)
+	result = append(result, validation.ValidateOneOf(string(s.Type), []any{string(ap.PersonType)}, "Type")...)
+	result = append(result, validation.ValidateNotEmpty(s.PreferredUsername.String(), "PreferredUsername")...)
+
+	return result
+}
diff --git a/modules/forgefed/actor_test.go b/modules/forgefed/actor_test.go
new file mode 100644
index 0000000000..a3c01eceb0
--- /dev/null
+++ b/modules/forgefed/actor_test.go
@@ -0,0 +1,225 @@
+// Copyright 2023, 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/validation"
+
+	ap "github.com/go-ap/activitypub"
+)
+
+func TestNewPersonId(t *testing.T) {
+	expected := PersonID{}
+	expected.ID = "1"
+	expected.Source = "forgejo"
+	expected.Schema = "https"
+	expected.Path = "api/v1/activitypub/user-id"
+	expected.Host = "an.other.host"
+	expected.Port = ""
+	expected.UnvalidatedInput = "https://an.other.host/api/v1/activitypub/user-id/1"
+	sut, _ := NewPersonID("https://an.other.host/api/v1/activitypub/user-id/1", "forgejo")
+	if sut != expected {
+		t.Errorf("expected: %v\n but was: %v\n", expected, sut)
+	}
+
+	expected = PersonID{}
+	expected.ID = "1"
+	expected.Source = "forgejo"
+	expected.Schema = "https"
+	expected.Path = "api/v1/activitypub/user-id"
+	expected.Host = "an.other.host"
+	expected.Port = "443"
+	expected.UnvalidatedInput = "https://an.other.host:443/api/v1/activitypub/user-id/1"
+	sut, _ = NewPersonID("https://an.other.host:443/api/v1/activitypub/user-id/1", "forgejo")
+	if sut != expected {
+		t.Errorf("expected: %v\n but was: %v\n", expected, sut)
+	}
+}
+
+func TestNewRepositoryId(t *testing.T) {
+	setting.AppURL = "http://localhost:3000/"
+	expected := RepositoryID{}
+	expected.ID = "1"
+	expected.Source = "forgejo"
+	expected.Schema = "http"
+	expected.Path = "api/activitypub/repository-id"
+	expected.Host = "localhost"
+	expected.Port = "3000"
+	expected.UnvalidatedInput = "http://localhost:3000/api/activitypub/repository-id/1"
+	sut, _ := NewRepositoryID("http://localhost:3000/api/activitypub/repository-id/1", "forgejo")
+	if sut != expected {
+		t.Errorf("expected: %v\n but was: %v\n", expected, sut)
+	}
+}
+
+func TestActorIdValidation(t *testing.T) {
+	sut := ActorID{}
+	sut.Source = "forgejo"
+	sut.Schema = "https"
+	sut.Path = "api/v1/activitypub/user-id"
+	sut.Host = "an.other.host"
+	sut.Port = ""
+	sut.UnvalidatedInput = "https://an.other.host/api/v1/activitypub/user-id/"
+	if sut.Validate()[0] != "userId should not be empty" {
+		t.Errorf("validation error expected but was: %v\n", sut.Validate())
+	}
+
+	sut = ActorID{}
+	sut.ID = "1"
+	sut.Source = "forgejo"
+	sut.Schema = "https"
+	sut.Path = "api/v1/activitypub/user-id"
+	sut.Host = "an.other.host"
+	sut.Port = ""
+	sut.UnvalidatedInput = "https://an.other.host/api/v1/activitypub/user-id/1?illegal=action"
+	if sut.Validate()[0] != "not all input was parsed, \nUnvalidated Input:\"https://an.other.host/api/v1/activitypub/user-id/1?illegal=action\" \nParsed URI: \"https://an.other.host/api/v1/activitypub/user-id/1\"" {
+		t.Errorf("validation error expected but was: %v\n", sut.Validate()[0])
+	}
+}
+
+func TestPersonIdValidation(t *testing.T) {
+	sut := PersonID{}
+	sut.ID = "1"
+	sut.Source = "forgejo"
+	sut.Schema = "https"
+	sut.Path = "path"
+	sut.Host = "an.other.host"
+	sut.Port = ""
+	sut.UnvalidatedInput = "https://an.other.host/path/1"
+
+	_, err := validation.IsValid(sut)
+	if validation.IsErrNotValid(err) && strings.Contains(err.Error(), "path: \"path\" has to be a person specific api path\n") {
+		t.Errorf("validation error expected but was: %v\n", err)
+	}
+
+	sut = PersonID{}
+	sut.ID = "1"
+	sut.Source = "forgejox"
+	sut.Schema = "https"
+	sut.Path = "api/v1/activitypub/user-id"
+	sut.Host = "an.other.host"
+	sut.Port = ""
+	sut.UnvalidatedInput = "https://an.other.host/api/v1/activitypub/user-id/1"
+	if sut.Validate()[0] != "Value forgejox is not contained in allowed values [forgejo gitea]" {
+		t.Errorf("validation error expected but was: %v\n", sut.Validate()[0])
+	}
+}
+
+func TestWebfingerId(t *testing.T) {
+	sut, _ := NewPersonID("https://codeberg.org/api/v1/activitypub/user-id/12345", "forgejo")
+	if sut.AsWebfinger() != "@12345@codeberg.org" {
+		t.Errorf("wrong webfinger: %v", sut.AsWebfinger())
+	}
+
+	sut, _ = NewPersonID("https://Codeberg.org/api/v1/activitypub/user-id/12345", "forgejo")
+	if sut.AsWebfinger() != "@12345@codeberg.org" {
+		t.Errorf("wrong webfinger: %v", sut.AsWebfinger())
+	}
+}
+
+func TestShouldThrowErrorOnInvalidInput(t *testing.T) {
+	var err any
+	// TODO: remove after test
+	//_, err = NewPersonId("", "forgejo")
+	//if err == nil {
+	//	t.Errorf("empty input should be invalid.")
+	//}
+
+	_, err = NewPersonID("http://localhost:3000/api/v1/something", "forgejo")
+	if err == nil {
+		t.Errorf("localhost uris are not external")
+	}
+	_, err = NewPersonID("./api/v1/something", "forgejo")
+	if err == nil {
+		t.Errorf("relative uris are not allowed")
+	}
+	_, err = NewPersonID("http://1.2.3.4/api/v1/something", "forgejo")
+	if err == nil {
+		t.Errorf("uri may not be ip-4 based")
+	}
+	_, err = NewPersonID("http:///[fe80::1ff:fe23:4567:890a%25eth0]/api/v1/something", "forgejo")
+	if err == nil {
+		t.Errorf("uri may not be ip-6 based")
+	}
+	_, err = NewPersonID("https://codeberg.org/api/v1/activitypub/../activitypub/user-id/12345", "forgejo")
+	if err == nil {
+		t.Errorf("uri may not contain relative path elements")
+	}
+	_, err = NewPersonID("https://myuser@an.other.host/api/v1/activitypub/user-id/1", "forgejo")
+	if err == nil {
+		t.Errorf("uri may not contain unparsed elements")
+	}
+
+	_, err = NewPersonID("https://an.other.host/api/v1/activitypub/user-id/1", "forgejo")
+	if err != nil {
+		t.Errorf("this uri should be valid but was: %v", err)
+	}
+}
+
+func Test_PersonMarshalJSON(t *testing.T) {
+	sut := ForgePerson{}
+	sut.Type = "Person"
+	sut.PreferredUsername = ap.NaturalLanguageValuesNew()
+	sut.PreferredUsername.Set("en", ap.Content("MaxMuster"))
+	result, _ := sut.MarshalJSON()
+	if string(result) != "{\"type\":\"Person\",\"preferredUsername\":\"MaxMuster\"}" {
+		t.Errorf("MarshalJSON() was = %q", result)
+	}
+}
+
+func Test_PersonUnmarshalJSON(t *testing.T) {
+	expected := &ForgePerson{
+		Actor: ap.Actor{
+			Type: "Person",
+			PreferredUsername: ap.NaturalLanguageValues{
+				ap.LangRefValue{Ref: "en", Value: []byte("MaxMuster")},
+			},
+		},
+	}
+	sut := new(ForgePerson)
+	err := sut.UnmarshalJSON([]byte(`{"type":"Person","preferredUsername":"MaxMuster"}`))
+	if err != nil {
+		t.Errorf("UnmarshalJSON() unexpected error: %v", err)
+	}
+	x, _ := expected.MarshalJSON()
+	y, _ := sut.MarshalJSON()
+	if !reflect.DeepEqual(x, y) {
+		t.Errorf("UnmarshalJSON() expected: %q got: %q", x, y)
+	}
+
+	expectedStr := strings.ReplaceAll(strings.ReplaceAll(`{
+		"id":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/10",
+		"type":"Person",
+		"icon":{"type":"Image","mediaType":"image/png","url":"https://federated-repo.prod.meissa.de/avatar/fa7f9c4af2a64f41b1bef292bf872614"},
+		"url":"https://federated-repo.prod.meissa.de/stargoose9",
+		"inbox":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/10/inbox",
+		"outbox":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/10/outbox",
+		"preferredUsername":"stargoose9",
+		"publicKey":{"id":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/10#main-key",
+			"owner":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/10",
+			"publicKeyPem":"-----BEGIN PUBLIC KEY-----\nMIIBoj...XAgMBAAE=\n-----END PUBLIC KEY-----\n"}}`,
+		"\n", ""),
+		"\t", "")
+	err = sut.UnmarshalJSON([]byte(expectedStr))
+	if err != nil {
+		t.Errorf("UnmarshalJSON() unexpected error: %v", err)
+	}
+	result, _ := sut.MarshalJSON()
+	if expectedStr != string(result) {
+		t.Errorf("UnmarshalJSON() expected: %q got: %q", expectedStr, result)
+	}
+}
+
+func TestForgePersonValidation(t *testing.T) {
+	sut := new(ForgePerson)
+	sut.UnmarshalJSON([]byte(`{"type":"Person","preferredUsername":"MaxMuster"}`))
+	if res, _ := validation.IsValid(sut); !res {
+		t.Errorf("sut expected to be valid: %v\n", sut.Validate())
+	}
+}
diff --git a/modules/forgefed/nodeinfo.go b/modules/forgefed/nodeinfo.go
new file mode 100644
index 0000000000..b22d2959d4
--- /dev/null
+++ b/modules/forgefed/nodeinfo.go
@@ -0,0 +1,19 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"fmt"
+)
+
+func (id ActorID) AsWellKnownNodeInfoURI() string {
+	wellKnownPath := ".well-known/nodeinfo"
+	var result string
+	if id.Port == "" {
+		result = fmt.Sprintf("%s://%s/%s", id.Schema, id.Host, wellKnownPath)
+	} else {
+		result = fmt.Sprintf("%s://%s:%s/%s", id.Schema, id.Host, id.Port, wellKnownPath)
+	}
+	return result
+}
diff --git a/modules/validation/validatable.go b/modules/validation/validatable.go
index fc38ad2524..94b5cc135c 100644
--- a/modules/validation/validatable.go
+++ b/modules/validation/validatable.go
@@ -6,20 +6,37 @@ package validation
 
 import (
 	"fmt"
+	"reflect"
 	"strings"
 	"unicode/utf8"
 
 	"code.gitea.io/gitea/modules/timeutil"
 )
 
+// ErrNotValid represents an validation error
+type ErrNotValid struct {
+	Message string
+}
+
+func (err ErrNotValid) Error() string {
+	return fmt.Sprintf("Validation Error: %v", err.Message)
+}
+
+// IsErrNotValid checks if an error is a ErrNotValid.
+func IsErrNotValid(err error) bool {
+	_, ok := err.(ErrNotValid)
+	return ok
+}
+
 type Validateable interface {
 	Validate() []string
 }
 
 func IsValid(v Validateable) (bool, error) {
 	if err := v.Validate(); len(err) > 0 {
+		typeof := reflect.TypeOf(v)
 		errString := strings.Join(err, "\n")
-		return false, fmt.Errorf(errString)
+		return false, ErrNotValid{fmt.Sprint(typeof, ": ", errString)}
 	}
 
 	return true, nil
diff --git a/modules/validation/validatable_test.go b/modules/validation/validatable_test.go
index fdc21f3223..919f5a3183 100644
--- a/modules/validation/validatable_test.go
+++ b/modules/validation/validatable_test.go
@@ -26,9 +26,13 @@ func Test_IsValid(t *testing.T) {
 		t.Errorf("sut expected to be valid: %v\n", sut.Validate())
 	}
 	sut = Sut{valid: false}
-	if res, _ := IsValid(sut); res {
+	res, err := IsValid(sut)
+	if res {
 		t.Errorf("sut expected to be invalid: %v\n", sut.Validate())
 	}
+	if err == nil || !IsErrNotValid(err) || err.Error() != "Validation Error: validation.Sut: invalid" {
+		t.Errorf("validation error expected, but was %v", err)
+	}
 }
 
 func Test_ValidateNotEmpty_ForString(t *testing.T) {
diff --git a/services/federation/federation_service.go b/services/federation/federation_service.go
index 478b00df96..5aba8b38c5 100644
--- a/services/federation/federation_service.go
+++ b/services/federation/federation_service.go
@@ -5,8 +5,12 @@ package federation
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 
+	"code.gitea.io/gitea/models/forgefed"
+	"code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/activitypub"
 	fm "code.gitea.io/gitea/modules/forgefed"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/validation"
@@ -26,5 +30,69 @@ func ProcessLikeActivity(ctx context.Context, form any, repositoryID int64) (int
 	}
 	log.Info("Activity validated:%v", activity)
 
+	// parse actorID (person)
+	actorURI := activity.Actor.GetID().String()
+	log.Info("actorURI was: %v", actorURI)
+	federationHost, err := GetFederationHostForURI(ctx, actorURI)
+	if err != nil {
+		return http.StatusInternalServerError, "Wrong FederationHost", err
+	}
+	if !activity.IsNewer(federationHost.LatestActivity) {
+		return http.StatusNotAcceptable, "Activity out of order.", fmt.Errorf("Activity already processed")
+	}
+
 	return 0, "", nil
 }
+
+func CreateFederationHostFromAP(ctx context.Context, actorID fm.ActorID) (*forgefed.FederationHost, error) {
+	actionsUser := user.NewActionsUser()
+	client, err := activitypub.NewClient(ctx, actionsUser, "no idea where to get key material.")
+	if err != nil {
+		return nil, err
+	}
+	body, err := client.GetBody(actorID.AsWellKnownNodeInfoURI())
+	if err != nil {
+		return nil, err
+	}
+	nodeInfoWellKnown, err := forgefed.NewNodeInfoWellKnown(body)
+	if err != nil {
+		return nil, err
+	}
+	body, err = client.GetBody(nodeInfoWellKnown.Href)
+	if err != nil {
+		return nil, err
+	}
+	nodeInfo, err := forgefed.NewNodeInfo(body)
+	if err != nil {
+		return nil, err
+	}
+	result, err := forgefed.NewFederationHost(nodeInfo, actorID.Host)
+	if err != nil {
+		return nil, err
+	}
+	err = forgefed.CreateFederationHost(ctx, &result)
+	if err != nil {
+		return nil, err
+	}
+	return &result, nil
+}
+
+func GetFederationHostForURI(ctx context.Context, actorURI string) (*forgefed.FederationHost, error) {
+	log.Info("Input was: %v", actorURI)
+	rawActorID, err := fm.NewActorID(actorURI)
+	if err != nil {
+		return nil, err
+	}
+	federationHost, err := forgefed.FindFederationHostByFqdn(ctx, rawActorID.Host)
+	if err != nil {
+		return nil, err
+	}
+	if federationHost == nil {
+		result, err := CreateFederationHostFromAP(ctx, rawActorID)
+		if err != nil {
+			return nil, err
+		}
+		federationHost = result
+	}
+	return federationHost, nil
+}
diff --git a/tests/integration/api_activitypub_repository_test.go b/tests/integration/api_activitypub_repository_test.go
index 19bf1cf094..67b18dac58 100644
--- a/tests/integration/api_activitypub_repository_test.go
+++ b/tests/integration/api_activitypub_repository_test.go
@@ -9,8 +9,11 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"testing"
+	"time"
 
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/forgefed"
+	"code.gitea.io/gitea/models/unittest"
 	"code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/activitypub"
 	forgefed_modules "code.gitea.io/gitea/modules/forgefed"
@@ -70,6 +73,47 @@ func TestActivityPubRepositoryInboxValid(t *testing.T) {
 	srv := httptest.NewServer(testWebRoutes)
 	defer srv.Close()
 
+	federatedRoutes := http.NewServeMux()
+	federatedRoutes.HandleFunc("/.well-known/nodeinfo",
+		func(res http.ResponseWriter, req *http.Request) {
+			// curl -H "Accept: application/json" https://federated-repo.prod.meissa.de/.well-known/nodeinfo
+			responseBody := fmt.Sprintf(`{"links":[{"href":"http://%s/api/v1/nodeinfo","rel":"http://nodeinfo.diaspora.software/ns/schema/2.1"}]}`, req.Host)
+			t.Logf("response: %s", responseBody)
+			// TODO: as soon as content-type will become important:  content-type: application/json;charset=utf-8
+			fmt.Fprint(res, responseBody)
+		})
+	federatedRoutes.HandleFunc("/api/v1/nodeinfo",
+		func(res http.ResponseWriter, req *http.Request) {
+			// curl -H "Accept: application/json" https://federated-repo.prod.meissa.de/api/v1/nodeinfo
+			responseBody := fmt.Sprintf(`{"version":"2.1","software":{"name":"forgejo","version":"1.20.0+dev-3183-g976d79044",` +
+				`"repository":"https://codeberg.org/forgejo/forgejo.git","homepage":"https://forgejo.org/"},` +
+				`"protocols":["activitypub"],"services":{"inbound":[],"outbound":["rss2.0"]},` +
+				`"openRegistrations":true,"usage":{"users":{"total":14,"activeHalfyear":2}},"metadata":{}}`)
+			fmt.Fprint(res, responseBody)
+		})
+	federatedRoutes.HandleFunc("/api/v1/activitypub/user-id/2",
+		func(res http.ResponseWriter, req *http.Request) {
+			// curl -H "Accept: application/json" https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/2
+			responseBody := fmt.Sprintf(`{"@context":["https://www.w3.org/ns/activitystreams","https://w3id.org/security/v1"],` +
+				`"id":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/2","type":"Person",` +
+				`"icon":{"type":"Image","mediaType":"image/png","url":"https://federated-repo.prod.meissa.de/avatars/1bb05d9a5f6675ed0272af9ea193063c"},` +
+				`"url":"https://federated-repo.prod.meissa.de/stargoose1","inbox":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/2/inbox",` +
+				`"outbox":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/2/outbox","preferredUsername":"stargoose1",` +
+				`"publicKey":{"id":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/2#main-key","owner":"https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/2",` +
+				`"publicKeyPem":"-----BEGIN PUBLIC KEY-----\nMIIBojANBgkqhkiG9w0BAQEFAAOCAY8AMIIBigKCAYEA18H5s7N6ItZUAh9tneII\nIuZdTTa3cZlLa/9ejWAHTkcp3WLW+/zbsumlMrWYfBy2/yTm56qasWt38iY4D6ul\n` +
+				`CPiwhAqX3REvVq8tM79a2CEqZn9ka6vuXoDgBg/sBf/BUWqf7orkjUXwk/U0Egjf\nk5jcurF4vqf1u+rlAHH37dvSBaDjNj6Qnj4OP12bjfaY/yvs7+jue/eNXFHjzN4E\n` +
+				`T2H4B/yeKTJ4UuAwTlLaNbZJul2baLlHelJPAsxiYaziVuV5P+IGWckY6RSerRaZ\nAkc4mmGGtjAyfN9aewe+lNVfwS7ElFx546PlLgdQgjmeSwLX8FWxbPE5A/PmaXCs\n` +
+				`nx+nou+3dD7NluULLtdd7K+2x02trObKXCAzmi5/Dc+yKTzpFqEz+hLNCz7TImP/\ncK//NV9Q+X67J9O27baH9R9ZF4zMw8rv2Pg0WLSw1z7lLXwlgIsDapeMCsrxkVO4\n` +
+				`LXX5AQ1xQNtlssnVoUBqBrvZsX2jUUKUocvZqMGuE4hfAgMBAAE=\n-----END PUBLIC KEY-----\n"}}`)
+			fmt.Fprint(res, responseBody)
+		})
+	federatedRoutes.HandleFunc("/",
+		func(res http.ResponseWriter, req *http.Request) {
+			t.Errorf("Unhandled request: %q", req.URL.EscapedPath())
+		})
+	federatedSrv := httptest.NewServer(federatedRoutes)
+	defer federatedSrv.Close()
+
 	onGiteaRun(t, func(*testing.T, *url.URL) {
 		appURL := setting.AppURL
 		setting.AppURL = srv.URL + "/"
@@ -81,14 +125,24 @@ func TestActivityPubRepositoryInboxValid(t *testing.T) {
 		repositoryID := 2
 		c, err := activitypub.NewClient(db.DefaultContext, actionsUser, "not used")
 		assert.NoError(t, err)
-		repoInboxURL := fmt.Sprintf("%s/api/v1/activitypub/repository-id/%v/inbox",
+		repoInboxURL := fmt.Sprintf(
+			"%s/api/v1/activitypub/repository-id/%v/inbox",
 			srv.URL, repositoryID)
 
-		activity := []byte(fmt.Sprintf(`{"type":"Like","startTime":"2024-03-27T00:00:00Z","actor":"%s/api/v1/activitypub/user-id/2","object":"%s/api/v1/activitypub/repository-id/%v"}`,
-			srv.URL, srv.URL, repositoryID))
+		activity := []byte(fmt.Sprintf(
+			`{"type":"Like",`+
+				`"startTime":"%s",`+
+				`"actor":"%s/api/v1/activitypub/user-id/2",`+
+				`"object":"%s/api/v1/activitypub/repository-id/%v"}`,
+			time.Now().UTC().Format(time.RFC3339),
+			federatedSrv.URL, srv.URL, repositoryID))
+		t.Logf("activity: %s", activity)
 		resp, err := c.Post(activity, repoInboxURL)
+
 		assert.NoError(t, err)
 		assert.Equal(t, http.StatusNoContent, resp.StatusCode)
+
+		unittest.AssertExistsAndLoadBean(t, &forgefed.FederationHost{HostFqdn: "127.0.0.1"})
 	})
 }