diff --git a/corim/entity.go b/corim/entity.go
index 49aa1468..13058f77 100644
--- a/corim/entity.go
+++ b/corim/entity.go
@@ -4,16 +4,21 @@
 package corim
 
 import (
+	"errors"
 	"fmt"
-
 	"github.com/veraison/corim/comid"
 )
 
+type IExtension interface {
+	Valid() error
+}
+
 // Entity stores an entity-map capable of CBOR and JSON serializations.
 type Entity struct {
 	EntityName string           `cbor:"0,keyasint" json:"name"`
 	RegID      *comid.TaggedURI `cbor:"1,keyasint,omitempty" json:"regid,omitempty"`
 	Roles      Roles            `cbor:"2,keyasint" json:"roles"`
+	Extension  IExtension       `cbor:"3,keyasint" json:"extensions"`
 }
 
 func NewEntity() *Entity {
@@ -58,6 +63,45 @@ func (o *Entity) SetRoles(roles ...Role) *Entity {
 	return o
 }
 
+// SetExtension adds the profile specific extension.
+func (o *Entity) SetExtension(extension IExtension) *Entity {
+	if o != nil {
+		o.Extension = extension
+	}
+	return o
+}
+
+// GetExtension gets the profile specific extension.
+func (o *Entity) GetExtension() (IExtension, error) {
+	if o != nil {
+		return o.Extension, nil
+	}
+	return nil, errors.New("no Entity present")
+}
+
+func (o *Entity) FromCBOR(data []byte) error {
+	if o != nil {
+		err := dm.Unmarshal(data, o)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (o *Entity) ToCBOR() ([]byte, error) {
+	if o != nil {
+		data, err := em.Marshal(o)
+		if err != nil {
+			return nil, err
+		} else {
+			return data, nil
+		}
+	} else {
+		return nil, fmt.Errorf("no entity to serialize")
+	}
+}
+
 // Valid checks for validity of the fields within each Entity
 func (o Entity) Valid() error {
 	if o.EntityName == "" {
@@ -72,6 +116,13 @@ func (o Entity) Valid() error {
 		return fmt.Errorf("invalid entity: %w", err)
 	}
 
+	// Check for user supplied Extensions
+	if o.Extension != nil {
+		if err := o.Extension.Valid(); err != nil {
+			return fmt.Errorf("invalid entity extensions: %w", err)
+		}
+	}
+
 	return nil
 }
 
diff --git a/corim/entity_extension.go b/corim/entity_extension.go
new file mode 100644
index 00000000..1e993058
--- /dev/null
+++ b/corim/entity_extension.go
@@ -0,0 +1,47 @@
+// Copyright 2021 Contributors to the Veraison project.
+// SPDX-License-Identifier: Apache-2.0
+
+package corim
+
+import (
+	"fmt"
+)
+
+type EntityExtension struct {
+	Param1 string `cbor:"0,keyasint" json:"param1"`
+	Param2 byte   `cbor:"1,keyasint,omitempty" json:"param2,omitempty"`
+}
+
+func (o EntityExtension) Valid() error {
+	if o.Param1 == "" {
+		return fmt.Errorf("mandatory Parameter Param1 missing")
+	}
+	if o.Param2 == 0x40 {
+		return fmt.Errorf("mandatory Parameter Param2 cannot be 0x40")
+	}
+
+	return nil
+}
+
+func (o *EntityExtension) FromCBOR(data []byte) error {
+	if o != nil {
+		err := dm.Unmarshal(data, o)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (o *EntityExtension) ToCBOR() ([]byte, error) {
+	if o != nil {
+		data, err := em.Marshal(o)
+		if err != nil {
+			return nil, err
+		} else {
+			return data, nil
+		}
+	} else {
+		return nil, fmt.Errorf("no entity to serialize")
+	}
+}
diff --git a/corim/entity_extension_test.go b/corim/entity_extension_test.go
new file mode 100644
index 00000000..6fefc1e9
--- /dev/null
+++ b/corim/entity_extension_test.go
@@ -0,0 +1,79 @@
+// Copyright 2021 Contributors to the Veraison project.
+// SPDX-License-Identifier: Apache-2.0
+
+package corim
+
+import (
+	"testing"
+
+	"fmt"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEntities_Extensions_Valid_ok(t *testing.T) {
+	ext := &EntityExtension{"my profile", 0x56}
+
+	e := NewEntity().
+		SetEntityName("ACME Ltd.").
+		SetRegID("http://acme.example").
+		SetRoles(RoleManifestCreator).
+		SetExtension(ext)
+	require.NotNil(t, e)
+
+	es := NewEntities().AddEntity(*e)
+	require.NotNil(t, es)
+
+	err := es.Valid()
+	assert.Nil(t, err)
+}
+
+func TestEntities_Extensions_ToCBOR_ok(t *testing.T) {
+	ext := &EntityExtension{"my profile", 0x56}
+
+	e := NewEntity().
+		SetEntityName("ACME Ltd.").
+		SetRegID("http://acme.example").
+		SetRoles(RoleManifestCreator).
+		SetExtension(ext)
+	require.NotNil(t, e)
+	data, err := e.ToCBOR()
+
+	require.Nil(t, err)
+	fmt.Printf("to CBOR Entity = %x", data)
+
+}
+
+func TestEntities_Extensions_FromCBOR_ok(t *testing.T) {
+	data := []byte{0xa4, 0x00, 0x69, 0x41, 0x43, 0x4d, 0x45, 0x20, 0x4c, 0x74, 0x64, 0x2e, 0x01, 0xd8, 0x20, 0x73, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x61, 0x63, 0x6d, 0x65, 0x2e, 0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x02, 0x81, 0x01, 0x03, 0xa2, 0x00, 0x6a, 0x6d, 0x79, 0x20, 0x70, 0x72, 0x6f, 0x66, 0x69, 0x6c, 0x65, 0x01, 0x18, 0x56}
+	//var ext1 EntityExtension
+	e := &Entity{Extension: &EntityExtension{}}
+
+	err := e.FromCBOR(data)
+	require.Nil(t, err)
+	ext, err := e.GetExtension()
+	require.Nil(t, err)
+	require.NotNil(t, ext)
+}
+
+func TestEntities_NoExtensions_ToCBOR_ok(t *testing.T) {
+	e := NewEntity().
+		SetEntityName("ACME Ltd.").
+		SetRegID("http://acme.example").
+		SetRoles(RoleManifestCreator)
+	require.NotNil(t, e)
+	data, err := e.ToCBOR()
+
+	require.Nil(t, err)
+	fmt.Printf("to CBOR Entity = %x", data)
+
+}
+
+func TestEntities_NoExtensions_FromCBOR_ok(t *testing.T) {
+	data := []byte{0xa4, 0x00, 0x69, 0x41, 0x43, 0x4d, 0x45, 0x20, 0x4c, 0x74, 0x64, 0x2e, 0x01, 0xd8, 0x20, 0x73, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x61, 0x63, 0x6d, 0x65, 0x2e, 0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x02, 0x81, 0x01, 0x03, 0x0F6}
+	e := &Entity{}
+	err := e.FromCBOR(data)
+	require.Nil(t, err)
+	require.Nil(t, err)
+
+}