diff --git a/src/restic/pack/blob_set.go b/src/restic/pack/blob_set.go
new file mode 100644
index 000000000..686ea9315
--- /dev/null
+++ b/src/restic/pack/blob_set.go
@@ -0,0 +1,109 @@
+package pack
+
+import "sort"
+
+// BlobSet is a set of blobs.
+type BlobSet map[Handle]struct{}
+
+// NewBlobSet returns a new BlobSet, populated with ids.
+func NewBlobSet(handles ...Handle) BlobSet {
+	m := make(BlobSet)
+	for _, h := range handles {
+		m[h] = struct{}{}
+	}
+
+	return m
+}
+
+// Has returns true iff id is contained in the set.
+func (s BlobSet) Has(h Handle) bool {
+	_, ok := s[h]
+	return ok
+}
+
+// Insert adds id to the set.
+func (s BlobSet) Insert(h Handle) {
+	s[h] = struct{}{}
+}
+
+// Delete removes id from the set.
+func (s BlobSet) Delete(h Handle) {
+	delete(s, h)
+}
+
+// Equals returns true iff s equals other.
+func (s BlobSet) Equals(other BlobSet) bool {
+	if len(s) != len(other) {
+		return false
+	}
+
+	for h := range s {
+		if _, ok := other[h]; !ok {
+			return false
+		}
+	}
+
+	return true
+}
+
+// Merge adds the blobs in other to the current set.
+func (s BlobSet) Merge(other BlobSet) {
+	for h := range other {
+		s.Insert(h)
+	}
+}
+
+// Intersect returns a new set containing the handles that are present in both sets.
+func (s BlobSet) Intersect(other BlobSet) (result BlobSet) {
+	result = NewBlobSet()
+
+	set1 := s
+	set2 := other
+
+	// iterate over the smaller set
+	if len(set2) < len(set1) {
+		set1, set2 = set2, set1
+	}
+
+	for h := range set1 {
+		if set2.Has(h) {
+			result.Insert(h)
+		}
+	}
+
+	return result
+}
+
+// Sub returns a new set containing all handles that are present in s but not in
+// other.
+func (s BlobSet) Sub(other BlobSet) (result BlobSet) {
+	result = NewBlobSet()
+	for h := range s {
+		if !other.Has(h) {
+			result.Insert(h)
+		}
+	}
+
+	return result
+}
+
+// List returns a slice of all Handles in the set.
+func (s BlobSet) List() Handles {
+	list := make(Handles, 0, len(s))
+	for h := range s {
+		list = append(list, h)
+	}
+
+	sort.Sort(list)
+
+	return list
+}
+
+func (s BlobSet) String() string {
+	str := s.List().String()
+	if len(str) < 2 {
+		return "{}"
+	}
+
+	return "{" + str[1:len(str)-1] + "}"
+}
diff --git a/src/restic/pack/handle.go b/src/restic/pack/handle.go
new file mode 100644
index 000000000..b47aa1293
--- /dev/null
+++ b/src/restic/pack/handle.go
@@ -0,0 +1,59 @@
+package pack
+
+import (
+	"fmt"
+	"restic/backend"
+)
+
+// Handle identifies a blob of a given type.
+type Handle struct {
+	ID   backend.ID
+	Type BlobType
+}
+
+func (h Handle) String() string {
+	name := h.ID.String()
+	if len(name) > 10 {
+		name = name[:10]
+	}
+	return fmt.Sprintf("<%s/%s>", h.Type, name)
+}
+
+// Handles is an ordered list of Handles that implements sort.Interface.
+type Handles []Handle
+
+func (h Handles) Len() int {
+	return len(h)
+}
+
+func (h Handles) Less(i, j int) bool {
+	if h[i].Type != h[j].Type {
+		return h[i].Type < h[j].Type
+	}
+
+	for k, b := range h[i].ID {
+		if b == h[j].ID[k] {
+			continue
+		}
+
+		if b < h[j].ID[k] {
+			return true
+		}
+
+		return false
+	}
+
+	return false
+}
+
+func (h Handles) Swap(i, j int) {
+	h[i], h[j] = h[j], h[i]
+}
+
+func (h Handles) String() string {
+	elements := make([]string, 0, len(h))
+	for _, e := range h {
+		elements = append(elements, e.String())
+	}
+	return fmt.Sprintf("%v", elements)
+}