diff --git a/frostfsid/frostfsid_contract.go b/frostfsid/frostfsid_contract.go
index a9cca0e..fd2d446 100644
--- a/frostfsid/frostfsid_contract.go
+++ b/frostfsid/frostfsid_contract.go
@@ -96,6 +96,7 @@ const (
 	groupSubjectsKeysPrefix      = 'G'
 	groupCounterKey              = 'c'
 	namespaceGroupsNamesPrefix   = 'm'
+	addressPrefix                = 'A'
 )
 
 func _deploy(data any, isUpdate bool) {
@@ -112,6 +113,27 @@ func _deploy(data any, isUpdate bool) {
 		storage.Put(ctx, adminKey, args.admin)
 	}
 
+	if isUpdate {
+		it := storage.Find(ctx, subjectKeysPrefix, storage.ValuesOnly)
+		for iterator.Next(it) {
+			subjectRaw := iterator.Value(it)
+			subject := std.Deserialize(subjectRaw.([]byte)).(Subject)
+			address := addressKey(contract.CreateStandardAccount(subject.PrimaryKey))
+			if storage.Get(ctx, address) != nil {
+				panic("frostfsid contract contains duplicate keys")
+			}
+			storage.Put(ctx, address, true)
+
+			for i := 0; i < len(subject.AdditionalKeys); i++ {
+				address = addressKey(contract.CreateStandardAccount(subject.AdditionalKeys[i]))
+				if storage.Get(ctx, address) != nil {
+					panic("frostfsid contract contains duplicate keys")
+				}
+				storage.Put(ctx, address, true)
+			}
+		}
+	}
+
 	storage.Put(ctx, groupCounterKey, 0)
 	storage.Put(ctx, namespaceKey(""), std.Serialize(Namespace{}))
 
@@ -182,6 +204,11 @@ func CreateSubject(ns string, key interop.PublicKey) {
 		panic("key is occupied")
 	}
 
+	allAddressKey := addressKey(addr)
+	if storage.Get(ctx, allAddressKey) != nil {
+		panic("key is occupied by another additional key")
+	}
+
 	nsKey := namespaceKey(ns)
 	data = storage.Get(ctx, nsKey).([]byte)
 	if data == nil {
@@ -197,6 +224,7 @@ func CreateSubject(ns string, key interop.PublicKey) {
 
 	nsSubjKey := namespaceSubjectKey(ns, addr)
 	storage.Put(ctx, nsSubjKey, []byte{1})
+	storage.Put(ctx, allAddressKey, true)
 
 	runtime.Notify("CreateSubject", interop.Hash160(addr))
 }
@@ -213,6 +241,11 @@ func AddSubjectKey(addr interop.Hash160, key interop.PublicKey) {
 		panic("incorrect public key length")
 	}
 
+	addressKey := addressKey(contract.CreateStandardAccount(key))
+	if storage.Get(ctx, addressKey) != nil {
+		panic("key is occupied")
+	}
+
 	saKey := subjectAdditionalKey(key, addr)
 	data := storage.Get(ctx, saKey).([]byte)
 	if data != nil {
@@ -230,6 +263,7 @@ func AddSubjectKey(addr interop.Hash160, key interop.PublicKey) {
 	subject.AdditionalKeys = append(subject.AdditionalKeys, key)
 
 	storage.Put(ctx, sKey, std.Serialize(subject))
+	storage.Put(ctx, addressKey, true)
 	runtime.Notify("AddSubjectKey", addr, key)
 }
 
@@ -269,6 +303,7 @@ func RemoveSubjectKey(addr interop.Hash160, key interop.PublicKey) {
 	subject.AdditionalKeys = additionalKeys
 
 	storage.Put(ctx, sKey, std.Serialize(subject))
+	storage.Delete(ctx, addressKey(contract.CreateStandardAccount(key)))
 	runtime.Notify("RemoveSubjectKey", addr, key)
 }
 
@@ -362,6 +397,7 @@ func DeleteSubject(addr interop.Hash160) {
 
 	for i := 0; i < len(subj.AdditionalKeys); i++ {
 		storage.Delete(ctx, subjectAdditionalKey(subj.AdditionalKeys[i], addr))
+		storage.Delete(ctx, addressKey(contract.CreateStandardAccount(subj.AdditionalKeys[i])))
 	}
 	storage.Delete(ctx, sKey)
 
@@ -1029,3 +1065,7 @@ func idToBytes(itemID int) []byte {
 	zeros := make([]byte, 8-ln)
 	return append(b, zeros...)
 }
+
+func addressKey(address []byte) []byte {
+	return append([]byte{addressPrefix}, address...)
+}