diff --git a/embed.go b/embed.go
index 2fee303..06f15d6 100644
--- a/embed.go
+++ b/embed.go
@@ -71,8 +71,8 @@ var (
 // embedding functions with inline tests
 
 func (lib *Library) embedMain() {
-	lib.EmbedShort(embedShortBase...)
-	lib.EmbedLong(embedLongBase...)
+	lib.UpgradeWithEmbeddedShort(embedShortBase...)
+	lib.UpgradeWthEmbeddedLong(embedLongBase...)
 
 	// inline tests
 	lib.MustEqual("concat", "0x")
@@ -110,7 +110,7 @@ func (lib *Library) embedMain() {
 }
 
 func (lib *Library) embedArithmetics() {
-	lib.EmbedShort(embedArithmeticsShort...)
+	lib.UpgradeWithEmbeddedShort(embedArithmeticsShort...)
 
 	lib.MustEqual("add(5,6)", "add(10,1)")
 	lib.MustEqual("add(5,6)", "u64/11")
@@ -153,8 +153,8 @@ func (lib *Library) embedArithmetics() {
 }
 
 func (lib *Library) embedBitwiseAndCmp() {
-	lib.EmbedShort(embedBitwiseAndCmpShort...)
-	lib.EmbedLong(embedBitwiseAndCmpLong...)
+	lib.UpgradeWithEmbeddedShort(embedBitwiseAndCmpShort...)
+	lib.UpgradeWthEmbeddedLong(embedBitwiseAndCmpLong...)
 
 	// comparison lexicographical (equivalent to bigendian for binary integers)
 	lib.MustTrue("lessThan(1,2)")
@@ -187,7 +187,7 @@ func (lib *Library) embedBitwiseAndCmp() {
 }
 
 func (lib *Library) embedBaseCrypto() {
-	lib.EmbedLong(embedBaseCrypto...)
+	lib.UpgradeWthEmbeddedLong(embedBaseCrypto...)
 
 	h := blake2b.Sum256([]byte{1})
 	lib.MustEqual("len(blake2b(1))", "u64/32")
@@ -204,7 +204,7 @@ func (lib *Library) embedBytecodeManipulation() {
 	//lib.embedLong("unwrapBytecodeArg", 3, lib.evalUnwrapBytecodeArg)
 	//lib.embedLong("parseBytecodePrefix", 1, lib.evalParseBytecodePrefix)
 	//lib.embedLong("evalBytecodeArg", 3, lib.evalEvalBytecodeArg)
-	lib.EmbedLong(embedBytecodeManipulation(lib)...)
+	lib.UpgradeWthEmbeddedLong(embedBytecodeManipulation(lib)...)
 
 	_, _, binCode, err := lib.CompileExpression("slice(0x01020304,1,2)")
 	AssertNoError(err)
diff --git a/extend.go b/extend.go
index b40558b..15a3c28 100644
--- a/extend.go
+++ b/extend.go
@@ -10,7 +10,7 @@ var extendWithUtilityFunctions = []*ExtendFunction{
 }
 
 func (lib *Library) extendBase() {
-	lib.Extend(extendWithUtilityFunctions...)
+	lib.UpgradeWithExtensions(extendWithUtilityFunctions...)
 
 	lib.MustError("require(nil, !!!requirement_failed)", "requirement failed")
 	lib.MustEqual("require(true, !!!something_wrong)", "true")
diff --git a/library.go b/library.go
index 100b745..85d0644 100644
--- a/library.go
+++ b/library.go
@@ -237,12 +237,12 @@ func (lib *Library) embedLongErr(sym string, requiredNumPar int, evalFun EvalFun
 	return dscr.funCode, nil
 }
 
-func (lib *Library) EmbedShort(funList ...*EmbedFunction) {
-	err := lib.EmbedShortErr(funList...)
+func (lib *Library) UpgradeWithEmbeddedShort(funList ...*EmbedFunction) {
+	err := lib.UpgradeWithEmbeddedShortErr(funList...)
 	AssertNoError(err)
 }
 
-func (lib *Library) EmbedShortErr(funList ...*EmbedFunction) (err error) {
+func (lib *Library) UpgradeWithEmbeddedShortErr(funList ...*EmbedFunction) (err error) {
 	for _, fun := range funList {
 		if _, err = lib.embedShortErr(fun.Sym, fun.RequiredNumPar, fun.EvalFun); err != nil {
 			return
@@ -251,12 +251,12 @@ func (lib *Library) EmbedShortErr(funList ...*EmbedFunction) (err error) {
 	return
 }
 
-func (lib *Library) EmbedLong(funList ...*EmbedFunction) {
-	err := lib.EmbedLongErr(funList...)
+func (lib *Library) UpgradeWthEmbeddedLong(funList ...*EmbedFunction) {
+	err := lib.UpgradeWithEmbedLongErr(funList...)
 	AssertNoError(err)
 }
 
-func (lib *Library) EmbedLongErr(funList ...*EmbedFunction) (err error) {
+func (lib *Library) UpgradeWithEmbedLongErr(funList ...*EmbedFunction) (err error) {
 	for _, fun := range funList {
 		if _, err = lib.embedLongErr(fun.Sym, fun.RequiredNumPar, fun.EvalFun); err != nil {
 			return
@@ -265,7 +265,7 @@ func (lib *Library) EmbedLongErr(funList ...*EmbedFunction) (err error) {
 	return
 }
 
-func (lib *Library) Extend(funList ...*ExtendFunction) {
+func (lib *Library) UpgradeWithExtensions(funList ...*ExtendFunction) {
 	for _, fun := range funList {
 		lib.extend(fun.Sym, fun.Source)
 	}
diff --git a/library_test.go b/library_test.go
index 21c15dc..a42552c 100644
--- a/library_test.go
+++ b/library_test.go
@@ -942,43 +942,3 @@ func TestLocalLibrary(t *testing.T) {
 	})
 
 }
-
-func TestSerde(t *testing.T) {
-	t.Run("descriptor", func(t *testing.T) {
-		fd := funDescriptor{
-			sym:               "dummy",
-			funCode:           5,
-			bytecode:          nil,
-			requiredNumParams: 0,
-			evalFun:           nil,
-		}
-		var buf bytes.Buffer
-		fd.write(&buf)
-		bin := buf.Bytes()
-
-		lib := New()
-		fd1 := funDescriptor{}
-		err := fd1.read(bytes.NewReader(bin), lib)
-		require.NoError(t, err)
-	})
-	t.Run("library", func(t *testing.T) {
-		lib := NewBase()
-		bin := lib.libraryBytes()
-		t.Logf("serialized base library: %d bytes", len(bin))
-		t.Logf("------ library original")
-		lib.PrintLibraryStats()
-
-		lib1 := New()
-		lib1.embedBase()
-		rdr := bytes.NewReader(bin)
-		err := lib1.read(rdr)
-		require.NoError(t, err)
-		t.Logf("------ library back")
-		lib1.PrintLibraryStats()
-
-		bin1 := lib1.libraryBytes()
-		t.Logf("serialized base library 1: %d bytes", len(bin1))
-		require.EqualValues(t, bin, bin1)
-
-	})
-}
diff --git a/serde.go b/serde.go
index cbf5843..aad259d 100644
--- a/serde.go
+++ b/serde.go
@@ -3,7 +3,6 @@ package easyfl
 import (
 	"bytes"
 	"encoding/binary"
-	"fmt"
 	"io"
 	"sort"
 
@@ -22,6 +21,9 @@ func (lib *Library) libraryBytes() []byte {
 	return buf.Bytes()
 }
 
+// currently only serialization is implemented. Deserialization is not.
+// Serialization is only used for calculating library hash, to support library upgrades
+
 func (lib *Library) write(w io.Writer) {
 	_ = binary.Write(w, binary.BigEndian, lib.numEmbeddedShort)
 	_ = binary.Write(w, binary.BigEndian, lib.numEmbeddedLong)
@@ -39,29 +41,6 @@ func (lib *Library) write(w io.Writer) {
 	}
 }
 
-func (lib *Library) read(r io.Reader) (err error) {
-	var numEmbeddedShort, numEmbeddedLong, numExtended uint16
-	if err = binary.Read(r, binary.BigEndian, &numEmbeddedShort); err != nil {
-		return err
-	}
-	if err = binary.Read(r, binary.BigEndian, &numEmbeddedLong); err != nil {
-		return err
-	}
-	if err = binary.Read(r, binary.BigEndian, &numExtended); err != nil {
-		return err
-	}
-	expected := numEmbeddedShort + numEmbeddedLong + numExtended
-
-	for lib.NumFunctions() < expected {
-		fd := funDescriptor{}
-		if err = fd.read(r, lib); err != nil {
-			return
-		}
-		lib.addDescriptor(&fd)
-	}
-	return nil
-}
-
 func (fd *funDescriptor) write(w io.Writer) {
 	// fun code
 	_ = binary.Write(w, binary.BigEndian, fd.funCode)
@@ -82,53 +61,3 @@ func (fd *funDescriptor) write(w io.Writer) {
 	_ = binary.Write(w, binary.BigEndian, uint16(len(fd.bytecode)))
 	_, _ = w.Write(fd.bytecode)
 }
-
-func (fd *funDescriptor) read(r io.Reader, lib *Library) (err error) {
-	// fun code
-	if err = binary.Read(r, binary.BigEndian, &fd.funCode); err != nil {
-		return err
-	}
-	// required number of parameters
-	var np byte
-	if err = binary.Read(r, binary.BigEndian, &np); err != nil {
-		return err
-	}
-	fd.requiredNumParams = int(np)
-	if np == 0xff {
-		fd.requiredNumParams = -1
-	}
-	// function name
-	var size byte
-	if err = binary.Read(r, binary.BigEndian, &size); err != nil {
-		return err
-	}
-	buf := make([]byte, size)
-	if _, err = r.Read(buf); err != nil {
-		return err
-	}
-	fd.sym = string(buf)
-	// bytecode
-	if err = binary.Read(r, binary.BigEndian, &size); err != nil {
-		return err
-	}
-	if size > 0 {
-		// extension
-		fd.bytecode = make([]byte, size)
-		if _, err = r.Read(fd.bytecode); err != nil {
-			return err
-		}
-		if fd.evalFun, err = lib.evalFunctionForBytecode(fd.sym, fd.bytecode); err != nil {
-			return err
-		}
-	} else {
-		// embedded
-		var sym string
-		if fd.evalFun, fd.requiredNumParams, sym, err = lib.functionByCode(fd.funCode); err != nil {
-			return fmt.Errorf("can't find embedded function '%s' with code %d: %w", fd.sym, fd.funCode, err)
-		}
-		if sym != fd.sym {
-			return fmt.Errorf("embedded function with code %d: expected name '%s', got '%s'", fd.funCode, fd.sym, sym)
-		}
-	}
-	return nil
-}