go/prf/hkdf_prf_key_manager_test.go - third_party/tink - Git at Google

 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
 ////////////////////////////////////////////////////////////////////////////////

 package prf_test

 import (
 	"encoding/hex"
 	"fmt"
 	"testing"

 	"github.com/golang/protobuf/proto"
 	"github.com/google/tink/go/core/registry"
 	"github.com/google/tink/go/prf"
 	"github.com/google/tink/go/prf/subtle"
 	"github.com/google/tink/go/subtle/random"
 	"github.com/google/tink/go/testutil"
 	commonpb "github.com/google/tink/go/proto/common_go_proto"
 	hkdfpb "github.com/google/tink/go/proto/hkdf_prf_go_proto"
 	tinkpb "github.com/google/tink/go/proto/tink_go_proto"
 )

 func TestGetPrimitiveHKDFBasic(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("HKDF PRF key manager not found: %s", err)
 	}
 	testKeys := genValidHKDFKeys()
 	for i := 0; i < len(testKeys); i++ {
 		serializedKey, _ := proto.Marshal(testKeys[i])
 		p, err := km.Primitive(serializedKey)
 		if err != nil {
 			t.Errorf("unexpected error in test case %d: %s", i, err)
 		}
 		if err := validateHKDFPrimitive(p, testKeys[i]); err != nil {
 			t.Errorf("%s", err)
 		}
 	}
 }

 func TestGetPrimitiveHKDFWithInvalidInput(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
 	}
 	// invalid key
 	testKeys := genInvalidHKDFKeys()
 	for i := 0; i < len(testKeys); i++ {
 		serializedKey, _ := proto.Marshal(testKeys[i])
 		if _, err := km.Primitive(serializedKey); err == nil {
 			t.Errorf("expect an error in test case %d", i)
 		}
 	}
 	if _, err := km.Primitive(nil); err == nil {
 		t.Errorf("expect an error when input is nil")
 	}
 	// empty input
 	if _, err := km.Primitive([]byte{}); err == nil {
 		t.Errorf("expect an error when input is empty")
 	}
 }

 func TestNewKeyHKDFMultipleTimes(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
 	}
 	serializedFormat, _ := proto.Marshal(testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, make([]byte, 0)))
 	keys := make(map[string]bool)
 	nTest := 26
 	for i := 0; i < nTest; i++ {
 		key, _ := km.NewKey(serializedFormat)
 		serializedKey, _ := proto.Marshal(key)
 		keys[string(serializedKey)] = true

 		keyData, _ := km.NewKeyData(serializedFormat)
 		serializedKey = keyData.Value
 		keys[string(serializedKey)] = true
 	}
 	if len(keys) != nTest*2 {
 		t.Errorf("key is repeated")
 	}
 }

 func TestNewKeyHKDFBasic(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
 	}
 	testFormats := genValidHKDFKeyFormats()
 	for i := 0; i < len(testFormats); i++ {
 		serializedFormat, _ := proto.Marshal(testFormats[i])
 		key, err := km.NewKey(serializedFormat)
 		if err != nil {
 			t.Errorf("unexpected error in test case %d: %s", i, err)
 		}
 		if err := validateHKDFKey(testFormats[i], key.(*hkdfpb.HkdfPrfKey)); err != nil {
 			t.Errorf("%s", err)
 		}
 	}
 }

 func TestNewKeyHKDFWithInvalidInput(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
 	}
 	// invalid key formats
 	testFormats := genInvalidHKDFKeyFormats()
 	for i := 0; i < len(testFormats); i++ {
 		serializedFormat, err := proto.Marshal(testFormats[i])
 		if err != nil {
 			fmt.Println("Error!")
 		}
 		if _, err := km.NewKey(serializedFormat); err == nil {
 			t.Errorf("expect an error in test case %d: %s", i, err)
 		}
 	}
 	if _, err := km.NewKey(nil); err == nil {
 		t.Errorf("expect an error when input is nil")
 	}
 	// empty input
 	if _, err := km.NewKey([]byte{}); err == nil {
 		t.Errorf("expect an error when input is empty")
 	}
 }

 func TestNewKeyDataHKDFBasic(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
 	}
 	testFormats := genValidHKDFKeyFormats()
 	for i := 0; i < len(testFormats); i++ {
 		serializedFormat, _ := proto.Marshal(testFormats[i])
 		keyData, err := km.NewKeyData(serializedFormat)
 		if err != nil {
 			t.Errorf("unexpected error in test case %d: %s", i, err)
 		}
 		if keyData.TypeUrl != testutil.HKDFPRFTypeURL {
 			t.Errorf("incorrect type url in test case %d", i)
 		}
 		if keyData.KeyMaterialType != tinkpb.KeyData_SYMMETRIC {
 			t.Errorf("incorrect key material type in test case %d", i)
 		}
 		key := new(hkdfpb.HkdfPrfKey)
 		if err := proto.Unmarshal(keyData.Value, key); err != nil {
 			t.Errorf("invalid key value")
 		}
 		if err := validateHKDFKey(testFormats[i], key); err != nil {
 			t.Errorf("invalid key")
 		}
 	}
 }

 func TestNewKeyDataHKDFWithInvalidInput(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("HKDF PRF key manager not found: %s", err)
 	}
 	// invalid key formats
 	testFormats := genInvalidHKDFKeyFormats()
 	for i := 0; i < len(testFormats); i++ {
 		serializedFormat, _ := proto.Marshal(testFormats[i])
 		if _, err := km.NewKeyData(serializedFormat); err == nil {
 			t.Errorf("expect an error in test case %d", i)
 		}
 	}
 	// nil input
 	if _, err := km.NewKeyData(nil); err == nil {
 		t.Errorf("expect an error when input is nil")
 	}
 }

 func TestHKDFDoesSupport(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("HKDF PRF key manager not found: %s", err)
 	}
 	if !km.DoesSupport(testutil.HKDFPRFTypeURL) {
 		t.Errorf("HKDFPRFKeyManager must support %s", testutil.HKDFPRFTypeURL)
 	}
 	if km.DoesSupport("some bad type") {
 		t.Errorf("HKDFPRFKeyManager must support only %s", testutil.HKDFPRFTypeURL)
 	}
 }

 func TestHKDFTypeURL(t *testing.T) {
 	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
 	if err != nil {
 		t.Errorf("HKDF PRF key manager not found: %s", err)
 	}
 	if km.TypeURL() != testutil.HKDFPRFTypeURL {
 		t.Errorf("incorrect GetKeyType()")
 	}
 }

 func genInvalidHKDFKeys() []proto.Message {
 	badVersionKey := testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, make([]byte, 0))
 	badVersionKey.Version++
 	shortKey := testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, make([]byte, 0))
 	shortKey.KeyValue = []byte{1, 1}
 	return []proto.Message{
 		// not a HKDFPRFKey
 		testutil.NewHKDFPRFParams(commonpb.HashType_SHA256, make([]byte, 0)),
 		// bad version
 		badVersionKey,
 		// key too short
 		shortKey,
 		// SHA-1
 		testutil.NewHKDFPRFKey(commonpb.HashType_SHA1, make([]byte, 0)),
 		// unknown hash type
 		testutil.NewHKDFPRFKey(commonpb.HashType_UNKNOWN_HASH, make([]byte, 0)),
 	}
 }

 func genInvalidHKDFKeyFormats() []proto.Message {
 	shortKeyFormat := testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, make([]byte, 0))
 	shortKeyFormat.KeySize = 1
 	return []proto.Message{
 		// not a HKDFPRFKeyFormat
 		testutil.NewHMACParams(commonpb.HashType_SHA256, 32),
 		// key too short
 		shortKeyFormat,
 		// SHA-1
 		testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA1, make([]byte, 0)),
 		// unknown hash type
 		testutil.NewHKDFPRFKeyFormat(commonpb.HashType_UNKNOWN_HASH, make([]byte, 0)),
 	}
 }

 func genValidHKDFKeyFormats() []*hkdfpb.HkdfPrfKeyFormat {
 	return []*hkdfpb.HkdfPrfKeyFormat{
 		testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, make([]byte, 0)),
 		testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA512, make([]byte, 0)),
 		testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, []byte{0x01, 0x03, 0x42}),
 		testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA512, []byte{0x01, 0x03, 0x42}),
 	}
 }

 func genValidHKDFKeys() []*hkdfpb.HkdfPrfKey {
 	return []*hkdfpb.HkdfPrfKey{
 		testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, make([]byte, 0)),
 		testutil.NewHKDFPRFKey(commonpb.HashType_SHA512, make([]byte, 0)),
 		testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, []byte{0x01, 0x03, 0x42}),
 		testutil.NewHKDFPRFKey(commonpb.HashType_SHA512, []byte{0x01, 0x03, 0x42}),
 	}
 }

 // Checks whether the given HKDFPRFKey matches the given key HKDFPRFKeyFormat
 func validateHKDFKey(format *hkdfpb.HkdfPrfKeyFormat, key *hkdfpb.HkdfPrfKey) error {
 	if format.KeySize != uint32(len(key.KeyValue)) ||
 		key.Params.Hash != format.Params.Hash {
 		return fmt.Errorf("key format and generated key do not match")
 	}
 	p, err := subtle.NewHKDFPRF(commonpb.HashType_name[int32(key.Params.Hash)], key.KeyValue, key.Params.Salt)
 	if err != nil {
 		return fmt.Errorf("cannot create primitive from key: %s", err)
 	}
 	return validateHKDFPrimitive(p, key)
 }

 // validateHKDFPrimitive checks whether the given primitive matches the given HKDFPRFKey
 func validateHKDFPrimitive(p interface{}, key *hkdfpb.HkdfPrfKey) error {
 	hkdfPrimitive := p.(prf.PRF)
 	prfPrimitive, err := subtle.NewHKDFPRF(commonpb.HashType_name[int32(key.Params.Hash)], key.KeyValue, key.Params.Salt)
 	if err != nil {
 		return fmt.Errorf("Could not create HKDF PRF with key material %q: %s", hex.EncodeToString(key.KeyValue), err)
 	}
 	data := random.GetRandomBytes(20)
 	res, err := hkdfPrimitive.ComputePRF(data, 16)
 	if err != nil {
 		return fmt.Errorf("prf computation failed: %s", err)
 	}
 	if len(res) != 16 {
 		return fmt.Errorf("prf computation did not produce 16 byte output")
 	}
 	res2, err := prfPrimitive.ComputePRF(data, 16)
 	if err != nil {
 		return fmt.Errorf("prf computation failed: %s", err)
 	}
 	if len(res2) != 16 {
 		return fmt.Errorf("prf computation did not produce 16 byte output")
 	}
 	if hex.EncodeToString(res) != hex.EncodeToString(res2) {
 		return fmt.Errorf("prf computation did not produce the same output for the same key and input")
 	}
 	return nil
 }
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.
	//
	////////////////////////////////////////////////////////////////////////////////

	package prf_test

	import (
	"encoding/hex"
	"fmt"
	"testing"

	"github.com/golang/protobuf/proto"
	"github.com/google/tink/go/core/registry"
	"github.com/google/tink/go/prf"
	"github.com/google/tink/go/prf/subtle"
	"github.com/google/tink/go/subtle/random"
	"github.com/google/tink/go/testutil"
	commonpb "github.com/google/tink/go/proto/common_go_proto"
	hkdfpb "github.com/google/tink/go/proto/hkdf_prf_go_proto"
	tinkpb "github.com/google/tink/go/proto/tink_go_proto"
	)

	func TestGetPrimitiveHKDFBasic(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("HKDF PRF key manager not found: %s", err)
	}
	testKeys := genValidHKDFKeys()
	for i := 0; i < len(testKeys); i++ {
	serializedKey, _ := proto.Marshal(testKeys[i])
	p, err := km.Primitive(serializedKey)
	if err != nil {
	t.Errorf("unexpected error in test case %d: %s", i, err)
	}
	if err := validateHKDFPrimitive(p, testKeys[i]); err != nil {
	t.Errorf("%s", err)
	}
	}
	}

	func TestGetPrimitiveHKDFWithInvalidInput(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
	}
	// invalid key
	testKeys := genInvalidHKDFKeys()
	for i := 0; i < len(testKeys); i++ {
	serializedKey, _ := proto.Marshal(testKeys[i])
	if _, err := km.Primitive(serializedKey); err == nil {
	t.Errorf("expect an error in test case %d", i)
	}
	}
	if _, err := km.Primitive(nil); err == nil {
	t.Errorf("expect an error when input is nil")
	}
	// empty input
	if _, err := km.Primitive([]byte{}); err == nil {
	t.Errorf("expect an error when input is empty")
	}
	}

	func TestNewKeyHKDFMultipleTimes(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
	}
	serializedFormat, _ := proto.Marshal(testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, make([]byte, 0)))
	keys := make(map[string]bool)
	nTest := 26
	for i := 0; i < nTest; i++ {
	key, _ := km.NewKey(serializedFormat)
	serializedKey, _ := proto.Marshal(key)
	keys[string(serializedKey)] = true

	keyData, _ := km.NewKeyData(serializedFormat)
	serializedKey = keyData.Value
	keys[string(serializedKey)] = true
	}
	if len(keys) != nTest*2 {
	t.Errorf("key is repeated")
	}
	}

	func TestNewKeyHKDFBasic(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
	}
	testFormats := genValidHKDFKeyFormats()
	for i := 0; i < len(testFormats); i++ {
	serializedFormat, _ := proto.Marshal(testFormats[i])
	key, err := km.NewKey(serializedFormat)
	if err != nil {
	t.Errorf("unexpected error in test case %d: %s", i, err)
	}
	if err := validateHKDFKey(testFormats[i], key.(*hkdfpb.HkdfPrfKey)); err != nil {
	t.Errorf("%s", err)
	}
	}
	}

	func TestNewKeyHKDFWithInvalidInput(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
	}
	// invalid key formats
	testFormats := genInvalidHKDFKeyFormats()
	for i := 0; i < len(testFormats); i++ {
	serializedFormat, err := proto.Marshal(testFormats[i])
	if err != nil {
	fmt.Println("Error!")
	}
	if _, err := km.NewKey(serializedFormat); err == nil {
	t.Errorf("expect an error in test case %d: %s", i, err)
	}
	}
	if _, err := km.NewKey(nil); err == nil {
	t.Errorf("expect an error when input is nil")
	}
	// empty input
	if _, err := km.NewKey([]byte{}); err == nil {
	t.Errorf("expect an error when input is empty")
	}
	}

	func TestNewKeyDataHKDFBasic(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("cannot obtain HKDF PRF key manager: %s", err)
	}
	testFormats := genValidHKDFKeyFormats()
	for i := 0; i < len(testFormats); i++ {
	serializedFormat, _ := proto.Marshal(testFormats[i])
	keyData, err := km.NewKeyData(serializedFormat)
	if err != nil {
	t.Errorf("unexpected error in test case %d: %s", i, err)
	}
	if keyData.TypeUrl != testutil.HKDFPRFTypeURL {
	t.Errorf("incorrect type url in test case %d", i)
	}
	if keyData.KeyMaterialType != tinkpb.KeyData_SYMMETRIC {
	t.Errorf("incorrect key material type in test case %d", i)
	}
	key := new(hkdfpb.HkdfPrfKey)
	if err := proto.Unmarshal(keyData.Value, key); err != nil {
	t.Errorf("invalid key value")
	}
	if err := validateHKDFKey(testFormats[i], key); err != nil {
	t.Errorf("invalid key")
	}
	}
	}

	func TestNewKeyDataHKDFWithInvalidInput(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("HKDF PRF key manager not found: %s", err)
	}
	// invalid key formats
	testFormats := genInvalidHKDFKeyFormats()
	for i := 0; i < len(testFormats); i++ {
	serializedFormat, _ := proto.Marshal(testFormats[i])
	if _, err := km.NewKeyData(serializedFormat); err == nil {
	t.Errorf("expect an error in test case %d", i)
	}
	}
	// nil input
	if _, err := km.NewKeyData(nil); err == nil {
	t.Errorf("expect an error when input is nil")
	}
	}

	func TestHKDFDoesSupport(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("HKDF PRF key manager not found: %s", err)
	}
	if !km.DoesSupport(testutil.HKDFPRFTypeURL) {
	t.Errorf("HKDFPRFKeyManager must support %s", testutil.HKDFPRFTypeURL)
	}
	if km.DoesSupport("some bad type") {
	t.Errorf("HKDFPRFKeyManager must support only %s", testutil.HKDFPRFTypeURL)
	}
	}

	func TestHKDFTypeURL(t *testing.T) {
	km, err := registry.GetKeyManager(testutil.HKDFPRFTypeURL)
	if err != nil {
	t.Errorf("HKDF PRF key manager not found: %s", err)
	}
	if km.TypeURL() != testutil.HKDFPRFTypeURL {
	t.Errorf("incorrect GetKeyType()")
	}
	}

	func genInvalidHKDFKeys() []proto.Message {
	badVersionKey := testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, make([]byte, 0))
	badVersionKey.Version++
	shortKey := testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, make([]byte, 0))
	shortKey.KeyValue = []byte{1, 1}
	return []proto.Message{
	// not a HKDFPRFKey
	testutil.NewHKDFPRFParams(commonpb.HashType_SHA256, make([]byte, 0)),
	// bad version
	badVersionKey,
	// key too short
	shortKey,
	// SHA-1
	testutil.NewHKDFPRFKey(commonpb.HashType_SHA1, make([]byte, 0)),
	// unknown hash type
	testutil.NewHKDFPRFKey(commonpb.HashType_UNKNOWN_HASH, make([]byte, 0)),
	}
	}

	func genInvalidHKDFKeyFormats() []proto.Message {
	shortKeyFormat := testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, make([]byte, 0))
	shortKeyFormat.KeySize = 1
	return []proto.Message{
	// not a HKDFPRFKeyFormat
	testutil.NewHMACParams(commonpb.HashType_SHA256, 32),
	// key too short
	shortKeyFormat,
	// SHA-1
	testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA1, make([]byte, 0)),
	// unknown hash type
	testutil.NewHKDFPRFKeyFormat(commonpb.HashType_UNKNOWN_HASH, make([]byte, 0)),
	}
	}

	func genValidHKDFKeyFormats() []*hkdfpb.HkdfPrfKeyFormat {
	return []*hkdfpb.HkdfPrfKeyFormat{
	testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, make([]byte, 0)),
	testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA512, make([]byte, 0)),
	testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA256, []byte{0x01, 0x03, 0x42}),
	testutil.NewHKDFPRFKeyFormat(commonpb.HashType_SHA512, []byte{0x01, 0x03, 0x42}),
	}
	}

	func genValidHKDFKeys() []*hkdfpb.HkdfPrfKey {
	return []*hkdfpb.HkdfPrfKey{
	testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, make([]byte, 0)),
	testutil.NewHKDFPRFKey(commonpb.HashType_SHA512, make([]byte, 0)),
	testutil.NewHKDFPRFKey(commonpb.HashType_SHA256, []byte{0x01, 0x03, 0x42}),
	testutil.NewHKDFPRFKey(commonpb.HashType_SHA512, []byte{0x01, 0x03, 0x42}),
	}
	}

	// Checks whether the given HKDFPRFKey matches the given key HKDFPRFKeyFormat
	func validateHKDFKey(format hkdfpb.HkdfPrfKeyFormat, key hkdfpb.HkdfPrfKey) error {
	if format.KeySize != uint32(len(key.KeyValue)) \|\|
	key.Params.Hash != format.Params.Hash {
	return fmt.Errorf("key format and generated key do not match")
	}
	p, err := subtle.NewHKDFPRF(commonpb.HashType_name[int32(key.Params.Hash)], key.KeyValue, key.Params.Salt)
	if err != nil {
	return fmt.Errorf("cannot create primitive from key: %s", err)
	}
	return validateHKDFPrimitive(p, key)
	}

	// validateHKDFPrimitive checks whether the given primitive matches the given HKDFPRFKey
	func validateHKDFPrimitive(p interface{}, key *hkdfpb.HkdfPrfKey) error {
	hkdfPrimitive := p.(prf.PRF)
	prfPrimitive, err := subtle.NewHKDFPRF(commonpb.HashType_name[int32(key.Params.Hash)], key.KeyValue, key.Params.Salt)
	if err != nil {
	return fmt.Errorf("Could not create HKDF PRF with key material %q: %s", hex.EncodeToString(key.KeyValue), err)
	}
	data := random.GetRandomBytes(20)
	res, err := hkdfPrimitive.ComputePRF(data, 16)
	if err != nil {
	return fmt.Errorf("prf computation failed: %s", err)
	}
	if len(res) != 16 {
	return fmt.Errorf("prf computation did not produce 16 byte output")
	}
	res2, err := prfPrimitive.ComputePRF(data, 16)
	if err != nil {
	return fmt.Errorf("prf computation failed: %s", err)
	}
	if len(res2) != 16 {
	return fmt.Errorf("prf computation did not produce 16 byte output")
	}
	if hex.EncodeToString(res) != hex.EncodeToString(res2) {
	return fmt.Errorf("prf computation did not produce the same output for the same key and input")
	}
	return nil
	}