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// Copyright 2022 Google LLC
//
// 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 keyderivation
import (
"fmt"
"google.golang.org/protobuf/proto"
"github.com/tink-crypto/tink-go/v2/keyset"
prfderpb "github.com/tink-crypto/tink-go/v2/proto/prf_based_deriver_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
// CreatePRFBasedKeyTemplate creates a PRF-Based Deriver key template with the
// specified PRF and derived key templates. If either the PRF or derived key
// templates are not supported by the registry, an error is returned.
func CreatePRFBasedKeyTemplate(prfKeyTemplate, derivedKeyTemplate *tinkpb.KeyTemplate) (*tinkpb.KeyTemplate, error) {
keyFormat := &prfderpb.PrfBasedDeriverKeyFormat{
PrfKeyTemplate: prfKeyTemplate,
Params: &prfderpb.PrfBasedDeriverParams{
DerivedKeyTemplate: derivedKeyTemplate,
},
}
serializedFormat, err := proto.Marshal(keyFormat)
if err != nil {
return nil, fmt.Errorf("failed to marshal key format: %s", err)
}
template := &tinkpb.KeyTemplate{
TypeUrl: prfBasedDeriverTypeURL,
OutputPrefixType: derivedKeyTemplate.GetOutputPrefixType(),
Value: serializedFormat,
}
// Verify `template` is derivable.
if _, err := keyset.NewHandle(template); err != nil {
return nil, err
}
return template, nil
}
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