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// Copyright 2025 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 ecies
import (
"bytes"
"fmt"
"github.com/tink-crypto/tink-go/v2/internal/internalapi"
"github.com/tink-crypto/tink-go/v2/internal/protoserialization"
"github.com/tink-crypto/tink-go/v2/key"
"github.com/tink-crypto/tink-go/v2/tink"
)
type hybridDecrypt struct {
rawHybridDecrypt tink.HybridDecrypt
prefix []byte
variant Variant
}
// NewHybridDecrypt creates a new instance of [tink.HybridDecrypt] from a
// [PrivateKey].
//
// This is an internal API.
func NewHybridDecrypt(privateKey *PrivateKey, _ internalapi.Token) (tink.HybridDecrypt, error) {
serializedPrivateKey, err := protoserialization.SerializeKey(privateKey)
if err != nil {
return nil, err
}
rawHybridDecrypt, err := (&privateKeyKeyManager{}).Primitive(serializedPrivateKey.KeyData().GetValue())
if err != nil {
return nil, err
}
return &hybridDecrypt{
rawHybridDecrypt: rawHybridDecrypt.(tink.HybridDecrypt),
prefix: privateKey.OutputPrefix(),
variant: privateKey.Parameters().(*Parameters).Variant(),
}, nil
}
func (e *hybridDecrypt) Decrypt(ciphertext, contextInfo []byte) ([]byte, error) {
if len(ciphertext) < len(e.prefix) {
return nil, fmt.Errorf("ciphertext too short")
}
if !bytes.Equal(e.prefix, ciphertext[:len(e.prefix)]) {
return nil, fmt.Errorf("ciphertext does not start with the expected prefix")
}
return e.rawHybridDecrypt.Decrypt(ciphertext[len(e.prefix):], contextInfo)
}
func hybridDecryptConstructor(k key.Key) (any, error) {
that, ok := k.(*PrivateKey)
if !ok {
return nil, fmt.Errorf("invalid key type, got %T, want %T", k, (*PrivateKey)(nil))
}
return NewHybridDecrypt(that, internalapi.Token{})
}
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