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// Copyright 2019 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 cryptofmt provides constants and convenience methods that define the
// format of ciphertexts and signatures.
package cryptofmt
import (
"fmt"
"github.com/tink-crypto/tink-go/v2/internal/outputprefix"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const (
// NonRawPrefixSize is the prefix size of Tink and Legacy key types.
NonRawPrefixSize = 5
// LegacyPrefixSize is the prefix size of legacy key types.
// The prefix starts with \x00 and followed by a 4-byte key id.
LegacyPrefixSize = NonRawPrefixSize
// LegacyStartByte is the first byte of the prefix of legacy key types.
LegacyStartByte = byte(0)
// TinkPrefixSize is the prefix size of Tink key types.
// The prefix starts with \x01 and followed by a 4-byte key id.
TinkPrefixSize = NonRawPrefixSize
// TinkStartByte is the first byte of the prefix of Tink key types.
TinkStartByte = byte(1)
// RawPrefixSize is the prefix size of Raw key types.
// Raw prefix is empty.
RawPrefixSize = 0
// RawPrefix is the empty prefix of Raw key types.
RawPrefix = ""
)
// OutputPrefix generates the prefix of ciphertexts produced by the crypto
// primitive obtained from key. The prefix can be either empty (for RAW-type
// prefix), or consists of a 1-byte indicator of the type of the prefix,
// followed by 4 bytes of the key ID in big endian encoding.
func OutputPrefix(key *tinkpb.Keyset_Key) (string, error) {
switch key.OutputPrefixType {
case tinkpb.OutputPrefixType_LEGACY, tinkpb.OutputPrefixType_CRUNCHY:
return string(outputprefix.Legacy(key.KeyId)), nil
case tinkpb.OutputPrefixType_TINK:
return string(outputprefix.Tink(key.KeyId)), nil
case tinkpb.OutputPrefixType_RAW:
return RawPrefix, nil
default:
return "", fmt.Errorf("crypto_format: unknown output prefix type")
}
}
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