/
compression.go
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/
compression.go
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// Copyright 2019 Finobo
//
// 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 aes256cbc
import (
"crypto/elliptic"
"github.com/ethereum/go-ethereum/crypto/ecies"
"github.com/ethereum/go-ethereum/crypto/secp256k1"
"github.com/pkg/errors"
)
const (
pubKeyBytesLenCompressed = 33
pubKeyBytesLenUncompressed = 65
compressedKeyPrefix = 4
)
// compress a 65 byte uncompressed public key
func compress(publicKey []byte) ([]byte, error) {
if len(publicKey) == pubKeyBytesLenUncompressed-1 && publicKey[0] != compressedKeyPrefix {
publicKey = append([]byte{4}, publicKey...)
}
if len(publicKey) != pubKeyBytesLenUncompressed {
return nil, errors.Errorf("length of uncompressed public key is invalid")
}
if publicKey[0] != compressedKeyPrefix {
return nil, errors.Errorf("missing compression prefix")
}
x, y := elliptic.Unmarshal(ecies.DefaultCurve, publicKey)
return secp256k1.CompressPubkey(x, y), nil
}
// decompress a 33 byte compressed public key
func decompress(publicKey []byte) []byte {
x, y := secp256k1.DecompressPubkey(publicKey)
return elliptic.Marshal(ecies.DefaultCurve, x, y)
}