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cipher.go
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/*
* Copyright 2018 The CovenantSQL Authors.
*
* 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 crypto implements Asymmetric, Symmetric Encryption and Hash function.
package crypto
import (
"bytes"
"crypto/aes"
"errors"
ec "github.com/btcsuite/btcd/btcec"
"github.com/CovenantSQL/CovenantSQL/crypto/asymmetric"
)
var errInvalidPadding = errors.New("invalid PKCS#7 padding")
// Implement PKCS#7 padding with block size of 16 (AES block size).
// AddPKCSPadding adds padding to a block of data.
func AddPKCSPadding(src []byte) []byte {
padding := aes.BlockSize - len(src)%aes.BlockSize
padtext := bytes.Repeat([]byte{byte(padding)}, padding)
return append(src, padtext...)
}
// RemovePKCSPadding removes padding from data that was added with addPKCSPadding.
func RemovePKCSPadding(src []byte) ([]byte, error) {
length := len(src)
padLength := int(src[length-1])
if padLength > aes.BlockSize || length < aes.BlockSize {
return nil, errInvalidPadding
}
return src[:length-padLength], nil
}
// EncryptAndSign (inputPublicKey, inData) MAIN PROCEDURE:
// 1. newPrivateKey, newPubKey := genSecp256k1Keypair()
// 2. encKey, HMACKey := SHA512(ECDH(newPrivateKey, inputPublicKey))
// 3. PaddedIn := PKCSPadding(in)
// 4. OutBytes := IV + newPubKey + AES-256-CBC(encKey, PaddedIn) + HMAC-SHA-256(HMACKey)
func EncryptAndSign(inputPublicKey *asymmetric.PublicKey, inData []byte) ([]byte, error) {
return ec.Encrypt((*ec.PublicKey)(inputPublicKey), inData)
}
// DecryptAndCheck (inputPrivateKey, inData) MAIN PROCEDURE:
// 1. Decrypt the inData
// 2. Verify the HMAC.
func DecryptAndCheck(inputPrivateKey *asymmetric.PrivateKey, inData []byte) ([]byte, error) {
return ec.Decrypt((*ec.PrivateKey)(inputPrivateKey), inData)
}