RSA加解密中必须考虑到的密钥长度、明文长度和密文长度问题。明文长度需要小于密钥长度，而密文长度则等于密钥长度。因此当加密内容长度大于密钥长度时，有效的RSA加解密就需要对内容进行分段。
这是因为，RSA算法本身要求加密内容也就是明文长度m必须0<m<密钥长度n。如果小于这个长度就需要进行padding，因为如果没有padding，就无法确定解密后内容的真实长度，字符串之类的内容问题还不大，以0作为结束符，但对二进制数据就很难，因为不确定后面的0是内容还是内容结束符。而只要用到padding，那么就要占用实际的明文长度，于是实际明文长度需要减去padding字节长度。我们一般使用的padding标准有NoPPadding、OAEPPadding、PKCS1Padding等，其中PKCS#1建议的padding就占用了11个字节。
这样，对于1024长度的密钥。128字节（1024bits）-减去11字节正好是117字节，但对于RSA加密来讲，padding也是参与加密的，所以，依然按照1024bits去理解，但实际的明文只有117字节了。
所以如果要对任意长度的数据进行加密，就需要将数据分段后进行逐一加密，并将结果进行拼接。同样，解码也需要分段解码，并将结果进行拼接。
Php实现
if (! function_exists('url_safe_base64_encode')) {
function url_safe_base64_encode ($data) {
return str_replace(array('+','/', '='),array('-','_', ''), base64_encode($data));
}
}
if (! function_exists('url_safe_base64_decode')) {
function url_safe_base64_decode ($data) {
$base_64 = str_replace(array('-','_'),array('+','/'), $data);
return base64_decode($base_64);
}
}
class XRsa
{
const CHAR_SET = "UTF-8";
const BASE_64_FORMAT = "UrlSafeNoPadding";
const RSA_ALGORITHM_KEY_TYPE = OPENSSL_KEYTYPE_RSA;
const RSA_ALGORITHM_SIGN = OPENSSL_ALGO_SHA256;
protected $public_key;
protected $private_key;
protected $key_len;
public function __construct($pub_key, $pri_key = null)
{
$this->public_key = $pub_key;
$this->private_key = $pri_key;
$pub_id = openssl_get_publickey($this->public_key);
$this->key_len = openssl_pkey_get_details($pub_id)['bits'];
}
/*
* 创建密钥对
*/
public static function createKeys($key_size = 2048)
{
$config = array(
"private_key_bits" => $key_size,
"private_key_type" => self::RSA_ALGORITHM_KEY_TYPE,
);
$res = openssl_pkey_new($config);
openssl_pkey_export($res, $private_key);
$public_key_detail = openssl_pkey_get_details($res);
$public_key = $public_key_detail["key"];
return [
"public_key" => $public_key,
"private_key" => $private_key,
];
}
/*
* 公钥加密
*/
public function publicEncrypt($data)
{
$encrypted = '';
$part_len = $this->key_len / 8 - 11;
$parts = str_split($data, $part_len);
foreach ($parts as $part) {
$encrypted_temp = '';
openssl_public_encrypt($part, $encrypted_temp, $this->public_key);
$encrypted .= $encrypted_temp;
}
return url_safe_base64_encode($encrypted);
}
/*
* 私钥解密
*/
public function privateDecrypt($encrypted)
{
$decrypted = "";
$part_len = $this->key_len / 8;
$base64_decoded = url_safe_base64_decode($encrypted);
$parts = str_split($base64_decoded, $part_len);
foreach ($parts as $part) {
$decrypted_temp = '';
openssl_private_decrypt($part, $decrypted_temp,$this->private_key);
$decrypted .= $decrypted_temp;
}
return $decrypted;
}
/*
* 私钥加密
*/
public function privateEncrypt($data)
{
$encrypted = '';
$part_len = $this->key_len / 8 - 11;
$parts = str_split($data, $part_len);
foreach ($parts as $part) {
$encrypted_temp = '';
openssl_private_encrypt($part, $encrypted_temp, $this->private_key);
$encrypted .= $encrypted_temp;
}
return url_safe_base64_encode($encrypted);
}
/*
* 公钥解密
*/
public function publicDecrypt($encrypted)
{
$decrypted = "";
$part_len = $this->key_len / 8;
$base64_decoded = url_safe_base64_decode($encrypted);
$parts = str_split($base64_decoded, $part_len);
foreach ($parts as $part) {
$decrypted_temp = '';
openssl_public_decrypt($part, $decrypted_temp,$this->public_key);
$decrypted .= $decrypted_temp;
}
return $decrypted;
}
/*
* 数据加签
*/
public function sign($data)
{
openssl_sign($data, $sign, $this->private_key, self::RSA_ALGORITHM_SIGN);
return url_safe_base64_encode($sign);
}
/*
* 数据签名验证
*/
public function verify($data, $sign)
{
$pub_id = openssl_get_publickey($this->public_key);
$res = openssl_verify($data, url_safe_base64_decode($sign), $pub_id, self::RSA_ALGORITHM_SIGN);
return $res;
}
}Go实现
package xrsa
import (
"encoding/pem"
"encoding/base64"
"crypto/x509"
"crypto/rsa"
"crypto/rand"
"errors"
"crypto"
"io"
"bytes"
"encoding/asn1"
)
const (
CHAR_SET = "UTF-8"
BASE_64_FORMAT = "UrlSafeNoPadding"
RSA_ALGORITHM_KEY_TYPE = "PKCS8"
RSA_ALGORITHM_SIGN = crypto.SHA256
)
type XRsa struct {
publicKey *rsa.PublicKey
privateKey *rsa.PrivateKey
}
// 生成密钥对
func CreateKeys(publicKeyWriter, privateKeyWriter io.Writer, keyLength int) error {
// 生成私钥文件
privateKey, err := rsa.GenerateKey(rand.Reader, keyLength)
if err != nil {
return err
}
derStream := MarshalPKCS8PrivateKey(privateKey)
block := &pem.Block{
Type: "PRIVATE KEY",
Bytes: derStream,
}
err = pem.Encode(privateKeyWriter, block)
if err != nil {
return err
}
// 生成公钥文件
publicKey := &privateKey.PublicKey
derPkix, err := x509.MarshalPKIXPublicKey(publicKey)
if err != nil {
return err
}
block = &pem.Block{
Type: "PUBLIC KEY",
Bytes: derPkix,
}
err = pem.Encode(publicKeyWriter, block)
if err != nil {
return err
}
return nil
}
func NewXRsa(publicKey []byte, privateKey []byte) (*XRsa, error) {
block, _ := pem.Decode(publicKey)
if block == nil {
return nil, errors.New("public key error")
}
pubInterface, err := x509.ParsePKIXPublicKey(block.Bytes)
if err != nil {
return nil, err
}
pub := pubInterface.(*rsa.PublicKey)
block, _ = pem.Decode(privateKey)
if block == nil {
return nil, errors.New("private key error!")
}
priv, err := x509.ParsePKCS8PrivateKey(block.Bytes)
if err != nil {
return nil, err
}
pri, ok := priv.(*rsa.PrivateKey)
if ok {
return &XRsa {
publicKey: pub,
privateKey: pri,
}, nil
} else {
return nil, errors.New("private key not supported")
}
}
// 公钥加密
func (r *XRsa) PublicEncrypt(data string) (string, error) {
partLen := r.publicKey.N.BitLen() / 8 - 11
chunks := split([]byte(data), partLen)
buffer := bytes.NewBufferString("")
for _, chunk := range chunks {
bytes, err := rsa.EncryptPKCS1v15(rand.Reader, r.publicKey, chunk)
if err != nil {
return "", err
}
buffer.Write(bytes)
}
return base64.RawURLEncoding.EncodeToString(buffer.Bytes()), nil
}
// 私钥解密
func (r *XRsa) PrivateDecrypt(encrypted string) (string, error) {
partLen := r.publicKey.N.BitLen() / 8
raw, err := base64.RawURLEncoding.DecodeString(encrypted)
chunks := split([]byte(raw), partLen)
buffer := bytes.NewBufferString("")
for _, chunk := range chunks {
decrypted, err := rsa.DecryptPKCS1v15(rand.Reader, r.privateKey, chunk)
if err != nil {
return "", err
}
buffer.Write(decrypted)
}
return buffer.String(), err
}
// 数据加签
func (r *XRsa) Sign(data string) (string, error) {
h := RSA_ALGORITHM_SIGN.New()
h.Write([]byte(data))
hashed := h.Sum(nil)
sign, err := rsa.SignPKCS1v15(rand.Reader, r.privateKey, RSA_ALGORITHM_SIGN, hashed)
if err != nil {
return "", err
}
return base64.RawURLEncoding.EncodeToString(sign), err
}
// 数据验签
func (r *XRsa) Verify(data string, sign string) error {
h := RSA_ALGORITHM_SIGN.New()
h.Write([]byte(data))
hashed := h.Sum(nil)
decodedSign, err := base64.RawURLEncoding.DecodeString(sign)
if err != nil {
return err
}
return rsa.VerifyPKCS1v15(r.publicKey, RSA_ALGORITHM_SIGN, hashed, decodedSign)
}
func MarshalPKCS8PrivateKey(key *rsa.PrivateKey) []byte {
info := struct {
Version int
PrivateKeyAlgorithm []asn1.ObjectIdentifier
PrivateKey []byte
}{}
info.Version = 0
info.PrivateKeyAlgorithm = make([]asn1.ObjectIdentifier, 1)
info.PrivateKeyAlgorithm[0] = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
info.PrivateKey = x509.MarshalPKCS1PrivateKey(key)
k, _ := asn1.Marshal(info)
return k
}
func split(buf []byte, lim int) [][]byte {
var chunk []byte
chunks := make([][]byte, 0, len(buf)/lim+1)
for len(buf) >= lim {
chunk, buf = buf[:lim], buf[lim:]
chunks = append(chunks, chunk)
}
if len(buf) > 0 {
chunks = append(chunks, buf[:len(buf)])
}
return chunks
}Java实现
package com.inspii;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.io.IOUtils;
import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;
public class XRsa {
public static final String CHARSET = "UTF-8";
public static final String RSA_ALGORITHM = "RSA";
public static final String RSA_ALGORITHM_SIGN = "SHA256WithRSA";
private RSAPublicKey publicKey;
private RSAPrivateKey privateKey;
public XRsa(String publicKey, String privateKey)
{
try {
KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
//通过X509编码的Key指令获得公钥对象
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKey));
this.publicKey = (RSAPublicKey) keyFactory.generatePublic(x509KeySpec);
//通过PKCS#8编码的Key指令获得私钥对象
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKey));
this.privateKey = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
} catch (Exception e) {
throw new RuntimeException("不支持的密钥", e);
}
}
public static Map<String, String> createKeys(int keySize){
//为RSA算法创建一个KeyPairGenerator对象
KeyPairGenerator kpg;
try{
kpg = KeyPairGenerator.getInstance(RSA_ALGORITHM);
}catch(NoSuchAlgorithmException e){
throw new IllegalArgumentException("No such algorithm-->[" + RSA_ALGORITHM + "]");
}
//初始化KeyPairGenerator对象,不要被initialize()源码表面上欺骗,其实这里声明的size是生效的
kpg.initialize(keySize);
//生成密匙对
KeyPair keyPair = kpg.generateKeyPair();
//得到公钥
Key publicKey = keyPair.getPublic();
String publicKeyStr = Base64.encodeBase64URLSafeString(publicKey.getEncoded());
//得到私钥
Key privateKey = keyPair.getPrivate();
String privateKeyStr = Base64.encodeBase64URLSafeString(privateKey.getEncoded());
Map<String, String> keyPairMap = new HashMap<String, String>();
keyPairMap.put("publicKey", publicKeyStr);
keyPairMap.put("privateKey", privateKeyStr);
return keyPairMap;
}
public String publicEncrypt(String data){
try{
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return Base64.encodeBase64URLSafeString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), publicKey.getModulus().bitLength()));
}catch(Exception e){
throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
}
}
public String privateDecrypt(String data){
try{
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decodeBase64(data), publicKey.getModulus().bitLength()), CHARSET);
}catch(Exception e){
throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
}
}
public String privateEncrypt(String data){
try{
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return Base64.encodeBase64URLSafeString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), publicKey.getModulus().bitLength()));
}catch(Exception e){
throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
}
}
public String publicDecrypt(String data){
try{
Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, publicKey);
return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decodeBase64(data), publicKey.getModulus().bitLength()), CHARSET);
}catch(Exception e){
throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
}
}
public String sign(String data){
try{
//sign
Signature signature = Signature.getInstance(RSA_ALGORITHM_SIGN);
signature.initSign(privateKey);
signature.update(data.getBytes(CHARSET));
return Base64.encodeBase64URLSafeString(signature.sign());
}catch(Exception e){
throw new RuntimeException("签名字符串[" + data + "]时遇到异常", e);
}
}
public boolean verify(String data, String sign){
try{
Signature signature = Signature.getInstance(RSA_ALGORITHM_SIGN);
signature.initVerify(publicKey);
signature.update(data.getBytes(CHARSET));
return signature.verify(Base64.decodeBase64(sign));
}catch(Exception e){
throw new RuntimeException("验签字符串[" + data + "]时遇到异常", e);
}
}
private static byte[] rsaSplitCodec(Cipher cipher, int opmode, byte[] datas, int keySize){
int maxBlock = 0;
if(opmode == Cipher.DECRYPT_MODE){
maxBlock = keySize / 8;
}else{
maxBlock = keySize / 8 - 11;
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
int offSet = 0;
byte[] buff;
int i = 0;
try{
while(datas.length > offSet){
if(datas.length-offSet > maxBlock){
buff = cipher.doFinal(datas, offSet, maxBlock);
}else{
buff = cipher.doFinal(datas, offSet, datas.length-offSet);
}
out.write(buff, 0, buff.length);
i++;
offSet = i * maxBlock;
}
}catch(Exception e){
throw new RuntimeException("加解密阀值为["+maxBlock+"]的数据时发生异常", e);
}
byte[] resultDatas = out.toByteArray();
IOUtils.closeQuietly(out);
return resultDatas;
}
}参考
github地址： https://github.com/liamylian/...
java
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