RSA加密/解密 Decryption error异常解决

import java.io.ByteArrayOutputStream;

import java.security.Key;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.NoSuchAlgorithmException;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.spec.InvalidKeySpecException;

import java.security.spec.PKCS8EncodedKeySpec;

import java.security.spec.X509EncodedKeySpec;

import java.util.HashMap;

import java.util.Map;

import javax.crypto.Cipher;

import org.apache.commons.codec.binary.Base64;

public class RSATest {

    private static final String ALGORITHM = "RSA";

    private static final String PUBLICK_EY = "PUBLICK_EY";

    private static final String PRIVATE_KEY = "PRIVATE_KEY";

    /**

     * 加密算法

     */

    private static final String CIPHER_DE = "RSA";

    /**

     * 解密算法

     */

    private static final String CIPHER_EN = "RSA";

    /**

     * 密钥长度

     */

    private static final Integer KEY_LENGTH = 1024;

    /**

     * RSA最大加密明文大小

     */

    private static final int MAX_ENCRYPT_BLOCK = 117;

    /**

     * RSA最大解密密文大小

     */

    private static final int MAX_DECRYPT_BLOCK = 128;

    /**

     * 生成秘钥对，公钥和私钥

     *

     * @return

     * @throws NoSuchAlgorithmException

     */

    public static Map<String, Object> genKeyPair() throws NoSuchAlgorithmException {

        Map<String, Object> keyMap = new HashMap<String, Object>();

        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);

        keyPairGenerator.initialize(KEY_LENGTH); // 秘钥字节数

        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        PublicKey publicKey = keyPair.getPublic();

        PrivateKey privateKey = keyPair.getPrivate();

        keyMap.put(PUBLICK_EY, publicKey);

        keyMap.put(PRIVATE_KEY, privateKey);

        return keyMap;

    }

    /**

     * 公钥加密

     *

     * @param data

     * @param publicKey

     * @return

     * @throws InvalidKeySpecException

     */

    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {

        // 得到公钥

        byte[] keyBytes = Base64.decodeBase64(publicKey.getBytes());

        X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(keyBytes);

        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);

        Key key = keyFactory.generatePublic(x509EncodedKeySpec);

        // 加密数据，分段加密

        Cipher cipher = Cipher.getInstance(CIPHER_EN);

        cipher.init(Cipher.ENCRYPT_MODE, key);

        int inputLength = data.length;

        ByteArrayOutputStream out = new ByteArrayOutputStream();

        int offset = 0;

        byte[] cache;

        int i = 0;

        while (inputLength - offset > 0) {

            if (inputLength - offset > MAX_ENCRYPT_BLOCK) {

                cache = cipher.doFinal(data, offset, MAX_ENCRYPT_BLOCK);

            } else {

                cache = cipher.doFinal(data, offset, inputLength - offset);

            }

            out.write(cache, 0, cache.length);

            i++;

            offset = i * MAX_ENCRYPT_BLOCK;

        }

        byte[] encryptedData = out.toByteArray();

        out.close();

        return encryptedData;

    }

    /**

     * 私钥解密

     *

     * @param data

     * @param privateKey

     * @return

     * @throws Exception

     */

    public static byte[] decryptByPrivateKey(byte[] data, String privateKey) throws Exception {

        // 得到私钥

        byte[] keyBytes = Base64.decodeBase64(privateKey.getBytes());

        PKCS8EncodedKeySpec pKCS8EncodedKeySpec = new PKCS8EncodedKeySpec(keyBytes);

        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);

        Key key = keyFactory.generatePrivate(pKCS8EncodedKeySpec);

        // 解密数据，分段解密

        Cipher cipher = Cipher.getInstance(CIPHER_DE);

        cipher.init(Cipher.DECRYPT_MODE, key);

        int inputLength = data.length;

        ByteArrayOutputStream out = new ByteArrayOutputStream();

        int offset = 0;

        byte[] cache;

        int i = 0;

        byte[] tmp;

        while (inputLength - offset > 0) {

            if (inputLength - offset > MAX_DECRYPT_BLOCK) {

                cache = cipher.doFinal(data, offset, MAX_DECRYPT_BLOCK);

            } else {

                cache = cipher.doFinal(data, offset, inputLength - offset);

            }

//            out.write(cache, 0, cache.length);

            out.write(cache);

            i++;

            offset = i * MAX_DECRYPT_BLOCK;

        }

        byte[] decryptedData = out.toByteArray();

        out.close();

        return decryptedData;

    }

    /**

     * 获取公钥

     *

     * @param keyMap

     * @return

     */

    public static String getPublicKey(Map<String, Object> keyMap) {

        Key key = (Key) keyMap.get(PUBLICK_EY);

        String str = new String(Base64.encodeBase64(key.getEncoded()));

        return str;

    }

    /**

     * 获取私钥

     *

     * @param keyMap

     * @return

     */

    public static String getPrivateKey(Map<String, Object> keyMap) {

        Key key = (Key) keyMap.get(PRIVATE_KEY);

        String str = new String(Base64.encodeBase64(key.getEncoded()));

        return str;

    }

    public static void main(String[] args) throws Exception {

        Map<String, Object> keyMap = RSATest.genKeyPair();

        String publicKey = RSATest.getPublicKey(keyMap);

        String privateKey = RSATest.getPrivateKey(keyMap);

        System.out.println("公钥：" + publicKey);

        System.out.println("私钥：" + privateKey);

        // 公钥加密

        String sourceStr = "<REQ><HEAD><ReqCode>WDIS</ReqCode><MsgNo>500</MsgNo><MsgId>20171113123408</MsgId><MsgRef>20171113123408</MsgRef><Teller>00000951</Teller><BchCde>800000000</BchCde><WorkDate>20171113</WorkDate><WorkTime>123408</WorkTime></HEAD><MSG><ApplSeq>1666645</ApplSeq><AppAdvice>同意</AppAdvice><AppConclusion>10</AppConclusion><ApptList><Result><ApptTyp>01</ApptTyp><CustName>林羽凡</CustName><IdTyp>20</IdTyp><IdNo>350521196211216597</IdNo><ApptStartDate>1962-11-21</ApptStartDate><ApptAge>55</ApptAge><CrtBch>800000001</CrtBch><CrtDt>2017-11-13</CrtDt><IndivInfo><IndivSex>10</IndivSex><IndivMarital>20</IndivMarital><IndivEdu>10</IndivEdu><IndivDegree>4</IndivDegree><RegProvince>110000</RegProvince><RegCity>110100</RegCity><LiveInfo>10</LiveInfo><LiveProvince>110000</LiveProvince><LiveCity>110100</LiveCity><LiveArea>110105</LiveArea><LiveAddr>北京市市辖区朝阳区xxxxxxx</LiveAddr><LiveZip>100000</LiveZip><LiveMj>299.66</LiveMj><LocalResid>10</LocalResid><IndivMobile>13522015858</IndivMobile><PositionOpt>10</PositionOpt><IndivEmpName>山东科技有限公司</IndivEmpName><IndivEmpTyp>Z</IndivEmpTyp><IndivMthInc>500000.0</IndivMthInc><MailOpt>A</MailOpt><MailProvince>110000</MailProvince><MailCity>110100</MailCity><MailArea>110105</MailArea><MailAddr>北京市市辖区朝阳区xxxxxxx</MailAddr><IndivProfsn>00</IndivProfsn><IndivIndtryPaper>Q</IndivIndtryPaper><IndivPro>1</IndivPro><PptyLive>Y</PptyLive></IndivInfo><ExtInfo><SpouseName>黄海涛</SpouseName><SpouseIdTyp>20</SpouseIdTyp><SpouseIdNo>110105198310200112</SpouseIdNo><SpouseMobile>13589565487</SpouseMobile></ExtInfo><RelList><Result><RelName>黄海涛</RelName><RelMobile>13589565487</RelMobile><RelRelation>06</RelRelation></Result><Result/></RelList></Result><Result><ApptRelation>06</ApptRelation><ApptTyp>02</ApptTyp><CustName>黄海涛</CustName><IdTyp>20</IdTyp><IdNo>110105198310200112</IdNo><ApptStartDate>1983-10-20</ApptStartDate><ApptAge>34</ApptAge><CrtBch>800000001</CrtBch><CrtDt>2017-11-13</CrtDt><IndivInfo><IndivSex>20</IndivSex><IndivMarital>20</IndivMarital><IndivDegree>0</IndivDegree><LiveAddr>北京市市辖区朝阳区xxxxxxx</LiveAddr><LiveMj>299.66</LiveMj><LocalResid>10</LocalResid><IndivMobile>13581829258</IndivMobile><PositionOpt>50</PositionOpt><IndivEmpName>个体</IndivEmpName><IndivEmpTyp>Z</IndivEmpTyp><MailOpt>A</MailOpt><MailAddr>北京市市辖区朝阳区xxxxxxx</MailAddr><PptyLive>Y</PptyLive></IndivInfo><ExtInfo><SpouseName>林羽凡</SpouseName><SpouseIdTyp>20</SpouseIdTyp><SpouseIdNo>350521196211216597</SpouseIdNo><SpouseMobile>135xxxxxxxx</SpouseMobile></ExtInfo><RelList><Result><RelName>黄海涛</RelName><RelMobile>135xxxxxxxx</RelMobile><RelRelation>06</RelRelation></Result></RelList></Result></ApptList><HouInfo><Location>朝阳区xxxxx</Location><HouseArea>299.66</HouseArea><CompDate>2009-01-01</CompDate><PropRight>12</PropRight><HouseKindList>01</HouseKindList><HouseClass>01</HouseClass><HouseType>09</HouseType><HouseFrameSign>99</HouseFrameSign><HouseCertKind>03</HouseCertKind><PptyProvince>110000</PptyProvince><PptyCity>110100</PptyCity><PptyArea>110105</PptyArea><PptyAddr>朝阳区xxxxx</PptyAddr><OwnerName>林羽凡</OwnerName><HouseCertNo>北京房权证朝字第907946号</HouseCertNo></HouInfo><GurtInfo><gurtAmt>2.0E7</gurtAmt><collateralValue>2.0E7</collateralValue><gurtStartDt>2017-11-02</gurtStartDt><gurtEndDt>2020-11-02</gurtEndDt><gurtSignDt>2017-11-02</gurtSignDt><collInd>Y</collInd><regSts>02</regSts><mortgagorTyp>01</mortgagorTyp><rightCertTyp>01</rightCertTyp><rightCertNo>京（2017）朝不动产证明第0075996号</rightCertNo><custName>林羽凡</custName><mortgageType>01</mortgageType><isRent>N</isRent><obligorName>林羽凡</obligorName></GurtInfo><ApplInfo><ApplCde>201711131200000131495</ApplCde><ApplSeq>1666645</ApplSeq><IdTyp>20</IdTyp><IdNo>350521196211216597</IdNo><CustName>林羽凡</CustName><ProPurAmt>2.0E7</ProPurAmt><Purpose>OTH</Purpose><AppOrigin>03</AppOrigin><DocChannel>SYS001</DocChannel><ApplyDt>2017-10-27</ApplyDt><FstPct>0</FstPct><FstPay>0</FstPay><ApplyAmt>2.0E7</ApplyAmt><ApprvAmt>2.0E7</ApprvAmt><ApplyTnr>36</ApplyTnr><ApplyTnrTyp>M</ApplyTnrTyp><ApprvTnr>36</ApprvTnr><ApprvTnrTyp>M</ApprvTnrTyp><LoanTyp>ZYYH002</LoanTyp><MtdCde>LM004</MtdCde><LoanFreq>1M</LoanFreq><MtdMode>RV</MtdMode><PriceIntRat>0.07799998999999999</PriceIntRat><CrtDt>2017-11-02</CrtDt><TypGrp>04</TypGrp><GutrOpt>20</GutrOpt><CrtBch>800000001</CrtBch><CrtBchInd>N</CrtBchInd><RepcOpt>NYF</RepcOpt><DueDayOpt>2</DueDayOpt><DueDay>21</DueDay><Form>04</Form></ApplInfo><MtdList><Result><MtdCde>LM004</MtdCde><MtdTyp>04</MtdTyp><LoanInstal>36</LoanInstal><ApplMtdRateTyp>1</ApplMtdRateTyp><ApplMtdRateFloat>64.2105</ApplMtdRateFloat></Result></MtdList><AcctList><Result><ApplAcKind>01</ApplAcKind><ApplAcTyp>01</ApplAcTyp><RpymAcBank>105100000017</RpymAcBank><RpymAcNam>于三</RpymAcNam><RpymAcNo>6217000010039470748</RpymAcNo><RpymIdTyp>20</RpymIdTyp><RpymMethod>1</RpymMethod></Result><Result><ApplAcKind>02</ApplAcKind><ApplAcTyp>01</ApplAcTyp><RpymAcBank>105100000017</RpymAcBank><RpymAcNam>林羽凡</RpymAcNam><RpymAcNo>5522450010194467</RpymAcNo><RpymIdTyp>20</RpymIdTyp><RpymIdNo>350521196211216597</RpymIdNo><RpymMethod>1</RpymMethod></Result></AcctList></MSG></REQ>";

        System.out.println("加密前：" + sourceStr);

        byte[] encryptStrByte = RSATest.encryptByPublicKey(sourceStr.getBytes(), publicKey);

        byte[] btt = Base64.encodeBase64(encryptStrByte);

        String encryptStr = new String(btt);

        System.out.println("加密后：" + encryptStr);

        System.out.println("长度：" + encryptStr.length());

        // 私钥解密

        byte[] decryptStrByte = RSATest.decryptByPrivateKey(Base64.decodeBase64(Base64.encodeBase64(encryptStrByte)), privateKey);

        String sourceStr_1 = new String(decryptStrByte);

        System.out.println("解密后：" + sourceStr_1);

    }

}

密钥长度修改为2048位时，报以下错误：

Exception in thread "main" javax.crypto.BadPaddingException: Decryption error

    at sun.security.rsa.RSAPadding.unpadV15(Unknown Source)

    at sun.security.rsa.RSAPadding.unpad(Unknown Source)

    at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:363)

    at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:389)

    at javax.crypto.Cipher.doFinal(Cipher.java:2223)

    at com.caxs.esign.util.MYtest.decryptByPrivateKey(MYtest.java:117)

    at com.caxs.esign.util.MYtest.main(MYtest.java:175)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

    at java.lang.reflect.Method.invoke(Unknown Source)

    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

这是由于最大解密长度不正确导致报错，MAX_DECRYPT_BLOCK应等于密钥长度/8（1byte=8bit），所以当密钥位数为2048时，最大解密长度应为256.

private static final int MAX_DECRYPT_BLOCK = 128;

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