Android接口安全 - RSA+AES混合加密方案

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/article/10571810.html

本文以Android客户端加密提交数据到Java服务端后进行解密为例子。

生成RSA公钥和密钥的方法请参考：

/article/10571809.html

Android端的加密思路需要4步：

1.生成AES密钥；

2.使用RSA公钥加密刚刚生成的AES密钥；

3.再使用第1步生成的AES密钥，通过AES加密需要提交给服务端的数据；

4.将第2与第3生成的内容传给服务端。

JAVA服务端的解密思路只需3步：

1.获取到客户端传过来的AES密钥密文和内容密文；

2.使用RSA私钥解密从客户端拿到的AES密钥密文；

3.再使用第2步解密出来的明文密钥，通过AES解密内容的密文。

AES的代码可以在JAVA和Android上通用

package com.dyhdyh.encrypt;

import java.io.UnsupportedEncodingException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/**
* AES
* @author dengyuhan
* @create 2016/3/31 15:43
*/
public class AES {
// /** 算法/模式/填充 **/
private static final String CipherMode = "AES/ECB/PKCS5Padding";
// private static final String CipherMode = "AES";

/**
* 生成一个AES密钥对象
* @return
*/
public static SecretKeySpec generateKey(){
try {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
kgen.init(128, new SecureRandom());
SecretKey secretKey = kgen.generateKey();
byte[] enCodeFormat = secretKey.getEncoded();
SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");
return key;
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
return null;
}

/**
* 生成一个AES密钥字符串
* @return
*/
public static String generateKeyString(){
return byte2hex(generateKey().getEncoded());
}

/**
* 加密字节数据
* @param content
* @param key
* @return
*/
public static byte[] encrypt(byte[] content,byte[] key) {
try {
Cipher cipher = Cipher.getInstance(CipherMode);
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"));
byte[] result = cipher.doFinal(content);
return result;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

/**
* 通过byte[]类型的密钥加密String
* @param content
* @param key
* @return 16进制密文字符串
*/
public static String encrypt(String content,byte[] key) {
try {
Cipher cipher = Cipher.getInstance(CipherMode);
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"));
byte[] data = cipher.doFinal(content.getBytes("UTF-8"));
String result = byte2hex(data);
return result;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

/**
* 通过String类型的密钥加密String
* @param content
* @param key
* @return 16进制密文字符串
*/
public static String encrypt(String content,String key) {
byte[] data = null;
try {
data = content.getBytes("UTF-8");
} catch (Exception e) {
e.printStackTrace();
}
data = encrypt(data,new SecretKeySpec(hex2byte(key), "AES").getEncoded());
String result = byte2hex(data);
return result;
}

/**
* 通过byte[]类型的密钥解密byte[]
* @param content
* @param key
* @return
*/
public static byte[] decrypt(byte[] content,byte[] key) {
try {
Cipher cipher = Cipher.getInstance(CipherMode);
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"));
byte[] result = cipher.doFinal(content);
return result;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

/**
* 通过String类型的密钥 解密String类型的密文
* @param content
* @param key
* @return
*/
public static String decrypt(String content, String key) {
byte[] data = null;
try {
data = hex2byte(content);
} catch (Exception e) {
e.printStackTrace();
}
data = decrypt(data, hex2byte(key));
if (data == null)
return null;
String result = null;
try {
result = new String(data, "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
return result;
}

/**
* 通过byte[]类型的密钥 解密String类型的密文
* @param content
* @param key
* @return
*/
public static String decrypt(String content,byte[] key) {
try {
Cipher cipher = Cipher.getInstance(CipherMode);
cipher.init(Cipher.DECRYPT_MODE,new SecretKeySpec(key, "AES"));
byte[] data = cipher.doFinal(hex2byte(content));
return new String(data, "UTF-8");
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

/**
* 字节数组转成16进制字符串
* @param b
* @return
*/
public static String byte2hex(byte[] b) { // 一个字节的数，
StringBuffer sb = new StringBuffer(b.length * 2);
String tmp = "";
for (int n = 0; n < b.length; n++) {
// 整数转成十六进制表示
tmp = (Integer.toHexString(b
& 0XFF));
if (tmp.length() == 1) {
sb.append("0");
}
sb.append(tmp);
}
return sb.toString().toUpperCase(); // 转成大写
}

/**
* 将hex字符串转换成字节数组
* @param inputString
* @return
*/
private static byte[] hex2byte(String inputString) {
if (inputString == null || inputString.length() < 2) {
return new byte[0];
}
inputString = inputString.toLowerCase();
int l = inputString.length() / 2;
byte[] result = new byte[l];
for (int i = 0; i < l; ++i) {
String tmp = inputString.substring(2 * i, 2 * i + 2);
result[i] = (byte) (Integer.parseInt(tmp, 16) & 0xFF);
}
return result;
}
}

Android - RSA实现

package com.dyhdyh.encrypt;

import android.util.Base64;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

/**
* 用于Android平台的RSA加密解密
*
* @desc
* @author dengyuhan
* @create 2016-3-31 下午2:36:18
*/
public class RSA {
private static final String ALGORITHM = "RSA";
private static final String TRANSFORMATION = "RSA";

/**
* 从文件中输入流中加载公钥
*
* @param in
*            公钥输入流
* @throws Exception
*             加载公钥时产生的异常
*/
public static RSAPublicKey loadPublicKey(InputStream in) throws Exception {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String readLine = null;
StringBuilder sb = new StringBuilder();
while ((readLine = br.readLine()) != null) {
if (readLine.charAt(0) == '-') {
continue;
} else {
sb.append(readLine);
sb.append('\r');
}
}
return loadPublicKey(sb.toString());
} catch (IOException e) {
throw new Exception("公钥数据流读取错误");
} catch (NullPointerException e) {
throw new Exception("公钥输入流为空");
}
}

/**
* 从字符串中加载公钥
*
* @param publicKeyStr
*            公钥数据字符串
* @return
* @throws Exception
*             加载公钥时产生的异常
*/
public static RSAPublicKey loadPublicKey(String publicKeyStr)
throws Exception {
try {
byte[] buffer = Base64.decode(publicKeyStr, Base64.DEFAULT);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
return (RSAPublicKey) keyFactory.generatePublic(keySpec);
} catch (NoSuchAlgorithmException e) {
throw new Exception("无此算法");
} catch (InvalidKeySpecException e) {
throw new Exception("公钥非法");
}catch (NullPointerException e) {
throw new Exception("公钥数据为空");
}
}

/**
* 从文件中加载私钥
*
* @param in
*            私钥输入流
* @return
* @throws Exception
*/
public static RSAPrivateKey loadPrivateKey(InputStream in) throws Exception {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String readLine = null;
StringBuilder sb = new StringBuilder();
while ((readLine = br.readLine()) != null) {
if (readLine.charAt(0) == '-') {
continue;
} else {
sb.append(readLine);
sb.append('\r');
}
}
return loadPrivateKey(sb.toString());
} catch (IOException e) {
throw new Exception("私钥数据读取错误");
} catch (NullPointerException e) {
throw new Exception("私钥输入流为空");
}
}

/**
* 从字符串中加载私钥
*
* @desc
* @param privateKeyStr
*            私钥字符串
* @return
* @throws Exception
*/
public static RSAPrivateKey loadPrivateKey(String privateKeyStr)
throws Exception {
try {
byte[] buffer = Base64.decode(privateKeyStr, Base64.DEFAULT);
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
} catch (NoSuchAlgorithmException e) {
throw new Exception("无此算法");
} catch (InvalidKeySpecException e) {
throw new Exception("私钥非法");
}catch (NullPointerException e) {
throw new Exception("私钥数据为空");
}
}

/**
* 公钥加密
*
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static String encryptByPublicKey(String data, RSAPublicKey publicKey)
throws Exception {
// 模长
int key_len = publicKey.getModulus().bitLength() / 8;
// 加密数据长度 <= 模长-11
String[] datas = splitString(data, key_len - 11);
String mi = "";
// 如果明文长度大于模长-11则要分组加密
for (String s : datas) {
mi += bcd2Str(encryptByPublicKey(s.getBytes(), publicKey));
}
return mi;
}

/**
* 公钥加密
* @desc
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static byte[] encryptByPublicKey(byte[] data, RSAPublicKey publicKey)
throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(data);
}

/**
* 私钥加密
* @desc
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static byte[] encryptByPrivateKey(byte[] data,
RSAPrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return cipher.doFinal(data);
}

/**
* 私钥加密
* @desc
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static String encryptByPrivateKey(String data,
RSAPrivateKey privateKey) throws Exception {
// 模长
int key_len = privateKey.getModulus().bitLength() / 8;
// 加密数据长度 <= 模长-11
String[] datas = splitString(data, key_len - 11);
String mi = "";
// 如果明文长度大于模长-11则要分组加密
for (String s : datas) {
mi += bcd2Str(encryptByPrivateKey(s.getBytes(), privateKey));
}
return mi;
}

/**
* 私钥解密
*
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static String decryptByPrivateKey(String data,
RSAPrivateKey privateKey) throws Exception {
// 模长
int key_len = privateKey.getModulus().bitLength() / 8;
byte[] bytes = data.getBytes();
byte[] bcd = ASCII_To_BCD(bytes, bytes.length);
// 如果密文长度大于模长则要分组解密
String ming = "";
byte[][] arrays = splitArray(bcd, key_len);
for (byte[] arr : arrays) {
ming += new String(decryptByPrivateKey(arr, privateKey));
}
return ming;
}

/**
* 私钥解密
* @desc
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static byte[] decryptByPrivateKey(byte[] data,
RSAPrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(data);
}

/**
* 公钥解密
* @desc
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static String decryptByPublicKey(String data,
RSAPublicKey publicKey) throws Exception {
// 模长
int key_len = publicKey.getModulus().bitLength() / 8;
byte[] bytes = data.getBytes();
byte[] bcd = ASCII_To_BCD(bytes, bytes.length);
// 如果密文长度大于模长则要分组解密
String ming = "";
byte[][] arrays = splitArray(bcd, key_len);
for (byte[] arr : arrays) {
ming += new String(decryptByPublicKey(arr, publicKey));
}
return ming;
}

/**
* 公钥解密
* @desc
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static byte[] decryptByPublicKey(byte[] data,
RSAPublicKey publicKey) throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.DECRYPT_MODE, publicKey);
return cipher.doFinal(data);
}

/**
* ASCII码转BCD码
*
*/
private static byte[] ASCII_To_BCD(byte[] ascii, int asc_len) {
byte[] bcd = new byte[asc_len / 2];
int j = 0;
for (int i = 0; i < (asc_len + 1) / 2; i++) {
bcd[i] = asc_to_bcd(ascii[j++]);
bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4));
}
return bcd;
}

private static byte asc_to_bcd(byte asc) {
byte bcd;

if ((asc >= '0') && (asc <= '9'))
bcd = (byte) (asc - '0');
else if ((asc >= 'A') && (asc <= 'F'))
bcd = (byte) (asc - 'A' + 10);
else if ((asc >= 'a') && (asc <= 'f'))
bcd = (byte) (asc - 'a' + 10);
else
bcd = (byte) (asc - 48);
return bcd;
}

/**
* BCD转字符串
*/
private static String bcd2Str(byte[] bytes) {
char temp[] = new char[bytes.length * 2], val;

for (int i = 0; i < bytes.length; i++) {
val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);
temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

val = (char) (bytes[i] & 0x0f);
temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');
}
return new String(temp);
}

/**
* 拆分字符串
*/
private static String[] splitString(String string, int len) {
int x = string.length() / len;
int y = string.length() % len;
int z = 0;
if (y != 0) {
z = 1;
}
String[] strings = new String[x + z];
String str = "";
for (int i = 0; i < x + z; i++) {
if (i == x + z - 1 && y != 0) {
str = string.substring(i * len, i * len + y);
} else {
str = string.substring(i * len, i * len + len);
}
strings[i] = str;
}
return strings;
}

/**
* 拆分数组
*/
private static byte[][] splitArray(byte[] data, int len) {
int x = data.length / len;
int y = data.length % len;
int z = 0;
if (y != 0) {
z = 1;
}
byte[][] arrays = new byte[x + z][];
byte[] arr;
for (int i = 0; i < x + z; i++) {
arr = new byte[len];
if (i == x + z - 1 && y != 0) {
System.arraycopy(data, i * len, arr, 0, y);
} else {
System.arraycopy(data, i * len, arr, 0, len);
}
arrays[i] = arr;
}
return arrays;
}
}

JAVA - RSA实现

package com.dyhdyh.encrypt;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

import org.bouncycastle.jce.provider.BouncyCastleProvider;

import sun.misc.BASE64Decoder;

/**
* 用于java平台的RSA加密解密
*
* @desc
* @author dengyuhan
* @create 2016-3-31 下午2:36:18
*/
public class RSA {
private static final String ALGORITHM = "RSA";
private static final String TRANSFORMATION = "RSA";

/**
* 从文件中输入流中加载公钥
*
* @param in
*            公钥输入流
* @throws Exception
*             加载公钥时产生的异常
*/
public static RSAPublicKey loadPublicKey(InputStream in) throws Exception {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String readLine = null;
StringBuilder sb = new StringBuilder();
while ((readLine = br.readLine()) != null) {
if (readLine.charAt(0) == '-') {
continue;
} else {
sb.append(readLine);
sb.append('\r');
}
}
return loadPublicKey(sb.toString());
} catch (IOException e) {
throw new Exception("公钥数据流读取错误");
} catch (NullPointerException e) {
throw new Exception("公钥输入流为空");
}
}

/**
* 从字符串中加载公钥
*
* @param publicKeyStr
*            公钥数据字符串
* @return
* @throws Exception
*             加载公钥时产生的异常
*/
public static RSAPublicKey loadPublicKey(String publicKeyStr)
throws Exception {
try {
BASE64Decoder base64Decoder = new BASE64Decoder();
byte[] buffer = base64Decoder.decodeBuffer(publicKeyStr);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
return (RSAPublicKey) keyFactory.generatePublic(keySpec);
} catch (NoSuchAlgorithmException e) {
throw new Exception("无此算法");
} catch (InvalidKeySpecException e) {
throw new Exception("公钥非法");
} catch (IOException e) {
throw new Exception("公钥数据内容读取错误");
} catch (NullPointerException e) {
throw new Exception("公钥数据为空");
}
}

/**
* 从文件中加载私钥
*
* @param in
*            私钥输入流
* @return
* @throws Exception
*/
public static RSAPrivateKey loadPrivateKey(InputStream in) throws Exception {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String readLine = null;
StringBuilder sb = new StringBuilder();
while ((readLine = br.readLine()) != null) {
if (readLine.charAt(0) == '-') {
continue;
} else {
sb.append(readLine);
sb.append('\r');
}
}
return loadPrivateKey(sb.toString());
} catch (IOException e) {
throw new Exception("私钥数据读取错误");
} catch (NullPointerException e) {
throw new Exception("私钥输入流为空");
}
}

/**
* 从字符串中加载私钥
*
* @desc
* @param privateKeyStr
*            私钥字符串
* @return
* @throws Exception
*/
public static RSAPrivateKey loadPrivateKey(String privateKeyStr)
throws Exception {
try {
BASE64Decoder base64Decoder = new BASE64Decoder();
byte[] buffer = base64Decoder.decodeBuffer(privateKeyStr);
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
} catch (NoSuchAlgorithmException e) {
throw new Exception("无此算法");
} catch (InvalidKeySpecException e) {
throw new Exception("私钥非法");
} catch (IOException e) {
throw new Exception("私钥数据内容读取错误");
} catch (NullPointerException e) {
throw new Exception("私钥数据为空");
}
}

/**
* 公钥加密
*
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static String encryptByPublicKey(String data, RSAPublicKey publicKey)
throws Exception {
// 模长
int key_len = publicKey.getModulus().bitLength() / 8;
// 加密数据长度 <= 模长-11
String[] datas = splitString(data, key_len - 11);
String mi = "";
// 如果明文长度大于模长-11则要分组加密
for (String s : datas) {
mi += bcd2Str(encryptByPublicKey(s.getBytes(), publicKey));
}
return mi;
}

/**
* 公钥加密
* @desc
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static byte[] encryptByPublicKey(byte[] data, RSAPublicKey publicKey)
throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(data);
}

/**
* 私钥加密
* @desc
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static byte[] encryptByPrivateKey(byte[] data,
RSAPrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return cipher.doFinal(data);
}

/**
* 私钥加密
* @desc
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static String encryptByPrivateKey(String data,
RSAPrivateKey privateKey) throws Exception {
// 模长
int key_len = privateKey.getModulus().bitLength() / 8;
// 加密数据长度 <= 模长-11
String[] datas = splitString(data, key_len - 11);
String mi = "";
// 如果明文长度大于模长-11则要分组加密
for (String s : datas) {
mi += bcd2Str(encryptByPrivateKey(s.getBytes(), privateKey));
}
return mi;
}

/**
* 私钥解密
*
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static String decryptByPrivateKey(String data,
RSAPrivateKey privateKey) throws Exception {
// 模长
int key_len = privateKey.getModulus().bitLength() / 8;
byte[] bytes = data.getBytes();
byte[] bcd = ASCII_To_BCD(bytes, bytes.length);
// 如果密文长度大于模长则要分组解密
String ming = "";
byte[][] arrays = splitArray(bcd, key_len);
for (byte[] arr : arrays) {
ming += new String(decryptByPrivateKey(arr, privateKey));
}
return ming;
}

/**
* 私钥解密
* @desc
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static byte[] decryptByPrivateKey(byte[] data,
RSAPrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION,new BouncyCastleProvider());
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(data);
}

/**
* 公钥解密
* @desc
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static String decryptByPublicKey(String data,
RSAPublicKey publicKey) throws Exception {
// 模长
int key_len = publicKey.getModulus().bitLength() / 8;
byte[] bytes = data.getBytes();
byte[] bcd = ASCII_To_BCD(bytes, bytes.length);
// 如果密文长度大于模长则要分组解密
String ming = "";
byte[][] arrays = splitArray(bcd, key_len);
for (byte[] arr : arrays) {
ming += new String(decryptByPublicKey(arr, publicKey));
}
return ming;
}

/**
* 公钥解密
* @desc
* @param data
* @param publicKey
* @return
* @throws Exception
*/
public static byte[] decryptByPublicKey(byte[] data,
RSAPublicKey publicKey) throws Exception {
Cipher cipher = Cipher.getInstance(TRANSFORMATION,new BouncyCastleProvider());
cipher.init(Cipher.DECRYPT_MODE, publicKey);
return cipher.doFinal(data);
}

/**
* ASCII码转BCD码
*
*/
private static byte[] ASCII_To_BCD(byte[] ascii, int asc_len) {
byte[] bcd = new byte[asc_len / 2];
int j = 0;
for (int i = 0; i < (asc_len + 1) / 2; i++) {
bcd[i] = asc_to_bcd(ascii[j++]);
bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4));
}
return bcd;
}

private static byte asc_to_bcd(byte asc) {
byte bcd;

if ((asc >= '0') && (asc <= '9'))
bcd = (byte) (asc - '0');
else if ((asc >= 'A') && (asc <= 'F'))
bcd = (byte) (asc - 'A' + 10);
else if ((asc >= 'a') && (asc <= 'f'))
bcd = (byte) (asc - 'a' + 10);
else
bcd = (byte) (asc - 48);
return bcd;
}

/**
* BCD转字符串
*/
private static String bcd2Str(byte[] bytes) {
char temp[] = new char[bytes.length * 2], val;

for (int i = 0; i < bytes.length; i++) {
val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);
temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

val = (char) (bytes[i] & 0x0f);
temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');
}
return new String(temp);
}

/**
* 拆分字符串
*/
private static String[] splitString(String string, int len) {
int x = string.length() / len;
int y = string.length() % len;
int z = 0;
if (y != 0) {
z = 1;
}
String[] strings = new String[x + z];
String str = "";
for (int i = 0; i < x + z; i++) {
if (i == x + z - 1 && y != 0) {
str = string.substring(i * len, i * len + y);
} else {
str = string.substring(i * len, i * len + len);
}
strings[i] = str;
}
return strings;
}

/**
* 拆分数组
*/
private static byte[][] splitArray(byte[] data, int len) {
int x = data.length / len;
int y = data.length % len;
int z = 0;
if (y != 0) {
z = 1;
}
byte[][] arrays = new byte[x + z][];
byte[] arr;
for (int i = 0; i < x + z; i++) {
arr = new byte[len];
if (i == x + z - 1 && y != 0) {
System.arraycopy(data, i * len, arr, 0, y);
} else {
System.arraycopy(data, i * len, arr, 0, len);
}
arrays[i] = arr;
}
return arrays;
}
}

JAVA的RSA跟Android的RSA有所不同：

1.加载key的时候，JAVA上用的是BASE64Decoder

BASE64Decoder base64Decoder = new BASE64Decoder();
byte[] buffer = base64Decoder.decodeBuffer(publicKeyStr);

而Android上用的Base64，这个地方只是API不一样，作用是一样的

byte[] buffer = Base64.decode(publicKeyStr, Base64.DEFAULT);

2.在JAVA平台上调用Cipher.getInstance()的时候，需要多传一个参数，也就是BouncyCastleProvider的实例：

Cipher cipher = Cipher.getInstance("RSA",new BouncyCastleProvider());

这个类jdk上是没有的，所以需要添加一个jar包bcprov-jdk15-143.jar

如果不这样做，JAVA上解密的时候就会抛出一个BadPaddingException

Exception in thread "main" javax.crypto.BadPaddingException: Blocktype mismatch: 0
at sun.security.rsa.RSAPadding.unpadV15(RSAPadding.java:332)
at sun.security.rsa.RSAPadding.unpad(RSAPadding.java:272)
at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:356)
at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:382)
at javax.crypto.Cipher.doFinal(Cipher.java:2087)
at com.dyhdyh.encrypt.RSA.decryptByPrivateKey(RSA.java:255)
at com.dyhdyh.encrypt.RSA.decryptByPrivateKey(RSA.java:238)

这是因为Android的加密标准与JAVA的加密标准不一致导致，Android上的RSA实现是"RSA/None/NoPadding"，而标准JDK实现是"RSA/None/PKCS1Padding"，这造成了在Android上加密后无法在服务器上解密

最后来看看怎样混合加密(这里只举一种方式，附件里有完整的)

Android上加密

1.将openssl生成出来的公钥，放入assets文件夹内（不一定要放这里，只要能拿到文件内容就行）。



2.加载放在assets文件里的公钥

//加载RSA公钥
RSAPublicKey rsaPublicKey = RSA.loadPublicKey(getAssets().open("rsa_public_key.pem"));

3.再生成一个AES的密钥，用于AES加密

//生成一个AES密钥
String aesKey=AES.generateKeyString();

4.通过RSA的公钥来加密刚刚生成的AES密钥

//用RSA公钥加密AES的密钥
String encryptAesKey = RSA.encryptByPublicKey(aesKey, rsaPublicKey);

5.最后使用AES来加密需要传输的数据，AES加密需要传入两个参数，第一个是明文数据，第二个是3步生成出来的密钥

//再使用AES加密内容，传给服务器
String encryptContent = AES.encrypt(content, aesKey);

6.第5步返回的字符串就是加密过后的数据，最后将4和5传给服务端，接下来就是服务端的事情了。

客户端传过来密文之后，接下来就需要服务端来解密了

JAVA解密

1.加载RSA私钥(这里的私钥是跟客户端的公钥是成对的)

//加载私钥
RSAPrivateKey privateKey = RSA.loadPrivateKey(new FileInputStream("G:/RSA密钥/pkcs8_rsa_private_key.pem"));

2.通过RSA的私钥解密客户端传来的AES-KEY（也就是客户端的第4），因为这个key是加过密的，所以我们需要先将key解密成明文

//解密AES-KEY
String decryptAesKey = RSA.decryptByPrivateKey(aesKey, privateKey);

3.AES-KEY加密成明文之后，现在可以拿这个key来解密客户端传过来的数据了

//AES解密数据
String decrypt = AES.decrypt(content, decryptAesKey);

RSA-AES混合加密就是这个样子，有什么问题请跟帖回复，我会继续改进

最后附上完整demo

http://download.csdn.net/detail/aa464971/9478798

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