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

// TODO Auto-generated method stub

HashMap map = RSAUtils.getKeys();

//生成公鑰和私鑰

RSAPublicKey publicKey = (RSAPublicKey) map.get("public");

RSAPrivateKey privateKey = (RSAPrivateKey) map.get("private");

//模

String modulus = publicKey.getModulus().toString();

//公鑰指數

String public_exponent = publicKey.getPublicExponent().toString();

//私鑰指數

String private_exponent = privateKey.getPrivateExponent().toString();

//明文

String ming = "123456789";

//使用模和指數生成公鑰和私鑰

RSAPublicKey pubKey = RSAUtils.getPublicKey(modulus, public_exponent);

RSAPrivateKey priKey = RSAUtils.getPrivateKey(modulus, private_exponent);

//加密后的密文

String mi = RSAUtils.encryptByPublicKey(ming, pubKey);

System.err.println(mi);

//解密后的明文

ming = RSAUtils.decryptByPrivateKey(mi, priKey);

System.err.println(ming);

}

package yyy.test.rsa;

import java.math.BigInteger;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.NoSuchAlgorithmException;

import java.security.interfaces.RSAPrivateKey;

import java.security.interfaces.RSAPublicKey;

import java.security.spec.RSAPrivateKeySpec;

import java.security.spec.RSAPublicKeySpec;

import java.util.HashMap;

import javax.crypto.Cipher;

public class RSAUtils {

/**

* 生成公鑰和私鑰

* @throws NoSuchAlgorithmException

*

*/

public static HashMap getKeys() throws NoSuchAlgorithmException{

HashMap map = new HashMap();

KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");

keyPairGen.initialize(1024);

KeyPair keyPair = keyPairGen.generateKeyPair();

RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

map.put("public", publicKey);

map.put("private", privateKey);

return map;

}

/**

* 使用模和指數生成RSA公鑰

* 注意：【此代碼用了默認補位方式，為RSA/None/PKCS1Padding，不同JDK默認的補位方式可能不同，如Android默認是RSA

* /None/NoPadding】

*

* @param modulus

* 模

* @param exponent

* 指數

* @return

*/

public static RSAPublicKey getPublicKey(String modulus, String exponent) {

try {

BigInteger b1 = new BigInteger(modulus);

BigInteger b2 = new BigInteger(exponent);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);

return (RSAPublicKey) keyFactory.generatePublic(keySpec);

} catch (Exception e) {

e.printStackTrace();

return null;

}

}

/**

* 使用模和指數生成RSA私鑰

* 注意：【此代碼用了默認補位方式，為RSA/None/PKCS1Padding，不同JDK默認的補位方式可能不同，如Android默認是RSA

* /None/NoPadding】

*

* @param modulus

* 模

* @param exponent

* 指數

* @return

*/

public static RSAPrivateKey getPrivateKey(String modulus, String exponent) {

try {

BigInteger b1 = new BigInteger(modulus);

BigInteger b2 = new BigInteger(exponent);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2);

return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);

} catch (Exception e) {

e.printStackTrace();

return null;

}

}

/**

* 公鑰加密

*

* @param data

* @param publicKey

* @return

* @throws Exception

*/

public static String encryptByPublicKey(String data, RSAPublicKey publicKey)

throws Exception {

Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.ENCRYPT_MODE, publicKey);

// 模長

int key_len = publicKey.getModulus().bitLength() / 8;

// 加密數據長度 <= 模長-11

String[] datas = splitString(data, key_len - 11);

String mi = "";

//如果明文長度大于模長-11則要分組加密

for (String s : datas) {

mi += bcd2Str(cipher.doFinal(s.getBytes()));

}

return mi;

}

/**

* 私鑰解密

*

* @param data

* @param privateKey

* @return

* @throws Exception

*/

public static String decryptByPrivateKey(String data, RSAPrivateKey privateKey)

throws Exception {

Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.DECRYPT_MODE, privateKey);

//模長

int key_len = privateKey.getModulus().bitLength() / 8;

byte[] bytes = data.getBytes();

byte[] bcd = ASCII_To_BCD(bytes, bytes.length);

System.err.println(bcd.length);

//如果密文長度大于模長則要分組解密

String ming = "";

byte[][] arrays = splitArray(bcd, key_len);

for(byte[] arr : arrays){

ming += new String(cipher.doFinal(arr));

}

return ming;

}

/**

* ASCII碼轉BCD碼

*

*/

public 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;

}

public 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轉字符串

*/

public 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

*/

public 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

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;

}

/**

*拆分數組

*/

public 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

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

Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");

android

Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding");

參考:

http://stackoverflow.com/questions/6069369/rsa-encryption-difference-between-java-and-android

http://stackoverflow.com/questions/2956647/rsa-encrypt-with-base64-encoded-public-key-in-android

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