java中RSA加解密的实现

关于加密数据长度和解密数据长度大家可以看一下我前一篇文章内的介绍：

关于RSA算法密钥长度/密文长度/明文长度的介绍

 

public static void main(String[] args) throws Exception {// TODO Auto-generated method stubHashMap<String, Object> map = RSAUtils.getKeys();//生成公钥和私钥RSAPublicKey publicKey = (RSAPublicKey) map.get("public");RSAPrivateKey privateKey = (RSAPrivateKey) map.get("private");//模String modulus = publicKey.getModulus().toString();//公钥指数String public_exponent = publicKey.getPublicExponent().toString();//私钥指数String private_exponent = privateKey.getPrivateExponent().toString();//明文String ming = "123456789";//使用模和指数生成公钥和私钥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);}

RSAUtils.java

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 {/** * 生成公钥和私钥 * @throws NoSuchAlgorithmException  * */public static HashMap<String, Object> getKeys() throws NoSuchAlgorithmException{HashMap<String, Object> map = new HashMap<String, Object>();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;}/** * 使用模和指数生成RSA公钥 * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA * /None/NoPadding】 *  * @param modulus *            模 * @param exponent *            指数 * @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;}}/** * 使用模和指数生成RSA私钥 * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA * /None/NoPadding】 *  * @param modulus *            模 * @param exponent *            指数 * @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;}}/** * 公钥加密 *  * @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);// 模长int key_len = publicKey.getModulus().bitLength() / 8;// 加密数据长度 <= 模长-11String[] 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(cipher.doFinal(s.getBytes()));}return mi;}/** * 私钥解密 *  * @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);//模长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(cipher.doFinal(arr));}return ming;}/** * ASCII码转BCD码 *  */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);elsebcd = (byte) (asc - 48);return bcd;}/** * BCD转字符串 */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<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  */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<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;}}

javaCipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");androidCipher cipher = Cipher.getInstance("RSA/ECB/NoPadding");参考:http://stackoverflow.com/questions/6069369/rsa-encryption-difference-between-java-and-androidhttp://stackoverflow.com/questions/2956647/rsa-encrypt-with-base64-encoded-public-key-in-android