Java RSA加密解密实现方法分析【附BASE64 jar包下载】

本文实例讲述了java rsa加密解密实现方法。分享给大家供大家参考，具体如下：

该工具类中用到了base64，需要借助第三方类库：javabase64-1.3.1.jar

javabase64-1.3.1.jar 本站。

注意：

rsa加密明文最大长度117字节，解密要求密文最大长度为128字节，所以在加密和解密的过程中需要分块进行。

rsa加密对明文的长度是有限制的，如果加密数据过大会抛出如下异常：

exception in thread "main" javax.crypto.illegalblocksizeexception: data must not be longer than 117 bytes
 at com.sun.crypto.provider.rsacipher.a(dashoa13*..)
 at com.sun.crypto.provider.rsacipher.enginedofinal(dashoa13*..)
 at javax.crypto.cipher.dofinal(dashoa13*..)

rsautils.java

package security;
import java.io.bytearrayoutputstream;
import java.security.key;
import java.security.keyfactory;
import java.security.keypair;
import java.security.keypairgenerator;
import java.security.privatekey;
import java.security.publickey;
import java.security.signature;
import java.security.interfaces.rsaprivatekey;
import java.security.interfaces.rsapublickey;
import java.security.spec.pkcs8encodedkeyspec;
import java.security.spec.x509encodedkeyspec;
import java.util.hashmap;
import java.util.map;
import javax.crypto.cipher;
/** *//**
 * <p>
 * rsa公钥/私钥/签名工具包
 * </p>
 * <p>
 * 罗纳德·李维斯特（ron [r]ivest）、阿迪·萨莫尔（adi [s]hamir）和伦纳德·阿德曼（leonard [a]dleman）
 * </p>
 * <p>
 * 字符串格式的密钥在未在特殊说明情况下都为base64编码格式<br/>
 * 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，<br/>
 * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全
 * </p>
 *
 * @author icewee
 * @date 2012-4-26
 * @version 1.0
 */
public class rsautils {
 /** *//**
 * 加密算法rsa
 */
 public static final string key_algorithm = "rsa";
 /** *//**
 * 签名算法
 */
 public static final string signature_algorithm = "md5withrsa";
 /** *//**
 * 获取公钥的key
 */
 private static final string public_key = "rsapublickey";
 /** *//**
 * 获取私钥的key
 */
 private static final string private_key = "rsaprivatekey";
 /** *//**
 * 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;
 /** *//**
 * <p>
 * 生成密钥对(公钥和私钥)
 * </p>
 *
 * @return
 * @throws exception
 */
 public static map<string, object> genkeypair() throws exception {
 keypairgenerator keypairgen = keypairgenerator.getinstance(key_algorithm);
 keypairgen.initialize(1024);
 keypair keypair = keypairgen.generatekeypair();
 rsapublickey publickey = (rsapublickey) keypair.getpublic();
 rsaprivatekey privatekey = (rsaprivatekey) keypair.getprivate();
 map<string, object> keymap = new hashmap<string, object>(2);
 keymap.put(public_key, publickey);
 keymap.put(private_key, privatekey);
 return keymap;
 }
 /** *//**
 * <p>
 * 用私钥对信息生成数字签名
 * </p>
 *
 * @param data 已加密数据
 * @param privatekey 私钥(base64编码)
 *
 * @return
 * @throws exception
 */
 public static string sign(byte[] data, string privatekey) throws exception {
 byte[] keybytes = base64utils.decode(privatekey);
 pkcs8encodedkeyspec pkcs8keyspec = new pkcs8encodedkeyspec(keybytes);
 keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
 privatekey privatek = keyfactory.generateprivate(pkcs8keyspec);
 signature signature = signature.getinstance(signature_algorithm);
 signature.initsign(privatek);
 signature.update(data);
 return base64utils.encode(signature.sign());
 }
 /** *//**
 * <p>
 * 校验数字签名
 * </p>
 *
 * @param data 已加密数据
 * @param publickey 公钥(base64编码)
 * @param sign 数字签名
 *
 * @return
 * @throws exception
 *
 */
 public static boolean verify(byte[] data, string publickey, string sign)
  throws exception {
 byte[] keybytes = base64utils.decode(publickey);
 x509encodedkeyspec keyspec = new x509encodedkeyspec(keybytes);
 keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
 publickey publick = keyfactory.generatepublic(keyspec);
 signature signature = signature.getinstance(signature_algorithm);
 signature.initverify(publick);
 signature.update(data);
 return signature.verify(base64utils.decode(sign));
 }
 /** *//**
 * <p>
 * 私钥解密
 * </p>
 *
 * @param encrypteddata 已加密数据
 * @param privatekey 私钥(base64编码)
 * @return
 * @throws exception
 */
 public static byte[] decryptbyprivatekey(byte[] encrypteddata, string privatekey)
  throws exception {
 byte[] keybytes = base64utils.decode(privatekey);
 pkcs8encodedkeyspec pkcs8keyspec = new pkcs8encodedkeyspec(keybytes);
 keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
 key privatek = keyfactory.generateprivate(pkcs8keyspec);
 cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
 cipher.init(cipher.decrypt_mode, privatek);
 int inputlen = encrypteddata.length;
 bytearrayoutputstream out = new bytearrayoutputstream();
 int offset = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段解密
 while (inputlen - offset > 0) {
  if (inputlen - offset > max_decrypt_block) {
  cache = cipher.dofinal(encrypteddata, offset, max_decrypt_block);
  } else {
  cache = cipher.dofinal(encrypteddata, offset, inputlen - offset);
  }
  out.write(cache, 0, cache.length);
  i++;
  offset = i * max_decrypt_block;
 }
 byte[] decrypteddata = out.tobytearray();
 out.close();
 return decrypteddata;
 }
 /** *//**
 * <p>
 * 公钥解密
 * </p>
 *
 * @param encrypteddata 已加密数据
 * @param publickey 公钥(base64编码)
 * @return
 * @throws exception
 */
 public static byte[] decryptbypublickey(byte[] encrypteddata, string publickey)
  throws exception {
 byte[] keybytes = base64utils.decode(publickey);
 x509encodedkeyspec x509keyspec = new x509encodedkeyspec(keybytes);
 keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
 key publick = keyfactory.generatepublic(x509keyspec);
 cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
 cipher.init(cipher.decrypt_mode, publick);
 int inputlen = encrypteddata.length;
 bytearrayoutputstream out = new bytearrayoutputstream();
 int offset = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段解密
 while (inputlen - offset > 0) {
  if (inputlen - offset > max_decrypt_block) {
  cache = cipher.dofinal(encrypteddata, offset, max_decrypt_block);
  } else {
  cache = cipher.dofinal(encrypteddata, offset, inputlen - offset);
  }
  out.write(cache, 0, cache.length);
  i++;
  offset = i * max_decrypt_block;
 }
 byte[] decrypteddata = out.tobytearray();
 out.close();
 return decrypteddata;
 }
 /** *//**
 * <p>
 * 公钥加密
 * </p>
 *
 * @param data 源数据
 * @param publickey 公钥(base64编码)
 * @return
 * @throws exception
 */
 public static byte[] encryptbypublickey(byte[] data, string publickey)
  throws exception {
 byte[] keybytes = base64utils.decode(publickey);
 x509encodedkeyspec x509keyspec = new x509encodedkeyspec(keybytes);
 keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
 key publick = keyfactory.generatepublic(x509keyspec);
 // 对数据加密
 cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
 cipher.init(cipher.encrypt_mode, publick);
 int inputlen = data.length;
 bytearrayoutputstream out = new bytearrayoutputstream();
 int offset = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段加密
 while (inputlen - offset > 0) {
  if (inputlen - offset > max_encrypt_block) {
  cache = cipher.dofinal(data, offset, max_encrypt_block);
  } else {
  cache = cipher.dofinal(data, offset, inputlen - offset);
  }
  out.write(cache, 0, cache.length);
  i++;
  offset = i * max_encrypt_block;
 }
 byte[] encrypteddata = out.tobytearray();
 out.close();
 return encrypteddata;
 }
 /** *//**
 * <p>
 * 私钥加密
 * </p>
 *
 * @param data 源数据
 * @param privatekey 私钥(base64编码)
 * @return
 * @throws exception
 */
 public static byte[] encryptbyprivatekey(byte[] data, string privatekey)
  throws exception {
 byte[] keybytes = base64utils.decode(privatekey);
 pkcs8encodedkeyspec pkcs8keyspec = new pkcs8encodedkeyspec(keybytes);
 keyfactory keyfactory = keyfactory.getinstance(key_algorithm);
 key privatek = keyfactory.generateprivate(pkcs8keyspec);
 cipher cipher = cipher.getinstance(keyfactory.getalgorithm());
 cipher.init(cipher.encrypt_mode, privatek);
 int inputlen = data.length;
 bytearrayoutputstream out = new bytearrayoutputstream();
 int offset = 0;
 byte[] cache;
 int i = 0;
 // 对数据分段加密
 while (inputlen - offset > 0) {
  if (inputlen - offset > max_encrypt_block) {
  cache = cipher.dofinal(data, offset, max_encrypt_block);
  } else {
  cache = cipher.dofinal(data, offset, inputlen - offset);
  }
  out.write(cache, 0, cache.length);
  i++;
  offset = i * max_encrypt_block;
 }
 byte[] encrypteddata = out.tobytearray();
 out.close();
 return encrypteddata;
 }
 /** *//**
 * <p>
 * 获取私钥
 * </p>
 *
 * @param keymap 密钥对
 * @return
 * @throws exception
 */
 public static string getprivatekey(map<string, object> keymap)
  throws exception {
 key key = (key) keymap.get(private_key);
 return base64utils.encode(key.getencoded());
 }
 /** *//**
 * <p>
 * 获取公钥
 * </p>
 *
 * @param keymap 密钥对
 * @return
 * @throws exception
 */
 public static string getpublickey(map<string, object> keymap)
  throws exception {
 key key = (key) keymap.get(public_key);
 return base64utils.encode(key.getencoded());
 }
}

base64utils.java

package security;
import java.io.bytearrayinputstream;
import java.io.bytearrayoutputstream;
import java.io.file;
import java.io.fileinputstream;
import java.io.fileoutputstream;
import java.io.inputstream;
import java.io.outputstream;
import it.sauronsoftware.base64.base64;
/** *//**
 * <p>
 * base64编码解码工具包
 * </p>
 * <p>
 * 依赖javabase64-1.3.1.jar
 * </p>
 *
 * @author icewee
 * @date 2012-5-19
 * @version 1.0
 */
public class base64utils {
 /** *//**
 * 文件读取缓冲区大小
 */
 private static final int cache_size = 1024;
 /** *//**
 * <p>
 * base64字符串解码为二进制数据
 * </p>
 *
 * @param base64
 * @return
 * @throws exception
 */
 public static byte[] decode(string base64) throws exception {
 return base64.decode(base64.getbytes());
 }
 /** *//**
 * <p>
 * 二进制数据编码为base64字符串
 * </p>
 *
 * @param bytes
 * @return
 * @throws exception
 */
 public static string encode(byte[] bytes) throws exception {
 return new string(base64.encode(bytes));
 }
 /** *//**
 * <p>
 * 将文件编码为base64字符串
 * </p>
 * <p>
 * 大文件慎用，可能会导致内存溢出
 * </p>
 *
 * @param filepath 文件绝对路径
 * @return
 * @throws exception
 */
 public static string encodefile(string filepath) throws exception {
 byte[] bytes = filetobyte(filepath);
 return encode(bytes);
 }
 /** *//**
 * <p>
 * base64字符串转回文件
 * </p>
 *
 * @param filepath 文件绝对路径
 * @param base64 编码字符串
 * @throws exception
 */
 public static void decodetofile(string filepath, string base64) throws exception {
 byte[] bytes = decode(base64);
 bytearraytofile(bytes, filepath);
 }
 /** *//**
 * <p>
 * 文件转换为二进制数组
 * </p>
 *
 * @param filepath 文件路径
 * @return
 * @throws exception
 */
 public static byte[] filetobyte(string filepath) throws exception {
 byte[] data = new byte[0];
 file file = new file(filepath);
 if (file.exists()) {
  fileinputstream in = new fileinputstream(file);
  bytearrayoutputstream out = new bytearrayoutputstream(2048);
  byte[] cache = new byte[cache_size];
  int nread = 0;
  while ((nread = in.read(cache)) != -1) {
  out.write(cache, 0, nread);
  out.flush();
  }
  out.close();
  in.close();
  data = out.tobytearray();
  }
 return data;
 }
 /** *//**
 * <p>
 * 二进制数据写文件
 * </p>
 *
 * @param bytes 二进制数据
 * @param filepath 文件生成目录
 */
 public static void bytearraytofile(byte[] bytes, string filepath) throws exception {
 inputstream in = new bytearrayinputstream(bytes);
 file destfile = new file(filepath);
 if (!destfile.getparentfile().exists()) {
  destfile.getparentfile().mkdirs();
 }
 destfile.createnewfile();
 outputstream out = new fileoutputstream(destfile);
 byte[] cache = new byte[cache_size];
 int nread = 0;
 while ((nread = in.read(cache)) != -1) {
  out.write(cache, 0, nread);
  out.flush();
 }
 out.close();
 in.close();
 }
}

rsatester.java

package security;
import java.util.map;
public class rsatester {
 static string publickey;
 static string privatekey;
 static {
 try {
  map<string, object> keymap = rsautils.genkeypair();
  publickey = rsautils.getpublickey(keymap);
  privatekey = rsautils.getprivatekey(keymap);
  system.err.println("公钥: \n\r" + publickey);
  system.err.println("私钥： \n\r" + privatekey);
 } catch (exception e) {
  e.printstacktrace();
 }
 }
 public static void main(string[] args) throws exception {
 test();
 testsign();
 }
 static void test() throws exception {
 system.err.println("公钥加密——私钥解密");
 string source = "这是一行没有任何意义的文字，你看完了等于没看，不是吗？";
 system.out.println("\r加密前文字：\r\n" + source);
 byte[] data = source.getbytes();
 byte[] encodeddata = rsautils.encryptbypublickey(data, publickey);
 system.out.println("加密后文字：\r\n" + new string(encodeddata));
 byte[] decodeddata = rsautils.decryptbyprivatekey(encodeddata, privatekey);
 string target = new string(decodeddata);
 system.out.println("解密后文字: \r\n" + target);
 }
 static void testsign() throws exception {
 system.err.println("私钥加密——公钥解密");
 string source = "这是一行测试rsa数字签名的无意义文字";
 system.out.println("原文字：\r\n" + source);
 byte[] data = source.getbytes();
 byte[] encodeddata = rsautils.encryptbyprivatekey(data, privatekey);
 system.out.println("加密后：\r\n" + new string(encodeddata));
 byte[] decodeddata = rsautils.decryptbypublickey(encodeddata, publickey);
 string target = new string(decodeddata);
 system.out.println("解密后: \r\n" + target);
 system.err.println("私钥签名——公钥验证签名");
 string sign = rsautils.sign(encodeddata, privatekey);
 system.err.println("签名:\r" + sign);
 boolean status = rsautils.verify(encodeddata, publickey, sign);
 system.err.println("验证结果:\r" + status);
 }
}

ps：关于加密解密感兴趣的朋友还可以参考本站在线工具：

文字在线加密解密工具（包含aes、des、rc4等）：

md5在线加密工具:
http://tools.jb51.net/password/createmd5password

在线散列/哈希算法加密工具:

在线md5/hash/sha-1/sha-2/sha-256/sha-512/sha-3/ripemd-160加密工具：

在线sha1/sha224/sha256/sha384/sha512加密工具：

更多关于java相关内容感兴趣的读者可查看本站专题：《java数学运算技巧总结》、《java数据结构与算法教程》、《java字符与字符串操作技巧总结》、《java操作dom节点技巧总结》和《java缓存操作技巧汇总》

希望本文所述对大家java程序设计有所帮助。