私钥加密-->公钥解密，反之亦然，但不安全。也可以当做数字签名。
public class RSACoder {
//非对称加密算法
public static final String KEY_ALGORITHM = "RSA" ;
//公钥
private static final String PUBLIC_KEY = "RSAPublicKey" ;
//私钥
private static final String PRIVATE_KEY = "RSAPrivateKey" ;
//密钥长度，默认1024位，512~65536位，必须是64的倍数
private static final int KEY_SIZE =512;
//私钥解密
public static byte [] decryptByPrivateKey( byte [] data, byte [] key) throws KeyException, Exception{
//取得私钥,
PKCS8EncodedKeySpec pkcs8KeySpec= new PKCS8EncodedKeySpec(key);
KeyFactory keyFactory=KeyFactory. getInstance( KEY_ALGORITHM );
PrivateKey privateKey=keyFactory.generatePrivate(pkcs8KeySpec);
//对数据解密
Cipher cipher=Cipher. getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher. DECRYPT_MODE , privateKey);
return cipher.doFinal(data);
}
//公钥解密
public static byte [] decryptByPublicKey( byte [] data, byte [] key) throws Exception{
X509EncodedKeySpec x509= new X509EncodedKeySpec(key);
KeyFactory keyFactory=KeyFactory. getInstance( KEY_ALGORITHM );
//生成公钥
PublicKey publicKey=keyFactory.generatePublic(x509);
//对数据解密
Cipher cipher=Cipher. getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher. DECRYPT_MODE , publicKey);
return cipher.doFinal(data);
}
//公钥加密
public static byte [] encrpytByPublicKey( byte [] data, byte [] key) throws Exception{
//取得公钥
X509EncodedKeySpec x509= new X509EncodedKeySpec(key);
KeyFactory keyFactory=KeyFactory. getInstance( KEY_ALGORITHM );
PublicKey pubKey=keyFactory.generatePublic(x509);
//对数据加密
Cipher cipher=Cipher. getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher. ENCRYPT_MODE , pubKey);
return cipher.doFinal(data);
}
//私钥加密
public static byte [] encryptByPrivate( byte [] data, byte [] key) throws Exception, GeneralSecurityException{
//取得私钥
PKCS8EncodedKeySpec pkcs8= new PKCS8EncodedKeySpec(key);
KeyFactory keyFactory=KeyFactory. getInstance( KEY_ALGORITHM );
//生成私钥
PrivateKey privateKey=keyFactory.generatePrivate(pkcs8);
//对数据加密
Cipher cipher=Cipher. getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher. ENCRYPT_MODE , privateKey);
return cipher.doFinal(data);
}
//取得私钥
public static byte [] getPrivateKey(Map<String,Object> keyMap){
Key key=(Key)keyMap.get( PRIVATE_KEY );
return key.getEncoded();
}
//取得公钥
public static byte [] getPublicKey(Map<String,Object> keyMap){
Key key=(Key)keyMap.get( PUBLIC_KEY );
return key.getEncoded();
}
//初始化密钥
public static Map<String,Object> initKey() throws Exception{
KeyPairGenerator keyPairGen=KeyPairGenerator.getInstance( KEY_ALGORITHM );
keyPairGen.initialize( KEY_SIZE );
KeyPair keyPair=keyPairGen.generateKeyPair();
//公钥
RSAPublicKey publicKey=(RSAPublicKey)keyPair.getPublic();
//私钥
RSAPrivateKey privateKey=(RSAPrivateKey)keyPair.getPrivate();
//封装密钥
Map<String,Object> keyMap= new HashMap<String,Object>(2);
keyMap.put( PRIVATE_KEY , privateKey);
keyMap.put( PUBLIC_KEY , publicKey);
return keyMap;
}
}
public class RSATest {
private static byte [] privateKey ;
private static byte [] publicKey ;
public static void initKey() throws Exception{
//初始化密钥
Map<String,Object> keyMap=RSACoder. initKey();
publicKey =RSACoder.getPublicKey(keyMap);
privateKey =RSACoder.getPrivateKey(keyMap);
System. out .println( "公钥:\n" +Base64.encodeBase64String ( publicKey ));
System. out .println( "私钥：\n" +Base64.encodeBase64String ( privateKey ));
}
public static void main(String[] args) throws GeneralSecurityException, Exception {
// TODO Auto-generated method stub
initKey();
String inputStr1= "RSA加密算法" ;
byte [] data1=inputStr1.getBytes();
System. out .println( "原文：\n" +inputStr1);
//私钥加密
byte [] encodeData1=RSACoder.encryptByPrivate(data1, privateKey );
System. err .println( "加密后：\n" +Base64.encodeBase64String (encodeData1));
//公钥解密
byte [] decodeData1=RSACoder.decryptByPublicKey(encodeData1, publicKey );
String outputStr1= new String(decodeData1);
System. err .println( "解密后：\n" +outputStr1);
assertEquals(inputStr1,outputStr1);
}
}