公钥加密也称为非对称加密、速度慢、加密和解密的钥匙不相同，某一个人持有私钥，任何人都可以知道公钥

import java.security.KeyPair;    import java.security.KeyPairGenerator;    import java.security.PrivateKey;    import java.security.PublicKey;    import java.util.Arrays;        import javax.crypto.Cipher;        /**    * RSA算法 公钥加密 非对称加密    * @author stone    * @date 2014-03-11 00:28:38    */    public class RSA {        public static final String KEY_ALGORITHM = "RSA";        public static final String CIPHER_ALGORITHM_ECB1 = "RSA/ECB/PKCS1Padding";        public static final String CIPHER_ALGORITHM_ECB2 = "RSA/ECB/OAEPWithSHA-1AndMGF1Padding"; //不能用        public static final String CIPHER_ALGORITHM_ECB3 = "OAEPWithSHA-256AndMGF1Padding"; //不能用                static PublicKey publicKey;        static PrivateKey privateKey;        static Cipher cipher;        static KeyPair keyPair;                public static void main(String[] args) throws Exception {            method1("斯柯达U*(Sfsad7f()*^%%$");            method2("斯柯达U*(Sfsad7f()*^%%$");            method3("斯柯达U*(Sfsad7f()*^%%$");                    }                /**        * 公钥加密，私钥解密    使用默认CIPHER_ALGORITHM_ECB1        * @param str        * @throws Exception        */        static void method1(String str) throws Exception {            KeyPairGenerator keyGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);            KeyPair keyPair = keyGenerator.generateKeyPair();            publicKey = keyPair.getPublic();            privateKey = keyPair.getPrivate();            cipher = Cipher.getInstance(KEY_ALGORITHM);            cipher.init(Cipher.ENCRYPT_MODE, publicKey); //公钥加密            byte[] encrypt = cipher.doFinal(str.getBytes());            System.out.println("公钥加密后1：" + Arrays.toString(encrypt));                        cipher.init(Cipher.DECRYPT_MODE, privateKey);//私钥解密            byte[] decrypt = cipher.doFinal(encrypt);            System.out.println("私钥解密后1：" + new String(decrypt));        }                /**        * 私钥加密，公钥解密    使用默认CIPHER_ALGORITHM_ECB1        * @param str        * @throws Exception        */        static void method2(String str) throws Exception {            KeyPairGenerator keyGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);            KeyPair keyPair = keyGenerator.generateKeyPair();            publicKey = keyPair.getPublic();            privateKey = keyPair.getPrivate();            cipher = Cipher.getInstance(KEY_ALGORITHM);            cipher.init(Cipher.ENCRYPT_MODE, privateKey); //私钥加密            byte[] encrypt = cipher.doFinal(str.getBytes());            System.out.println("私钥加密后2：" + Arrays.toString(encrypt));                        cipher.init(Cipher.DECRYPT_MODE, publicKey);//公钥解密            byte[] decrypt = cipher.doFinal(encrypt);            System.out.println("公钥解密后2：" + new String(decrypt));        }                /**        * 私钥加密，公钥解密    使用CIPHER_ALGORITHM_ECB1 = RSA/ECB/PKCS1Padding        * @param str        * @throws Exception        */        static void method3(String str) throws Exception {            KeyPairGenerator keyGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);            KeyPair keyPair = keyGenerator.generateKeyPair();            publicKey = keyPair.getPublic();            privateKey = keyPair.getPrivate();            cipher = Cipher.getInstance(CIPHER_ALGORITHM_ECB1);            cipher.init(Cipher.ENCRYPT_MODE, privateKey); //私钥加密            byte[] encrypt = cipher.doFinal(str.getBytes());            System.out.println("私钥加密后3：" + Arrays.toString(encrypt));                        cipher.init(Cipher.DECRYPT_MODE, publicKey);//公钥解密            byte[] decrypt = cipher.doFinal(encrypt);            System.out.println("公钥解密后3：" + new String(decrypt));        }    }