非對稱加密RSA實現

RSA是一種被廣泛接受並實現，提供私鑰加密和公鑰解密或者私鑰加密公鑰解密的算法。相對比較慢，底層是大數字因子分解。

 package password.rsa;


import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;


import javax.crypto.Cipher;


import org.apache.commons.codec.binary.Base64;


public class RSA2 {
public static String RSA = "RSA";
private static final String src = "password";


public static void main(String[] args) {
try {
jdkRSA();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}


// rsa實現非對稱加密
public static void jdkRSA() throws Exception {
// 1.初始化密鑰
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(RSA);
keyPairGenerator.initialize(512);
KeyPair generateKeyPair = keyPairGenerator.generateKeyPair();


// 初始化公鑰
RSAPublicKey rsaPublicKey = (RSAPublicKey) generateKeyPair.getPublic();
// 初始化私鑰
RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) generateKeyPair.getPrivate();
System.out.println("public key公鑰：" + Base64.encodeBase64String(rsaPublicKey.getEncoded()));
System.out.println("private key私鑰：" + Base64.encodeBase64String(rsaPrivateKey.getEncoded()));
// 2.私鑰加密——公鑰解密,加密：
PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
KeyFactory keyFactory = KeyFactory.getInstance(RSA);
PrivateKey generatePrivate = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
Cipher instance = Cipher.getInstance(RSA);
instance.init(Cipher.ENCRYPT_MODE, rsaPrivateKey);
byte[] doFinal = instance.doFinal(src.getBytes());
System.out.println("用公鑰加密，私鑰解密——加密：" + Base64.encodeBase64String(doFinal));
// 3.私鑰加密——公鑰解密：解密：
X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
keyFactory = KeyFactory.getInstance(RSA);
PublicKey generatePublic = keyFactory.generatePublic(x509EncodedKeySpec);
Cipher instance2 = Cipher.getInstance(RSA);
instance2.init(Cipher.DECRYPT_MODE, generatePublic);
doFinal = instance2.doFinal(doFinal);
System.out.println("公鑰解密結果：" + new String(doFinal));
// 4.公鑰加密——私鑰解密,加密：
x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
keyFactory = KeyFactory.getInstance(RSA);
generatePublic = keyFactory.generatePublic(x509EncodedKeySpec);
instance2 = Cipher.getInstance(RSA);
instance2.init(Cipher.ENCRYPT_MODE, generatePublic);
doFinal = instance2.doFinal(src.getBytes());
System.out.println("公鑰加密結果：" + Base64.encodeBase64String(doFinal));
// 5.公鑰加密——私鑰解密,解密：
new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
keyFactory = KeyFactory.getInstance(RSA);
generatePrivate = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
instance = Cipher.getInstance(RSA);
instance.init(Cipher.DECRYPT_MODE, rsaPrivateKey);
doFinal = instance.doFinal(doFinal);


System.out.println("用私鑰加密，公鑰解密——解密：" + new String(doFinal));


}


}