Example introduction of RSA encryption and decryption

RSAsecurity.java

package com.mstf.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 com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
 
/*RSA 工具类。提供加密，解密，生成密钥对等方法。 
RSA加密原理概述   
RSA的安全性依赖于大数的分解，公钥和私钥都是两个大素数（大于100的十进制位）的函数。
据猜测，从一个密钥和密文推断出明文的难度等同于分解两个大素数的积   
密钥的产生：   
 1.选择两个大素数 p,q ,计算 n=p*q;   
 2.随机选择加密密钥 e ,要求 e 和 (p-1)*(q-1)互质   
 3.利用 Euclid 算法计算解密密钥 d , 使其满足 e*d = 1(mod(p-1)*(q-1)) (其中 n,d 也要互质)   
 4:至此得出公钥为 (n,e) 私钥为 (n,d)   
 RSA速度   
 * 由于进行的都是大数计算，使得RSA最快的情况也比DES慢上100倍，无论 是软件还是硬件实现。   
 * 速度一直是RSA的缺陷。一般来说只用于少量数据 加密。*/
public class RSAsecurity {
 
	public static String src = "admin";
 
	public void priENpubDE() {
 
		try {
			// 初始化秘钥
			KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
			// 秘钥长度
			keyPairGenerator.initialize(1024);
			// 初始化秘钥对
			KeyPair keyPair = keyPairGenerator.generateKeyPair();
			// 公钥
			RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
			// 私钥
			RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();
 
			// 2.私钥加密，公钥解密----加密
			// 生成私钥
			PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
			KeyFactory keyFactory = KeyFactory.getInstance("RSA");
			PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
			// Cipher类为加密和解密提供密码功能，通过getinstance实例化对象
			Cipher cipher = Cipher.getInstance("RSA");
			// 初始化加密
			cipher.init(Cipher.ENCRYPT_MODE, privateKey);
			byte[] result = cipher.doFinal(src.getBytes());
			System.out.println("私钥加密，公钥解密----加密:" + Base64.encode(result));
 
			// 3.私钥加密，公钥解密----解密
			// 生成公钥
			X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
			keyFactory = KeyFactory.getInstance("RSA");
			PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
			cipher = Cipher.getInstance("RSA");
			// 初始化解密
			cipher.init(Cipher.DECRYPT_MODE, publicKey);
			result = cipher.doFinal(result);
			System.out.println("私钥加密，公钥解密----解密:" + new String(result));
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
 
	}
 
	public void pubENpriDE() {
		try {
			// 1.初始化秘钥
			KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
			// 秘钥长度
			keyPairGenerator.initialize(512);
			// 初始化秘钥对
			KeyPair keyPair = keyPairGenerator.generateKeyPair();
			// 公钥
			RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
			// 私钥
			RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();
 
			// 2.公钥加密，私钥解密----加密
			X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
			KeyFactory keyFactory = KeyFactory.getInstance("RSA");
			PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
			// 初始化加密
			// Cipher类为加密和解密提供密码功能，通过getinstance实例化对象
			Cipher cipher = Cipher.getInstance("RSA");
			cipher.init(Cipher.ENCRYPT_MODE, publicKey);
			// 加密字符串
			byte[] result = cipher.doFinal(src.getBytes());
			System.out.println("公钥加密，私钥解密----加密:" + Base64.encode(result));
 
			// 3.公钥加密，私钥解密-----解密
			PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
			keyFactory = KeyFactory.getInstance("RSA");
			PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
			// 初始化解密
			cipher.init(Cipher.DECRYPT_MODE, privateKey);
			// 解密字符串
			result = cipher.doFinal(result);
			System.out.println("公钥加密，私钥解密-----解密:" + new String(result));
 
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
 
	}
}

RSAtest.java

package com.mstf.rsa;
 
import com.mstf.rsa.RSAsecurity;
 
public class RSAtest {
	public static void main(String[] args) {
		RSAsecurity rsAsecurity = new RSAsecurity();
		System.out.println("私钥加密公钥解密例：");
		rsAsecurity.priENpubDE();
		System.out.println("公钥加密私钥解密例：");
		rsAsecurity.pubENpriDE();
	}
}

　　

The above is the detailed content of Example introduction of RSA encryption and decryption. For more information, please follow other related articles on the PHP Chinese website!