前言
-
簡介
RSA公開密鑰密碼體制是一種使用不同的加密密鑰與解密密鑰，“由已知加密密鑰推導出解密密鑰在計算上是不可行的”密碼體制。 -
原理
根據數論，尋求兩個大素數比較簡單，而將它們的乘積進行因式分解卻極其困難，因此可以將乘積公開作為加密密鑰，即公鑰，而兩個大素數組合成私鑰。公鑰是可發布的供任何人使用，私鑰則為自己所有，供解密之用。 -
運算速度
由於進行的都是大數計算，使得RSA最快的情況也比DES慢上好幾倍，無論是軟件還是硬件實現。速度一直是RSA的缺陷。一般來說只用於少量數據加密。RSA的速度比對應同樣安全級別的對稱密碼算法要慢1000倍左右。
具體實現
- 實現類
import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
/**
* @Description RSA加密算法
* @author coisini
* @date Jul 5, 2021
* @Version 1.0
*/
public class RSAUtil {
private static final String ALGO = "RSA";
private static final String CHARSET = "UTF-8";
/**
* 公鑰 由generateKeyPair()生成
*/
private static final String PUBLIC_KEY = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCaaI4MBywkCjIppZnraqN3pbrcZTq/t0+aMBo8K3pK9BDD6XkM6N2Yfcva7BSFbUWuAcI7piXak0UKn9CElDuhNzUSgQn4IXKxIt3Iva5cV83qYumj+0yRjjLT8Muu1Y1rgBZjY9oBwhVoV+Twg25+UJ+6Q6HM4xTwQQJDoyy4jwIDAQAB";
/**
* 私鑰 由generateKeyPair()生成
*/
private static final String PRIVATE_KEY = "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";
/**
* 生成密鑰對
* @throws NoSuchAlgorithmException
*/
private static void generateKeyPair() throws NoSuchAlgorithmException {
// KeyPairGenerator 類用於生成公鑰和私鑰對，基於RSA算法生成對象
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(ALGO);
// 初始化密鑰對生成器，密鑰大小為 96-1024 位
keyPairGen.initialize(1024, new SecureRandom());
// 生成一個密鑰對，保存在 keyPair 中
KeyPair keyPair = keyPairGen.generateKeyPair();
// 得到私鑰
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
// 得到公鑰
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
String publicKeyString = new String(Base64.getEncoder().encode(publicKey.getEncoded()));
// 得到私鑰字符串
String privateKeyString = new String(Base64.getEncoder().encode((privateKey.getEncoded())));
System.out.println(publicKeyString);
System.out.println(privateKeyString);
}
/**
* RSA公鑰加密
* @param data 加密字符串
* @return 密文
* @throws Exception 加密過程中的異常信息
*/
private static String encryptByPublicKey(String data) throws Exception {
// base64 編碼的公鑰
byte[] decoded = Base64.getDecoder().decode(PUBLIC_KEY);
RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(ALGO).generatePublic(new X509EncodedKeySpec(decoded));
// RSA加密
Cipher cipher = Cipher.getInstance(ALGO);
// 公鑰加密
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
return Base64.getEncoder().encodeToString(cipher.doFinal(data.getBytes(CHARSET)));
}
/**
* RSA私鑰解密
* @param data 加密字符串
* @return 明文
* @throws Exception 解密過程中的異常信息
*/
private static String decryptByPrivateKey(String data) throws Exception {
byte[] inputByte = Base64.getDecoder().decode(data.getBytes(CHARSET));
// base64 編碼的私鑰
byte[] decoded = Base64.getDecoder().decode(PRIVATE_KEY);
RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(ALGO).generatePrivate(new PKCS8EncodedKeySpec(decoded));
// RSA 解密
Cipher cipher = Cipher.getInstance(ALGO);
// 私鑰解密
cipher.init(Cipher.DECRYPT_MODE, priKey);
return new String(cipher.doFinal(inputByte));
}
/**
* 私鑰加密
* 前端公鑰解密
* @param data 加密字符串
* @return 密文
* @throws Exception 加密過程中的異常信息
*/
public static String encryptByPrivateKey(String data) throws Exception {
// 獲取私鑰
PrivateKey privateKey = getPrivateKey(PRIVATE_KEY);
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
byte[] cipherText = cipher.doFinal(data.getBytes());
String cipherStr = Base64.getEncoder().encodeToString(cipherText);
return cipherStr;
}
/**
* 公鑰解密
* @param data 解密字符串
* @return 明文
* @throws Exception 解密過程中的異常信息
*/
public static String decryptByPublicKey(String data) throws Exception {
// 獲取公鑰
PublicKey publicKey = getPublicKey(PUBLIC_KEY);
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, publicKey);
byte[] cipherText = Base64.getDecoder().decode(data);
byte[] decryptText = cipher.doFinal(cipherText);
return new String(decryptText);
}
/**
* 將base64編碼后的私鑰字符串轉成PrivateKey實例
* @param privateKey 私鑰
* @return PrivateKey實例
* @throws Exception 異常信息
*/
private static PrivateKey getPrivateKey(String privateKey) throws Exception {
byte[] keyBytes = Base64.getDecoder().decode(privateKey);
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(ALGO);
return keyFactory.generatePrivate(keySpec);
}
/**
* 將base64編碼后的公鑰字符串轉成PublicKey實例
* @param publicKey 公鑰
* @return PublicKey實例
* @throws Exception 異常信息
*/
private static PublicKey getPublicKey(String publicKey) throws Exception {
byte[] keyBytes = Base64.getDecoder().decode(publicKey);
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(ALGO);
return keyFactory.generatePublic(keySpec);
}
public static void main(String[] args) {
String data = "RSA encrypt!";
try {
// generateKeyPair();
String encryDataByPublicKey = encryptByPublicKey(data);
System.out.println("encryDataByPublicKey: " + encryDataByPublicKey);
String decryDataByPrivateKey = decryptByPrivateKey(encryDataByPublicKey);
System.out.println("decryDataByPrivateKey: " + decryDataByPrivateKey);
String encryDataByPrivateKey = encryptByPrivateKey(data);
System.out.println("encryDataByPrivateKey: " + encryDataByPrivateKey);
String decryDataByPublicKey = decryptByPublicKey(encryDataByPrivateKey);
System.out.println("decryDataByPublicKey: " + decryDataByPublicKey);
} catch (Exception e) {
e.printStackTrace();
}
}
}
- 結果如下所示：
