Java是一種廣泛使用的編程語言，可以用于各種應用和領域，包括加密和安全。RSA是一種非對稱加密算法，用于加密和解密數據，并保護它們免受非法訪問和攻擊。同時，PFX和CER是兩種常用的數字證書格式，用于驗證和證明所需的加密和認證信息。

RSA算法：
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.util.Base64;
public class RSA {
public static void main(String[] args) throws Exception {
String message = "Hello, World!";
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
keyPairGenerator.initialize(2048);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
PrivateKey privateKey = keyPair.getPrivate();
PublicKey publicKey = keyPair.getPublic();
Signature signature = Signature.getInstance("SHA256withRSA");
signature.initSign(privateKey);
signature.update(message.getBytes("UTF-8"));
byte[] sign = signature.sign();
System.out.println(Base64.getEncoder().encodeToString(sign));
signature.initVerify(publicKey);
signature.update(message.getBytes("UTF-8"));
boolean result = signature.verify(sign);
System.out.println(result);
}
}
PFX格式：
import java.io.FileInputStream;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.cert.Certificate;
public class PFX {
public static void main(String[] args) throws Exception {
String password = "password";
String path = "example.pfx";
KeyStore keyStore = KeyStore.getInstance("PKCS12");
keyStore.load(new FileInputStream(path), password.toCharArray());
String alias = keyStore.aliases().nextElement();
PrivateKey privateKey = (PrivateKey) keyStore.getKey(alias, password.toCharArray());
Certificate certificate = keyStore.getCertificate(alias);
byte[] encoded = certificate.getEncoded();
}
}
CER格式：
import java.io.FileInputStream;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
public class CER {
public static void main(String[] args) throws Exception {
String path = "example.cer";
FileInputStream fis = new FileInputStream(path);
CertificateFactory certificateFactory = CertificateFactory.getInstance("X509");
Certificate certificate = certificateFactory.generateCertificate(fis);
byte[] encoded = certificate.getEncoded();
}
}

在Java中，RSA，PFX和CER都被廣泛應用于加密和安全領域，可以通過相應的API和庫輕松實現。無論是加密和解密數據，還是驗證和證明加密和認證信息，Java提供了全方位的支持和便捷的操作。