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学会几招，轻松用Java加密字符串，保护你的信息安全

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在信息化时代，数据安全至关重要。Java作为一门强大的编程语言，提供了多种加密字符串的方法，可以帮助我们保护敏感信息。以下是一些简单实用的方法，让你轻松掌握Java加密字符串的技巧。

一、使用Java内置的java.util.Base64

java.util.Base64是Java 8及以上版本提供的一个简单类，用于实现Base64编码和解码。Base64编码并不是一种安全的加密方法，但可以用于将二进制数据转换为文本格式，以便于存储或传输。

1. 编码字符串

import java.util.Base64;

public class Base64Example {
    public static void main(String[] args) {
        String originalString = "Hello, World!";
        String encodedString = Base64.getEncoder().encodeToString(originalString.getBytes());
        System.out.println("Encoded String: " + encodedString);
    }
}

2. 解码字符串

import java.util.Base64;

public class Base64Example {
    public static void main(String[] args) {
        String encodedString = "SGVsbG8sIFdvcmxkIQ==";
        String decodedString = new String(Base64.getDecoder().decode(encodedString));
        System.out.println("Decoded String: " + decodedString);
    }
}

二、使用java.security.MessageDigest

MessageDigest类可以用于生成信息摘要，如MD5、SHA-1和SHA-256等。这些摘要函数可以用于校验数据的完整性，但不适合用作安全的加密。

1. 使用MD5

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Example {
    public static void main(String[] args) {
        String originalString = "Hello, World!";
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(originalString.getBytes());
            byte[] digest = md.digest();
            StringBuilder sb = new StringBuilder();
            for (byte b : digest) {
                sb.append(String.format("%02x", b));
            }
            System.out.println("MD5: " + sb.toString());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }
}

2. 使用SHA-256

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SHA256Example {
    public static void main(String[] args) {
        String originalString = "Hello, World!";
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            md.update(originalString.getBytes());
            byte[] digest = md.digest();
            StringBuilder sb = new StringBuilder();
            for (byte b : digest) {
                sb.append(String.format("%02x", b));
            }
            System.out.println("SHA-256: " + sb.toString());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }
}

三、使用对称加密算法（如AES）

对称加密算法使用相同的密钥进行加密和解密。AES是一种广泛使用的对称加密算法。

1. 加密字符串

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class AESEncryptionExample {
    public static void main(String[] args) {
        try {
            // 生成密钥
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(128);
            SecretKey secretKey = keyGenerator.generateKey();
            byte[] keyBytes = secretKey.getEncoded();
            SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

            // 加密字符串
            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
            String originalString = "Hello, World!";
            byte[] encryptedBytes = cipher.doFinal(originalString.getBytes());
            System.out.println("Encrypted String: " + new String(encryptedBytes));

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2. 解密字符串

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class AESDecryptionExample {
    public static void main(String[] args) {
        try {
            // 生成密钥
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(128);
            SecretKey secretKey = keyGenerator.generateKey();
            byte[] keyBytes = secretKey.getEncoded();
            SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

            // 解密字符串
            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
            String encryptedString = "U29tZSBvdGhlciB3b3JrcyBhIHdvcmxkIQ==";
            byte[] encryptedBytes = new String(Base64.getDecoder().decode(encryptedString)).getBytes();
            byte[] decryptedBytes = cipher.doFinal(encryptedBytes);
            System.out.println("Decrypted String: " + new String(decryptedBytes));

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

四、使用非对称加密算法（如RSA）

非对称加密算法使用一对密钥：公钥和私钥。公钥用于加密，私钥用于解密。

1. 生成密钥对

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;

public class RSAKeyPairExample {
    public static void main(String[] args) {
        try {
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
            keyPairGenerator.initialize(2048);
            KeyPair keyPair = keyPairGenerator.generateKeyPair();
            PublicKey publicKey = keyPair.getPublic();
            PrivateKey privateKey = keyPair.getPrivate();
            
            System.out.println("Public Key: " + publicKey);
            System.out.println("Private Key: " + privateKey);
            
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }
}

2. 使用公钥加密

”`java import javax.crypto.Cipher; import java.security.KeyFactory; import java.security.NoSuchAlgorithmException; import java.security.PublicKey; import java.security.spec.X509EncodedKeySpec;

public class RSAEncryptionExample {

public static void main(String[] args) {
    try {
        String publicKeyPEM = "-----BEGIN PUBLIC KEY-----\n" +
                "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAr6B5Rc6s7V0\n" +
                "V9wz0L7Gy1Ry0L6Lz3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3\n" +
                "G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7\n" +
                "Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3\n" +
                "R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6\n" +
                "H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3\n" +
                "G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7Y5R6H3G6V3R6R3G7
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