【JAVA】算法

start

 1.SHA-256算法（单向、验证完整性/一致性，暂时安全）

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SHA256Example {

    public static String hashWithSHA256(String text) {

        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            byte[] hash = digest.digest(text.getBytes(StandardCharsets.UTF_8));
            return bytesToHexString(hash);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("Error: Unable to find SHA-256 algorithm.", e);
        }

    }

    public static String bytesToHexString(byte[] bytes) {
        StringBuilder hexString = new StringBuilder();
        for (byte b : bytes) {
            String hex = Integer.toHexString(0xff & b);
            if (hex.length() == 1) {
                hexString.append("0");
            }
            hexString.append(hex);
        }
        return hexString.toString();
    }

    public static void main(String[] args) {
        String text = "Hello,World!";
        String sha256hash = hashWithSHA256(text);
        System.out.println("Original:" + text);
        System.out.println("SHA-256:" + sha256hash);
    }

}

 

 2.MD5算法（单向、验证完整性、一致性，有安全漏洞）

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Example {
    public static String getMD5Hash(String text) {
        try {
            MessageDigest mDigest = MessageDigest.getInstance("MD5");
            byte[] hashBytes = mDigest.digest(text.getBytes(StandardCharsets.UTF_8));
            StringBuilder sBuilder = new StringBuilder();
            for (byte b : hashBytes) {
                sBuilder.append(String.format("%02x", b));
            }
            return sBuilder.toString();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("MD5 algorithm not found", e);
        }
    }

    public static void main(String[] args) {
        String text = "Hello,world!";
        String md5Hash = getMD5Hash(text);
        System.out.println("Original:" + text);
        System.out.println("MD5:" + md5Hash);
    }

}

 

 3.SHA3-256算法（）

import org.bouncycastle.jcajce.provider.digest.SHA3;
import org.bouncycastle.util.encoders.Hex;

import java.nio.charset.StandardCharsets;

public class SHA3_256Example {
    public static void main(String[] args) {
        String input = "Hello, World!";
        String sha3_256Hash = getSHA3_256Hash(input);
        System.out.println("SHA3-256 Hash: " + sha3_256Hash);
    }

    public static String getSHA3_256Hash(String input) {
        // 创建一个SHA3.Digest256实例
        SHA3.Digest256 digest = new SHA3.Digest256();

        // 对输入的字符串进行散列
        byte[] hashBytes = digest.digest(input.getBytes(StandardCharsets.UTF_8));

        // 将散列后的字节数组转换为十六进制字符串
        return new String(Hex.encode(hashBytes));
    }
}

Java8以前需要第三方库支持。

<dependencies>
    <!-- Other dependencies -->
    <dependency>
        <groupId>org.bouncycastle</groupId>
        <artifactId>bcprov-jdk15on</artifactId>
        <version>1.70</version>
    </dependency>
</dependencies>

Java9开始，JDK中已经支持SHA3-256的算法。无需第三方。

 3.AES算法（对称加密算法）

import java.nio.charset.StandardCharsets;
import java.util.Base64;

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

public class AESExample {
    public AESExample() {
        String input = "Hello,World!";
        try {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(256);
            SecretKey secretKey = keyGenerator.generateKey();

            // 加密
            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);
            byte[] encryptedData = cipher.doFinal(input.getBytes(StandardCharsets.UTF_8));
            String encryptedDataString = Base64.getEncoder().encodeToString(encryptedData);
            System.out.println("Encrypted data:" + encryptedDataString);

            // 解密
            cipher.init(Cipher.DECRYPT_MODE, secretKey);
            byte[] decryptedData = cipher.doFinal(encryptedData);
            String decryptedDataString = new String(decryptedData, StandardCharsets.UTF_8);
            System.out.println("Decrypted data:" + decryptedDataString);

        } catch (Exception e) {
            throw new RuntimeException("Error:", e);
        }
    }

    public static void main(String[] args) {
        new AESExample();
    }
}

4.RSA算法（非对称加密算法）

import java.nio.charset.StandardCharsets;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.Base64;

import javax.crypto.Cipher;

public class RSAExample {
    public static void main(String[] args) {
        String input = "Hello,world!";

        try {
            // 生成SA密钥
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
            keyPairGenerator.initialize(2048);
            KeyPair keyPair = keyPairGenerator.generateKeyPair();
            // 公钥
            PublicKey publicKey = keyPair.getPublic();
            System.out.println("公钥："+publicKey.toString());
            // 私钥
            PrivateKey privateKey = keyPair.getPrivate();
            System.out.println("私钥："+privateKey.toString());

            // 使用公钥加密数据
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            byte[] encryptedData = cipher.doFinal(input.getBytes(StandardCharsets.UTF_8));
            String encryptedDataString = Base64.getEncoder().encodeToString(encryptedData);
            System.out.println("Encryted Data:" + encryptedDataString);

            // 使用私钥解密数据
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            byte[] decrytedData = cipher.doFinal(encryptedData);
            String decrytedDataString = new String(decrytedData, StandardCharsets.UTF_8);
            System.out.println("Decryted Data:" + decrytedDataString);

        } catch (Exception e) {
            throw new RuntimeException("Error:", e);
        }
    }
}

 

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