Java Backend Development: API Crypto Extensions with Java Bouncy Castle

Since the popularity of the Internet, encryption technology has played an important role in information security. API encryption has become one of the best ways to protect API security. In fact, API encryption has become a security necessity for many Internet companies today. Java Bouncy Castle, as one of the Java encryption libraries, can help us implement API encryption and extension.

First, we need to understand what Java Bouncy Castle is. Bouncy Castle is a Java encryption library that provides implementations of many encryption algorithms and protocols, such as AES, RSA, ECDSA, PGP, TLS, etc. In addition, it also supports some professional encryption requirements, such as SM2, SM3, SM4 and other Chinese national encryption algorithms. The security of Bouncy Castle has been widely recognized, and it has been widely used not only in the Java field, but also in other programming languages.

We can add Bouncy Castle to our Java project through Maven or Gradle. The following is an example of referencing Bouncy Castle through Maven:

<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-jdk15on</artifactId>
    <version>1.56</version>
</dependency>

Next, let’s look at how to use Java Bouncy Castle for API encryption extensions. The following is an example of using Bouncy Castle to implement AES encryption:

import org.bouncycastle.jce.provider.BouncyCastleProvider;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.Key;
import java.security.Security;
import java.util.Base64;

public class AesEncryptionUtil {

    private static final String ALGORITHM = "AES";
    private static final String CIPHER_MODE_FACTORY = "AES/CBC/PKCS7Padding";
    private static final String CHARSET = "UTF-8";

    /**
     * 加密
     *
     * @param data 待加密的字符串
     * @param key  密钥
     * @param iv   初始向量
     * @return 加密后的字符串
     */
    public static String encrypt(String data, String key, String iv) {
        Security.addProvider(new BouncyCastleProvider());
        try {
            byte[] dataBytes = data.getBytes(CHARSET);
            byte[] keyBytes = key.getBytes(CHARSET);
            byte[] ivBytes = iv.getBytes(CHARSET);

            Key secretKeySpec = new SecretKeySpec(keyBytes, ALGORITHM);
            IvParameterSpec ivParameterSpec = new IvParameterSpec(ivBytes);

            Cipher cipher = Cipher.getInstance(CIPHER_MODE_FACTORY, "BC");
            cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);

            byte[] encryptedBytes = cipher.doFinal(dataBytes);

            return Base64.getEncoder().encodeToString(encryptedBytes);
        } catch (Exception e) {
            throw new RuntimeException("加密失败", e);
        }
    }

    /**
     * 解密
     *
     * @param data 加密后的字符串
     * @param key  密钥
     * @param iv   初始向量
     * @return 解密后的字符串
     */
    public static String decrypt(String data, String key, String iv) {
        Security.addProvider(new BouncyCastleProvider());
        try {
            byte[] dataBytes = Base64.getDecoder().decode(data);
            byte[] keyBytes = key.getBytes(CHARSET);
            byte[] ivBytes = iv.getBytes(CHARSET);

            Key secretKeySpec = new SecretKeySpec(keyBytes, ALGORITHM);
            IvParameterSpec ivParameterSpec = new IvParameterSpec(ivBytes);

            Cipher cipher = Cipher.getInstance(CIPHER_MODE_FACTORY, "BC");
            cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);

            byte[] decryptedBytes = cipher.doFinal(dataBytes);

            return new String(decryptedBytes, StandardCharsets.UTF_8);
        } catch (Exception e) {
            throw new RuntimeException("解密失败", e);
        }
    }

}

We used the AES encryption algorithm provided by Bouncy Castle, specified the initial vector and padding method during encryption and decryption, and encoded and decoded through Base64. When using this method to implement API encryption, attention should be paid to the secure transmission of keys and initial vectors to avoid being intercepted and stolen by attackers.

Bouncy Castle library can help us achieve more secure API encryption, and we can implement more complex encryption algorithms based on Bouncy Castle. Through the examples above, we can clearly understand how to use Java Bouncy Castle for API encryption extensions.

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