Java implements an AES/ECB/PKCS5Padding encryption and decryption algorithm tool class

  • Encryption algorithm: AES
  • Mode: the ECB
  • Complement method: PKCS5Padding

1. The tools

import lombok.Getter;
import lombok.Setter;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.Base64Utils;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.BufferedInputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.MessageDigest;

/**
 * Created by @author yihui in 19:12 20/1/2.
 */
@Slf4j
public class EncryptUtil {
    private static final String KEY_ALGORITHM = "AES";
    /** * algorithm/mode/complement mode */
    private static final String DEFAULT_CIPHER_ALGORITHM = "AES/ECB/PKCS5Padding";
    private static final String CODE = "utf-8";

    @Setter
    @Getter
    public static String encryptKey;

    public static String encrypt(String content) {
        return encrypt(content, encryptKey);
    }

    /** * encrypt **@param content
     * @param key
     * @return
     * @throws Exception
     */
    public static String encrypt(String content, String key) {
        try {
            byte[] encrypted = encrypt2bytes(content, key);
            return Base64Utils.encodeToString(encrypted);
        } catch (Exception e) {
            log.error("failed to encrypt: {} of {}", content, e);
            return null; }}public static byte[] encrypt2bytes(String content, String key) {
        try {
            byte[] raw = key.getBytes(CODE);
            SecretKeySpec secretKeySpec = new SecretKeySpec(raw, KEY_ALGORITHM);
            Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
            return cipher.doFinal(content.getBytes(CODE));
        } catch (Exception e) {
            log.error("failed to encrypt: {} of {}", content, e);
            return null; }}public static String decrypt(String content) {
        try {
            return decrypt(content, encryptKey);
        } catch (Exception e) {
            log.error("failed to decrypt: {}, e: {}", content, e);
            return null; }}/** * decrypt **@param content
     * @param key
     * @return
     * @throws Exception
     */
    public static String decrypt(String content, String key) throws Exception {
        return decrypt(Base64Utils.decodeFromString(content), key);
    }

    public static String decrypt(byte[] content, String key) throws Exception {
        if (key == null) {
            log.error("AES key should not be null");
            return null;
        }

        byte[] raw = key.getBytes(CODE);
        SecretKeySpec keySpec = new SecretKeySpec(raw, KEY_ALGORITHM);
        Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, keySpec);
        try {
            byte[] original = cipher.doFinal(content);
            return new String(original, CqODE);
        } catch (Exception e) {
            log.error("failed to decrypt content: {}/ key: {}, e: {}", content, key, e);
            return null; }}}Copy the code

Notice that the implementation above provides two ways

  • One is using Base64 encoded output after AES encryption, corresponding to decrypting base64 encoded data
  • One is to return a byte array directly after AES encryption. Also decodes byte arrays directly

2. The test case

We provide two encrypted files for decryption use;

Base64 encryption

@Test
public void testEncrypt(a) throws Exception {
    String abc = "Hello, grey Blog!";
    String key = "JC66fRd3wj85k8Hr";
    String out = EncryptUtil.encrypt(abc, key);
    System.out.println(out);

    System.out.println(EncryptUtil.decrypt(out, key));
}
Copy the code

The output is as follows:

B TKrN7VKrqsAQ4JqygeHOlG21Sd3IRJ3Y11k4kOdOG4s = Hello, one is graylog!
Copy the code

Byte array encryption and decryption

@Test
public void testEncryptByte(a) throws Exception {
    String abc = "Hello, grey Blog!";
    String key = "JC66fRd3wj85k8Hr";
    byte[] out = EncryptUtil.encrypt2bytes(abc, key);
    System.out.println(new String(out));

    System.out.println(EncryptUtil.decrypt(out, key));
}
Copy the code

The output is as follows:

// Encrypted byte array, that is garbled... δ M ��� D���Y8�� Hello, a gray Blog!
Copy the code

Why the above two differences?

If we take the encrypted byte array, just get a String from new String(), and decrypt the String, we will find that the decryption fails

Briefly modify the above test case

@Test
public void testEncryptByte(a) throws Exception {
    String abc = "Hello, grey Blog!";
    String key = "JC66fRd3wj85k8Hr";
    byte[] out = EncryptUtil.encrypt2bytes(abc, key);
    String enc = new String(out, "utf-8");
    System.out.println(enc);

    System.out.println(EncryptUtil.decrypt(enc.getBytes("utf-8"), key));
}
Copy the code

After execution, decryption failed

Why does this happen?

  • enc = new String(out, "utf-8") 与 enc.getBytes("utf-8")Byte array to string; These two processes will result in the resulting byte array, which is inconsistent with the original!!

Decrypt the case of the remote resource

Finally give an instance case to decrypt the remotely encrypted binary file

private void binKey(String uri, String key) throws Exception {
    // This file is a binary uploaded directly without base64 encoding
    URL url = new URL(uri);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    InputStream stream = connection.getInputStream();
    int lenth = connection.getContentLength();
    byte[] out = new byte[lenth];
    stream.read(out);
    stream.close();
    String ans = decrypt(out, key);
    System.out.println(ans);
}

public void testDe(a) throws Exception {
    String key = "5JRHMJn8xHnMDRXa";
    binKey("http://q8rnsprw0.bkt.clouddn.com/mwzz/b0001", key);
}
Copy the code

II. The other

1. A gray Blog:liuyueyi.github.io/hexblog

A gray personal blog, recording all the study and work in the blog, welcome everyone to go to stroll

2. Statement

As far as the letter is not as good, the above content is purely one’s opinion, due to the limited personal ability, it is inevitable that there are omissions and mistakes, if you find bugs or have better suggestions, welcome criticism and correction, don’t hesitate to appreciate

  • Micro Blog address: Small Gray Blog
  • QQ: a gray /3302797840

3. Scan attention

A gray blog