前言：

    專案中除了登陸，支付等介面採用rsa非對稱加密，之外的採用aes對稱加密，今天我們來認識一下aes加密。

     其他幾種加密方式：

什麼是aes加密？

     高階加密標準（英語：Advanced Encryption Standard，縮寫：AES），在密碼學中又稱Rijndael加密法，是美國聯邦政府採用的一種區塊加密標準。這個標準用來替代原先的DES，已經被多方分析且廣為全世界所使用。

接下來我們來實際看下具體怎麼實現：

對於AesUtils類常量簡介：

    private final static String HEX = "0123456789ABCDEF
 
";
    private  static final String CBC_PKCS5_PADDING = "AES/CBC/PKCS5Padding";//AES是加密方式 CBC是工作模式 PKCS5Padding是填充模式
    private  static final String AES = "AES";//AES 加密
    private  static final String  SHA1PRNG="SHA1PRNG";//// SHA1PRNG 強隨機種子演算法, 要區別4.2以上版本的呼叫方法

如何生成一個隨機Key？

    /*
     * 生成隨機數，可以當做動態的金鑰 加密和解密的金鑰必須一致，不然將不能解密
     
 
*/
    public static String generateKey() {
        try {
            SecureRandom localSecureRandom = SecureRandom.getInstance(SHA1PRNG);
            byte[] bytes_key = new byte[20];
            localSecureRandom.nextBytes(bytes_key);
            String str_key = toHex(bytes_key);
            
 
return str_key;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

Aes金鑰處理

    // 對金鑰進行處理
    private static byte[] getRawKey(byte[] seed) throws Exception {
        KeyGenerator kgen = KeyGenerator.getInstance(AES);
        //for android
        SecureRandom sr = null;
        // 在4.2以上版本中，SecureRandom獲取方式發生了改變
        if (android.os.Build.VERSION.SDK_INT >= 17) {
            sr = SecureRandom.getInstance(SHA1PRNG, "Crypto");
        } else {
            sr = SecureRandom.getInstance(SHA1PRNG);
        }
        // for Java
        // secureRandom = SecureRandom.getInstance(SHA1PRNG);
        sr.setSeed(seed);
        kgen.init(128, sr); //256 bits or 128 bits,192bits
        //AES中128位金鑰版本有10個加密迴圈，192位元金鑰版本有12個加密迴圈，256位元金鑰版本則有14個加密迴圈。
        SecretKey skey = kgen.generateKey();
        byte[] raw = skey.getEncoded();
        return raw;
    }

Aes加密過程

 /*
     * 加密
     */
    public static String encrypt(String key, String cleartext) {
        if (TextUtils.isEmpty(cleartext)) {
            return cleartext;
        }
        try {
            byte[] result = encrypt(key, cleartext.getBytes());
            return Base64Encoder.encode(result);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /*
    * 加密
    */
    private static byte[] encrypt(String key, byte[] clear) throws Exception {
        byte[] raw = getRawKey(key.getBytes());
        SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
        Cipher cipher = Cipher.getInstance(CBC_PKCS5_PADDING);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
        byte[] encrypted = cipher.doFinal(clear);
        return encrypted;
    }

Aes解密過程

    /*
     * 解密
     */
    public static String decrypt(String key, String encrypted) {
        if (TextUtils.isEmpty(encrypted)) {
            return encrypted;
        }
        try {
            byte[] enc = Base64Decoder.decodeToBytes(encrypted);
            byte[] result = decrypt(key, enc);
            return new String(result);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /*
     * 解密
     */
    private static byte[] decrypt(String key, byte[] encrypted) throws Exception {
        byte[] raw = getRawKey(key.getBytes());
        SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
        Cipher cipher = Cipher.getInstance(CBC_PKCS5_PADDING);
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

二進位制轉字元

 //二進位制轉字元
    public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2 * buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
    }

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
    }

測試程式：

  List<Person> personList = new ArrayList<>();
        int testMaxCount = 1000;//測試的最大資料條數
        //新增測試資料
        for (int i = 0; i < testMaxCount; i++) {
            Person person = new Person();
            person.setAge(i);
            person.setName(String.valueOf(i));
            personList.add(person);
        }
        //FastJson生成json資料
        String jsonData = JsonUtils.objectToJsonForFastJson(personList);
        Log.e("MainActivity", "AES加密前json資料 ---->" + jsonData);
        Log.e("MainActivity", "AES加密前json資料長度 ---->" + jsonData.length());

        //生成一個動態key
        String secretKey = AesUtils.generateKey();
        Log.e("MainActivity", "AES動態secretKey ---->" + secretKey);

        //AES加密
        long start = System.currentTimeMillis();
        String encryStr = AesUtils.encrypt(secretKey, jsonData);
        long end = System.currentTimeMillis();
        Log.e("MainActivity", "AES加密耗時 cost time---->" + (end - start));
        Log.e("MainActivity", "AES加密後json資料 ---->" + encryStr);
        Log.e("MainActivity", "AES加密後json資料長度 ---->" + encryStr.length());

        //AES解密
        start = System.currentTimeMillis();
        String decryStr = AesUtils.decrypt(secretKey, encryStr);
        end = System.currentTimeMillis();
        Log.e("MainActivity", "AES解密耗時 cost time---->" + (end - start));
        Log.e("MainActivity", "AES解密後json資料 ---->" + decryStr);

執行耗時：

資料前後變化：

由此可見對稱Aes效率還是比較高的

 補充關於Base64Decoder類和Base64Encoder類

package com.whoislcj.testhttp.utils;

import android.text.TextUtils;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

public class Base64Decoder extends FilterInputStream {

    private static final char[] chars = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u',
            'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

    // A mapping between char values and six-bit integers
    private static final int[] ints = new int[128];
    static {
        for (int i = 0; i < 64; i++) {
            ints[chars[i]] = i;
        }
    }

    private int charCount;
    private int carryOver;

    /***
     * Constructs a new Base64 decoder that reads input from the given
     * InputStream.
     * 
     * @param in
     *            the input stream
     */
    private Base64Decoder(InputStream in) {
        super(in);
    }

    /***
     * Returns the next decoded character from the stream, or -1 if end of
     * stream was reached.
     * 
     * @return the decoded character, or -1 if the end of the input stream is
     *         reached
     * @exception IOException
     *                if an I/O error occurs
     */
    public int read() throws IOException {
        // Read the next non-whitespace character
        int x;
        do {
            x = in.read();
            if (x == -1) {
                return -1;
            }
        } while (Character.isWhitespace((char) x));
        charCount++;

        // The '=' sign is just padding
        if (x == '=') {
            return -1; // effective end of stream
        }

        // Convert from raw form to 6-bit form
        x = ints[x];

        // Calculate which character we're decoding now
        int mode = (charCount - 1) % 4;

        // First char save all six bits, go for another
        if (mode == 0) {
            carryOver = x & 63;
            return read();
        }
        // Second char use previous six bits and first two new bits,
        // save last four bits
        else if (mode == 1) {
            int decoded = ((carryOver << 2) + (x >> 4)) & 255;
            carryOver = x & 15;
            return decoded;
        }
        // Third char use previous four bits and first four new bits,
        // save last two bits
        else if (mode == 2) {
            int decoded = ((carryOver << 4) + (x >> 2)) & 255;
            carryOver = x & 3;
            return decoded;
        }
        // Fourth char use previous two bits and all six new bits
        else if (mode == 3) {
            int decoded = ((carryOver << 6) + x) & 255;
            return decoded;
        }
        return -1; // can't actually reach this line
    }

    /***
     * Reads decoded data into an array of bytes and returns the actual number
     * of bytes read, or -1 if end of stream was reached.
     * 
     * @param buf
     *            the buffer into which the data is read
     * @param off
     *            the start offset of the data
     * @param len
     *            the maximum number of bytes to read
     * @return the actual number of bytes read, or -1 if the end of the input
     *         stream is reached
     * @exception IOException
     *                if an I/O error occurs
     */
    public int read(byte[] buf, int off, int len) throws IOException {
        if (buf.length < (len + off - 1)) {
            throw new IOException("The input buffer is too small: " + len + " bytes requested starting at offset " + off + " while the buffer " + " is only " + buf.length + " bytes long.");
        }

        // This could of course be optimized
        int i;
        for (i = 0; i < len; i++) {
            int x = read();
            if (x == -1 && i == 0) { // an immediate -1 returns -1
                return -1;
            } else if (x == -1) { // a later -1 returns the chars read so far
                break;
            }
            buf[off + i] = (byte) x;
        }
        return i;
    }

    /***
     * Returns the decoded form of the given encoded string, as a String. Note
     * that not all binary data can be represented as a String, so this method
     * should only be used for encoded String data. Use decodeToBytes()
     * otherwise.
     * 
     * @param encoded
     *            the string to decode
     * @return the decoded form of the encoded string
     */
    public static String decode(String encoded) {
        if (TextUtils.isEmpty(encoded)) {
            return "";
        }
        return new String(decodeToBytes(encoded));
    }

    /***
     * Returns the decoded form of the given encoded string, as bytes.
     * 
     * @param encoded
     *            the string to decode
     * @return the decoded form of the encoded string
     */
    public static byte[] decodeToBytes(String encoded) {
        byte[] bytes = encoded.getBytes();
        Base64Decoder in = new Base64Decoder(new ByteArrayInputStream(bytes));
        ByteArrayOutputStream out = new ByteArrayOutputStream((int) (bytes.length * 0.75));
        try {
            byte[] buf = new byte[4 * 1024]; // 4K buffer
            int bytesRead;
            while ((bytesRead = in.read(buf)) != -1) {
                out.write(buf, 0, bytesRead);
            }
            return out.toByteArray();
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            try {
                in.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
            try {
                out.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
}

package com.whoislcj.testhttp.utils;

import java.io.ByteArrayOutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Base64Encoder extends FilterOutputStream {

    private static final char[] chars = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u',
            'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

    private int charCount;
    private int carryOver;
    // 是否每76位元組換行
    private boolean isWrapBreak = true;

    /***
     * Constructs a new Base64 encoder that writes output to the given
     * OutputStream.
     * 
     * @param out
     *            the output stream
     */
    private Base64Encoder(OutputStream out) {
        super(out);
    }

    /***
     * Constructs a new Base64 encoder that writes output to the given
     * OutputStream.
     * 
     * @param out
     *            the output stream
     */
    private Base64Encoder(OutputStream out, boolean isWrapBreak) {
        this(out);
        this.isWrapBreak = isWrapBreak;
    }

    /***
     * Writes the given byte to the output stream in an encoded form.
     * 
     * @exception IOException
     *                if an I/O error occurs
     */
    public void write(int b) throws IOException {
        // Take 24-bits from three octets, translate into four encoded chars
        // Break lines at 76 chars
        // If necessary, pad with 0 bits on the right at the end
        // Use = signs as padding at the end to ensure encodedLength % 4 == 0

        // Remove the sign bit,
        // thanks to Christian Schweingruber <[email protected]>
        if (b < 0) {
            b += 256;
        }

        // First byte use first six bits, save last two bits
        if (charCount % 3 == 0) {
            int lookup = b >> 2;
            carryOver = b & 3; // last two bits
            out.write(chars[lookup]);
        }
        // Second byte use previous two bits and first four new bits,
        // save last four bits
        else if (charCount % 3 == 1) {
            int lookup = ((carryOver << 4) + (b >> 4)) & 63;
            carryOver = b & 15; // last four bits
            out.write(chars[lookup]);
        }
        // Third byte use previous four bits and first two new bits,
        // then use last six new bits
        else if (charCount % 3 == 2) {
            int lookup = ((carryOver << 2) + (b >> 6)) & 63;
            out.write(chars[lookup]);
            lookup = b & 63; // last six bits
            out.write(chars[lookup]);
            carryOver = 0;
        }
        charCount++;

        // Add newline every 76 output chars (that's 57 input chars)
        if (this.isWrapBreak && charCount % 57 == 0) {
            out.write('\n');
        }
    }

    /***
     * Writes the given byte array to the output stream in an encoded form.
     * 
     * @param buf
     *            the data to be written
     * @param off
     *            the start offset of the data
     * @param len
     *            the length of the data
     * @exception IOException
     *                if an I/O error occurs
     */
    public void write(byte[] buf, int off, int len) throws IOException {
        // This could of course be optimized
        for (int i = 0; i < len; i++) {
            write(buf[off + i]);
        }
    }

    /***
     * Closes the stream, this MUST be called to ensure proper padding is
     * written to the end of the output stream.
     * 
     * @exception IOException
     *                if an I/O error occurs
     */
    public void close() throws IOException {
        // Handle leftover bytes
        if (charCount % 3 == 1) { // one leftover
            int lookup = (carryOver << 4) & 63;
            out.write(chars[lookup]);
            out.write('=');
            out.write('=');
        } else if (charCount % 3 == 2) { // two leftovers
            int lookup = (carryOver << 2) & 63;
            out.write(chars[lookup]);
            out.write('=');
        }
        super.close();
    }

    /***
     * Returns the encoded form of the given unencoded string.<br>
     * 預設是否每76位元組換行
     * 
     * @param bytes
     *            the bytes to encode
     * @return the encoded form of the unencoded string
     * @throws IOException
     */
    public static String encode(byte[] bytes) {
        return encode(bytes, true);
    }

    /***
     * Returns the encoded form of the given unencoded string.
     * 
     * @param bytes
     *            the bytes to encode
     * @param isWrapBreak
     *            是否每76位元組換行
     * @return the encoded form of the unencoded string
     * @throws IOException
     */
    public static String encode(byte[] bytes, boolean isWrapBreak) {
        ByteArrayOutputStream out = new ByteArrayOutputStream((int) (bytes.length * 1.4));
        Base64Encoder encodedOut = new Base64Encoder(out, isWrapBreak);
        try {
            encodedOut.write(bytes);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            try {
                encodedOut.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return out.toString();
    }

    // public static void main(String[] args) throws Exception {
    // if (args.length != 1) {
    // System.err
    // .println("Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");
    // return;
    // }
    // Base64Encoder encoder = null;
    // BufferedInputStream in = null;
    // try {
    // encoder = new Base64Encoder(System.out);
    // in = new BufferedInputStream(new FileInputStream(args[0]));
    //
    // byte[] buf = new byte[4 * 1024]; // 4K buffer
    // int bytesRead;
    // while ((bytesRead = in.read(buf)) != -1) {
    // encoder.write(buf, 0, bytesRead);
    // }
    // } finally {
    // if (in != null)
    // in.close();
    // if (encoder != null)
    // encoder.close();
    // }
    // }
}