AES加密方式是目前來看值得選擇的加密方式，但是在Android中使用AES加密時，有些坑看似不大，卻讓很多人栽了跟頭。
Android 4.2之後SHA1PRNG強隨意種子演算法呼叫不同，需要區別呼叫，這個你造嗎。
下面貼出部分關鍵程式碼，程式碼與網路上普遍存在的AES加密程式碼大同小異，不做過多解釋。但是解決了那些大部分程式碼中存在的密文不唯一、解密不出明文的問題。

AESCrypt.java中關鍵程式碼

public byte[] getRawKey(byte[] seed) throws Exception {     
        KeyGenerator kgen = KeyGenerator.getInstance("AES"
 
);   
        // SHA1PRNG 強隨機種子演算法, 要區別4.2以上版本的呼叫方法  
         SecureRandom sr = null;  
       if (android.os.Build.VERSION.SDK_INT >=  17) {  
         sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");  
       } else {  
         sr = SecureRandom.getInstance("SHA1PRNG");  
       }   
        sr.setSeed(seed);     
        kgen.init(AESUtil.ENCRYPT_BITS, sr); //256 bits or 128 bits,192 bits  
 

        SecretKey skey = kgen.generateKey();     
        byte[] raw = skey.getEncoded();     
        return raw;     
    } 

    public byte[] encrypting(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES"
 
);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(clear);
        return encrypted;
    }

    public byte[] decrypting(byte[] raw, byte[] encrypted) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

對外封裝的AESUtil.java

    /**
     * 設定編碼位數。可選值為：256、192、128
     * @param encryptBits
     */
    public void setEncryptBits(int encryptBits){
        if(encryptBits==256||encryptBits==192||encryptBits==128){
            ENCRYPT_BITS = encryptBits;
        }
    }

    public String encrypt(String seed, String cleartext) throws Exception {
        byte[] rawKey = mAESCrypt.getRawKey(seed.getBytes());
        byte[] result = mAESCrypt.encrypting(rawKey, cleartext.getBytes());
        return mAESCrypt.toHex(result);
    }

    public String decrypt(String seed, String encrypted) throws Exception {
        byte[] rawKey = mAESCrypt.getRawKey(seed.getBytes());
        byte[] encryptedstr = mAESCrypt.toByte(encrypted);
        byte[] result = mAESCrypt.decrypting(rawKey, encryptedstr);
        return new String(result);
    }

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