AESEncryption.java

package com.arialyy.frame.util;

import android.support.annotation.NonNull;

import java.io.File;
import java.security.SecureRandom;

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


/**
 * AES加密
 *
 * @author lyy
 */
public class AESEncryption {
    /**
     * 4.4的要Cipher cipher = Cipher.getInstance("AES/ECB/ZeroBytePadding");
     */
    private static final int JELLY_BEAN_4_2 = 17;

    /**
     * 加密文件
     *
     * @param filePath 原始文件路径
     * @return 加密后的文件路径
     */
    public static String encryptFile(@NonNull String filePath) {
        File file = new File(filePath);
        return "";
    }

    /**
     * 加密函数
     *
     * @param seed      密钥
     * @param cleartext 说要进行加密的密码
     * @return 返回的是16进制的加密类型
     * @throws Exception
     */
    public static String encryptString(String seed, String cleartext) throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] result = encryptByte(rawKey, cleartext.getBytes());
        return toHex(result);
    }

    /**
     * 解密函数
     *
     * @param seed      密钥
     * @param encrypted 进行加密后的密码
     * @return 返回原来的密码
     * @throws Exception
     */
    public static String decryptString(String seed, String encrypted) throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] enc    = toByte(encrypted);
        byte[] result = decryptByte(rawKey, enc);
        return new String(result);
    }

    /**
     * 获取key
     *
     * @param seed
     * @return
     * @throws Exception
     */
    private static byte[] getRawKey(byte[] seed) throws Exception {
        KeyGenerator kgen = KeyGenerator.getInstance("AES");

        SecureRandom sr = null;
        if (android.os.Build.VERSION.SDK_INT >= JELLY_BEAN_4_2) {
            sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
        } else {
            sr = SecureRandom.getInstance("SHA1PRNG");
        }
        // SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");      
        sr.setSeed(seed);
        kgen.init(128, sr); // 192 and 256 bits may not be available
        SecretKey skey = kgen.generateKey();
        return skey.getEncoded();
    }

    /**
     * 4.3以上的要用cipher = Cipher.getInstance("AES/ECB/ZeroBytePadding");
     * 加密byte流
     *
     * @param raw
     * @param clear
     * @return
     * @throws Exception
     */
    private static byte[] encryptByte(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher        cipher   = null;
        if (android.os.Build.VERSION.SDK_INT > JELLY_BEAN_4_2) {
            cipher = Cipher.getInstance("AES/ECB/ZeroBytePadding");
        } else {
            cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        }
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        return cipher.doFinal(clear);
    }

    /**
     * 4.3以上的要用cipher = Cipher.getInstance("AES/ECB/ZeroBytePadding");
     * 解密byte流
     *
     * @param raw
     * @param encrypted
     * @return
     * @throws Exception
     */
    private static byte[] decryptByte(byte[] raw, byte[] encrypted) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher        cipher   = null;
        if (android.os.Build.VERSION.SDK_INT > JELLY_BEAN_4_2) {
            cipher = Cipher.getInstance("AES/ECB/ZeroBytePadding");
        } else {
            cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        }
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        return cipher.doFinal(encrypted);
    }

    public static String toHex(String txt) {
        return toHex(txt.getBytes());
    }

    public static String fromHex(String hex) {
        return new String(toByte(hex));
    }

    public static byte[] toByte(String hexString) {
        int    len    = hexString.length() / 2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++)
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2), 16).byteValue();
        return result;
    }

    /**
     * 把用户的key转换为16为的key
     * AES算法的秘钥要求16位
     *
     * @param buf
     * @return
     */
    public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2 * buf.length);
        for (byte aBuf : buf) {
            appendHex(result, aBuf);
        }
        return result.toString();
    }

    private final static String HEX = "0123456789ABCDEF";

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

}