Android AES加解密特點及實現

AES介紹

AES： 高級加密標準（Advanced Encryption Standard）
作爲新一代的數據集加密標準，匯聚了強安全性、高性能、高效率、易用和靈活等優點，設計有三個密鑰長度(128bit,192bit,256bit)，與DES相比，加密強度更高，更安全。

特點

密鑰爲128位時，也就是16byte，加密後的byte數組長度爲：(原文byte數組長度 / 16) ＋16
解密密鑰不匹配時，java方法會拋出異常。

Android實現

import android.util.Base64;

import java.security.Key;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AESUtil {
    // Const string for AES encrypt
    private static final String ALGORITHM = "AES";
    private static final String ALGORITHM_PADDING = "AES/CBC/PKCS5Padding";
    private static final String RAN_TIME_STR = "1234567890123456";
    // Use CBC mode, need a iv to enhance the strength of encryption
    private static final IvParameterSpec IV_PARAMETER_SPEC = new IvParameterSpec(RAN_TIME_STR.getBytes());

    /**
     * Do AES encryption
     *
     * @param key  The key for encryption
     * @param data Source to be encrypted.
     * @return Encrypted bytes
     */
    public static byte[] encrypt(String key, byte[] data) throws Exception {
        Key k = toKey(key.getBytes());
        byte[] raw = k.getEncoded();
        SecretKeySpec secretKeySpec = new SecretKeySpec(raw, ALGORITHM);
        Cipher cipher = Cipher.getInstance(ALGORITHM_PADDING);
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, IV_PARAMETER_SPEC);
        return cipher.doFinal(data);
    }

    /**
     * Do AES decryption
     *
     * @param key  The key for decryption
     * @param data Source to be decrypted
     * @return Decrypted bytes
     */
    public static byte[] decrypt(String key, byte[] data) throws Exception {
        Key k = toKey(key.getBytes());
        byte[] raw = k.getEncoded();
        SecretKeySpec secretKeySpec = new SecretKeySpec(raw, ALGORITHM);
        Cipher cipher = Cipher.getInstance(ALGORITHM_PADDING);
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, IV_PARAMETER_SPEC);
        return cipher.doFinal(data);
    }

    /**
     * Constructs a secret key from the given byte array.
     *
     * @param key The key material of the secret key.
     * @return Secret key
     */
    private static Key toKey(byte[] key) {
        return new SecretKeySpec(key, ALGORITHM);
    }

    /**
     * Change bytes to Hex string
     *
     * @param bytesData Source bytes
     * @return Hex string
     */
    public static String bytes2Hex(byte[] bytesData) {
        String tmp;
        StringBuilder des = new StringBuilder();

        for (byte byteData : bytesData) {
            tmp = (Integer.toHexString(byteData & 0xFF));
            if (tmp.length() == 1) {
                des.append("0");
            }
            des.append(tmp);
        }

        return des.toString();
    }

    /**
     * Encode a common string to base64 string
     *
     * @param strSrc Common string to be encoded
     * @return Base64 string
     */
    public static String base64Encode(String strSrc) {
        return Base64.encodeToString(strSrc.getBytes(), Base64.DEFAULT);
    }

    /**
     * Decode a base64 string to common string
     *
     * @param strSrc Base64 string to be decoded
     * @return Common string
     */
    public static String base64Decode(String strSrc) {
        return new String(Base64.decode(strSrc.getBytes(), Base64.DEFAULT));
    }
}