使用AES對文件的加解密

使用AES對文件的加解密:

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.Key;
import java.security.SecureRandom;

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

/**
* 使用AES對文件進行加密和解密
*
*/
public
class CipherUtil {
    /**
     * 使用AES對文件進行加密和解密
     *
     */
    private
static String type =
"AES";

    /**
     * 把文件srcFile加密後存儲爲destFile
     * @param srcFile     加密前的文件
     * @param destFile    加密後的文件
     * @param privateKey  密鑰
     * @throws GeneralSecurityException
     * @throws IOException
     */
    public
void encrypt(String srcFile, String destFile, String privateKey)
throws GeneralSecurityException, IOException {
        Key key = getKey(privateKey);
        Cipher cipher = Cipher.getInstance(type + 
"/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, key);

        FileInputStream fis = null;
        FileOutputStream fos = null;
        try {
            fis = new FileInputStream(srcFile);
            fos = new FileOutputStream(mkdirFiles(destFile));

            crypt(fis, fos, cipher);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fis !=
null) {
                fis.close();
            }
            if (fos !=
null) {
                fos.close();
            }
        }
    }

    /**
     * 把文件srcFile解密後存儲爲destFile
     * @param srcFile     解密前的文件
     * @param destFile    解密後的文件
     * @param privateKey  密鑰
     * @throws GeneralSecurityException
     * @throws IOException
     */
    public
void decrypt(String srcFile, String destFile, String privateKey)
throws GeneralSecurityException, IOException {
        Key key = getKey(privateKey);
        Cipher cipher = Cipher.getInstance(type + 
"/ECB/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, key);

        FileInputStream fis = null;
        FileOutputStream fos = null;
        try {
            fis = new FileInputStream(srcFile);
            fos = new FileOutputStream(mkdirFiles(destFile));

            crypt(fis, fos, cipher);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fis !=
null) {
                fis.close();
            }
            if (fos !=
null) {
                fos.close();
            }
        }
    }

    /**
     * 根據filePath創建相應的目錄
     * @param filePath      要創建的文件路經
     * @return  file        文件
     * @throws IOException
     */
    private File mkdirFiles(String filePath)
throws IOException {
        File file = new File(filePath);
        if (!file.getParentFile().exists()) {
            file.getParentFile().mkdirs();
        }
        file.createNewFile();

        return file;
    }

    /**
     * 生成指定字符串的密鑰
     * @param secret        要生成密鑰的字符串
     * @return secretKey    生成後的密鑰
     * @throws GeneralSecurityException
     */
    private
static Key getKey(String secret)
throws GeneralSecurityException {
        KeyGenerator kgen = KeyGenerator.getInstance(type);
        kgen.init(128, new SecureRandom(secret.getBytes()));
        SecretKey secretKey = kgen.generateKey();
        return secretKey;
    }

    /**
     * 加密解密流
     * @param in        加密解密前的流
     * @param out       加密解密後的流
     * @param cipher    加密解密
     * @throws IOException
     * @throws GeneralSecurityException
     */
    private
static
void crypt(InputStream in, OutputStream out, Cipher cipher)
throws IOException, GeneralSecurityException {
        int blockSize = cipher.getBlockSize() *
1000;
        int outputSize = cipher.getOutputSize(blockSize);

        byte[] inBytes =
new
byte[blockSize];
        byte[] outBytes =
new
byte[outputSize];

        int inLength =
0;
        boolean more =
true;
        while (more) {
            inLength = in.read(inBytes);
            if (inLength == blockSize) {
                int outLength = cipher.update(inBytes,
0, blockSize, outBytes);
                out.write(outBytes, 0, outLength);
            } else {
                more = false;
            }
        }
        if (inLength >
0)
            outBytes = cipher.doFinal(inBytes, 0, inLength);
        else
            outBytes = cipher.doFinal();
        out.write(outBytes);
    }
}