拿来主义之_AES加解密(CBC模式)

高级加密标准（英语：Advanced Encryption
Standard，缩写：AES），在密码学中又称Rijndael加密法，是美国联邦*采用的一种区块加密标准。这个标准用来替代原先的DES，已经被多方分析且广为全世界所使用。经过五年的甄选流程，高级加密标准由美国国家标准与技术研究院（NIST）于2001年11月26日发布于FIPS
PUB 197，并在2002年5月26日成为有效的标准。2006年，高级加密标准已然成为对称**加密中最流行的算法之一。

密码说明

严格地说，AES和Rijndael加密法并不完全一样（虽然在实际应用中二者可以互换），因为Rijndael加密法可以支持更大范围的区块和**长度：AES的区块长度固定为128
比特，**长度则可以是128，192或256比特；而Rijndael使用的**和区块长度可以是32位的整数倍，以128位为下限，256比特为上限。加密过程中使用的**是由Rijndael**生成方案产生。
大多数AES计算是在一个特别的有限域完成的。
AES加密过程是在一个4×4的字节矩阵上运作，这个矩阵又称为“状态（state）”，其初值就是一个明文区块（矩阵中一个元素大小就是明文区块中的一个Byte）。（Rijndael加密法因支持更大的区块，其矩阵行数可视情况增加）加密时，各轮AES加密循环（除最后一轮外）均包含4个步骤：
AddRoundKey — 矩阵中的每一个字节都与该次轮秘钥（round key）做XOR运算；每个子**由**生成方案产生。
SubBytes — 通过非线性的替换函数，用查找表的方式把每个字节替换成对应的字节。 ShiftRows —
将矩阵中的每个横列进行循环式移位。 MixColumns — 为了充分混合矩阵中各个直行的操作。这个步骤使用线性转换来混合每列的四个字节。
最后一个加密循环中省略MixColumns步骤，而以另一个AddRoundKey取代。

加密标准

对称密码*的发展趋势将以分组密码为重点。分组密码算法通常由**扩展算法和加密（解密）算法两部分组成。**扩展算法将b字节用户主**扩展成r个子**。加密算法由一个密码学上的弱函数f与r个子**迭代r次组成。混乱和**扩散是分组密码算法设计的基本原则。抵御已知明文的差分和线性攻击，可变长**和分组是该*的设计要点。
AES是美国国家标准技术研究所NIST旨在取代DES的21世纪的加密标准。
AES的基本要求是，采用对称分组密码*，**的长度最少支持为128、192、256，分组长度128位，算法应易于各种硬件和软件实现。1998年NIST开始AES第一轮分析、测试和征集，共产生了15个候选算法。1999年3月完成了第二轮AES2的分析、测试。2000年10月2日美国*正式宣布选中比利时密码学家Joan
Daemen 和 Vincent Rijmen 提出的一种密码算法RIJNDAEL 作为 AES.
在应用方面，尽管DES在安全上是脆弱的，但由于快速DES芯片的大量生产，使得DES仍能暂时继续使用，为提高安全强度，通常使用独立**的三级DES。但是DES迟早要被AES代替。流密码*较之分组密码在理论上成熟且安全，但未被列入下一代加密标准。
AES加密数据块分组长度必须为128比特，**长度可以是128比特、192比特、256比特中的任意一个（如果数据块及**长度不足时，会补齐）。AES加密有很多轮的重复和变换。大致步骤如下：1、**扩展（KeyExpansion），2、初始轮（Initial
Round），3、重复轮（Rounds），每一轮又包括：SubBytes、ShiftRows、MixColumns、AddRoundKey，4、最终轮（Final
Round），最终轮没有MixColumns。

效果

代码

AESCBCActivity

package tsou.com.encryption.activity.AES;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.UnsupportedEncodingException;

import tsou.com.encryption.R;
import tsou.com.encryption.aescbc.AES;

/**
 * CBC模式自设定秘钥,需要设置偏移量
 * <p>
 * 什么是aes加密？
 * <p>
 * 高级加密标准（英语：Advanced Encryption Standard，缩写：AES），
 * 在密码学中又称Rijndael加密法，
 * 是美国联邦*采用的一种区块加密标准。这个标准用来替代原先的DES，
 * 已经被多方分析且广为全世界所使用
 */
public class AESCBCActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText encryptionContext;
    private Button encryption;
    private TextView tvEncryption;
    private Button decode;
    private TextView tvDecode;
    private Activity mActivity;
    private Context mContext;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_aes);
        mActivity = this;
        mContext = this;
        encryptionContext = (EditText) findViewById(R.id.et_encryption_context);
        encryption = (Button) findViewById(R.id.btn_encryption);
        tvEncryption = (TextView) findViewById(R.id.tv_encryption);
        decode = (Button) findViewById(R.id.btn_decode);
        tvDecode = (TextView) findViewById(R.id.tv_decode);
        initListener();
    }

    private void initListener() {
        encryption.setOnClickListener(this);
        decode.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.btn_encryption://加密
                String encryptionString = encryptionContext.getText().toString().trim();
                if (TextUtils.isEmpty(encryptionString)) {
                    Toast.makeText(mContext, "请输入加密内容", Toast.LENGTH_SHORT).show();
                    return;
                }
                try {
                    String encrypt = AES.getInstance().encrypt(encryptionString.getBytes("UTF8"));

                    tvEncryption.setText(encrypt);
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                }

                break;
            case R.id.btn_decode://解密
                String decodeString = tvEncryption.getText().toString().trim();
                if (TextUtils.isEmpty(decodeString)) {
                    Toast.makeText(mContext, "请先加密", Toast.LENGTH_SHORT).show();
                    return;
                }
                String decrypt = AES.getInstance().decrypt(decodeString);

                tvDecode.setText(decrypt);
                break;
        }
    }
}

AES

package tsou.com.encryption.aescbc;

import java.io.UnsupportedEncodingException;

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

/**
 * http://blog.csdn.net/qq_33237207/article/details/53114122
 */
public class AES {
    private final String CIPHERMODEPADDING = "AES/CBC/PKCS5Padding";// AES/CBC/PKCS7Padding

    private SecretKeySpec skforAES = null;
    private static String ivParameter = "1234huangxiaoguo";// **默认偏移，可更改

    private byte[] iv = ivParameter.getBytes();
    private IvParameterSpec IV;
    String sKey = "huangxiaoguo1234";// key必须为16位，可更改为自己的key

    private static AES instance = null;

    public static AES getInstance() {
        if (instance == null) {
            synchronized (AES.class) {
                if (instance == null) {
                    instance = new AES();
                }
            }
        }
        return instance;
    }

    public AES() {
        byte[] skAsByteArray;
        try {
            skAsByteArray = sKey.getBytes("ASCII");
            skforAES = new SecretKeySpec(skAsByteArray, "AES");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        IV = new IvParameterSpec(iv);
    }

    public String encrypt(byte[] plaintext) {
        byte[] ciphertext = encrypt(CIPHERMODEPADDING, skforAES, IV, plaintext);
        String base64_ciphertext = Base64Encoder.encode(ciphertext);
        return base64_ciphertext;
    }

    public String decrypt(String ciphertext_base64) {
        byte[] s = Base64Decoder.decodeToBytes(ciphertext_base64);
        String decrypted = new String(decrypt(CIPHERMODEPADDING, skforAES, IV,
                s));
        return decrypted;
    }

    private byte[] encrypt(String cmp, SecretKey sk, IvParameterSpec IV,
                           byte[] msg) {
        try {
            Cipher c = Cipher.getInstance(cmp);
            c.init(Cipher.ENCRYPT_MODE, sk, IV);
            return c.doFinal(msg);
        } catch (Exception nsae) {
        }
        return null;
    }

    private byte[] decrypt(String cmp, SecretKey sk, IvParameterSpec IV,
                           byte[] ciphertext) {
        try {
            Cipher c = Cipher.getInstance(cmp);
            c.init(Cipher.DECRYPT_MODE, sk, IV);
            return c.doFinal(ciphertext);
        } catch (Exception nsae) {
        }
        return null;
    }
}

Base64Decoder

package tsou.com.encryption.aescbc;

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

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
     */
    public 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) {
        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 = null;
        try {
            bytes = encoded.getBytes("UTF-8");
        } catch (UnsupportedEncodingException ignored) {
        }

        Base64Decoder in = new Base64Decoder(new ByteArrayInputStream(bytes));

        ByteArrayOutputStream out = new ByteArrayOutputStream(
                (int) (bytes.length * 0.67));

        try {
            byte[] buf = new byte[4 * 1024]; // 4K buffer
            int bytesRead;
            while ((bytesRead = in.read(buf)) != -1) {
                out.write(buf, 0, bytesRead);
            }
            out.close();

            return out.toByteArray();
        } catch (IOException ignored) {
            return null;
        }
    }

//  public static void main(String[] args) throws Exception {
//      if (args.length != 1) {
//          System.err.println("Usage: java Base64Decoder fileToDecode");
//          return;
//      }
//
//      Base64Decoder decoder = null;
//      try {
//          decoder = new Base64Decoder(new BufferedInputStream(
//                  new FileInputStream(args[0])));
//          byte[] buf = new byte[4 * 1024]; // 4K buffer
//          int bytesRead;
//          while ((bytesRead = decoder.read(buf)) != -1) {
//              System.out.write(buf, 0, bytesRead);
//          }
//      } finally {
//          if (decoder != null)
//              decoder.close();
//      }
//  }
}

Base64Encoder

package tsou.com.encryption.aescbc;

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

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;

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

    /***
     * 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 <[e-mail]>
        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 (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. The encoder uses
     * the ISO-8859-1 (Latin-1) encoding to convert the string to bytes. For
     * greater control over the encoding, encode the string to bytes yourself
     * and use encode(byte[]).
     *
     * @param unencoded
     *            the string to encode
     * @return the encoded form of the unencoded string
     */
    public static String encode(String unencoded) {
        byte[] bytes = null;
        try {
            bytes = unencoded.getBytes("UTF-8");
        } catch (UnsupportedEncodingException ignored) {
        }
        return encode(bytes);
    }

    /***
     * Returns the encoded form of the given unencoded string.
     *
     * @param bytes
     *            the bytes to encode
     * @return the encoded form of the unencoded string
     */
    public static String encode(byte[] bytes) {
        ByteArrayOutputStream out = new ByteArrayOutputStream(
                (int) (bytes.length * 1.37));
        Base64Encoder encodedOut = new Base64Encoder(out);

        try {
            encodedOut.write(bytes);
            encodedOut.close();

            return out.toString("UTF-8");
        } catch (IOException ignored) {
            return null;
        }
    }

//    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();
//        }
//    }
}

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