Java最简单的DES加密算法实现案例

base64.java

package com.mstf.des;
 
import java.io.unsupportedencodingexception;
 
/**
 * base64编码/解码
 * @author ceet
 *
 */
public class base64 {
 
  public static string encode(string data) {
    return new string(encode(data.getbytes()));
  }
 
  public static string decode(string data) {
    try {
      return new string(decode(data.tochararray()),"utf-8");
    } catch (unsupportedencodingexception e) {
      e.printstacktrace();
      return null;
    } 
  }
 
  private static char[] alphabet = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789+/="
      .tochararray();
 
  private static byte[] codes = new byte[256];
 
  static {
    for (int i = 0; i < 256; i++) {
      codes[i] = -1;
    }
    for (int i = 'a'; i <= 'z'; i++) {
      codes[i] = (byte) (i - 'a');
    }
 
    for (int i = 'a'; i <= 'z'; i++) {
      codes[i] = (byte) (26 + i - 'a');
    }
    for (int i = '0'; i <= '9'; i++) {
      codes[i] = (byte) (52 + i - '0');
    }
    codes['+'] = 62;
    codes['/'] = 63;
  }
 
  public static char[] encode(byte[] data) {
    char[] out = new char[((data.length + 2) / 3) * 4];
    for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
      boolean quad = false;
      boolean trip = false;
 
      int val = (0xff & (int) data[i]);
      val <<= 8;
      if ((i + 1) < data.length) {
        val |= (0xff & (int) data[i + 1]);
        trip = true;
      }
      val <<= 8;
      if ((i + 2) < data.length) {
        val |= (0xff & (int) data[i + 2]);
        quad = true;
      }
      out[index + 3] = alphabet[(quad ? (val & 0x3f) : 64)];
      val >>= 6;
      out[index + 2] = alphabet[(trip ? (val & 0x3f) : 64)];
      val >>= 6;
      out[index + 1] = alphabet[val & 0x3f];
      val >>= 6;
      out[index + 0] = alphabet[val & 0x3f];
    }
    return out;
  }
 
  public static byte[] decode(char[] data) {
    int templen = data.length;
    for (int ix = 0; ix < data.length; ix++) {
      if ((data[ix] > 255) || codes[data[ix]] < 0) {
        --templen;
      }
    }
    int len = (templen / 4) * 3;
    if ((templen % 4) == 3) {
      len += 2;
    }
    if ((templen % 4) == 2) {
      len += 1;
 
    }
    byte[] out = new byte[len];
 
    int shift = 0;
    int accum = 0;
    int index = 0;
 
    for (int ix = 0; ix < data.length; ix++) {
      int value = (data[ix] > 255) ? -1 : codes[data[ix]];
 
      if (value >= 0) {
        accum <<= 6;
        shift += 6;
        accum |= value;
        if (shift >= 8) {
          shift -= 8;
          out[index++] = (byte) ((accum >> shift) & 0xff);
        }
      }
    }
 
    if (index != out.length) {
      throw new error("miscalculated data length (wrote " + index
          + " instead of " + out.length + ")");
    }
 
    return out;
  }
}

desutil.java

package com.mstf.des;
 
import java.security.key;
import java.security.securerandom;
 
import javax.crypto.cipher;
import javax.crypto.keygenerator;
 
/**
 * des对称算法(加密/解密)
 *
 * @author ceet
 *
 */
public class desutil {
 
  private key key;
 
  public desutil(string strkey) {
    setkey(strkey);
  }
 
  public void setkey(string strkey) {
    try {
      keygenerator generator = keygenerator.getinstance("des");
      generator.init(new securerandom(strkey.getbytes())); // 根据参数生成key
      this.key = generator.generatekey();
    } catch (exception e) {
      e.printstacktrace();
    }
  }
 
  public string encrypt(string source) {
    return encrypt(source, "utf-8");
  }
 
  public string decrypt(string encrypteddata) {
    return decrypt(encrypteddata, "utf-8");
  }
 
  public string encrypt(string source, string charset) {
    string encrypt = null;
    try {
      byte[] ret = encrypt(source.getbytes(charset));
      encrypt = new string(base64.encode(ret));
    } catch (exception e) {
      e.printstacktrace();
      encrypt = null;
    }
    return encrypt;
  }
 
  public string decrypt(string encrypteddata, string charset) {
    string descrypteddata = null;
    try {
      byte[] ret = descrypt(base64.decode(encrypteddata.tochararray()));
      descrypteddata = new string(ret, charset);
    } catch (exception e) {
      e.printstacktrace();
      descrypteddata = null;
    }
    return descrypteddata;
  }
 
  private byte[] encrypt(byte[] primarydata) {
    try {
      cipher cipher = cipher.getinstance("des"); // cipher对象实际完成加密操作
      cipher.init(cipher.encrypt_mode, this.key); // 用密钥初始化cipher对象(加密)
 
      return cipher.dofinal(primarydata);
    } catch (exception e) {
      e.printstacktrace();
      return null;
    }
  }
 
  private byte[] descrypt(byte[] encrypteddata) {
    try {
      cipher cipher = cipher.getinstance("des"); // cipher对象实际完成解密操作
      cipher.init(cipher.decrypt_mode, this.key); // 用密钥初始化cipher对象(解密)
 
      return cipher.dofinal(encrypteddata);
    } catch (exception e) {
      e.printstacktrace();
      return null;
    }
  }
 
  public static void main(string[] args) {
    string code = "ceet";
    desutil desutil = new desutil("key");
    string encrypt = desutil.encrypt(code);
    string decrypt = desutil.decrypt(encrypt);
    system.out.println("原内容：" + code);
    system.out.println("加密：" + encrypt);
    system.out.println("解密：" + decrypt);
  }
}

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