68 lines
1.6 KiB
Java
68 lines
1.6 KiB
Java
/**
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* 对公众平台发送给公众账号的消息加解密示例代码.
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*
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* @copyright Copyright (c) 1998-2014 Tencent Inc.
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*/
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// ------------------------------------------------------------------------
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package com.qq.weixin.mp.aes;
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import java.nio.charset.Charset;
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import java.util.Arrays;
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/**
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* 提供基于PKCS7算法的加解密接口.
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*/
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class PKCS7Encoder {
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static Charset CHARSET = Charset.forName("utf-8");
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static int BLOCK_SIZE = 32;
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/**
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* 获得对明文进行补位填充的字节.
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*
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* @param count 需要进行填充补位操作的明文字节个数
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* @return 补齐用的字节数组
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*/
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static byte[] encode(int count) {
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// 计算需要填充的位数
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int amountToPad = BLOCK_SIZE - (count % BLOCK_SIZE);
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if (amountToPad == 0) {
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amountToPad = BLOCK_SIZE;
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}
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// 获得补位所用的字符
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char padChr = chr(amountToPad);
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String tmp = new String();
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for (int index = 0; index < amountToPad; index++) {
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tmp += padChr;
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}
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return tmp.getBytes(CHARSET);
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}
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/**
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* 删除解密后明文的补位字符
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*
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* @param decrypted 解密后的明文
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* @return 删除补位字符后的明文
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*/
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static byte[] decode(byte[] decrypted) {
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int pad = (int) decrypted[decrypted.length - 1];
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if (pad < 1 || pad > 32) {
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pad = 0;
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}
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return Arrays.copyOfRange(decrypted, 0, decrypted.length - pad);
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}
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/**
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* 将数字转化成ASCII码对应的字符，用于对明文进行补码
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*
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* @param a 需要转化的数字
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* @return 转化得到的字符
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*/
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static char chr(int a) {
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byte target = (byte) (a & 0xFF);
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return (char) target;
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}
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}
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