怎样对邮件正文分段加密及解密

/** 公钥加密

	 * $crtpath  证书[绝对路径/证书名称]

	 * $mailcont 需要加密的内容

	 * $sign     分界符

	 * 需要 splitCN(),subCNchar(),is_utf8()三个函数

	 **/

	function public_encrypt($crtpath, $mailcont, $sign = false) {

		$fp = fopen($crtpath, "r");

		$crt = fread($fp, 8192);

		fclose($fp);

		$pubKey = openssl_get_publickey($crt);

		//从证书中解析公钥

		$keyData = openssl_pkey_get_details($pubKey);

		$blocks = $this->splitCN($mailcont, 0, 30);

		$chrtext = null;

		$encodes = array ();

		foreach ($blocks as $n => $block) {

			if (!openssl_public_encrypt($block, $chrtext, $keyData['key'])) {

				echo "<br/>" . openssl_error_string() . "<br/>";

			}

			$encodes[] = $chrtext;

		}

		$chrtext = implode($sign, $encodes);

		return $chrtext;

	}



	/** 私钥解密

	 * $keypath  私钥[绝对路径/私钥名称]

	 * $chrtext  需要解密的内容

	 * $sign     分界符

	 **/

	function private_decrypt($keypath, $chrtext, $sign = false) {

		$fp = fopen($keypath, "r");

		$key = fread($fp, 8192);

		fclose($fp);

		$cipher = openssl_pkey_get_private($key);

		$decodes = explode($sign, $chrtext);

		$strnull = "";

		$dcyCont = null;

		foreach ($decodes as $n => $decode) {

			openssl_private_decrypt($decode, $dcyCont, $cipher);

			$strnull .= $dcyCont;

		}

		return $strnull;

	}



	/** 截取汉字 *

	 * $str     要截取的字符串

	 * $start   截取的起始位置

	 * $length  要截取的长度

	 * $charset 字符串编码

	 **/

	function subCNchar($str, $start = 0, $length, $charset = "utf-8") {

		if (strlen($str) <= $length)

			return $str;



		$re['utf-8'] = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf]{2}|[\xf0-\xff][\x80-\xbf]{3}/";

		$re['gb2312'] = "/[\x01-\x7f]|[\xb0-\xf7][\xa0-\xfe]/";

		$re['gbk'] = "/[\x01-\x7f]|[\x81-\xfe][\x40-\xfe]/";

		$re['big5'] = "/[\x01-\x7f]|[\x81-\xfe]([\x40-\x7e]|\xa1-\xfe])/";

		preg_match_all($re[$charset], $str, $match);



		$slice = join("", array_slice($match[0], $start, $length));



		return $slice;

	}



	/** 将字符串按规定长度分段截取并放入数组

	 * $cont   要处理的字符串

	 * $n      起始位置

	 * $subnum 限定的截取长度(字节)

	 **/

	function splitCN($cont, $n = 0, $subnum) {

		//$len = strlen($cont) / 3;

		for ($i = $n; $i < strlen($cont); $i += $subnum) {

			$res = $this->subCNchar($cont, $i, $subnum);

			if (!empty ($res)) {

				$arrr[] = $res;

			}

		}

		return $arrr;

	}

//------------具体调用-------------

/**************** 公钥加密 ****************/

			$crtpath = "/path/xxx.crt";

			//邮件正文段落连接符

			$sign = "%^&_&^%";

			//加密

			$chrtext = $referen->public_encrypt($crtpath,$mailcont,$sign);

//-------------私钥解密------------

$keyname = "xxx.key";

		$keypath = "/path/" . $keyname;

		$dcyCont = $referen->private_decrypt($keypath,$phcont,$sign);

$mailcont = "邮件正文………超过1024字节………邮件正文";

$mailcont_english = "mail content………more than 1024 KB………mail content";

$crtpath = "/usr/nc-home/webpost/mailbox/d00/1/y/u/yushuai.niu/.user/certkey/wxd.crt";

exec("chmod 777 {$crtpath}");

$fp = fopen($crtpath, "r");

$crt = fread($fp, 8192);

fclose($fp);

$pubKey = openssl_get_publickey($crt);

//从证书中解析公钥

$keyData = openssl_pkey_get_details($pubKey);

$blocks = str_split($mailcont, 100);

$decodes = array();

foreach ($blocks as $block) {

	//公钥加密

	if (!openssl_public_encrypt($block, $chrtext, $keyData['key'])) {

		echo "<br/>" . openssl_error_string() . "<br/>";

	}

	$decodes[] = $chrtext;

	$chrtext .= $chrtext;

}

echo "chrtext-->>>$chrtext<br/>";



$keypath = "/usr/nc-home/webpost/mailbox/d00/1/y/u/yushuai.niu/.user/secretkey/wxd.key";

exec("chmod 777 {$keypath}");

$fp = fopen($keypath, "r");

$key = fread($fp, 8192);

fclose($fp);

$cipher = openssl_pkey_get_private($key);

foreach($decodes as $decode){

	openssl_private_decrypt($decode, $dcyCont, $cipher);

	$dcyCont .= $dcyCont;

}



echo "dcyCont-->>>$dcyCont<br/>";