Interface des encryption?
I need to do DES encryption on the interface. I don’t understand it well. Please give me some advice and recommend some DES encryption information
In fact, I want to find a universal one that is compatible with all four terminals. Currently, I found an article about DES encryption that is universal for PHP, JAVA, C#, and Object-C. I tried it myself. The content encrypted by PHP can be decrypted by Android and IOS. It’s just that when the encrypted content contains Chinese, the mobile terminal will report an error. It seems that the comments in the original article said that encrypting long data on iOS will report an error, but I’m not sure about the details because I haven’t encountered this error==
Reply content:
I need to do DES encryption on the interface. I don’t understand it well. Please give me some advice and recommend some DES encryption information
In fact, I want to find a universal one that is compatible with all four terminals. Currently, I found an article about DES encryption that is universal for PHP, JAVA, C#, and Object-C. I tried it myself. The content encrypted by PHP can be decrypted by Android and IOS. It’s just that when the encrypted content contains Chinese, the mobile terminal will report an error. It seems that the comments in the original article said that encrypting long data on iOS will report an error, but I’m not sure about the details because I haven’t encountered this error==
http://blog.csdn.net/cdh1213/...
ThinkPHP’s DES algorithm
<?php // +---------------------------------------------------------------------- // | ThinkPHP [ WE CAN DO IT JUST THINK IT ] // +---------------------------------------------------------------------- // | Copyright (c) 2009 http://thinkphp.cn All rights reserved. // +---------------------------------------------------------------------- // | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 ) // +---------------------------------------------------------------------- // | Author: liu21st <liu21st@gmail.com> // +---------------------------------------------------------------------- namespace Think\Crypt\Driver; /** * Des 加密实现类 * Converted from JavaScript to PHP by Jim Gibbs, June 2004 Paul Tero, July 2001 * Optimised for performance with large blocks by Michael Hayworth, November 2001 * http://www.netdealing.com */ class Des { /** * 加密字符串 * @param string $str 字符串 * @param string $key 加密key * @param integer $expire 有效期(秒) * @return string */ public static function encrypt($str, $key,$expire=0) { if ($str == "") { return ""; } $expire = sprintf('%010d', $expire ? $expire + time():0); $str = $expire.$str; return self::_des($key,$str,1); } /** * 解密字符串 * @param string $str 字符串 * @param string $key 加密key * @return string */ public static function decrypt($str, $key) { if ($str == "") { return ""; } $data = self::_des($key,$str,0); $expire = substr($data,0,10); if($expire > 0 && $expire < time()) { return ''; } $data = substr($data,10); return $data; } /** * Des算法 * @param string $str 字符串 * @param string $key 加密key * @return string */ private static function _des($key, $message, $encrypt, $mode=0, $iv=null) { //declaring this locally speeds things up a bit $spfunction1 = array (0x1010400,0,0x10000,0x1010404,0x1010004,0x10404,0x4,0x10000,0x400,0x1010400,0x1010404,0x400,0x1000404,0x1010004,0x1000000,0x4,0x404,0x1000400,0x1000400,0x10400,0x10400,0x1010000,0x1010000,0x1000404,0x10004,0x1000004,0x1000004,0x10004,0,0x404,0x10404,0x1000000,0x10000,0x1010404,0x4,0x1010000,0x1010400,0x1000000,0x1000000,0x400,0x1010004,0x10000,0x10400,0x1000004,0x400,0x4,0x1000404,0x10404,0x1010404,0x10004,0x1010000,0x1000404,0x1000004,0x404,0x10404,0x1010400,0x404,0x1000400,0x1000400,0,0x10004,0x10400,0,0x1010004); $spfunction2 = array (-0x7fef7fe0,-0x7fff8000,0x8000,0x108020,0x100000,0x20,-0x7fefffe0,-0x7fff7fe0,-0x7fffffe0,-0x7fef7fe0,-0x7fef8000,-0x80000000,-0x7fff8000,0x100000,0x20,-0x7fefffe0,0x108000,0x100020,-0x7fff7fe0,0,-0x80000000,0x8000,0x108020,-0x7ff00000,0x100020,-0x7fffffe0,0,0x108000,0x8020,-0x7fef8000,-0x7ff00000,0x8020,0,0x108020,-0x7fefffe0,0x100000,-0x7fff7fe0,-0x7ff00000,-0x7fef8000,0x8000,-0x7ff00000,-0x7fff8000,0x20,-0x7fef7fe0,0x108020,0x20,0x8000,-0x80000000,0x8020,-0x7fef8000,0x100000,-0x7fffffe0,0x100020,-0x7fff7fe0,-0x7fffffe0,0x100020,0x108000,0,-0x7fff8000,0x8020,-0x80000000,-0x7fefffe0,-0x7fef7fe0,0x108000); $spfunction3 = array (0x208,0x8020200,0,0x8020008,0x8000200,0,0x20208,0x8000200,0x20008,0x8000008,0x8000008,0x20000,0x8020208,0x20008,0x8020000,0x208,0x8000000,0x8,0x8020200,0x200,0x20200,0x8020000,0x8020008,0x20208,0x8000208,0x20200,0x20000,0x8000208,0x8,0x8020208,0x200,0x8000000,0x8020200,0x8000000,0x20008,0x208,0x20000,0x8020200,0x8000200,0,0x200,0x20008,0x8020208,0x8000200,0x8000008,0x200,0,0x8020008,0x8000208,0x20000,0x8000000,0x8020208,0x8,0x20208,0x20200,0x8000008,0x8020000,0x8000208,0x208,0x8020000,0x20208,0x8,0x8020008,0x20200); $spfunction4 = array (0x802001,0x2081,0x2081,0x80,0x802080,0x800081,0x800001,0x2001,0,0x802000,0x802000,0x802081,0x81,0,0x800080,0x800001,0x1,0x2000,0x800000,0x802001,0x80,0x800000,0x2001,0x2080,0x800081,0x1,0x2080,0x800080,0x2000,0x802080,0x802081,0x81,0x800080,0x800001,0x802000,0x802081,0x81,0,0,0x802000,0x2080,0x800080,0x800081,0x1,0x802001,0x2081,0x2081,0x80,0x802081,0x81,0x1,0x2000,0x800001,0x2001,0x802080,0x800081,0x2001,0x2080,0x800000,0x802001,0x80,0x800000,0x2000,0x802080); $spfunction5 = array (0x100,0x2080100,0x2080000,0x42000100,0x80000,0x100,0x40000000,0x2080000,0x40080100,0x80000,0x2000100,0x40080100,0x42000100,0x42080000,0x80100,0x40000000,0x2000000,0x40080000,0x40080000,0,0x40000100,0x42080100,0x42080100,0x2000100,0x42080000,0x40000100,0,0x42000000,0x2080100,0x2000000,0x42000000,0x80100,0x80000,0x42000100,0x100,0x2000000,0x40000000,0x2080000,0x42000100,0x40080100,0x2000100,0x40000000,0x42080000,0x2080100,0x40080100,0x100,0x2000000,0x42080000,0x42080100,0x80100,0x42000000,0x42080100,0x2080000,0,0x40080000,0x42000000,0x80100,0x2000100,0x40000100,0x80000,0,0x40080000,0x2080100,0x40000100); $spfunction6 = array (0x20000010,0x20400000,0x4000,0x20404010,0x20400000,0x10,0x20404010,0x400000,0x20004000,0x404010,0x400000,0x20000010,0x400010,0x20004000,0x20000000,0x4010,0,0x400010,0x20004010,0x4000,0x404000,0x20004010,0x10,0x20400010,0x20400010,0,0x404010,0x20404000,0x4010,0x404000,0x20404000,0x20000000,0x20004000,0x10,0x20400010,0x404000,0x20404010,0x400000,0x4010,0x20000010,0x400000,0x20004000,0x20000000,0x4010,0x20000010,0x20404010,0x404000,0x20400000,0x404010,0x20404000,0,0x20400010,0x10,0x4000,0x20400000,0x404010,0x4000,0x400010,0x20004010,0,0x20404000,0x20000000,0x400010,0x20004010); $spfunction7 = array (0x200000,0x4200002,0x4000802,0,0x800,0x4000802,0x200802,0x4200800,0x4200802,0x200000,0,0x4000002,0x2,0x4000000,0x4200002,0x802,0x4000800,0x200802,0x200002,0x4000800,0x4000002,0x4200000,0x4200800,0x200002,0x4200000,0x800,0x802,0x4200802,0x200800,0x2,0x4000000,0x200800,0x4000000,0x200800,0x200000,0x4000802,0x4000802,0x4200002,0x4200002,0x2,0x200002,0x4000000,0x4000800,0x200000,0x4200800,0x802,0x200802,0x4200800,0x802,0x4000002,0x4200802,0x4200000,0x200800,0,0x2,0x4200802,0,0x200802,0x4200000,0x800,0x4000002,0x4000800,0x800,0x200002); $spfunction8 = array (0x10001040,0x1000,0x40000,0x10041040,0x10000000,0x10001040,0x40,0x10000000,0x40040,0x10040000,0x10041040,0x41000,0x10041000,0x41040,0x1000,0x40,0x10040000,0x10000040,0x10001000,0x1040,0x41000,0x40040,0x10040040,0x10041000,0x1040,0,0,0x10040040,0x10000040,0x10001000,0x41040,0x40000,0x41040,0x40000,0x10041000,0x1000,0x40,0x10040040,0x1000,0x41040,0x10001000,0x40,0x10000040,0x10040000,0x10040040,0x10000000,0x40000,0x10001040,0,0x10041040,0x40040,0x10000040,0x10040000,0x10001000,0x10001040,0,0x10041040,0x41000,0x41000,0x1040,0x1040,0x40040,0x10000000,0x10041000); $masks = array (4294967295,2147483647,1073741823,536870911,268435455,134217727,67108863,33554431,16777215,8388607,4194303,2097151,1048575,524287,262143,131071,65535,32767,16383,8191,4095,2047,1023,511,255,127,63,31,15,7,3,1,0); //create the 16 or 48 subkeys we will need $keys = self::_createKeys ($key); $m=0; $len = strlen($message); $chunk = 0; //set up the loops for single and triple des $iterations = ((count($keys) == 32) ? 3 : 9); //single or triple des if ($iterations == 3) {$looping = (($encrypt) ? array (0, 32, 2) : array (30, -2, -2));} else {$looping = (($encrypt) ? array (0, 32, 2, 62, 30, -2, 64, 96, 2) : array (94, 62, -2, 32, 64, 2, 30, -2, -2));} $message .= (chr(0) . chr(0) . chr(0) . chr(0) . chr(0) . chr(0) . chr(0) . chr(0)); //pad the message out with null bytes //store the result here $result = ""; $tempresult = ""; if ($mode == 1) { //CBC mode $cbcleft = (ord($iv{$m++}) << 24) | (ord($iv{$m++}) << 16) | (ord($iv{$m++}) << 8) | ord($iv{$m++}); $cbcright = (ord($iv{$m++}) << 24) | (ord($iv{$m++}) << 16) | (ord($iv{$m++}) << 8) | ord($iv{$m++}); $m=0; } //loop through each 64 bit chunk of the message while ($m < $len) { $left = (ord($message{$m++}) << 24) | (ord($message{$m++}) << 16) | (ord($message{$m++}) << 8) | ord($message{$m++}); $right = (ord($message{$m++}) << 24) | (ord($message{$m++}) << 16) | (ord($message{$m++}) << 8) | ord($message{$m++}); //for Cipher Block Chaining mode, xor the message with the previous result if ($mode == 1) {if ($encrypt) {$left ^= $cbcleft; $right ^= $cbcright;} else {$cbcleft2 = $cbcleft; $cbcright2 = $cbcright; $cbcleft = $left; $cbcright = $right;}} //first each 64 but chunk of the message must be permuted according to IP $temp = (($left >> 4 & $masks[4]) ^ $right) & 0x0f0f0f0f; $right ^= $temp; $left ^= ($temp << 4); $temp = (($left >> 16 & $masks[16]) ^ $right) & 0x0000ffff; $right ^= $temp; $left ^= ($temp << 16); $temp = (($right >> 2 & $masks[2]) ^ $left) & 0x33333333; $left ^= $temp; $right ^= ($temp << 2); $temp = (($right >> 8 & $masks[8]) ^ $left) & 0x00ff00ff; $left ^= $temp; $right ^= ($temp << 8); $temp = (($left >> 1 & $masks[1]) ^ $right) & 0x55555555; $right ^= $temp; $left ^= ($temp << 1); $left = (($left << 1) | ($left >> 31 & $masks[31])); $right = (($right << 1) | ($right >> 31 & $masks[31])); //do this either 1 or 3 times for each chunk of the message for ($j=0; $j<$iterations; $j+=3) { $endloop = $looping[$j+1]; $loopinc = $looping[$j+2]; //now go through and perform the encryption or decryption for ($i=$looping[$j]; $i!=$endloop; $i+=$loopinc) { //for efficiency $right1 = $right ^ $keys[$i]; $right2 = (($right >> 4 & $masks[4]) | ($right << 28)) ^ $keys[$i+1]; //the result is attained by passing these bytes through the S selection functions $temp = $left; $left = $right; $right = $temp ^ ($spfunction2[($right1 >> 24 & $masks[24]) & 0x3f] | $spfunction4[($right1 >> 16 & $masks[16]) & 0x3f] | $spfunction6[($right1 >> 8 & $masks[8]) & 0x3f] | $spfunction8[$right1 & 0x3f] | $spfunction1[($right2 >> 24 & $masks[24]) & 0x3f] | $spfunction3[($right2 >> 16 & $masks[16]) & 0x3f] | $spfunction5[($right2 >> 8 & $masks[8]) & 0x3f] | $spfunction7[$right2 & 0x3f]); } $temp = $left; $left = $right; $right = $temp; //unreverse left and right } //for either 1 or 3 iterations //move then each one bit to the right $left = (($left >> 1 & $masks[1]) | ($left << 31)); $right = (($right >> 1 & $masks[1]) | ($right << 31)); //now perform IP-1, which is IP in the opposite direction $temp = (($left >> 1 & $masks[1]) ^ $right) & 0x55555555; $right ^= $temp; $left ^= ($temp << 1); $temp = (($right >> 8 & $masks[8]) ^ $left) & 0x00ff00ff; $left ^= $temp; $right ^= ($temp << 8); $temp = (($right >> 2 & $masks[2]) ^ $left) & 0x33333333; $left ^= $temp; $right ^= ($temp << 2); $temp = (($left >> 16 & $masks[16]) ^ $right) & 0x0000ffff; $right ^= $temp; $left ^= ($temp << 16); $temp = (($left >> 4 & $masks[4]) ^ $right) & 0x0f0f0f0f; $right ^= $temp; $left ^= ($temp << 4); //for Cipher Block Chaining mode, xor the message with the previous result if ($mode == 1) {if ($encrypt) {$cbcleft = $left; $cbcright = $right;} else {$left ^= $cbcleft2; $right ^= $cbcright2;}} $tempresult .= (chr($left>>24 & $masks[24]) . chr(($left>>16 & $masks[16]) & 0xff) . chr(($left>>8 & $masks[8]) & 0xff) . chr($left & 0xff) . chr($right>>24 & $masks[24]) . chr(($right>>16 & $masks[16]) & 0xff) . chr(($right>>8 & $masks[8]) & 0xff) . chr($right & 0xff)); $chunk += 8; if ($chunk == 512) {$result .= $tempresult; $tempresult = ""; $chunk = 0;} } //for every 8 characters, or 64 bits in the message //return the result as an array return ($result . $tempresult); } //end of des /** * createKeys * this takes as input a 64 bit key (even though only 56 bits are used) * as an array of 2 integers, and returns 16 48 bit keys * @param string $key 加密key * @return string */ private static function _createKeys ($key) { //declaring this locally speeds things up a bit $pc2bytes0 = array (0,0x4,0x20000000,0x20000004,0x10000,0x10004,0x20010000,0x20010004,0x200,0x204,0x20000200,0x20000204,0x10200,0x10204,0x20010200,0x20010204); $pc2bytes1 = array (0,0x1,0x100000,0x100001,0x4000000,0x4000001,0x4100000,0x4100001,0x100,0x101,0x100100,0x100101,0x4000100,0x4000101,0x4100100,0x4100101); $pc2bytes2 = array (0,0x8,0x800,0x808,0x1000000,0x1000008,0x1000800,0x1000808,0,0x8,0x800,0x808,0x1000000,0x1000008,0x1000800,0x1000808); $pc2bytes3 = array (0,0x200000,0x8000000,0x8200000,0x2000,0x202000,0x8002000,0x8202000,0x20000,0x220000,0x8020000,0x8220000,0x22000,0x222000,0x8022000,0x8222000); $pc2bytes4 = array (0,0x40000,0x10,0x40010,0,0x40000,0x10,0x40010,0x1000,0x41000,0x1010,0x41010,0x1000,0x41000,0x1010,0x41010); $pc2bytes5 = array (0,0x400,0x20,0x420,0,0x400,0x20,0x420,0x2000000,0x2000400,0x2000020,0x2000420,0x2000000,0x2000400,0x2000020,0x2000420); $pc2bytes6 = array (0,0x10000000,0x80000,0x10080000,0x2,0x10000002,0x80002,0x10080002,0,0x10000000,0x80000,0x10080000,0x2,0x10000002,0x80002,0x10080002); $pc2bytes7 = array (0,0x10000,0x800,0x10800,0x20000000,0x20010000,0x20000800,0x20010800,0x20000,0x30000,0x20800,0x30800,0x20020000,0x20030000,0x20020800,0x20030800); $pc2bytes8 = array (0,0x40000,0,0x40000,0x2,0x40002,0x2,0x40002,0x2000000,0x2040000,0x2000000,0x2040000,0x2000002,0x2040002,0x2000002,0x2040002); $pc2bytes9 = array (0,0x10000000,0x8,0x10000008,0,0x10000000,0x8,0x10000008,0x400,0x10000400,0x408,0x10000408,0x400,0x10000400,0x408,0x10000408); $pc2bytes10 = array (0,0x20,0,0x20,0x100000,0x100020,0x100000,0x100020,0x2000,0x2020,0x2000,0x2020,0x102000,0x102020,0x102000,0x102020); $pc2bytes11 = array (0,0x1000000,0x200,0x1000200,0x200000,0x1200000,0x200200,0x1200200,0x4000000,0x5000000,0x4000200,0x5000200,0x4200000,0x5200000,0x4200200,0x5200200); $pc2bytes12 = array (0,0x1000,0x8000000,0x8001000,0x80000,0x81000,0x8080000,0x8081000,0x10,0x1010,0x8000010,0x8001010,0x80010,0x81010,0x8080010,0x8081010); $pc2bytes13 = array (0,0x4,0x100,0x104,0,0x4,0x100,0x104,0x1,0x5,0x101,0x105,0x1,0x5,0x101,0x105); $masks = array (4294967295,2147483647,1073741823,536870911,268435455,134217727,67108863,33554431,16777215,8388607,4194303,2097151,1048575,524287,262143,131071,65535,32767,16383,8191,4095,2047,1023,511,255,127,63,31,15,7,3,1,0); //how many iterations (1 for des, 3 for triple des) $iterations = ((strlen($key) >= 24) ? 3 : 1); //stores the return keys $keys = array (); // size = 32 * iterations but you don't specify this in php //now define the left shifts which need to be done $shifts = array (0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0); //other variables $m=0; $n=0; for ($j=0; $j<$iterations; $j++) { //either 1 or 3 iterations $left = (ord($key{$m++}) << 24) | (ord($key{$m++}) << 16) | (ord($key{$m++}) << 8) | ord($key{$m++}); $right = (ord($key{$m++}) << 24) | (ord($key{$m++}) << 16) | (ord($key{$m++}) << 8) | ord($key{$m++}); $temp = (($left >> 4 & $masks[4]) ^ $right) & 0x0f0f0f0f; $right ^= $temp; $left ^= ($temp << 4); $temp = (($right >> 16 & $masks[16]) ^ $left) & 0x0000ffff; $left ^= $temp; $right ^= ($temp << -16); $temp = (($left >> 2 & $masks[2]) ^ $right) & 0x33333333; $right ^= $temp; $left ^= ($temp << 2); $temp = (($right >> 16 & $masks[16]) ^ $left) & 0x0000ffff; $left ^= $temp; $right ^= ($temp << -16); $temp = (($left >> 1 & $masks[1]) ^ $right) & 0x55555555; $right ^= $temp; $left ^= ($temp << 1); $temp = (($right >> 8 & $masks[8]) ^ $left) & 0x00ff00ff; $left ^= $temp; $right ^= ($temp << 8); $temp = (($left >> 1 & $masks[1]) ^ $right) & 0x55555555; $right ^= $temp; $left ^= ($temp << 1); //the right side needs to be shifted and to get the last four bits of the left side $temp = ($left << 8) | (($right >> 20 & $masks[20]) & 0x000000f0); //left needs to be put upside down $left = ($right << 24) | (($right << 8) & 0xff0000) | (($right >> 8 & $masks[8]) & 0xff00) | (($right >> 24 & $masks[24]) & 0xf0); $right = $temp; //now go through and perform these shifts on the left and right keys for ($i=0; $i < count($shifts); $i++) { //shift the keys either one or two bits to the left if ($shifts[$i] > 0) { $left = (($left << 2) | ($left >> 26 & $masks[26])); $right = (($right << 2) | ($right >> 26 & $masks[26])); } else { $left = (($left << 1) | ($left >> 27 & $masks[27])); $right = (($right << 1) | ($right >> 27 & $masks[27])); } $left = $left & -0xf; $right = $right & -0xf; //now apply PC-2, in such a way that E is easier when encrypting or decrypting //this conversion will look like PC-2 except only the last 6 bits of each byte are used //rather than 48 consecutive bits and the order of lines will be according to //how the S selection functions will be applied: S2, S4, S6, S8, S1, S3, S5, S7 $lefttemp = $pc2bytes0[$left >> 28 & $masks[28]] | $pc2bytes1[($left >> 24 & $masks[24]) & 0xf] | $pc2bytes2[($left >> 20 & $masks[20]) & 0xf] | $pc2bytes3[($left >> 16 & $masks[16]) & 0xf] | $pc2bytes4[($left >> 12 & $masks[12]) & 0xf] | $pc2bytes5[($left >> 8 & $masks[8]) & 0xf] | $pc2bytes6[($left >> 4 & $masks[4]) & 0xf]; $righttemp = $pc2bytes7[$right >> 28 & $masks[28]] | $pc2bytes8[($right >> 24 & $masks[24]) & 0xf] | $pc2bytes9[($right >> 20 & $masks[20]) & 0xf] | $pc2bytes10[($right >> 16 & $masks[16]) & 0xf] | $pc2bytes11[($right >> 12 & $masks[12]) & 0xf] | $pc2bytes12[($right >> 8 & $masks[8]) & 0xf] | $pc2bytes13[($right >> 4 & $masks[4]) & 0xf]; $temp = (($righttemp >> 16 & $masks[16]) ^ $lefttemp) & 0x0000ffff; $keys[$n++] = $lefttemp ^ $temp; $keys[$n++] = $righttemp ^ ($temp << 16); } } //for each iterations //return the keys we've created return $keys; } //end of des_createKeys }
php DESede encryption and decryption

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C# is widely used in enterprise-level applications, game development, mobile applications and web development. 1) In enterprise-level applications, C# is often used for ASP.NETCore to develop WebAPI. 2) In game development, C# is combined with the Unity engine to realize role control and other functions. 3) C# supports polymorphism and asynchronous programming to improve code flexibility and application performance.

How to deploy a C# .NET app to Azure or AWS? The answer is to use AzureAppService and AWSElasticBeanstalk. 1. On Azure, automate deployment using AzureAppService and AzurePipelines. 2. On AWS, use Amazon ElasticBeanstalk and AWSLambda to implement deployment and serverless compute.

Multiple calls to session_start() will result in warning messages and possible data overwrites. 1) PHP will issue a warning, prompting that the session has been started. 2) It may cause unexpected overwriting of session data. 3) Use session_status() to check the session status to avoid repeated calls.

AI can help optimize the use of Composer. Specific methods include: 1. Dependency management optimization: AI analyzes dependencies, recommends the best version combination, and reduces conflicts. 2. Automated code generation: AI generates composer.json files that conform to best practices. 3. Improve code quality: AI detects potential problems, provides optimization suggestions, and improves code quality. These methods are implemented through machine learning and natural language processing technologies to help developers improve efficiency and code quality.

session_start()iscrucialinPHPformanagingusersessions.1)Itinitiatesanewsessionifnoneexists,2)resumesanexistingsession,and3)setsasessioncookieforcontinuityacrossrequests,enablingapplicationslikeuserauthenticationandpersonalizedcontent.

How to build applications using .NET? Building applications using .NET can be achieved through the following steps: 1) Understand the basics of .NET, including C# language and cross-platform development support; 2) Learn core concepts such as components and working principles of the .NET ecosystem; 3) Master basic and advanced usage, from simple console applications to complex WebAPIs and database operations; 4) Be familiar with common errors and debugging techniques, such as configuration and database connection issues; 5) Application performance optimization and best practices, such as asynchronous programming and caching.

HTML5 brings five key improvements: 1. Semantic tags improve code clarity and SEO effects; 2. Multimedia support simplifies video and audio embedding; 3. Form enhancement simplifies verification; 4. Offline and local storage improves user experience; 5. Canvas and graphics functions enhance the visualization of web pages.

MySQL functions can be used for data processing and calculation. 1. Basic usage includes string processing, date calculation and mathematical operations. 2. Advanced usage involves combining multiple functions to implement complex operations. 3. Performance optimization requires avoiding the use of functions in the WHERE clause and using GROUPBY and temporary tables.
