ceasar - NDDCoder

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<?php
		function chuyendoi($a){
			$b="";
			if($a>='a' && $a<='z'){
				$b= ord($a)-ord('a');
			}
			if($a>='A' && $a<='Z'){
				$b= ord($a)-ord('A');
			}
			return $b;
		}

function ceasar($a, $k){
			$c=""; $p="";
			$d="";
			if($a>='A' && $a<='Z'){
				$p=ord($a)-ord('A');
				$c=($p+$k)%26;
				$d= $c+ord('A');
			}
			if($a>='a' && $a<='z' ){
			
				$p=ord($a)-ord('a');
				$c=($p+$k)%26;
				$d= $c+ord('a');
			}
			return chr($d);
		}
		function decryption_ceasar($a, $k){
			$c=""; $p="";
			$d="";
			if($a>='A' && $a<='Z' ){
				$p=ord($a)-ord('A');
				$c=($p-$k+26)%26;
				$d= $c+ord('A');
			}
			if($a>='a' && $a<='z'){
				$p=ord($a)-ord('a');
				$c=($p-$k+26)%26;
				$d= $c+ord('a');
			}

return chr($d);
		}
		function mahoa($key)	{
			$plt= file_get_contents('E:\\Example.txt');
			$ciphertext="";
			$autokey= $key.$plt;
			for($i=0; $i<strlen($plt);$i++){
				$ciphertext .= ceasar($plt[$i], chuyendoi($autokey[$i]));
			}
			return $ciphertext;
		}
		echo mahoa('hujk');

function giaima($ciphertext ,$key){
		$decryption="";
		for($i=0; $i<strlen($ciphertext);$i++){
			$decryption .= decryption_Ceasar( $ciphertext[$i] , chuyendoi($key[$i]) );
			$key .= $decryption;
		}
		return $decryption;
	}
	function write_file($myfile){
		$a = fopen($myfile, "w") or die("Unable to open file!");
		fwrite($a, mahoa('hujk'));
		fclose($a);
	}
	echo write_file('E:\\Exout.txt');
	
 ?>