Encryption and decryption with PHP

Question

I'm trying to implement encryption and decryption functions in PHP but it is not just working right. Here is the algorithm:

Encryption key is a master code: 1234567890.
Encryption alphabet is a-z, A-Z, 0-9, =
Encrypt each symbol after the signature that belongs to the encryption alphabet. Skip the others.
Symbol is encrypted by a shift (to the right) in the encrypted alphabet. The shift amount is given by the current digit of the encryption key. The current digit of the encryption key is shifted to the right after each usage and cycled from the end to beginning.

Here is my current code:

    function tnsencrypt($master_code,$text) { //the text to be encrypted $plain_text= $text;

//letters of alphabet array $alphabet=array('0','1','2','3','4','5','6','7','8','9','=','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z');

//$alphabet_len = count($alphabet); //$signature_len = 17; // signature=TnpMsgE //$master_code_len = 10; $mcursor = 0;

//positions of the letters in alphabet : The array_flip() function returns an array with all the original keys as values, and all original values as keys. $flip=array_flip($alphabet); //plaintext array $plain_text=str_split($plain_text); $master_code=str_split($master_code);

$n=count($plain_text); $encrypted_text=''; for ($i=0; $i }

}

//echo $encrypted_text; return $encrypted_text; }

function tnsdecrypt($master_code,$text) { //the text to be decrypted $encrypted_text= $text;

//letters of alphabet array $alphabet=array('0','1','2','3','4','5','6','7','8','9','=','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'); //positions of the letters in alphabet : The array_flip() function returns an array with all the original keys as values, and all original values as keys. $flip=array_flip($alphabet);

//plaintext array $encrypted_text=str_split($encrypted_text); $master_code=str_split($master_code);

$n=count($encrypted_text); $decrypted_text=''; for ($i=0; $i

} else {
    $decrypted_text.= $encrypted_text[$i];  
}
//move mcursor
$mcursor = ($mcursor+1)%10;
}

//echo $encrypted_text; return $decrypted_text;

}

if(isset($_POST["text"])) { $text = $_POST["text"]; $shifttext = $_POST["shifttext"]; echo "
Encrypted Text: ".tnsencrypt($shifttext,$text); echo "
Decrypted Text: ".tnsdecrypt($shifttext,tnsencrypt($shifttext,$text));

}

?>

Here is my result:

Original text: val1=1234567 val2=abcdef val3=ABCDEF

Encrypted text: vjt8F666666F 3hr7Dddddnn 2gq7CCCCMMM

Encrypted Text: vjt8F666666F hr7Dddddnn gq7CCCCMMM

Decrypted Text: val1=1234567 al2=abcdef al3=ABCDEF

As you can see, a couple of characters are missing on the encryption and that affected the decryption as well. The missing ones are v on line 2 and v on line 3

Any ideas why?

Encryption and decryption with PHP

Answers (1)

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