PHP MCRYPT encrypt/decrypt returns invisible strange characters?

Question

mcrypt_decrypt is giving me additional invisible characters which are NOT VISIBLE by just echoing out on the page. Can ONLY BE SEEN by writing it to the text file. Means, just displaying on the page is OK and hard to be noticed.

Here is the code sample by Googling. Please guide me what is the correct usage is there's something wrong:

function encrypt ($pure_string, $key) {
    $iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $encrypted_string = mcrypt_encrypt(MCRYPT_BLOWFISH, $encryption_key, $pure_string, MCRYPT_MODE_ECB, $iv);
    return $encrypted_string;
}

function decrypt ($encrypted_string, $key) {
    $iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $decrypted_string = mcrypt_decrypt(MCRYPT_BLOWFISH, $encryption_key, $encrypted_string, MCRYPT_MODE_ECB, $iv);
    return $decrypted_string;
}

but when i try it:

$encrypted_string = encrypt("This is the original string.", "ABC123");
echo decrypt($encrypted_string, "ABC123");

.. i am getting something like:

This is the original string.�������

This strange characters �� are actually not visible when you/ i just echo it. Can only be seen by writing into the text file.

So what am i missing please?
Is there any perfect way to achieve this encrypt/decrypt?

Thank you.

possible duplicate of PHP decryption fails on some strings with trim()'s — Baba
– Baba, Commented Jun 3, 2013 at 11:31
@Baba NO this is not a duplicate. Totally different problem. This is also not the trim issue. — 夏期劇場
– 夏期劇場, Commented Jun 3, 2013 at 11:33
Added it has duplicate because .. there so many issues with your encryption MCRYPT_RAND , MCRYPT_MODE_ECB lack of PKCS7 padding , padding oracle attacks .. you can lean a lot of the example class with having to duplicate the answer here — Baba
– Baba, Commented Jun 3, 2013 at 11:35

Logarytm Całkowy · Accepted Answer · 2013-06-03 11:28:53Z

2

You can use trim($string, "\0\4") to cut out these characters.

answered Jun 3, 2013 at 11:28

Logarytm Całkowy

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2 Comments

夏期劇場 Over a year ago

This works actually, even i'm not sure it is the good solution or not. At least the �� characters goes away.

Baba Over a year ago

You would have so many problems in future .. you proper padding .. its not difficult

Nickolay Olshevsky · Accepted Answer · 2013-06-03 11:47:04Z

2

This is padding. ECB mode requires input to be multiple of cipher block size, so additional bytes are added (most likely it is PKCS#5 padding).

To remove PKCS#5 padding you can use following code:

$dec_s = strlen($decrypted);
$padding = ord($decrypted[$dec_s-1]);
$decrypted = substr($decrypted, 0, -$padding);

edited Jun 3, 2013 at 11:47

answered Jun 3, 2013 at 11:28

Nickolay Olshevsky

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3 Comments

夏期劇場 Over a year ago

So what is the correct usage please, since i really don't know.

夏期劇場 Over a year ago

o_O sorry but it is returning blank string "". Lets say $decrypted = "This is the original string.��" . Also, is it about to put in the Decryption (after Decrypting the String) right?

Nickolay Olshevsky Over a year ago

Hm, what actually characters are at the end? Can you show the ord($decrypted[strlen($decrypted)-1]) ?

matt · Accepted Answer · 2013-10-10 13:23:50Z

2

rtrim() will remove the padding that mcrypt added...

answered Oct 10, 2013 at 13:23

matt

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Comments

mistykr · Accepted Answer · 2015-11-18 02:59:32Z

-2

function encrypt ($pure_string, $key) {

=> $key

$encrypted_string = mcrypt_encrypt(MCRYPT_BLOWFISH, $encryption_key, $pure_string, MCRYPT_MODE_ECB, $iv);

=> $encryption_key

not equal

answered Nov 18, 2015 at 2:59

mistykr

1

1 Comment

Tom Over a year ago

If its code example, please wrap it in appropriate way for highlighting and make sure syntax is correct. Also, little explanation is usually useful.

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