PHP: Encrypt/Decrypt Short String

Question

I need to encrypt and decrypt short strings (Ex. 'product1234'). I have used mcrypt_encrypt and mcrypt_decrypt with various ciphers. The problem is that invariably it throws in extended characters into resulting string, which causes some issues with certain aspects of my application code that I cannot control.

So, the question is whether there is either a cipher that reduces the list of characters that are used in the encrypted string (i.e. leaving out things such as '+', '\', or '/').

Please show us the code which exhibits the problem, as it is hard to envision. It is very likely you can correct the issue via base64_encode() — Michael Berkowski
– Michael Berkowski, Commented Jun 18, 2012 at 2:02
@Michael base64_encode will always output a longer string than the original — Mahn
– Mahn, Commented Jun 18, 2012 at 2:15
What do you want to achieve? Cryptographic security? Just shortening the number of characters? — Cameron Martin
– Cameron Martin, Commented Jun 18, 2012 at 2:16
@Mahn I understood the request to be limiting the character set, not necessarily the length. — Michael Berkowski
– Michael Berkowski, Commented Jun 18, 2012 at 2:18
If you want to achieve a short string, but only using certain characters, you could gzip encode the string, then encode it in an arbitrary base (depending on what characters you want to use). — Cameron Martin
– Cameron Martin, Commented Jun 18, 2012 at 2:19

Ja͢ck · Accepted Answer · 2012-06-18 02:08:44Z

7

You can make base64_encode web safe:

function base64url_encode($plainText)
{
    return strtr(base64_encode($plainText), '+/=', '-_,');
}

function base64url_decode($b64Text)
{
    return base64_decode(strtr($b64Text, '-_,' '+/='));
}

Or use hexadecimal encoding:

bin2hex($plainText);

hex2bin($hexText);

answered Jun 18, 2012 at 2:08

Ja͢ck

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1 Comment

PersianMan Over a year ago

Thanks. just one comma is forgotten: return base64_decode(strtr($b64Text, '-_,', '+/='));

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