Integer to code and back

[Tom]

I need to convert an integer to a unique code string consisting only of
capital letters and numbers.
I also need to be able to convert it back to an integer again.

Example:

10 =DFG56JKG4 =10

How do I accomplish that?
Googling has not helped.

Regards

[Dan M]

Re: Integer to code and back

On Wed, 03 Jan 2007 19:05:14 +0100, Tom wrote:

I need to convert an integer to a unique code string consisting only of
capital letters and numbers.
I also need to be able to convert it back to an integer again.
>
Example:
>
10 =DFG56JKG4 =10
>
How do I accomplish that?
Googling has not helped.
>
Regards

What is the logic used to map from integer to string?

[=?UTF-8?B?SXbDoW4gU8OhbmNoZXogT3J0ZWdh?=]

Re: Integer to code and back

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Dan M wrote:

On Wed, 03 Jan 2007 19:05:14 +0100, Tom wrote:
>

>10 =DFG56JKG4 =10
>>
>How do I accomplish that?

>
What is the logic used to map from integer to string?

I guess that Tom has absolutely no idea on how to do that.

Viable possibilities:
- - A hash table.
- - A simetric encryption function.

- --
- ----------------------------------
Iván Sánchez Ortega -ivansanchez-algarroba-escomposlinux-punto-org-

http://acm.asoc.fi.upm.es/~mr/ ; http://acm.asoc.fi.upm.es/~ivan/
MSN:i_eat_s_p_a _m_for_breakfas t@hotmail.com
Jabber:ivansanc hez@jabber.org ; ivansanchez@kde talk.net
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[Tom]

Re: Integer to code and back

>>

>What is the logic used to map from integer to string?

>
I guess that Tom has absolutely no idea on how to do that.

Exactly!

I have triede base64_decode / encode but it fails as it uses non
alphanumerics.
So does base32

Viable possibilities:
- - A hash table.

Hmm doesn't ring a bell, and google gives me oodles of stuff that is not
directly related.
Could you please provide me with an example in pseudo code or something?

- - A simetric encryption function.

Well, same result when googling. The concept exists but apparently everybody
knows it so well they don't explain it but just refer to it :-D
An example please?

Thanks for answering!

Tom

[Michael Fesser]

Re: Integer to code and back

..oO(Tom)

>I need to convert an integer to a unique code string consisting only of
>capital letters and numbers.
>I also need to be able to convert it back to an integer again.
>
>Example:
>
>10 =DFG56JKG4 =10

Just curious: Why do you need that? The integer itself is unique and
consists only of numbers ... so what's the purpose of the "encoding"?

Micha

[=?UTF-8?B?SXbDoW4gU8OhbmNoZXogT3J0ZWdh?=]

Re: Integer to code and back

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Hash: SHA1

Tom wrote:

>- - A hash table.

>
Hmm doesn't ring a bell, and google gives me oodles of stuff that is not
directly related.
Could you please provide me with an example in pseudo code or something?

Basically, you generate a table that you store somewhere, and relates every
integer you can think of with its hash.

Got a new integer? Calculate the hash and store it in the table. Got a hash?
Check if it exists in the table.

How you exactly hash the integers is your problem, tough.

>- - A simetric encryption function.

>
Well, same result when googling. The concept exists but apparently
everybody knows it so well they don't explain it but just refer to it :-D
An example please?

RTFM. php.net/mcrypt

- --
- ----------------------------------
Iván Sánchez Ortega -ivansanchez-algarroba-escomposlinux-punto-org-

Un ordenador no es un televisor ni un microondas, es una herramienta
compleja.
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[Michael Fesser]

Re: Integer to code and back

..oO(Iván Sánchez Ortega)

>Basically, you generate a table that you store somewhere, and relates every
>integer you can think of with its hash.

A hash is not unique.

Micha

[Tom]

Re: Integer to code and back

Got a new integer? Calculate the hash and store it in the table. Got a

hash?
Check if it exists in the table.

Ah, good idea. Thanks.

>>- - A simetric encryption function.

>>
>Well, same result when googling. The concept exists but apparently
>everybody knows it so well they don't explain it but just refer to it :-D
>An example please?

>
RTFM. php.net/mcrypt

1) How was I supposed to link "simetric encryption" to "mcrypt" ??? :-D :-D
2) Are you sure you it shouldn't be spelled "symmetric" ?

Tom

[Tom]

Re: Integer to code and back


"Michael Fesser" <netizen@gmx.de wrote in message
news:rn6op2tglc g7uda14oblqpm7c k8bkefthj@4ax.c om...

.oO(Tom)
>

>>I need to convert an integer to a unique code string consisting only of
>>capital letters and numbers.
>>I also need to be able to convert it back to an integer again.
>>
>>Example:
>>
>>10 =DFG56JKG4 =10

>
Just curious: Why do you need that? The integer itself is unique and
consists only of numbers ... so what's the purpose of the "encoding"?

The purpose is to use it in links.
Each code will link to a given row in a database and then show an image.
But I don't want script kiddies to fetch all images iteratively :-)

Tom

[Moot]

Re: Integer to code and back

Michael Fesser wrote:

.oO(Tom)
>

I need to convert an integer to a unique code string consisting only of
capital letters and numbers.
I also need to be able to convert it back to an integer again.

Example:

10 =DFG56JKG4 =10

>
Just curious: Why do you need that? The integer itself is unique and
consists only of numbers ... so what's the purpose of the "encoding"?
>
Micha

I'm curious as well...a number is already unique, what benefit are you
looking to get from the encoding?

Heck, if all you want is a way to convert a number to an alphanumeric
string and back reliably without any kind of obfuscation, then you
could just convert the int to hex and voila, you've got an alphanumeric
string that contains 0-9 and A-F which can easily be converted back to
decimal notation.

- Moot

[Kimmo Laine]

Re: Integer to code and back

"Tom" <no@spam.please wrote in message
news:459c2564$0 $49209$14726298 @news.sunsite.d k...

2) Are you sure you it shouldn't be spelled "symmetric" ?

I'm pretty sure it's "symmetric" , but let's find out, shall we...

http://www.googlefight.com/index.php?lang=en_GB&word1=symmetric&word2=simetric

"symmetric" 28,000,000 results vs. "simetric" 104,000 results...

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[Toby Inkster]

Re: Integer to code and back

Michael Fesser wrote:

A hash is not unique.

For small[1] integers $i, md5($i) should be unique.

____
1. Say, lower than 1,000,000,000

--
Toby A Inkster BSc (Hons) ARCS
Contact Me ~ http://tobyinkster.co.uk/contact

[Toby Inkster]

Re: Integer to code and back

Tom wrote:

10 =DFG56JKG4 =10
>
How do I accomplish that?

How about this...

define('MYSECRE T','Some unguessable string');

function int2code ($i)
{
$md5 = strtoupper(md5( MYSECRET.$i));
$mdStart = substr($md5, 0, 4);
$mdEnd = substr($md5, 28, 4);
return $mdStart.$i.$md End;
}

function code2int ($code)
{
preg_match('/^([A-F0-9]{4})([0-9]+)([A-F0-9]{4})$/', $code, $matches);
$i = $matches[2];

$md5 = strtoupper(md5( MYSECRET.$i));
$mdStart = substr($md5, 0, 4);
$mdEnd = substr($md5, 28, 4);
if ($mdStart.$i.$m dEnd==$code)
return $i;

return FALSE; // Invalid code!
}

--
Toby A Inkster BSc (Hons) ARCS
Contact Me ~ http://tobyinkster.co.uk/contact

[Toby Inkster]

Re: Integer to code and back

Iván Sánchez Ortega wrote:

Viable possibilities:
- - A hash table.
- - A simetric encryption function.

Possibility three:
- including the unencrypted integer in the query string, but signing it.

I've posted example code for this in my reply to Tom's post.

--
Toby A Inkster BSc (Hons) ARCS
Contact Me ~ http://tobyinkster.co.uk/contact

[Kimmo Laine]

Re: Integer to code and back

"Toby Inkster" <usenet200701@t obyinkster.co.u kwrote in message
news:j20v64-v48.ln1@ophelia .g5n.co.uk...

Michael Fesser wrote:
>

>A hash is not unique.

>
For small[1] integers $i, md5($i) should be unique.

Unique yes, but md5 is one-way, and the op wanted a way to convert integers
to strings and back to integers. How do you convert an md5 digest to
integer?

--
"Ohjelmoija on organismi joka muuttaa kofeiinia koodiksi" - lpk
http://outolempi.net/ahdistus/ - Satunnaisesti päivittyvä nettisarjis
spam@outolempi. net | rot13(xvzzb@bhg byrzcv.arg)