Generating a 20 character code from a string

Hey,
I need to create a simple encyption. When given a string, my program will need to return a 20 digit long alphanumeric string. These strings may be over 20 characters in the first place. Each string has to encrypt to the same result everytime, therefore each string should also give a different result from one another.

E.g.

String1 = "Thisisthefirststring"
String2 = "Thisisthesecondstring"

$result1 = "slkjdisuej23ndj90k3n"
$result2 = "dhsj4keod901kdjdnsm"

If the program was the run again the same results would be given.

$result1 = "slkjdisuej23ndj90k3n"
$result2 = "dhsj4keod901kdjdnsm"

What is the best way for me to do this?>

 

Using hashing and rotating functions:

www.php.net/md5
www.php.net/sha1

www.php.net/str_rot13
www.php.net/base64_encode

Reverse it?
www.php.net/strrev

Then cut it using substr:
www.php.net/substr



Jay

 

Thanks thats great