This is not homework and I didn't have a code sample as I was trying to find a way to do this. I have the bits already concatenated. I have a hex MD5hash of the concatenated string.

You gave me the thought to use a Solaris like SUM of the string. So I did this:

$pinc=join("$data1","$data2","$data3");
$digest2 = md5_hex($pinc);
$pin=unpack("%32C*",$digest2) % 65535;

print "[$pinc],[$digest2],[$pin]";
[download]

and I get:

[ilikeyoumy@email.comilikepie]
[be256d5090d0875e7812428991d70026]
[1961]
[download]

This seems to work.

Do you have an opinion on this?

Thanks!

That could result in something larger than 9999 (up to 65535) and it could result in 1, 2, 3 digit pins (you'll never get 0123, but you will get 123).

What's with quotes around variable names?
Why start with the hex form?
Why calculate a hash *and* a checksum?

Using a MD5 hash will produce a good distribution of PINs.
Solution using MD5 hash:

my $pinc = join('', $data1, $data2, $data3);
my $pin = sprintf('%04d', unpack('N', md5($pinc)) % 10000);
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Using CRC32 will *probably* produce a good distribution of PINs, but I don't personally know that.
Using CRC32 will probably be faster than MD5, but it probably won't be noticeable unless you do millions of these in a row.
Solution using CRC32:

my $pinc = join('', $data1, $data2, $data3);
my $pin = sprintf('%04d', unpack('%32C*', $pinc) % 10000);
[download]

I quote the variables as they may contain *@%, etc. I figured it was safer. I started with hex as when I used a straight md5 hash, I did not get 4 digit numbers all the time. I don't entirely understand the code I used, but it worked, so I used it. So, that u=included a hash and a checksum. Why do you use '' as a separator in the join when it works without one? Thanks for the code snippets. I researched the modulus some but did not understand it very well, so I opted for a checksum. I'll probably use one in my application. I am sure you would cringe at the rest of my code. For example, I needed to strip both - and \r\n from a string but never managed to do it in one search/replace. So I had to do in on two lines: $data=~ s/\n\r//g; $data=~ s/-//g; Thanks!