Yes I read that. I'm a noob when it comes to cryptography. How do you actually verify it? Is there software for this?
EDIT: Ok, I guess maybe I'm being unclear. Here is an example of a previous transaction from SatoshiDice.
http://www.satoshidice.com/full.php?tx=38f381893d3cdcc8f7ea3e11d098f8e7b4daa60e904a62ef0ab4798fa996def8hmac_sha512(nJawTR7RIrciXb3JIYp9Qoh7YJ1QALxlnQJw3veDN4UkecWcMNa2woxV6y891GXz,38f381893d3cdcc8f7ea3e11d098f8e7b4daa60e904a62ef0ab4798fa996def8) -> 003edf82a3b5a6680a6ede36a573cbf59f7f8d9f1200884755573c66d6d68190
003e -> 62
So that's lucky number was 62. How do you get from:
ThisnJawTR7RIrciXb3JIYp9Qoh7YJ1QALxlnQJw3veDN4UkecWcMNa2woxV6y891GX
And this38f381893d3cdcc8f7ea3e11d098f8e7b4daa60e904a62ef0ab4798fa996def8
To this003edf82a3b5a6680a6ede36a573cbf59f7f8d9f1200884755573c66d6d68190
Do we just take it for granted that this is somehow correct?
Download and install Python. It's free, and comes with all the crypto libraries you need.
Then you can calculate lucky numbers for yourself, as follows.
Your example is from before the rule-change of Jan 3rd. Before then, all the bets in a transaction got the same lucky number. Here's how you would calculate it for your example (the bold parts are the parts you type). See how it spits out '62' at the end?
$ python
Python 2.7.3 (default, Sep 26 2012, 21:51:14)
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import hashlib, hmac
>>> txid = '38f381893d3cdcc8f7ea3e11d098f8e7b4daa60e904a62ef0ab4798fa996def8'
>>> secret = 'nJawTR7RIrciXb3JIYp9Qoh7YJ1QALxlnQJw3veDN4UkecWcMNa2woxV6y891GXz'
>>> int(hmac.new(secret, txid, hashlib.sha512).hexdigest()[:4], 16)
62
>>>
For bets made after Jan 2nd 2013, the lucky number is different for each bet in the transaction, so you need to specify the output number (nout), as follows. Let's use
a bet I made as an example, and calculate all 10 lucky numbers:
$ python
Python 2.7.3 (default, Sep 26 2012, 21:51:14)
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import hashlib, hmac
>>> txid = 'df7a5cb1ed439f1e0f314cfed88f77ab0f0fdf4a4d2e4714a8287834791fbd95'
>>> secret = 'DIGtgGbebAIjJeuh1tlzMW5Xzs8ds0V9azgs40JvWOd24NpFEttZEFM32OHgEqFd'
>>> for nout in range(10): print nout, int(hmac.new(secret, "%s:%d" % (txid, nout), hashlib.sha512).hexdigest()[:4], 16)
0 10351
1 37909
2 63099
3 19569
4 13550
5 36796
6 28032
7 53908
8 64653
9 36560
>>>
See how they match up with the numbers shown on the SD page (although the SD page shows them in the wrong order, it does now show the 'Idx' column so you can match them up):
Thank you dooglus for explaining this so clearly! I didn't realize SD allows you to split a single transaction into multiple bets now. From what I understand, there was an update to the Bitcoin network not too long ago that doesn't actually allow you to use the exact same transaction ID twice.
