user16888: For Bitcoin it is common knowledge that 6 confirmations suffices. For the hundred of Alt Coins however, I'm not sure what the best practise to be protected enough from double-spents and the likes is.
I saw Bter.com requires different confirmations varying on which Altcoin you want to deposit.
For example COMM-coin requires 10 confirmations, but BBQ coin 6, and Infinitecoin only 4.
Is there a mathematical method behind this? How do they know how many confirmations to require?

user7043: Yes, there is a mathematical grounding behind this, namely Poisson distribution. See Satoshi's original paper (last pages) for some details about calculating the odds of a successful double spend attack given a certain portion of the networks computation capacity. This also means of course that networks with a larger hashing power are more susceptible to an attack than networks with lower hashing power.

16888: <p>For Bitcoin it is common knowledge that 6 confirmations suffices. For the hundred of Alt Coins however, I'm not sure what the best practise to be protected enough from double-spents and the likes is.</p>

<p>I saw Bter.com requires different confirmations varying on which Altcoin you want to deposit.</p>

<p>For example COMM-coin requires 10 confirmations, but BBQ coin 6, and Infinitecoin only 4.</p>

<p>Is there a mathematical method behind this? How do they know how many confirmations to require?</p>
 7043: <p>Yes, there is a mathematical grounding behind this, namely <a href="http://en.wikipedia.org/wiki/Poisson_distribution" rel="nofollow">Poisson distribution</a>. See <a href="https://bitcoin.org/bitcoin.pdf" rel="nofollow">Satoshi's original paper</a> (last pages) for some details about calculating the odds of a successful double spend attack given a certain portion of the networks computation capacity. This also means of course that networks with a larger hashing power are more susceptible to an attack than networks with lower hashing power.</p>
