Thanks for your answer. I'll try to add a more protective way to encrypt data sent.
30 days was ab arbitrary delay, I'll change it to 2 days after the transaction has been completed.
For now, I don't have any mechanism against tainted coins.
I got a small amount of bitcoins (less than 2BTC) on my account so, you can't get the same coins you sent me.
I've developped a solid algorythm for that.
For example
A sends 1BTC.
* BitLaundry sends A 1BTC from the "bank".
* Bank total amount is now 2BTC (but dillued).
B sends 0.5BTC.
* BitLaundry sends B 0.5BTC from the "bank" (A + amount before).
* Bank total amount is now 2BTC (but dillued).
C sends 0.3BTC.
* BitLaundry sends C 0.3BTC from the "bank" (A + B + amount before).
* Bank total amount is now 2BTC (but dillued).
D sends 1BTC.
* BitLaundry sends D 1BTC from the "bank" (A + B + C + amount before).
* Bank total amount is now 2BTC (but dillued).
Maybe show how diluted the bank is (like X BTC spreaded over X Addresses), but for mixer this requires a lot of volume, and you should have a back up plan.