Master of Science thesis Fighting Spam

Exception
{
Debugger.debug(getClass(), 1, "BlindFactors received... User: " + username);
CoinSet coinset = null;
boolean found = false;
int i = 0;
while(i < coinSets.size())
{
coinset = ((CoinSet) coinSets.elementAt(i));
if(coinset.username.equals(username))
{
coinSets.remove(i);
found = true;
break;
}
i++;
}
//Not found?
if(!found)
{
String error =
"Username unknown. Probably a BlindingFactorPacket was sent before the
corresponding CurrencyExchangePacket.";
Debugger.debug(getClass(), 1, error);
throw new Exception(error);
}
//Validate certificate
try
{
Debugger.debug(getClass(), 1, "Verifying the certificate...");
cp.certificate.verify(RSPublicKey);
}
catch(Exception e)
{
String error = "The certificate supplied is invalid. Verification of the RS
signature failed.";
Debugger.debug(getClass(), 1, error);
throw new Exception(error);
}
Debugger.debug(getClass(), 1, "Certificate succesfully verified.");
//Calculate the amount of the coins on the way
boolean amountAddedForSet = false;
double amount = 0.0;
Debugger.debug(getClass(), 1, "Unblinding and verifying the coins....");
//Check that all coins are the same (except the blinded one in each set).
for(int c = 0; c < coinset.blindedCoins.length; c++)
{
amountAddedForSet = false;
//This loop goes through the coins in each set
//Since the sets MUST be the same size, the loop runs to coins[0].lenght and
not coins[c].length
for(int r = 0; r < coinset.blindedCoins[0].length; r++)
{
//Do we have a blindingfactor?
if(r != coinset.blindingFactorIndexes[c])
{
Debugger.debug(getClass(), 1,
"Verifying coin " + (1 + c *
coinset.blindedCoins[0].length + r) + " of "
+ (coinset.blindedCoins.length *
coinset.blindedCoins[0].length) + "...");
//Check the contents of the coin
compareCoins(coinset.blindedCoins[c][r], cp.getRSABlindingFactor(c,
r), cp.coins[c][r],
cp.certificate);
//Calculate the amount of all the coins
if(!amountAddedForSet)
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