private static bool EvalAddPopularPasswordPattern(List <QePatternInstance>[] vPatterns,
char[] vPassword, int i, char[] vSub, double dblCostPerMod)
{
ulong uDictSize;
if (!PopularPasswords.IsPopularPassword(vSub, out uDictSize))
{
return(false);
}
int n = vSub.Length;
int d = HammingDistribution(vSub, 0, vPassword, i, n);
double dblCost = Log2((double)uDictSize);
// dblCost += log2(n binom d)
int k = Math.Min(d, n - d);
for (int j = n; j > (n - k); --j)
{
dblCost += Log2(j);
}
for (int j = k; j >= 2; --j)
{
dblCost -= Log2(j);
}
dblCost += dblCostPerMod * (double)d;
vPatterns[i].Add(new QePatternInstance(i, n, PatternId.Dictionary,
dblCost));
return(true);
}
private static void FindPopularPasswords(char[] password, List <QePatternInstance>[] patterns)
{
var passwordLength = password.Length;
var lower = new char[passwordLength];
var leet = new char[passwordLength];
for (var index = 0; index < passwordLength; ++index)
{
var character = password[index];
lower[index] = char.ToLower(character);
leet[index] = char.ToLower(DecodeLeetChar(character));
}
var erased = default(char);
Debug.Assert(erased == char.MinValue);
var maximumLength = Math.Min(passwordLength, PopularPasswords.MaxLength);
for (var subLength = maximumLength; subLength >= 3; --subLength)
{
if (!PopularPasswords.ContainsLength(subLength))
{
continue;
}
var substring = new char[subLength];
for (var index = 0; index <= (passwordLength - subLength); ++index)
{
if (Array.IndexOf(lower, erased, index, subLength) >= 0)
{
continue;
}
Array.Copy(lower, index, substring, 0, subLength);
if (!EvalAddPopularPasswordPattern(patterns, password, index, substring, 0.0))
{
Array.Copy(leet, index, substring, 0, subLength);
if (EvalAddPopularPasswordPattern(patterns, password, index, substring, 1.5))
{
Array.Clear(lower, index, subLength);
Debug.Assert(lower[index] == erased);
}
}
else
{
Array.Clear(lower, index, subLength);
Debug.Assert(lower[index] == erased);
}
}
}
}
