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 = HammingDist(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[] vPassword,
List <QePatternInstance>[] vPatterns)
{
int n = vPassword.Length;
char[] vLower = new char[n];
char[] vLeet = new char[n];
for (int i = 0; i < n; ++i)
{
char ch = vPassword[i];
vLower[i] = char.ToLower(ch);
vLeet[i] = char.ToLower(DecodeLeetChar(ch));
}
char chErased = default(char); // The value that Array.Clear uses
Debug.Assert(chErased == char.MinValue);
int nMaxLen = Math.Min(n, PopularPasswords.MaxLength);
for (int nSubLen = nMaxLen; nSubLen >= 3; --nSubLen)
{
if (!PopularPasswords.ContainsLength(nSubLen))
{
continue;
}
char[] vSub = new char[nSubLen];
for (int i = 0; i <= (n - nSubLen); ++i)
{
if (Array.IndexOf <char>(vLower, chErased, i, nSubLen) >= 0)
{
continue;
}
Array.Copy(vLower, i, vSub, 0, nSubLen);
if (!EvalAddPopularPasswordPattern(vPatterns, vPassword,
i, vSub, 0.0))
{
Array.Copy(vLeet, i, vSub, 0, nSubLen);
if (EvalAddPopularPasswordPattern(vPatterns, vPassword,
i, vSub, 1.5))
{
Array.Clear(vLower, i, nSubLen); // Not vLeet
Debug.Assert(vLower[i] == chErased);
}
}
else
{
Array.Clear(vLower, i, nSubLen);
Debug.Assert(vLower[i] == chErased);
}
}
MemUtil.ZeroArray <char>(vSub);
}
MemUtil.ZeroArray <char>(vLower);
MemUtil.ZeroArray <char>(vLeet);
}