function PassphraseQuality(
const Password :
string): Extended;
// returns computed Quality in range 0.0 to 1.0
// source extracted from Delphi Encryption Compendium, DEC
// Convert to Delphi 2009 by Fabian (Nickname: xZise)
function Diff(
const AWord1, AWord2 : Word) : Word;
overload;
begin
if AWord1 > AWord2
then
Result := AWord1 - AWord2
else
Result := AWord2 - AWord1;
end;
function Diff(
const AByte1, AByte2 : Byte) : Byte;
overload;
begin
if AByte1 > AByte2
then
Result := AByte1 - AByte2
else
Result := AByte2 - AByte1;
end;
{$IFDEF Unicode}
function Entropy(P: PWordArray; L: Integer): Extended;
{$ELSE}
function Entropy(P: PByteArray; L: Integer): Extended;
{$ENDIF}
var
Freq: Extended;
I: Integer;
{$IFDEF Unicode}
Accu:
array [Word]
of LongWord;
{$ELSE}
Accu:
array [Byte]
of LongWord;
{$ENDIF}
begin
Result := 0.0;
if L <= 0
then Exit;
FillChar(Accu, SizeOf(Accu), 0);
for I := 0
to L-1
do Inc(Accu[P[I]]);
for I := 0
to High(Accu)
do
if Accu[I] <> 0
then
begin
Freq := Accu[I] / L;
Result := Result - Freq * (Ln(Freq) / Ln(2));
end;
end;
function Differency: Extended;
var
S:
string;
L,I: Integer;
begin
Result := 0.0;
L := Length(Password);
if L <= 1
then Exit;
SetLength(S, L-1);
for I := 2
to L
do
begin
{$IFDEF Unicode}
Word(S[I-1]) := Diff(Word(Password[I-1]), Word(Password[I]));
{$ELSE}
Byte(S[I-1]) := Diff(Byte(Password[I-1]), Byte(Password[I]));
{$ENDIF}
end;
Result := Entropy(Pointer(S), Length(S));
end;
function KeyDiff: Extended;
const
TableDE = '
^1234567890ß´qwertzuiopü+asdfghjklöä#<yxcvbnm,.-°!"§$%&/()=?`QWERTZUIOPÜ*ASDFGHJKLÖÄ''
>YXCVBNM;:_';
var
S:
string;
L,I,J: Integer;
begin
Result := 0.0;
L := Length(Password);
if L <= 1
then Exit;
S := Password;
UniqueString(S);
for I := 1
to L
do
begin
J := Pos(S[I], TableDE);
if J > 0
then S[I] := Char(J);
end;
for I := 2
to L
do
begin
{$IFDEF Unicode}
Word(S[I-1]) := Diff(Word(S[I-1]), Word(S[I]));
{$ELSE}
Byte(S[I-1]) := Diff(Byte(S[I-1]), Byte(S[I]));
{$ENDIF}
end;
Result := Entropy(Pointer(S), L-1);
end;
const
GoodLength = 10.0;
// good length of Passphrases
var
L: Extended;
begin
Result := Entropy(Pointer(Password), Length(Password));
if Result <> 0
then
begin
Result := Result * (Ln(Length(Password)) / Ln(GoodLength));
L := KeyDiff + Differency;
if L <> 0
then L := L / 64;
Result := Result * L;
if Result < 0
then Result := -Result;
if Result > 1
then Result := 1;
end;
end;