Title: How to encrypt text using key numbers
function Encrypt(Text : string; Key1, Key2, Key3, Key4 : Integer) : string;
var
BufS, Hexa, Hexa1, Hexa2 : string;
BufI, BufI2, Sc, Sl, Num1, Num2, Num3, Num4, Res1, Res2, Res3, Res4 : Integer;
begin
Sl := Length(Text);
Sc := 0;
BufS := '';
if (Key1 in [1 .. 120]) and (Key2 in [1 .. 120]) and (Key3 in [1 .. 120]) and (Key4 in [1 .. 120]) then
begin
BufI := Key1 * Key4;
BufI2 := Key3 * Key2;
BufI := BufI - BufI2;
if BufI = 0 then
begin
Result := '';
Exit;
end;
end
else
begin
Result := '';
Exit;
end;
repeat
Inc(Sc);
if Sc Sl then Num1 := 0 else Num1 := Ord(Text[Sc]);
Inc(Sc);
if Sc Sl then Num2 := 0 else Num2 := Ord(Text[Sc]);
Inc(Sc);
if Sc Sl then Num3 := 0 else Num3 := Ord(Text[Sc]);
Inc(sc);
if Sc Sl then Num4 := 0 else Num4 := Ord(Text[Sc]);
Res1 := Num1 * Key1;
BufI := Num2 * Key3;
Res1 := Res1 + BufI;
Res2 := Num1 * Key2;
BufI := Num2 * Key4;
Res2 := Res2 + BufI;
Res3 := Num3 * Key1;
BufI := Num4 * Key3;
Res3 := Res3 + BufI;
Res4 := Num3 * Key2;
BufI := Num4 * Key4;
Res4 := Res4 + BufI;
for BufI := 1 to 4 do
begin
case BufI of
1 : Hexa := IntToHex(Res1, 4);
2 : Hexa := IntToHex(Res2, 4);
3 : Hexa := IntToHex(Res3, 4);
4 : Hexa := IntToHex(Res4, 4);
end;
Hexa1 := '$' + Hexa[1] + Hexa[2];
Hexa2 := '$' + Hexa[3] + Hexa[4];
if (Hexa1 = '$00') and (Hexa2 = '$00') then
begin
Hexa1 := '$FF';
Hexa2 := '$FF';
end;
if Hexa1 = '$00' then Hexa1 := '$FE';
if Hexa2 = '$00' then
begin
Hexa2 := Hexa1;
Hexa1 := '$FD';
end;
BufS := BufS + Chr(StrToInt(Hexa1)) + Chr(StrToInt(Hexa2));
end;
until Sc = Sl;
Result := BufS;
end;
function Decrypt(Text : string; Key1, Key2, Key3, Key4 : Integer) : string;
var
BufS, Hexa1, Hexa2 : string;
BufI, BufI2, Divzr, Sc, Sl, Num1, Num2, Num3, Num4, Res1, Res2, Res3, Res4 : Integer;
begin
Sl := Length(Text);
Sc := 0;
BufS := '';
if (Key1 in [1 .. 120]) and (Key2 in [1 .. 120]) and (Key3 in [1 .. 120]) and (Key4 in [1 .. 120]) then
begin
Divzr := Key1 * Key4;
BufI2 := Key3 * Key2;
Divzr := Divzr - BufI2;
if Divzr = 0 then
begin
Result := '';
Exit;
end;
end
else
begin
Result := '';
Exit;
end;
repeat
for BufI := 1 to 4 do
begin
Inc(Sc);
Hexa1 := IntToHex(Ord(Text[Sc]), 2);
Inc(Sc);
Hexa2 := IntToHex(Ord(Text[Sc]), 2);
if Hexa1 = 'FF' then
begin
Hexa1 := '00';
Hexa2 := '00';
end;
if Hexa1 = 'FE' then Hexa1 := '00';
if Hexa1 = 'FD' then
begin
Hexa1 := Hexa2;
Hexa2 := '00';
end;
case BufI of
1 : Res1 := StrToInt('$' + Hexa1 + Hexa2);
2 : Res2 := StrToInt('$' + Hexa1 + Hexa2);
3 : Res3 := StrToInt('$' + Hexa1 + Hexa2);
4 : Res4 := StrToInt('$' + Hexa1 + Hexa2);
end;
end;
BufI := Res1 * Key4;
BufI2 := Res2 * Key3;
Num1 := BufI - BufI2;
Num1 := Num1 div Divzr;
BufI := Res2 * Key1;
BufI2 := Res1 * Key2;
Num2 := BufI - BufI2;
Num2 := Num2 div Divzr;
BufI := Res3 * Key4;
BufI2 := Res4 * Key3;
Num3 := BufI - BufI2;
Num3 := Num3 div Divzr;
BufI := Res4 * Key1;
BufI2 := Res3 * Key2;
Num4 := BufI - BufI2;
Num4 := Num4 div Divzr;
BufS := BufS + Chr(Num1) + Chr(Num2) + Chr(Num3) + Chr(Num4);
until Sc = Sl;
Result := BufS;
end;