fgint.pas

RSA的加密算法的应用DEMO 也是用来加密的。

   str2 := '';
   initialize8(trans);
   For i := 1 To length(str256) Do str2 := str2 + trans[ord(str256[i])];
End;


Procedure ConvertBase64to2(Const str64 : String; Var str2 : String);
Var
   trans : Array[0..255] Of String;
   i : longint;
Begin
   str2 := '';
   initialize6(trans);
   For i := 1 To length(str64) Do str2 := str2 + trans[ord(str64[i])];
End;


Procedure ConvertBase2to256(str2 : String; Var str256 : String);
Var
   i, len8 : longint;
   g : char;
Begin
   str256 := '';
   While (length(str2) Mod 8) <> 0 Do str2 := '0' + str2;
   len8 := length(str2) Div 8;
   For i := 1 To len8 Do
   Begin
      zeronetochar8(g, copy(str2, 1, 8));
      str256 := str256 + g;
      delete(str2, 1, 8);
   End;
End;


Procedure ConvertBase2to64(str2 : String; Var str64 : String);
Var
   i, len6 : longint;
   g : integer;
Begin
   str64 := '';
   While (length(str2) Mod 6) <> 0 Do str2 := '0' + str2;
   len6 := length(str2) Div 6;
   For i := 1 To len6 Do
   Begin
      zeronetochar6(g, copy(str2, 1, 6));
      str64 := str64 + chr64[g];
      delete(str2, 1, 6);
   End;
End;


// Convert base 256 strings to base 16 (HexaDecimal) strings and visa versa

Procedure ConvertBase256StringToHexString(Str256 : String; Var HexStr : String);
Var
   i : longint;
   b : byte;
Begin
   HexStr := '';
   For i := 1 To length(str256) Do
   Begin
      b := ord(str256[i]);
      If (b Shr 4) < 10 Then HexStr := HexStr + chr(48 + (b Shr 4))
      Else HexStr := HexStr + chr(55 + (b Shr 4));
      If (b And 15) < 10 Then HexStr := HexStr + chr(48 + (b And 15))
      Else HexStr := HexStr + chr(55 + (b And 15));
   End;
End;


Procedure ConvertHexStringToBase256String(HexStr : String; Var Str256 : String);
Var
   i : longint;
   b, h1, h2 : byte;
Begin
   Str256 := '';
   For i := 1 To (length(Hexstr) Div 2) Do
   Begin
      h2 := ord(HexStr[2 * i]);
      h1 := ord(HexStr[2 * i - 1]);
      If h1 < 58 Then b := ((h1 - 48) Shl 4) Else b := ((h1 - 55) Shl 4);
      If h2 < 58 Then b := (b Or (h2 - 48)) Else b := (b Or (h2 - 55));
      Str256 := Str256 + chr(b);
   End;
End;


// Convert base 256 strings to base 64 strings and visa versa, PGP style

Procedure PGPConvertBase256to64(Var str256, str64 : String);
Var
   temp, x, a : String;
   i, len6 : longint;
   g : integer;
   trans : Array[0..255] Of String;
Begin
   initialize8(trans);
   temp := '';
   For i := 1 To length(str256) Do temp := temp + trans[ord(str256[i])];
   If (length(temp) Mod 6) = 0 Then a := '' Else
      If (length(temp) Mod 6) = 4 Then
      Begin
         temp := temp + '00';
         a := '='
      End
      Else
      Begin
         temp := temp + '0000';
         a := '=='
      End;
   str64 := '';
   len6 := length(temp) Div 6;
   For i := 1 To len6 Do
   Begin
      x := copy(temp, 1, 6);
      zeronetochar6(g, x);
      str64 := str64 + PGPchr64[g];
      delete(temp, 1, 6);
   End;
   str64 := str64 + a;
End;


Procedure PGPConvertBase64to256(str64 : String; Var str256 : String);
Var
   temp, x : String;
   i, j, len8 : longint;
   g : char;
   trans : Array[0..255] Of String;
Begin
   initialize6PGP(trans);
   temp := '';
   str256 := '';
   If str64[length(str64) - 1] = '=' Then j := 2 Else
      If str64[length(str64)] = '=' Then j := 1 Else j := 0;
   For i := 1 To (length(str64) - j) Do temp := temp + trans[ord(str64[i])];
   If j <> 0 Then delete(temp, length(temp) - 2 * j + 1, 2 * j);
   len8 := length(temp) Div 8;
   For i := 1 To len8 Do
   Begin
      x := copy(temp, 1, 8);
      zeronetochar8(g, x);
      str256 := str256 + g;
      delete(temp, 1, 8);
   End;
End;

// Convert base 64 strings to base 2 strings, PGP style


Procedure PGPConvertBase64to2(str64 : String; Var str2 : String);
Var
   i, j : longint;
   trans : Array[0..255] Of String;
Begin
   str2 := '';
   initialize6(trans);
   If str64[length(str64) - 1] = '=' Then j := 2 Else
      If str64[length(str64)] = '=' Then j := 1 Else j := 0;
   For i := 1 To (length(str64) - j) Do str2 := str2 + trans[ord(str64[i])];
   delete(str2, length(str2) - 2 * j + 1, 2 * j);
End;


// Convert a base 10 string to a FGInt

Procedure Base10StringToFGInt(Base10 : String; Var FGInt : TFGInt);
Var
   i, size : longint;
   j : int64;
   S : String;
   sign : TSign;

   Procedure GIntDivByIntBis1(Var GInt : TFGInt; by : int64; Var modres : int64);
   Var
      i, size : longint;
      rest : int64;
   Begin
      size := GInt.Number[0];
      modres := 0;
      For i := size Downto 1 Do
      Begin
         modres := modres * 1000000000;
         rest := modres + GInt.Number[i];
         GInt.Number[i] := rest Div by;
         modres := rest Mod by;
      End;
      While (GInt.Number[size] = 0) And (size > 1) Do size := size - 1;
      If size <> GInt.Number[0] Then
      Begin
         SetLength(GInt.Number, size + 1);
         GInt.Number[0] := size;
      End;
   End;

Begin
   While (Not (Base10[1] In ['-', '0'..'9'])) And (length(Base10) > 1) Do
      delete(Base10, 1, 1);
   If copy(Base10, 1, 1) = '-' Then
   Begin
      Sign := negative;
      delete(Base10, 1, 1);
   End
   Else Sign := positive;
   While (length(Base10) > 1) And (copy(Base10, 1, 1) = '0') Do delete(Base10, 1, 1);
   size := length(Base10) Div 9;
   If (length(Base10) Mod 9) <> 0 Then size := size + 1;
   SetLength(FGInt.Number, size + 1);
   FGInt.Number[0] := size;
   For i := 1 To size - 1 Do
   Begin
      FGInt.Number[i] := StrToInt(copy(Base10, length(Base10) - 8, 9));
      delete(Base10, length(Base10) - 8, 9);
   End;
   FGInt.Number[size] := StrToInt(Base10);

   S := '';
   While (FGInt.Number[0] <> 1) Or (FGInt.Number[1] <> 0) Do
   Begin
      GIntDivByIntBis1(FGInt, 2, j);
      S := inttostr(j) + S;
   End;
   S := '0' + S;
   FGIntDestroy(FGInt);
   Base2StringToFGInt(S, FGInt);
   FGInt.Sign := sign;
End;


// Convert a FGInt to a base 10 string

Procedure FGIntToBase10String(Const FGInt : TFGInt; Var Base10 : String);
Var
   S : String;
   j : int64;
   temp : TFGInt;
Begin
   FGIntCopy(FGInt, temp);
   Base10 := '';
   While (temp.Number[0] > 1) Or (temp.Number[1] > 0) Do
   Begin
      FGIntDivByIntBis(temp, 1000000000, j);
      S := IntToStr(j);
      While Length(S) < 9 Do S := '0' + S;
      Base10 := S + Base10;
   End;
   Base10 := '0' + Base10;
   While (length(Base10) > 1) And (Base10[1] = '0') Do delete(Base10, 1, 1);
   If FGInt.Sign = negative Then Base10 := '-' + Base10;
End;



// Destroy a FGInt to free memory

Procedure FGIntDestroy(Var FGInt : TFGInt);
Begin
   FGInt.Number := Nil;
End;


// Compare 2 FGInts in absolute value, returns
// Lt if FGInt1 > FGInt2, St if FGInt1 < FGInt2, Eq if FGInt1 = FGInt2,
// Er otherwise

Function FGIntCompareAbs(Const FGInt1, FGInt2 : TFGInt) : TCompare;
Var
   size1, size2, i : longint;
Begin
   FGIntCompareAbs := Er;
   size1 := FGInt1.Number[0];
   size2 := FGInt2.Number[0];
   If size1 > size2 Then FGIntCompareAbs := Lt Else
      If size1 < size2 Then FGIntCompareAbs := St Else
      Begin
         i := size2;
         While (FGInt1.Number[i] = FGInt2.Number[i]) And (i > 1) Do i := i - 1;
         If FGInt1.Number[i] = FGInt2.Number[i] Then FGIntCompareAbs := Eq Else
            If FGInt1.Number[i] < FGInt2.Number[i] Then FGIntCompareAbs := St Else
               If FGInt1.Number[i] > FGInt2.Number[i] Then FGIntCompareAbs := Lt;
      End;
End;


// Add 2 FGInts, FGInt1 + FGInt2 = Sum

Procedure FGIntAdd(Const FGInt1, FGInt2 : TFGInt; Var Sum : TFGInt);
Var
   i, size1, size2, size : longint;
   rest : integer;
   Trest : int64;
Begin
   size1 := FGInt1.Number[0];
   size2 := FGInt2.Number[0];
   If size1 < size2 Then FGIntAdd(FGInt2, FGInt1, Sum) Else
   Begin
      If FGInt1.Sign = FGInt2.Sign Then
      Begin
         Sum.Sign := FGInt1.Sign;
         SetLength(Sum.Number, size1 + 2);
         rest := 0;
         For i := 1 To size2 Do
         Begin
            Trest := FGInt1.Number[i] + FGInt2.Number[i] + rest;
            Sum.Number[i] := Trest And 2147483647;
            rest := Trest Shr 31;
         End;
         For i := (size2 + 1) To size1 Do
         Begin
            Trest := FGInt1.Number[i] + rest;
            Sum.Number[i] := Trest And 2147483647;
            rest := Trest Shr 31;
         End;
         size := size1 + 1;
         Sum.Number[0] := size;
         Sum.Number[size] := rest;
         While (Sum.Number[size] = 0) And (size > 1) Do size := size - 1;
         If Sum.Number[0] > size Then SetLength(Sum.Number, size + 1);
         Sum.Number[0] := size;
      End
      Else
      Begin
         If FGIntCompareAbs(FGInt2, FGInt1) = Lt Then FGIntAdd(FGInt2, FGInt1, Sum)
         Else
         Begin
            SetLength(Sum.Number, size1 + 1);
            rest := 0;
            For i := 1 To size2 Do
            Begin
               Trest := 2147483648 + FGInt1.Number[i] - FGInt2.Number[i] + rest;
               Sum.Number[i] := Trest And 2147483647;
               If (Trest > 2147483647) Then rest := 0 Else rest := -1;
            End;
            For i := (size2 + 1) To size1 Do
            Begin
               Trest := 2147483648 + FGInt1.Number[i] + rest;
               Sum.Number[i] := Trest And 2147483647;