خوارزمية التشفير الشهيرة RC5
كود :
{ *********************************************************************** }
{ }
{ Delphi Encryption Library }
{ Encryption / Decryption stream - RC5 }
{ }
{ Copyright (c) 2004 by Matveev Igor Vladimirovich }
{ With offers and wishes write: teap_leap@mail.ru }
{ }
{ *********************************************************************** }
unit RC5;
interface
uses
SysUtils, Classes;
type
TRC5Block = array[1..2] of LongWord;
const
Rounds = 12;
BlockSize = 8;
BufferSize = 2048;
KeySize = 64;
KeyLength = 2 * (Rounds + 1);
P32 = $b7e15163;
Q32 = $9e3779b9;
var
Key : string;
KeyPtr : PChar;
S : array[0..KeyLength-1] of LongWord;
////////////////////////////////////////////////////////////////////////////////
// Autres fonctions
procedure Initialize(AKey: string); // Initialisation
procedure CalculateSubKeys; // Sous-clés de préparer
function EncipherBlock(var Block): Boolean; // Bloc Encrypt (8 octets)
function DecipherBlock(var Block): Boolean; // Unité de décodage
////////////////////////////////////////////////////////////////////////////////
// Fonction principale
function EncryptCopy(DestStream, SourseStream : TStream; Count: Int64;
Key : string): Boolean; // Chiffrer les données / d'une filière à une autre
function DecryptCopy(DestStream, SourseStream : TStream; Count: Int64;
Key : string): Boolean; // Déchiffrer des données / d'une filière à une autre
function EncryptStream(DataStream: TStream; Count: Int64;
Key: string): Boolean; // Crypter le contenu du flux
function DecryptStream(DataStream: TStream; Count: Int64;
Key: string): Boolean; // Décrypter le flux de contenu
implementation
////////////////////////////////////////////////////////////////////////////////
function ROL(a, s: LongWord): LongWord;
asm
mov ecx, s
rol eax, cl
end;
////////////////////////////////////////////////////////////////////////////////
function ROR(a, s: LongWord): LongWord;
asm
mov ecx, s
ror eax, cl
end;
////////////////////////////////////////////////////////////////////////////////
procedure InvolveKey;
var
TempKey : string;
i, j : Integer;
K1, K2 : LongWord;
begin
// Déployer la clé d'une longueur de 64 caractères
TempKey := Key;
i := 1;
while ((Length(TempKey) mod KeySize) <> 0) do
begin
TempKey := TempKey + TempKey[i];
Inc(i);
end;
// Now shorten the key down to one KeySize block by combining the bytes
i := 1;
j := 0;
while (i < Length(TempKey)) do
begin
Move((KeyPtr+j)^, K1, 4);
Move(TempKey[i], K2, 4);
K1 := ROL(K1, K2) xor K2;
Move(K1, (KeyPtr+j)^, 4);
j := (j + 4) mod KeySize;
Inc(i, 4);
end;
end;
////////////////////////////////////////////////////////////////////////////////
procedure Initialize(AKey: string);
begin
Key := AKey;
GetMem(KeyPtr, KeySize);
FillChar(KeyPtr^, KeySize, #0);
InvolveKey;
end;
////////////////////////////////////////////////////////////////////////////////
{$R-,Q-}
procedure CalculateSubKeys;
var
i, j, k : Integer;
L : array[0..15] of LongWord;
A, B : LongWord;
begin
// Copy the key into L
Move(KeyPtr^, L, KeySize);
// Now initialize the S table
S[0] := P32;
for i := 1 to KeyLength-1 do
S[i] := S[i-1] + Q32;
// Now scramble the S table with the key
i := 0;
j := 0;
A := 0;
B := 0;
for k := 1 to 3*KeyLength do
begin
A := ROL((S[i] + A + B), 3);
S[i] := A;
B := ROL((L[j] + A + B), (A + B));
L[j] := B;
i := (i + 1) mod KeyLength;
j := (j + 1) mod 16;
end;
end;
////////////////////////////////////////////////////////////////////////////////
function EncipherBlock(var Block): Boolean;
var
RC5Block : TRC5Block absolute Block;
i : Integer;
begin
Inc(RC5Block[1], S[0]);
Inc(RC5Block[2], S[1]);
for i := 1 to Rounds do
begin
RC5Block[1] := ROL((RC5Block[1] xor RC5Block[2]), RC5Block[2]) + S[2*i];
RC5Block[2] := ROL((RC5Block[2] xor RC5Block[1]), RC5Block[1]) + S[2*i+1];
end;
Result := TRUE;
end;
////////////////////////////////////////////////////////////////////////////////
function DecipherBlock(var Block): Boolean;
var
RC5Block : TRC5Block absolute Block;
i : Integer;
begin
for i := Rounds downto 1 do
begin
RC5Block[2] := ROR((RC5Block[2]-S[2*i+1]), RC5Block[1]) xor RC5Block[1];
RC5Block[1] := ROR((RC5Block[1]-S[2*i]), RC5Block[2]) xor RC5Block[2];
end;
Dec(RC5Block[2], S[1]);
Dec(RC5Block[1], S[0]);
Result := TRUE;
end;
////////////////////////////////////////////////////////////////////////////////
// Mise en oeuvre des principales fonctions
function EncryptCopy(DestStream, SourseStream : TStream; Count: Int64;
Key : string): Boolean;
var
Buffer : TRC5Block;
PrCount : Int64;
AddCount : Byte;
begin
Result := True;
try
if Key = '' then
begin
DestStream.CopyFrom(SourseStream, Count);
Exit;
end;
Initialize(Key);
CalculateSubKeys;
PrCount := 0;
while Count - PrCount >= 8 do
begin
SourseStream.Read(Buffer, BlockSize);
EncipherBlock(Buffer);
DestStream.Write(Buffer, BlockSize);
Inc(PrCount, 8);
end;
AddCount := Count - PrCount;
if Count - PrCount <> 0 then
begin
SourseStream.Read(Buffer, AddCount);
DestStream.Write(Buffer, AddCount);
end;
except
Result := False;
end;
end;
////////////////////////////////////////////////////////////////////////////////
function DecryptCopy(DestStream, SourseStream : TStream; Count: Int64;
Key : string): Boolean;
var
Buffer : TRC5Block;
PrCount : Int64;
AddCount : Byte;
begin
Result := True;
try
if Key = '' then
begin
DestStream.CopyFrom(SourseStream, Count);
Exit;
end;
Initialize(Key);
CalculateSubKeys;
PrCount := 0;
while Count - PrCount >= 8 do
begin
SourseStream.Read(Buffer, BlockSize);
DecipherBlock(Buffer);
DestStream.Write(Buffer, BlockSize);
Inc(PrCount, 8);
end;
AddCount := Count - PrCount;
if Count - PrCount <> 0 then
begin
SourseStream.Read(Buffer, AddCount);
DestStream.Write(Buffer, AddCount);
end;
except
Result := False;
end;
end;
////////////////////////////////////////////////////////////////////////////////
function EncryptStream(DataStream: TStream; Count: Int64; Key: string): Boolean;
var
Buffer : TRC5Block;
PrCount : Int64;
begin
Result := True;
try
if Key = '' then
begin
DataStream.Seek(Count, soFromCurrent);
Exit;
end;
Initialize(Key);
CalculateSubKeys;
PrCount := 0;
while Count - PrCount >= 8 do
begin
DataStream.Read(Buffer, BlockSize);
EncipherBlock(Buffer);
DataStream.Seek(-BlockSize, soFromCurrent);
DataStream.Write(Buffer, BlockSize);
Inc(PrCount, 8);
end;
except
Result := False;
end;
end;
////////////////////////////////////////////////////////////////////////////////
function DecryptStream(DataStream: TStream; Count: Int64; Key: string): Boolean;
var
Buffer : TRC5Block;
PrCount : Int64;
begin
Result := True;
try
if Key = '' then
begin
DataStream.Seek(Count, soFromCurrent);
Exit;
end;
Initialize(Key);
CalculateSubKeys;
PrCount := 0;
while Count - PrCount >= 8 do
begin
DataStream.Read(Buffer, BlockSize);
DecipherBlock(Buffer);
DataStream.Seek(-BlockSize, soFromCurrent);
DataStream.Write(Buffer, BlockSize);
Inc(PrCount, 8);
end;
except
Result := False;
end;
end;
// Fonctions Fin / main ...
////////////////////////////////////////////////////////////////////////////////
{$R+,Q+}
end.
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