unit EZCrypt;

interface

uses Windows, Classes;

type
TWordTriple = Array[0..2] of Word;

function FileEncrypt(InFile, OutFile: String; Key: TWordTriple): boolean;
function FileDecrypt(InFile, OutFile: String; Key: TWordTriple): boolean;
function TextEncrypt(const s: string; Key: TWordTriple): string;
function TextDecrypt(const s: string; Key: TWordTriple): string;
function MemoryEncrypt(Src: Pointer; SrcSize: Cardinal; Target: Pointer; TargetSize: Cardinal; Key: TWordTriple): boolean;
function MemoryDecrypt(Src: Pointer; SrcSize: Cardinal; Target: Pointer; TargetSize: Cardinal; Key: TWordTriple): boolean;

implementation

function MemoryEncrypt(Src: Pointer; SrcSize: Cardinal; Target: Pointer; TargetSize: Cardinal; Key: TWordTriple): boolean;
var
pIn, pOut: ^byte;
i : Cardinal;
begin
if SrcSize = TargetSize then
begin
pIn := Src;
pOut := Target;
for i := 1 to SrcSize do
begin
pOut^ := pIn^ xor (Key[2] shr 8);
Key[2] := Byte(pIn^ + Key[2]) * Key[0] + Key[1];
inc(pIn);
inc(pOut);
end;
Result := True;
end else
Result := False;
end;

function MemoryDecrypt(Src: Pointer; SrcSize: Cardinal; Target: Pointer; TargetSize: Cardinal; Key: TWordTriple): boolean;
var
pIn, pOut: ^byte;
i : Cardinal;
begin
if SrcSize = TargetSize then
begin
pIn := Src;
pOut := Target;
for i := 1 to SrcSize do
begin
pOut^ := pIn^ xor (Key[2] shr 8);
Key[2] := byte(pOut^ + Key[2]) * Key[0] + Key[1];
inc(pIn);
inc(pOut);
end;
Result := True;
end else
Result := False;
end;

function TextCrypt(const s: string; Key: TWordTriple; Encrypt: Boolean): string;
var
bOK: Boolean;
begin
SetLength(Result, Length(s));
if Encrypt then
bOK := MemoryEncrypt(PChar(s), Length(s), PChar(Result), Length(Result), Key)
else
bOK := MemoryDecrypt(PChar(s), Length(s), PChar(Result), Length(Result), Key);
if not bOK then Result := '';
end;

function FileCrypt(InFile, OutFile: String; Key: TWordTriple; Encrypt: Boolean): boolean;
var
MIn, MOut: TMemoryStream;
begin
MIn := TMemoryStream.Create;
MOut := TMemoryStream.Create;
Try
MIn.LoadFromFile(InFile);
MOut.SetSize(MIn.Size);
if Encrypt then
Result := MemoryEncrypt(MIn.Memory, MIn.Size, MOut.Memory, MOut.Size, Key)
else
Result := MemoryDecrypt(MIn.Memory, MIn.Size, MOut.Memory, MOut.Size, Key);
MOut.SaveToFile(OutFile);
finally
MOut.Free;
MIn.Free;
end;
end;

function TextEncrypt(const s: string; Key: TWordTriple): string;
begin
Result := TextCrypt(s, Key, True);
end;

function TextDecrypt(const s: string; Key: TWordTriple): string;
begin
Result := TextCrypt(s, Key, False);
end;

function FileEncrypt(InFile, OutFile: String; Key: TWordTriple): boolean;
begin
Result := FileCrypt(InFile, OutFile, Key, True);
end;

function FileDecrypt(InFile, OutFile: String; Key: TWordTriple): boolean;
begin
Result := FileCrypt(InFile, OutFile, Key, False);
end;