本文整理自网络，侵删。
unit EncryptIt; interface USES Classes; const C1 = 52845; C2 = 22719; function Encrypt(const S: String; Key: Word): String; function Decrypt(const S: String; Key: Word): String; procedure EncryptFile(INFName, OutFName : String; Key : Word); procedure DecryptFile(INFName, OutFName : String; Key : Word); implementation function Encrypt(const S: String; Key: Word): String; var I: Integer; begin Result := S; for I := 1 to Length(S) do begin Result[I] := char(byte(S[I]) xor (Key shr 8)); Key := (byte(Result[I]) + Key) * C1 + C2; end; end; function Decrypt(const S: String; Key: Word): String; var I: Integer; begin Result := S; for I := 1 to Length(S) do begin Result[I] := char(byte(S[I]) xor (Key shr 8)); Key := (byte(S[I]) + Key) * C1 + C2; end; end; procedure EncryptFile(INFName, OutFName : String; Key : Word); VAR MS, SS : TMemoryStream; X : Integer; C : Byte; begin MS := TMemoryStream.Create; SS := TMemoryStream.Create; TRY MS.LoadFromFile(INFName); MS.Position := 0; FOR X := 0 TO MS.Size - 1 DO begin MS.Read(C, 1); C := (C xor (Key shr 8)); Key := (C + Key) * C1 + C2; SS.Write(C,1); end; SS.SaveToFile(OutFName); FINALLY SS.Free; MS.Free; end; end; procedure DecryptFile(INFName, OutFName : String; Key : Word); VAR MS, SS : TMemoryStream; X : Integer; C, O : Byte; begin MS := TMemoryStream.Create; SS := TMemoryStream.Create; TRY MS.LoadFromFile(INFName); MS.Position := 0; FOR X := 0 TO MS.Size - 1 DO begin MS.Read(C, 1); O := C; C := (C xor (Key shr 8)); Key := (O + Key) * C1 + C2; SS.Write(C,1); end; SS.SaveToFile(OutFName); FINALLY SS.Free; MS.Free; end; end; end.
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