{
Copyright:      2002 Hagen Reddmann
Author:        Hagen Reddmann, HaReddmann bei T-Online punkt de
Remarks:        All rights reserved
Version:        open source, developed on D5
Description:    derivate of RC5 stream cipher with internal cipher feedback and stronger keysetup
                includes secure one way pseudo random number generator
}

unit RCx;
{$A+,B-,C-,D-,E-,F-,G+,H+,I-,J+,K-,L-,M-,N+,O+,P+,Q-,R-,S-,T-,U+,V+,W-,X+,Y-,Z1} 

interface

type
  TRCxContext = record
    D: array[Byte] of Byte;
    I,J,F: Byte;
  end;

procedure RCxInit(var RCx: TRCxContext; const Key; KeySize: Integer); overload;
procedure RCxInit(var RCx: TRCxContext; const Key: String); overload;
procedure RCxEncode(var RCx: TRCxContext; const Source; var Dest; Count: Integer); overload;
function RCxEncode(var RCx: TRCxContext; const Value: String): String; overload;
procedure RCxDecode(var RCx: TRCxContext; const Source; var Dest; Count: Integer); overload;
function RCxDecode(var RCx: TRCxContext; const Value: String): String; overload;
procedure RCxDone(var RCx: TRCxContext); overload;

// all in one encode/decode
function RCxEncode(const Value, Password: String): String; overload;
function RCxDecode(const Value, Password: String): String; overload;

// random number generator based on RCx
procedure RCxSeed(const Seed; SeedSize: Integer); overload;
procedure RCxSeed(const Seed: String); overload;
procedure RCxRandomize; overload;
function RCxRandom(Range: Cardinal = 0): Cardinal; overload;
function RCxRandomString(Length: Integer): String; overload;

implementation

uses Windows;

type
  PByteArray = ^TByteArray;
  TByteArray = array[0..MaxInt -1] of Byte;

procedure RCxInit(var RCx: TRCxContext; const Key; KeySize: Integer);
var
  R,S,T,K: Byte;
  L: Integer;
  M: array[Byte] of Byte;
begin
  with RCx do
  try
    L := 0;
    for S := 0 to 255 do
    begin
      D[S] := S;
      M[S] := TByteArray(Key)[S mod KeySize] xor L;
      L := (L + M[S] * 257) mod MaxInt +1;
    end;
    I := 0;
    J := 0;
    R := L;
    F := L shr 8;
    for S := 0 to 255 do
    begin
      Inc(R, D[S] + M[S]);
      T := D[S];
      D[S] := D[R];
      D[R] := T;
    end;
  finally
    R := 0;
    S := 0;
    T := 0;
    L := 0;
    FillChar(M, SizeOf(M), 0);
  end;
end;

procedure RCxInit(var RCx: TRCxContext; const Key: String);
begin
  RCxInit(RCx, Pointer(Key)^, Length(Key));
end;

procedure RCxDone(var RCx: TRCxContext);
begin
  FillChar(RCx, SizeOf(RCx), 0);
end;

procedure RCxEncode(var RCx: TRCxContext; const Source; var Dest; Count: Integer);
var
  S: TByteArray absolute Source;
  O: TByteArray absolute Dest;
  C: Integer;
  T,K: Byte;
begin
  with RCx do
    for C := 0 to Count -1 do
    begin
      Inc(I);
      T := D[I];
      Inc(J, T);
      D[I] := D[J] xor F;
      D[J] := T - F;
      Inc(T, D[I]);

      K := S[C];
      O[C] := K xor D[T];
      F := F xor K;
    end;
end;

procedure RCxDecode(var RCx: TRCxContext; const Source; var Dest; Count: Integer);
var
  S: TByteArray absolute Source;
  O: TByteArray absolute Dest;
  C: Integer;
  T,K: Byte;
begin
  with RCx do
    for C := 0 to Count -1 do
    begin
      Inc(I);
      T := D[I];
      Inc(J, T);
      D[I] := D[J] xor F;
      D[J] := T - F;
      Inc(T, D[I]);

      K := S[C] xor D[T];
      O[C] := K;
      F := F xor K;
    end;
end;

function RCxEncode(var RCx: TRCxContext; const Value: String): String;
var
  Count: Integer;
begin
  Count := Length(Value);
  SetLength(Result, Count);
  RCxEncode(RCx, Value[1], Result[1], Count);
end;

function RCxDecode(var RCx: TRCxContext; const Value: String): String;
var
  Count: Integer;
begin
  Count := Length(Value);
  SetLength(Result, Count);
  RCxDecode(RCx, Value[1], Result[1], Count);
end;

function RCxEncode(const Value, Password: String): String;
var
  RCx: TRCxContext;
begin
  RCxInit(RCx, Password);
  try
    Result := RCxEncode(RCx, Value);
  finally
    RCxDone(RCx);
  end;
end;

function RCxDecode(const Value, Password: String): String;
var
  RCx: TRCxContext;
begin
  RCxInit(RCx, Password);
  try
    Result := RCxDecode(RCx, Value);
  finally
    RCxDone(RCx);
  end;
end;

var
  FRCxRegister: TRCxContext;

procedure RCxSeed(const Seed; SeedSize: Integer);
begin
  RCxInit(FRCxRegister, Seed, SeedSize);
end;

procedure RCxSeed(const Seed: String);
begin
  RCxSeed(Pointer(Seed)^, Length(Seed));
end;

procedure RCxRandomize;
var
  Tick: Cardinal;
begin
  Tick := GetTickCount;
  FRCxRegister.F := Tick;
  FRCxRegister.I := Tick shr 8;
  FRCxRegister.J := Tick shr 16;
  RCxEncode(FRCxRegister, FRCxRegister.D, FRCxRegister.D, SizeOf(FRCxRegister.D));
end;

function RCxRandom(Range: Cardinal): Cardinal;
type
  PCardinal = ^Cardinal;
begin
  RCxEncode(FRCxRegister, FRCxRegister.D, FRCxRegister.D, SizeOf(FRCxRegister.D));
  Result := PCardinal(@FRCxRegister.D)^;
  if Range > 1 then Result := Result mod Range;
end;

function RCxRandomString(Length: Integer): String;
var
  I: Integer;
begin
  SetLength(Result, Length);
  for I := 1 to Length do
  begin
    RCxEncode(FRCxRegister, FRCxRegister.D, FRCxRegister.D, SizeOf(FRCxRegister.D));
    Result[I] := Char(FRCxRegister.D[0]);
  end;
end;

const
  FRCxSeed: TGUID = '{F4D35205-2B59-42B0-8B8F-239855B6DD2B}';
initialization
  RCxSeed(FRCxSeed, SizeOf(FRCxSeed));
finalization
end.