求RC4 加密算法详细原理

RC4 算法是RSA公司的，不过没有注册版权。
不知谁有详细的原理说明。

#include <stdio.h>#define buf_size 1024typedef struct rc4_key
{
   unsigned char state[256];
   unsigned char x;
   unsigned char y;
} rc4_key;#define swap_byte(x,y) t = *(x); *(x) = *(y); *(y) = tvoid prepare_key(unsigned char *key_data_ptr, int key_data_len, rc4_key *key)
{
  int i;
  unsigned char t;
  unsigned char swapByte;
  unsigned char index1;
  unsigned char index2;
  unsigned char* state;
  short counter;  state = &key->state[0];
  for(counter = 0; counter < 256; counter++)
  state[counter] = counter;
  key->x = 0;
  key->y = 0;
  index1 = 0;
  index2 = 0;
  for(counter = 0; counter < 256; counter++)
  {
    index2 = (key_data_ptr[index1] + state[counter] + index2) % 256;
    swap_byte(&state[counter], &state[index2]);
    index1 = (index1 + 1) % key_data_len;
  }
}void rc4(unsigned char *buffer_ptr, int buffer_len, rc4_key *key)
{
  unsigned char t;
  unsigned char x;
  unsigned char y;
  unsigned char* state;
  unsigned char xorIndex;
  short counter;  x = key->x;
  y = key->y;
  state = &key->state[0];
  for(counter = 0; counter < buffer_len; counter++)
  {
    x = (x + 1) % 256;
    y = (state[x] + y) % 256;
    swap_byte(&state[x], &state[y]);
    xorIndex = (state[x] + state[y]) % 256;
    buffer_ptr[counter] ^= state[xorIndex];
  }
  key->x = x;
  key->y = y;
}int main(int argc, char* argv[])
{
  char seed[256];
  char data[512];
  char buf[buf_size];
  char digit[5];
  int hex, rd,i;
  int n;
  rc4_key key;  if (argc < 2)
  {
    fprintf(stderr,"%s key <in >out\n",argv[0]);
    exit(1);
  }
  strcpy(data,argv[1]);
  n = strlen(data);
  if (n&1)
  {
    strcat(data,"0");
    n++;
  }
  n/=2;
  strcpy(digit,"AA");
  for (i=0;i<n;i++)
  {
    digit[2] = data[i*2];
    digit[3] = data[i*2+1];
    sscanf(digit,"%x",&hex);
    seed[i] = hex;
  }  prepare_key(seed,n,&key);
  rd = fread(buf,1,buf_size,stdin);
  while (rd>0)
  {
    rc4(buf,rd,&key);
    fwrite(buf,1,rd,stdout);
    rd = fread(buf,1,buf_size,stdin);
  }
}

The RC5 encryption algorithm is a new fast symmetric block cipher
developed by Ron Rivest for RSA Laboratories. Intended as a possible
successor to the Data Encryption Standard, RC5 has a variable word
size, a variable number of rounds, and a variable-length secret key,
so the user can explicitly manipulate the trade-off between higher
speed and higher security. RC5 is suitable for hardware or software
implementations; the encryption and decryption algorithms are
exceptionally simple. A novel feature of RC5 is the heavy use of
data-dependent rotations.

谢谢crossbow(La Vida Es Amor)
有没有原理说明？

VB版rc4算法Public Sub main()
Dim key As String
For i = 1 To 16
Randomize
key = key & Chr(Rnd * 255)
Next i
MsgBox RC4(RC4("Welcome To Plindge Studio!", key), key)
End Sub
Public Function RC4(inp As String, key As String) As String
Dim S(0 To 255) As Byte, K(0 To 255) As Byte, i As Long
Dim j As Long, temp As Byte, Y As Byte, t As Long, x As Long
Dim Outp As String For i = 0 To 255
S(i) = i
Nextj = 1
For i = 0 To 255
If j > Len(key) Then j = 1
K(i) = Asc(Mid(key, j, 1))
j = j + 1
Next ij = 0
For i = 0 To 255
j = (j + S(i) + K(i)) Mod 256
temp = S(i)
S(i) = S(j)
S(j) = temp
Next ii = 0
j = 0
For x = 1 To Len(inp)
i = (i + 1) Mod 256
j = (j + S(i)) Mod 256
temp = S(i)
S(i) = S(j)
S(j) = temp
t = (S(i) + (S(j) Mod 256)) Mod 256
Y = S(t)Outp = Outp & Chr(Asc(Mid(inp, x, 1)) Xor Y)
Next
RC4 = Outp
End Function

这是我自己编的RC4的Delphi实现。
加密再解密与源码不同，真是郁闷，请高手帮我看看由什么问题？？？-----------------------------------------------------------------------------
Unit RC4;interfaceuses SysUtils, Classes;type
  TRC4 = class(TObject)
  Private
    S_Box: array[Low(Byte)..High(Byte)] of Byte;      {类RC4算法S-盒}
    R_Box: array[Low(Byte)..High(Byte)] of Byte;      {密文或明文数组}
    Key: String;                                      {类RC4算法密钥}
    Code: String;                                     {密文或明文}    procedure Set_Key;                                {类RC4算法初始化}
    procedure Set_Code;                               {计算密文或明文}
    function Get_Code():String;                       {获得密文或明文}
  public
    constructor Create;
    property sKey: String read Key write Key;
    property sCode: String read Get_Code write Code;
end;
implementation{-------------------------------------------------------------------------------
类  名：TRC4
方法名：Create
返回值：无
参  数：无
功  能：构造器
-------------------------------------------------------------------------------}
constructor TRC4.Create;
begin
end;{-------------------------------------------------------------------------------
类  名：TRC4
方法名：Set_Key
返回值：无
参  数：无
功  能：初始化S-盒（参考RC4算法）
-------------------------------------------------------------------------------}
procedure TRC4.Set_Key;
var
  J,KeyLength: Word;
  I,SwapByte: Byte;
  K_Box: array[Low(Byte)..High(Byte)] of Byte;
begin
  I := 0;
  J := 0;
  KeyLength := Length(Key);
  for I:= Low(Byte) to High(Byte) do begin
    S_Box[I] := I;
    K_Box[I] := Byte(Key[(I mod KeyLength) + 1]);
  end;
  for I := Low(Byte) to High(Byte) do begin
    J := (J + S_Box[I] + K_Box[I]) mod (High(Byte)+1);
    SwapByte := S_Box[I];
    S_Box[I] := S_Box[J];
    S_Box[J] := SwapByte;
  end;
end;{Set_Key}{-------------------------------------------------------------------------------
类  名：TRC4
方法名：Set_Code
返回值：无
参  数：无
功  能：计算密文或明文（参考RC4算法）
-------------------------------------------------------------------------------}
procedure TRC4.Set_Code;
var
  I,J,T,SwapByte: Byte;
  X: WORD;
begin
  Set_Key;  I := 0;
  J := 0;  for X := Low(Byte) to Length(Code)-1 do begin
    I := (I + 1) mod (High(Byte)+1);
    J := (J + S_Box[I]) mod (High(Byte)+1);
    SwapByte := S_Box[I];
    S_Box[I] := S_Box[J];
    S_Box[J] := SwapByte;
    T := (S_Box[I]+ S_Box[J]) mod (High(Byte)+1);
    R_Box[X] := Byte(Code[X]) xor S_Box[T];
  end;end;{Set_Code}{-------------------------------------------------------------------------------
类  名：TRC4
方法名：Get_Code
返回值：密文或明文
参  数：无
功  能：获得密文或明文
-------------------------------------------------------------------------------}
function TRC4.Get_Code():String;
var
  I: Byte;
begin
  Set_Code;  for I := Low(Byte) to Length(Code)-1 do begin
      Result := Result + AnsiChar(R_Box[I]);
  end;
end;{Get_Code}end.

已找到RC4算法的简单描述，请帮我看看上述Delphi实现有什么问题？
算法如下：
--------------------------------------------------------------------------------
１、初始化
原文：初始化S-盒也很容易。首先，进行线性填充：S[0]=1,S[1]=1,...,S[255]=255。然后用密钥填充另一个256字节数组，不断重复密钥直至填充到整个数组中：K[0],K[1],...,K[255]。
将指针J设为0。然后：
    对于I=0至255
    J=(J+S[I]+K[I]) mod 256
    交换S[I]和S[J]
2、加密或解密
原文：它有一个8*8的S-盒：S[0],S[1],...,S[255]。所有项都是数字0到数字255的置换，并且这个置换是一个可变长度密钥的函数。它有两个计数器：I和J,初值为0。
要产生一个随机字节，需要按下列步骤进行：
    I=(I+1) mod 256
    J=(J+S[I]) mod 256
    交换S[I]和S[J]
    T=(S[I]+S[J]) mod 256
    K=S[T]
    字节K与明文异或产生密文或者与密文异或产生明文。
----------------------------------------------------------------------------

呵呵，有Code的
const
  RC4_BufSize = 16;class procedure TCipher_RC4.GetContext(var ABufSize, AKeySize, AUserSize: Integer);
begin
  ABufSize := RC4_BufSize;
  AKeySize := 256;
  AUserSize := 256 * 2;
end;class function TCipher_RC4.TestVector: Pointer;
asm
         MOV   EAX,OFFSET @Vector
         RET
@Vector: DB    02Dh,08Fh,0EEh,042h,087h,07Bh,0AEh,072h
         DB    0F8h,02Bh,08Ch,0A5h,012h,014h,0A8h,07Eh
         DB    07Eh,08Ch,0DBh,05Eh,096h,049h,06Ch,09Ch
         DB    0EEh,05Eh,020h,06Ch,07Ah,067h,002h,05Dh
end;procedure TCipher_RC4.Encode(Data: Pointer);
var
  D: PByteArray;
  B: PByte;
  X,S: Byte;
begin
  D := User;
  B := Data;
  for X := 0 to RC4_BufSize -1 do
  begin
    Inc(FI);
    S := D[FI];
    Inc(FJ, S);
    D[FI] := D[FJ];
    D[FJ] := S;
    B^    := B^ xor D[(D[FI] + S) and $FF];
    Inc(B);
  end;
end;procedure TCipher_RC4.Decode(Data: Pointer);
begin
  Encode(Data);
end;procedure TCipher_RC4.Init(const Key; Size: Integer; IVector: Pointer);
var
  K: array[0..255] of Byte;
  D: PByteArray;
  I,J,S: Integer;
begin
  InitBegin(Size);
  FI := 0;
  FJ := 0;
  J := 0;
  D := User;
  for I := 0 to 255 do
  begin
    D[I] := I;
    K[I] := PByteArray(@Key)[I mod Size];
  end;
  for I := 0 to 255 do
  begin
    J := (J + D[I] + K[I]) and $FF;
    S := D[I];
    D[I] := D[J];
    D[J] := S;
  end;
  InitEnd(IVector);
{Save the Key}
  Move(D[0], D[256], 256);
  FSI := FI;
  FSJ := FJ;
  FillChar(K, SizeOf(K), 0);
end;procedure TCipher_RC4.Done;
begin
  inherited Done;
  FI := FSI;
  FJ := FSJ;
  Move(PByteArray(User)[256], User^, 256);
end;

调试易

求RC4 加密算法详细原理

解决方案 »