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#include <windows.h>
#define buf_size 1024
typedef struct{
void* (__stdcall *GenerateKey)(char* key);
void (__stdcall *FreeKey)(void* key);
void (__stdcall *EncryptMem)(BYTE* data, int size, void* key);
void (__stdcall *DecryptMem)(BYTE* data, int size, void* key);
char* Name;
char* Info;
char* Author;
char* Site;
char* Email;
DWORD Version;
WORD uid;
} Cryptor;
typedef struct rc4_key
{
BYTE state[256];
BYTE x;
BYTE y;
} rc4_key;
#define swap_byte(x,y) t = *(x); *(x) = *(y); *(y) = t
void prepare_key(BYTE *key_data_ptr, size_t key_data_len, rc4_key *key)
{
int i = 0;
BYTE t = 0;
BYTE index1 = 0;
BYTE index2 = 0;
BYTE* state = 0;
unsigned long counter = 0;
state = &key->state[0];
for(counter = 0; counter < 256; counter++)
state[counter] = (BYTE)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(BYTE *buffer_ptr, int buffer_len, rc4_key *key)
{
BYTE t = 0;
BYTE x = 0;
BYTE y = 0;
BYTE* state = 0;
BYTE xorIndex = 0;
DWORD counter = 0;
BYTE old_state[256];
x = key->x;
y = key->y;
state = &key->state[0];
memcpy(old_state, key->state, 256);
for(counter = 0; counter < (DWORD)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];
}
memcpy(key->state, old_state, 256);
//key->x = x;
//key->y = y;
}
void zero_fill(BYTE * pBuf, size_t bufSize)
{
size_t i;
for(i = 0; i < bufSize; i++)
pBuf[i] = 0;
}
void* __stdcall GenerateKey(char* pwd)
{
rc4_key* key;
key = (rc4_key*)malloc(sizeof(rc4_key));
zero_fill((BYTE*)key, sizeof(key));
prepare_key(pwd, strlen(pwd), key);
return key;
}
void __stdcall FreeKey(void* key)
{
free(key);
}
void __stdcall EncryptMem(BYTE* data, int size, void* key)
{
rc4(data, size, key);
}
void __stdcall DecryptMem(BYTE* data, int size, void* key)
{
rc4(data, size, key);
}
Cryptor cryptor =
{
GenerateKey,
FreeKey,
EncryptMem,
DecryptMem,
"RC4",
"Old, very easy to crack stream cipher",
"Unknown",
"http://ru.wikipedia.org/wiki/RC4",
"nomail",
0x00000100,
0xDEAD
};
__declspec(dllexport) Cryptor* GetCryptor()
{
return &cryptor;
}
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