RC4.hh

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#ifndef COSA_RC4_HH
#define COSA_RC4_HH

#include "Cosa/Types.h"

class RC4 {
public:
  RC4(const void* key, size_t len)
  {
    restart(key, len);
  }

  void restart(const void* key, size_t len);

  char encrypt(char c)
  {
    m_x += 1;
    uint8_t sx = m_state[m_x];
    m_y += sx;
    uint8_t sy = m_state[m_y];
    m_state[m_x] = sy;
    m_state[m_y] = sx;
    uint8_t ix = sx + sy;
    return (c ^ m_state[ix]);
  }

  void encrypt(void* buf, size_t n)
  {
    for (char* bp = (char*) buf; n--; bp++)
      *bp = encrypt(*bp);
  }

  void encrypt(void* dest, const void* src, size_t n)
  {
    char* dp = (char*) dest;
    const char* sp = (const char*) src;
    while (n--) *dp++ = encrypt(*sp++);
  }

  char decrypt(char c)
  {
    return (encrypt(c));
  }

  void decrypt(void* buf, size_t n)
  {
    for (char* bp = (char*) buf; n--; bp++)
      *bp = decrypt(*bp);
  }

  void decrypt(void* dest, const void* src, size_t n)
  {
    char* dp = (char*) dest;
    const char* sp = (const char*) src;
    while (n--) *dp++ = decrypt(*sp++);
  }

private:
  uint8_t m_state[256];
  uint8_t m_x;
  uint8_t m_y;
};

#endif