Cryptographic Foibles

Using Poor Random Numbers

直接看 Chromium project 怎麼解：

In Windows platform,

uint32 RandUint32() {
  uint32 number;
  CHECK_EQ(rand_s(&number), 0);
  return number;
}

In POSIX platform,

class URandomFd {
 public:
  URandomFd() {
    fd_ = open("/dev/urandom", O_RDONLY);
    CHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno;
  }

  ~URandomFd() {
    close(fd_);
  }

  int fd() const { return fd_; }

 private:
  int fd_;
};

base::LazyInstance g_urandom_fd(base::LINKER_INITIALIZED);

uint64 RandUint64() {
  uint64 number;

  int urandom_fd = g_urandom_fd.Pointer()->fd();
  bool success = file_util::ReadFromFD(
      urandom_fd,
      reinterpret_cast(&number),
      sizeof(number));
  CHECK(success);

  return number;
}

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Creating Your Own Cryptographic Functions

Do not, under any circumstances, create your own encryption algorithm.