Add basic secure AES based random number generator.

Signed-off-by: Stefan Westerfeld <stefan@space.twc.de>

src/Makefile.am

@@ -5,6 +5,9 @@ COMMON_SRC = utils.hh utils.cc convcode.hh convcode.cc
 audiowmark_SOURCES = audiowmark.cc wavdata.cc wavdata.hh fft.cc fft.hh $(COMMON_SRC)
 audiowmark_LDFLAGS = $(SNDFILE_LIBS) $(FFTW_LIBS)
 
-noinst_PROGRAMS = testconvcode
+noinst_PROGRAMS = testconvcode testrandom
 
 testconvcode_SOURCES = testconvcode.cc $(COMMON_SRC)
+
+testrandom_SOURCES = testrandom.cc
+testrandom_LDFLAGS = $(LIBGCRYPT_LIBS)

src/testrandom.cc

+#include "utils.hh"
+
+#include <sys/time.h>
+#include <gcrypt.h>
+
+using std::vector;
+using std::string;
+
+static double
+gettime()
+{
+  timeval tv;
+  gettimeofday (&tv, 0);
+
+  return tv.tv_sec + tv.tv_usec / 1000000.0;
+}
+
+static constexpr auto GCRY_CIPHER = GCRY_CIPHER_AES128;
+
+class Random
+{
+  vector<unsigned char> aes_key = vector<unsigned char> (16);
+  gcry_cipher_hd_t      aes_ctr_cipher;
+
+  void
+  die_on_error (const char *func, gcry_error_t error)
+  {
+    if (error)
+      {
+        fprintf (stderr, "%s failed: %s/%s\n", func, gcry_strsource (error), gcry_strerror (error));
+
+        exit (1); /* can't recover here */
+      }
+  }
+public:
+  enum class Stream {
+    up_down = 1,
+    mix = 2,
+    bit_order = 3
+  };
+  Random (uint64_t seed, Stream stream)
+  {
+    vector<unsigned char> ctr = get_start_counter (seed, stream);
+    printf ("CTR: ");
+    for (auto ch : ctr)
+      printf ("%02x ", ch);
+    printf ("\n");
+
+    gcry_error_t gcry_ret = gcry_cipher_open (&aes_ctr_cipher, GCRY_CIPHER, GCRY_CIPHER_MODE_CTR, 0);
+    die_on_error ("gcry_cipher_open", gcry_ret);
+
+    gcry_ret = gcry_cipher_setkey (aes_ctr_cipher, &aes_key[0], aes_key.size());
+    die_on_error ("gcry_cipher_setkey", gcry_ret);
+
+    gcry_ret = gcry_cipher_setctr (aes_ctr_cipher, &ctr[0], ctr.size());
+    die_on_error ("gcry_cipher_setctr", gcry_ret);
+  }
+  ~Random()
+  {
+    gcry_cipher_close (aes_ctr_cipher);
+  }
+  vector<unsigned char>
+  get_start_counter (uint64_t seed, Stream stream)
+  {
+    gcry_error_t     gcry_ret;
+    gcry_cipher_hd_t cipher_hd;
+
+    gcry_ret = gcry_cipher_open (&cipher_hd, GCRY_CIPHER, GCRY_CIPHER_MODE_ECB, 0);
+    die_on_error ("gcry_cipher_open", gcry_ret);
+
+    gcry_ret = gcry_cipher_setkey (cipher_hd, &aes_key[0], aes_key.size());
+    die_on_error ("gcry_cipher_setkey", gcry_ret);
+
+    vector<unsigned char> cipher_text (16);
+    vector<unsigned char> plain_text (16);
+
+    /* this has to be endian independent: use big endian order */
+    plain_text[0] = seed >> 56;
+    plain_text[1] = seed >> 48;
+    plain_text[2] = seed >> 40;
+    plain_text[3] = seed >> 32;
+    plain_text[4] = seed >> 24;
+    plain_text[5] = seed >> 16;
+    plain_text[6] = seed >> 8;
+    plain_text[7] = seed;
+
+    plain_text[8] = uint8_t (stream);
+
+    printf ("[[ ");
+    for (auto ch : plain_text)
+      printf ("%02x ", ch);
+    printf (" ]]\n");
+
+    gcry_ret = gcry_cipher_encrypt (cipher_hd, &cipher_text[0], cipher_text.size(),
+                                               &plain_text[0],  plain_text.size());
+    die_on_error ("gcry_cipher_encrypt", gcry_ret);
+
+    gcry_cipher_close (cipher_hd);
+
+    printf ("[[ ");
+    for (auto ch : cipher_text)
+      printf ("%02x ", ch);
+    printf (" ]]\n");
+
+    return cipher_text;
+  }
+  uint64_t operator()()
+  {
+    const size_t block_size = 8;
+    unsigned char zeros[block_size] = { 0, };
+    unsigned char cipher_text[block_size];
+
+    gcry_error_t gcry_ret = gcry_cipher_encrypt (aes_ctr_cipher, cipher_text, block_size, zeros, block_size);
+    die_on_error ("gcry_cipher_encrypt", gcry_ret);
+
+    printf ("[[ ");
+    for (auto ch : cipher_text)
+      printf ("%02x ", ch);
+    printf (" ]]\n");
+    /* this has to be endian independent: use big endian order */
+    uint64_t result = (uint64_t (cipher_text[0]) << 56)
+                    + (uint64_t (cipher_text[1]) << 48)
+                    + (uint64_t (cipher_text[2]) << 40)
+                    + (uint64_t (cipher_text[3]) << 32)
+                    + (uint64_t (cipher_text[4]) << 24)
+                    + (uint64_t (cipher_text[5]) << 16)
+                    + (uint64_t (cipher_text[6]) << 8)
+                    + cipher_text[7];
+    return result;
+  }
+};
+
+int
+main (int argc, char **argv)
+{
+  Random rng (0xf00f1234b00b5678U, Random::Stream::bit_order);
+  for (size_t i = 0; i < 20; i++)
+    {
+      uint64_t x = rng();
+      printf ("%016lx\n", x);
+    }
+}