User's Manual

Chapter 3 Using the Intel Random Number Generator 21
Generating Random Numbers
Step 3: Initialize the Random Algorithm
To initialize the random algorithm, you must pass the algorithm object, the algorithm
chooser, and a surrender context. As mentioned before, the algorithm chooser does
not need to be a session chooser; a simple software chooser will suffice, so this call is
also identical to a software implementation.
Step 4: Seed the Random Object
In this step, you will seed the random object using the seed generated by the Intel
RNG. If the RNG cannot be found, or fails during processing, you can ask the user to
enter a seed value.
Note: If the Intel RNG is not working at start-up, and there are no seed bits available
from hardware randomness, then a very high-security application might
want to inform the user and exit.
First, acquire the random seed. To do this you must supply a function,
GenerateSeed,
to retrieve the random seed from hardware. An example of the
GenerateSeed function
is shown in the previous section, “Obtaining a Random Seed from Hardware” on
page 16:
Once you have the random seed and its length, pass both into
B_RandomUpdate. This
B_ALGORITHM_METHOD *RANDOM_CHOOSER[] = {
&AM_SHA_RANDOM,
(B_ALGORITHM_METHOD *)NULL_PTR
};
if ((status = B_RandomInit
(randomAlgorithm, RANDOM_CHOOSER,
(A_SURRENDER_CTX *)NULL_PTR)) != 0)
break;
#define BYTES_TO_GENERATE = 128
randomSeedLen = BYTES_TO_GENERATE;
randomSeed = (unsigned char *)T_malloc (randomSeedLen);
GenerateSeed (randomSeed, randomSeedLen);