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Diffstat (limited to 'doc/manual')
| -rw-r--r-- | doc/manual/rng.rst | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/doc/manual/rng.rst b/doc/manual/rng.rst index 7eb229a5e..ba838ce8e 100644 --- a/doc/manual/rng.rst +++ b/doc/manual/rng.rst @@ -25,6 +25,10 @@ The major interfaces are into the state of the RNG. The additional input could be anything which parameterizes this request. +.. cpp:function:: void RandomNumberGenerator::randomize_with_ts_input(byte* data, size_t length) + + Creates a buffer with some timestamp values and calls ``randomize_with_input`` + .. cpp:function:: byte RandomNumberGenerator::next_byte() Generates a single random byte and returns it. Note that calling this @@ -40,24 +44,39 @@ HMAC_DRBG ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ HMAC DRBG is a random number generator designed by NIST and specified -in SP 800-90A. It can be instantiated with any hash function but is -typically used with SHA-256, SHA-384, or SHA-512. +in SP 800-90A. It seems to be the most conservative generator of the +NIST approved options. -HMAC DRBG seems to be the most conservative generator of the NIST -approved options. +It can be instantiated with any HMAC but is typically used with +SHA-256, SHA-384, or SHA-512, as these are the hash functions approved +for this use by NIST. System_RNG ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In ``system_rng.h``, objects of ``System_RNG`` reference a single -(process global) reference to the system PRNG (/dev/urandom or -CryptGenRandom). +(process global) reference to the system PRNG (such as +``/dev/urandom`` or ``CryptGenRandom``). + +You can also use the function ``system_rng()`` which returns a +reference to the global handle to the system RNG. AutoSeeded_RNG ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -This instantiates a new instance of a userspace PRNG, seeds it with -a default entropy pool. +AutoSeeded_RNG is type naming a 'best available' userspace PRNG. The +exact definition of this has changed over time and may change in the +future, fortunately there is no compatability concerns when changing +such an RNG. + +Note well: like most other classes in Botan, it is not safe to share +an instance of ``AutoSeeded_RNG`` among multiple threads without +serialization. + +The current version uses the HMAC_DRBG with SHA-384. The initial seed +is generated either by the system PRNG (if available) or a default set +of entropy sources. These are also used for periodic reseeding of the +RNG state. ANSI X9.31 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |