Part 1: General - Computer Security Resource Center - National ...

March, 2007
2. The protocols trigger an alarm after a certain reasonable number of detected error
conditions, and
3. The key dependent computations are obscured from the observer to prevent or minimize
the detection of key dependent characteristics.
4.2.7 Random Number Generation
Random number generators (RNGs) are required for the generation of keying material (e.g., keys
and IVs). Two classes of RNGs are defined: deterministic and non-deterministic. Deterministic
Random bit Generators (DRBGs), sometimes called deterministic random number generators or
pseudorandom number generators, use cryptographic algorithms and the associated keying
material to generate random bits; Non-Deterministic Random Bit Generators (NRBGs),
sometimes called true RNGs, produce output that is dependent on some unpredictable physical
source that is outside human control.
[FIPS186-3] defines a DRBG that may be used to generate random bits for cryptographic
applications (e.g., key or IV generation). The DRBG is initialized with a secret starting value,
called a RNG seed. An “attacker” with knowledge of the DRBG output should not be able to
determine the seed other than by exhaustive guessing.
40