Glossary - True Random Number Generators - True Random Bits

Glossary of words concerning true random number generation

API = Application Program Interface

Can be realized by a DLL. Functions implemented in the DLL can be used by various programming languages, e.g. Delphi, C++ or Visual Basic.

Diehard tests

DIEHARD contains 15 statistical random bit tests and can be regarded as an "acid test" for every random number generator. A lot of generators, like RAN2 from Numerical Recipes, don't pass this test. The Diehard tests habe been developed by George Marsaglia. Description of the Diehard tests (PDF).

DLL = Dynamic Link Library

Windows files which contain functions or procedures that can be used by various programming languages. Look here how to call a DLL function in Delphi for ZRANDOM USB.

Electronic shielding

Electronic noise sources which are used to generate random numbers need to be shielded by a metallic frame in order to avoid interferences due to electromagnetic sources in the environment. There are a lot of disturbing electromagnetic sources in computer frames, e.g. power supply, CPU, graphic display adaptor, sound card, etc. For this reason noise sources of physical random number generators must not be integrated on PC plug-in cards.

Electronic noise

Every electronic component produces electronic noise due the stochastic movement of electrons. The effective noise voltage depends on temperature, frequency bandwidth, and resistance of the noise source. Typical noise levels are in the nV range.

FIPS PUB 140-1

A couple of statistical random bit tests: Monobit-Test, Poker-Test, Runs-Test, and Long-Run-Test. These tests are recommended if the random bits are used for cryptographic applications. The tests are carried out with 20.000 random bits. Here you will find more information about these tests.

Noise sampling

Physical random bits can be obtained by sampling amplified electronic noise (a very large amplification factor is needed).

It is important to realize a sufficiently broad frequency bandwidth.

True random bits / numbers = Physical random bits / numbers

Random bits / numbers created by use of a physical process like radioactive decay or electronic noise. Physical random bits can be sampled from the noise. These random bits are non-deterministic, i.e. unpredictable. It is very important not to use a sample rate which is too high in relation to the noise energy spectrum. Decimal random numbers can be obtained by combination of several random bits. The true random bits of the TRNG ZRANDOM USB are 100% physically generated.

Vernam encoding / encryption

The Vernam code (one-time pad) is the only encoding principle which allows a 100% secure data transfer. The Vernam encoding is very simple and clear: every data bit is combined with a random bit by the XOR function (exclusive logical OR). Every data bit is "flipped" with a probability of 50% (1 becomes 0, 0 becomes 1).Therefore, the number of needed random bits is equal to the number of data bits.It is completely impossible to decrypt the encrypted file without knowledge of the related random bit file. This is a crucial difference to all encryption methods which use limited keys (like PGP). Absolute security is only given in case of usage of true (physically generated) random bits. Sender and recipient need to exchange random bit files. This can be done during a personal meeting via CD for example. One CD (650 MB) is enough to encrypt about 100.000 closely written pages.

XOR mode (XOR = Exclusive-OR function)

For each resulting random bit one physically generated random bit and one pseudo random bit are used. The XOR procedure is explained in the following table:

pseudo bit	physical bit	resulting bit
0	0	0
0	1	1
1	0	1
1	1	0

The XOR function allows to run the physical random bit generator with maximum speed (much faster than recommended for pure physical random bit generation) because the statistical properties of the resulting bit sequence is determined by the statistical properties of a very good pseudo random bit algorithm. Random bits created by an algorithm are completely deterministic if directly used. In order to get a non-deterministic random bit sequence every pseudo bit is "controlled" by a physically generated random bit as shown in the table above. Therefore the XOR mode is a semi-physical random bit generation procedure. The XOR random bits of the TRNG ZRANDOM USB are 50% physically generated.

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