93 lines
3.3 KiB
ReStructuredText
93 lines
3.3 KiB
ReStructuredText
.. _random_api:
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Random Number Generation
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########################
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The random API subsystem provides random number generation APIs in both
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cryptographically and non-cryptographically secure instances. Which
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random API to use is based on the cryptographic requirements of the
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random number. The non-cryptographic APIs will return random values
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much faster if non-cryptographic values are needed.
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The cryptographically secure random functions shall be compliant to the
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FIPS 140-2 [NIST02]_ recommended algorithms. Hardware based random-number
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generators (RNG) can be used on platforms with appropriate hardware support.
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Platforms without hardware RNG support shall use the `CTR-DRBG algorithm
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<https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf>`_.
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The algorithm can be provided by `TinyCrypt <https://01.org/tinycrypt>`_
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or `mbedTLS <https://tls.mbed.org/ctr-drbg-source-code>`_ depending on
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your application performance and resource requirements.
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.. note::
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The CTR-DRBG generator needs an entropy source to establish and
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maintain the cryptographic security of the PRNG.
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.. _random_kconfig:
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Kconfig Options
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***************
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These options can be found in the following path :zephyr_file:`subsys/random/Kconfig`.
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:kconfig:option:`CONFIG_TEST_RANDOM_GENERATOR`
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For testing, this option permits random number APIs to return values
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that are not truly random.
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The random number generator choice group allows selection of the RNG
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source function for the system via the RNG_GENERATOR_CHOICE choice group.
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An override of the default value can be specified in the SOC or board
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.defconfig file by using:
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.. code-block:: none
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choice RNG_GENERATOR_CHOICE
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default XOSHIRO_RANDOM_GENERATOR
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endchoice
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The random number generators available include:
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:kconfig:option:`CONFIG_TIMER_RANDOM_GENERATOR`
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enables number generator based on system timer clock. This number
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generator is not random and used for testing only.
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:kconfig:option:`CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR`
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enables a random number generator that uses the enabled hardware
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entropy gathering driver to generate random numbers.
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:kconfig:option:`CONFIG_XOSHIRO_RANDOM_GENERATOR`
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enables the Xoshiro128++ pseudo-random number generator, that uses the
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entropy driver as a seed source.
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The CSPRNG_GENERATOR_CHOICE choice group provides selection of the
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cryptographically secure random number generator source function. An
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override of the default value can be specified in the SOC or board
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.defconfig file by using:
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.. code-block:: none
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choice CSPRNG_GENERATOR_CHOICE
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default CTR_DRBG_CSPRNG_GENERATOR
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endchoice
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The cryptographically secure random number generators available include:
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:kconfig:option:`CONFIG_HARDWARE_DEVICE_CS_GENERATOR`
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enables a cryptographically secure random number generator using the
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hardware random generator driver
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:kconfig:option:`CONFIG_CTR_DRBG_CSPRNG_GENERATOR`
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enables the CTR-DRBG pseudo-random number generator. The CTR-DRBG is
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a FIPS140-2 recommended cryptographically secure random number generator.
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Personalization data can be provided in addition to the entropy source
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to make the initialization of the CTR-DRBG as unique as possible.
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:kconfig:option:`CONFIG_CS_CTR_DRBG_PERSONALIZATION`
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CTR-DRBG Initialization Personalization string
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API Reference
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*************
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.. doxygengroup:: random_api
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