raspberrypi: implement os.urandom #4213
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Since the datasheet cast some doubt on the strength of the "rosc_hw->randombit", I use the SHA256 hash function to create a high quality random seed from random values of uncertain entropy, as well as to generate a sequence of random values from that seed using SHA256 as a cryptographically-secure random number generator. In practice, it produces over 100kB/s of random data which does not have any gross problems according to _PractRand_.
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@joelburton please check this out. You should be able to download a uf2 with this feature enabled here: https://github.com/adafruit/circuitpython/suites/2064177672/artifacts/41696731 -- if you get a chance to test with it, let us know the result. |
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@jepler : works great for me; thanks for your help here, everyone! <3 |
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The new ADC methods are: init(), read_uv() and block(). The new ADCBlock class has methods: init() and connect(). See related discussions in adafruit#3943, adafruit#4213. Signed-off-by: Damien George <damien@micropython.org>
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Since the datasheet cast some doubt on the strength of the "rosc_hw->randombit", I use the SHA256 hash function to create a high quality random seed from random values of uncertain entropy, as well as to generate a sequence of random values from that seed using SHA256 as a cryptographically-secure random number generator.
In practice, it produces over 100kB/s of random data which does not have any gross problems according to PractRand (analyzing limited amounts of data, about 16 megabytes). Most uses for urandom in CircuitPython (across the Adafruit bundle, Community bundle and the Learn system) are not security-critical; however, it is used in an implementation of RSA which is crypto-strength.
Closes #4196.