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https://github.com/hdl-util/rand
Random number generators such as LFSRs, LHCAs
https://github.com/hdl-util/rand
Last synced: about 1 month ago
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Random number generators such as LFSRs, LHCAs
- Host: GitHub
- URL: https://github.com/hdl-util/rand
- Owner: hdl-util
- License: other
- Created: 2020-06-26T15:23:57.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2020-06-27T22:23:30.000Z (over 4 years ago)
- Last Synced: 2024-05-20T17:36:13.032Z (7 months ago)
- Language: SystemVerilog
- Homepage:
- Size: 15.6 KB
- Stars: 2
- Watchers: 3
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE-APACHE
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README
# rand
[](https://travis-ci.com/hdl-util/rand)
SystemVerilog code for arbitrary width random number utilities.
## Why?
Needed an arbitrary width LFSR implementation. The one I've included works for 4 through 64 bits, but is easily extensible with the addition of more constants found using [mlpolygen](https://bitbucket.org/gallen/mlpolygen/src/default/).
## Usage
### Linear Feedback Shift Register (LFSR / Xorshift)
1. Take files from `src/` and add them to your own project. If you use [hdlmake](https://hdlmake.readthedocs.io/en/master/), you can add this repository itself as a remote module.
1. Other helpful modules are also available in this GitHub organization.
1. Consult the testbench in `test/xorshift_tb.sv` for example usage.
1. Read through the parameter descriptions in `xorshift.sv` and tailor any instantiations to your situation.
1. Please create an issue if you run into a problem or have any questions.
#### Caveats
* Does not encompass all values (2 ** WIDTH-1 is missing)
* Predictable values, not suitable for any security-related application
### Ring oscillator
See `src/ring_oscillator.sv`. Because the toggle rate of a ring oscillator depends on logic delays and noise, it can act as a source for truly random n-bit word data.
#### Caveats
* This holds if and only if the sampling clock is lower than the natural oscillating frequency
* The quality of the produced random numbers is poor
* It can be improved by passing it through an LHCA, in which case, it will pass all the [DieHard tests](https://en.wikipedia.org/wiki/Diehard_tests)
### Linear Hybrid Cellular Automata (LHCA)
See `src/lhca.sv`. LFSR generalization suitable for cryptographic applications when sourced with a ring oscillator.
## To-do List
* [x] [Xorshift](https://en.wikipedia.org/wiki/Xorshift) (LFSR)
* [x] [Ring oscillators](https://en.wikipedia.org/wiki/Ring_oscillator)
* [x] [LHCA backed by Ring Oscillators](https://electronics.stackexchange.com/questions/263656/hardware-sources-of-entropy-on-an-fpga)
* [ ] [CBRNG](https://en.wikipedia.org/wiki/Counter-based_random_number_generator_(CBRNG)#Squares_RNG)
* Making the Squares RNG arbitrary width seems non-trivial, unfortunately
* More upon request
## Reference Documents
*These documents are not hosted here!*
* [High Speed True Random Number Generators in Xilinx FPGAs](http://forums.xilinx.com/xlnx/attachments/xlnx/EDK/27322/1/HighSpeedTrueRandomNumberGeneratorsinXilinxFPGAs.pdf)
* This is the primary source for the LHCA concept