https://github.com/opencoff/mt-arc4random
Thread-Aware, thread-safe user-space port of OpenBSD arc4random (chacha20)
https://github.com/opencoff/mt-arc4random
Last synced: 8 months ago
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Thread-Aware, thread-safe user-space port of OpenBSD arc4random (chacha20)
- Host: GitHub
- URL: https://github.com/opencoff/mt-arc4random
- Owner: opencoff
- License: bsd-2-clause
- Created: 2015-10-07T21:54:09.000Z (over 10 years ago)
- Default Branch: master
- Last Pushed: 2016-06-19T23:14:26.000Z (about 10 years ago)
- Last Synced: 2025-01-10T20:21:46.387Z (over 1 year ago)
- Language: C
- Homepage:
- Size: 20.5 KB
- Stars: 5
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# mt-arc4random
This is a thread-Aware, thread-safe version of OpenBSD arc4random (chacha20 based).
I cleaned it up and made it portable to all POSIX like OSes. It
builds cleanly on OS X, Linux and OpenBSD. In theory, it should just
work on any modern Unix.
## How is it Thread Aware?
First, I converted every internal function to accept a context
variable and prevented them from assuming any global state.
Next, I stashed a per-thread context using the pthread TLS API
`pthread_getspecific()` and `pthread_setspecific()`.
Lastly, I rewrote the publicly visible functions to fetch the
context before calling any internal functions.
## How do you provide entropy (seed) in a portable way?
This implementation uses an "external" function named
`getentropy()`. On OpenBSD, this is a syscall.
I have provided an implementation of `getentropy()` for POSIX systems
via `/dev/urandom`.
## Building and Using this
Using this is very simple:
* If you are on OpenBSD:
- Include the supplied `arc4random.h` in every place where you expect
to call `arc4random()`. This is *mandatory* - otherwise, you
will have a fun time debugging crashes.
- Add `arc4random.c` to your build.
* If you are any Unix like platform:
- Add the two files `arc4random.c` and `posix_entropy.c` to your
build system.
- Include the supplied `arc4random.h` in every place where you expect
to call `arc4random()`
* Use the well-known APIs - `arc4random()` and
`arc4random_buf()` as you always do.
## Testing and Performance
There's a small benchmark program called `t_arcrand`; to build it
just run `make`. It should work on any modern Unix. Tested on
OpenBSD, Linux, OS X Darwin.
When run on a retina MacBook Pro 13” (2013) running OS X Yosemite:
./t_arc4rand 16 32 64 256 512
size, arc4rand, sysrand, speed-up
16, 12.2966, 279.9628, 22.77
32, 11.3687, 268.2029, 23.59
64, 9.9161, 238.8743, 24.09
256, 9.3164, 217.1194, 23.30
512, 8.3054, 204.1270, 24.58
The results show the CPU cycles consumed by `arc4random_buf()` to
generate "n" bytes of random data. The third column labeled
`sysrand` is the CPU cycles consumed by reading from `/dev/urandom`.
And the last column is the relative speedup between the two.
On debian Linux (sid) x86_64 on a Core-i7 Laptop running the
Linux 4.5 kernel, I see:
./t_arc4rand 16 32 64 256 512
size, arc4rand, sysrand, speed-up
16, 9.6997, 255.6211, 26.35
32, 7.9821, 251.2072, 31.47
64, 7.5916, 220.8430, 29.09
256, 7.4764, 206.5079, 27.62
512, 7.2225, 201.9913, 27.97
## RFC 4122 UUID Generation
There is a short implementatin of RFC 4122
Random number based UUID generation in randuuid.c. This
uses the underlying `arc4random()` implementation. The
signature for that function is simple enough
`void randuuid(uint8_t* buf, size_t n)`.
### Java bindings
The UUID generator has a JNI binding specified in the java/
directory.
## How is it licensed?
I don't have any special licensing terms; my changes are subject to
the original licensing terms in the file `arc4random.c`.
--
Sudhi Herle
Wed Oct 7 15:07:53 PDT 2015