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.IX Title "Math::Prime::Util::ChaCha 3pm"
.TH Math::Prime::Util::ChaCha 3pm 2024-01-10 "perl v5.38.2" "User Contributed Perl Documentation"
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.SH NAME
Math::Prime::Util::ChaCha \- Pure Perl ChaCha20 CSPRNG
.SH VERSION
.IX Header "VERSION"
Version 0.73
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.SH DESCRIPTION
.IX Header "DESCRIPTION"
A pure Perl implementation of ChaCha20 with a CSPRNG interface.
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.SS csrand
.IX Subsection "csrand"
Takes a binary string as input and seeds the internal CSPRNG.
.SS srand
.IX Subsection "srand"
A method for sieving the CSPRNG with a small value.  This will not be secure
but can be useful for simulations and emulating the system \f(CW\*(C`srand\*(C'\fR.
.PP
With no argument, chooses a random number, seeds and returns the number.
With a single integer argument, seeds and returns the number.
.SS irand
.IX Subsection "irand"
Returns a random 32\-bit integer.
.SS irand64
.IX Subsection "irand64"
Returns a random 64\-bit integer.
.SS random_bytes
.IX Subsection "random_bytes"
Takes an unsigned number \f(CW\*(C`n\*(C'\fR as input and returns that many random bytes
as a single binary string.
.SS ""
.IX Subsection ""
.SH AUTHORS
.IX Header "AUTHORS"
Dana Jacobsen <dana@acm.org>
.SH ACKNOWLEDGEMENTS
.IX Header "ACKNOWLEDGEMENTS"
Daniel J. Bernstein wrote the ChaCha family of stream ciphers in 2008 as
an update to the popular Salsa20 cipher from 2005.
.PP
RFC7539: "ChaCha20 and Poly1305 for IETF Protocols" was used to create both
the C and Perl implementations.  Test vectors from that document are used
here as well.
.PP
For final optimizations I got ideas from Christopher Madsen's
Crypt::Salsa20 for how to best work around some of Perl's aggressive
dynamic typing.
Our core is still about 20% slower than Salsa20.
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2017 by Dana Jacobsen <dana@acm.org>
.PP
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.