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.\" ========================================================================
.\"
.IX Title "Math::Prime::Util::ChaCha 3pm"
.TH Math::Prime::Util::ChaCha 3pm "2022-10-20" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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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 \s-1CSPRNG\s0 interface.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "csrand"
.IX Subsection "csrand"
Takes a binary string as input and seeds the internal \s-1CSPRNG.\s0
.SS "srand"
.IX Subsection "srand"
A method for sieving the \s-1CSPRNG\s0 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
\&\s-1RFC7539:\s0 \*(L"ChaCha20 and Poly1305 for \s-1IETF\s0 Protocols\*(R" 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.