📄 encryptaes.htm

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<TITLE>DES encryption</TITLE>
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	<PARAM NAME="Keyword" VALUE="Encryption, AES">
	<PARAM NAME="Keyword" VALUE="Advanced Encryption Standard (AES)">
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<H2><A NAME="encryptaes"></A>AES encryption</H2>

<P>If an AES key is specified in the <A
HREF="connproperties.htm">Option/Connections</A> dialogue, it
will be is used to encrypt sound transmitted to that host using
the
<a href="http://csrc.nist.gov/encryption/aes/">Advanced Encryption Standard</a>
(AES) algorithm
(<a href="http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf">FIPS-197</a>),
which supports encryption with keys of 128, 192, and 256 bits.
In order to decrypt sound encoded with AES, the connection on the
receiving machine must specify an identical AES key. 

The AES key phrase can be as long as 255 characters.  The actual AES
key is created by applying the
<a href="http://www.fourmilab.ch/md5/rfc1321.html"><B>MD5</B></a>
algorithm to the given key phrase to generate the 128 bit AES key.
You can specify a 256 bit AES key by entering two separate key phrases
with a "+" character between them, for example:

<p>
<center>
<tt>nebulous concepts+dubious reasoning</tt>
</center>

<p>
The first 128 bits of the key will be generated from the portion
of the key before the plus sign, and the second from the characters
after it.  For maximum security, you should use long and difficult to
guess key phrases.  Of course, you must balance this against
the difficulty in remembering and entering them.  But there's no point
specifying a 256 bit key if it's generated from two easy to guess
words.

<p>

If the "Hex" box is checked to the right of the AES key in the
<A HREF="connproperties.htm">Option/Connections</A> dialogue,
the key is specified as a hexadecimal number
consisting of the digits from 0 to 9 and the letters A-F.
(Letters may be upper or lower case.)  Hexadecimal keys may
range from one to 64 digits; the key length is the smallest of
128, 192, or 256 bits which contains the number of digits
given.  If the digits specified do not fill the next larger
key size, the least significant digits of the key are filled
with zeroes.  No hashing or other transformation is performed
on a hexadecimal key; it is used precisely as specified.  If you
have a high-security key generator, for example, based on
<a href="http://www.fourmilab.ch/hotbits/">radioactive decay</a>,
you can employ the keys it creates without worrying about
the security of the algorithms <i>Speak Freely</i> uses when
keys are specified as text strings.

<P><i>Speak Freely</i> will continue to correctly receive unencrypted
sound  from a given host even if an AES key is specified
for the connection.</P>

<P>Since AES encryption is not specified as a part of the
<A HREF="protocol.htm">RTP and VAT protocols</A>, it can be
used only when transmitting in <i>Speak Freely</i> protocol.</P>

<P>The AES algorithm has been placed in the public domain
and may be used in any manner, commercial or noncommercial,
without a license.</P>

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