📄 encryptkeys.htm

📁 g729 coding ipaddressing
💻 HTM
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" Content="text/html; charset=Windows-1252">
<TITLE>Key generation, management, and exchange</TITLE>
</HEAD>

<BODY BGCOLOR="#FFFFFF" TEXT="#000000">

<OBJECT TYPE="application/x-oleobject" CLASSID="clsid:1e2a7bd0-dab9-11d0-b93a-00c04fc99f9e">
	<PARAM NAME="Keyword" VALUE="Encryption, keys">
</OBJECT>

<H2><A NAME="encryptkeys"></A>Key generation, management, and exchange</H2>

<P>Unlike PGP, <i>Speak Freely</i> is a conventional secret key
cryptographic system.  Why?  Because the RSA public key
cryptosystem is the subject of U.S. Patent 4,405,929 and I have
no desire to thread through the legal maze that PGP had to run
in order to become both legal and freely available.  Rather
than replicating the public key functionality of PGP, <i>Speak
Freely</i> cooperates with a copy of PGP installed on your machine,
delegating the public key encryption of a session key to PGP. 
If you have PGP installed on your machine, please turn to the
section on <A HREF="encryptpgp.htm">PGP key exchange</A>. 
Users without access to PGP or who, for some reason or another,
can't execute PGP from within <i>Speak Freely</i> can use the
following technique to generate and exchange session keys.</P>

<P>First of all, make up a key.  You could pick a long nonsense
phrase like,</P>

<p>
<blockquote>
        The fribbits seem glinky today, don't you think?
</blockquote>

<P>or some gibberish pounding on the keyboard.  (But watch
out!  That's often a lot less random that you might think. 
That's how the Russians used to make one-time pads for spies. 
The alternation of left and right hand keystrokes on mechanical
typewriters was clearly evident from captured pads.)</P>

<P>But why go to the trouble when <i>Speak Freely</i> will make up a
key for you on the spot?  The Options/Create Key menu item
computes a seed value from the time, date, and a variety of
information about your computer and uses it to generate a
hash code using the MD5 algorithm.  The key is displayed in a
dialogue box:</P>

<p>
<center>
<img src="../images/genkey.png" alt="" width=329 height=114>
</center>

<P>Each time you press the "New Key" button, another key is
generated, containing 128 bits of information, the same as an
AES, Blowfish, or IDEA key and more than twice the 56 bits of a DES key.  The
text of the key is automatically selected and may be copied to
the clipboard with Ctrl+C and pasted into a key field in the <A
HREF="connproperties.htm">Options/Connection</A> dialogue box
and an electronic mail message to the person you want to speak
with.  The message might read something like:</P>

<p>
<blockquote>
<tt>Hi!  I'd like to talk to you around 21:00 your time tonight with Speak
Freely.  I've generated a key of:</tt>
<p>
<center>
<tt>            NHCG-AJHP-ILJN-DHAI-NFEI-CPKO-PINJ-JIAA</tt>
</center>
<p>
<tt>for this conversation.  Please paste this key into the IDEA encryption box
when you set up the connection to my machine.  I'm looking forward to chatting
with you!</tt>
</blockquote>

<P>Encrypt the message with whatever tool you use to protect
your electronic mail, and send it winging its way over the
Internet.</P>

<P>When your friend receives the message and decrypts it, she
will know the key to use for your forthcoming conversation. 
You can either generate a new random key for each conversation
(as PGP does) or, if you trust the other person (and yourself!)
to keep the key secret, use it for multiple conversations with
that individual.</P>

<P>If you use a public key cryptosystem, this technique permits
you to exchange keys for conversations with people you've never
previously communicated with in any manner, as long as you
trust their published public keys to actually be theirs.  Of
course when you let <i>Speak Freely</i> generate the key,
you're trusting me to not have installed a "back door" that
allows me to know what key you'll get, or to have accidentally
introduced a bug which makes the keys predictable.</P>

</BODY>
</HTML>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -