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diff --git a/api/2.0.1/node16.html b/api/2.0.1/node16.html new file mode 100644 index 0000000..ab02a07 --- /dev/null +++ b/api/2.0.1/node16.html @@ -0,0 +1,120 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> + +<!--Converted with LaTeX2HTML 2008 (1.71) +original version by: Nikos Drakos, CBLU, University of Leeds +* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan +* with significant contributions from: + Jens Lippmann, Marek Rouchal, Martin Wilck and others --> +<HTML> +<HEAD> +<TITLE>The ElGamal and DSA algorithms</TITLE> +<META NAME="description" CONTENT="The ElGamal and DSA algorithms"> +<META NAME="keywords" CONTENT="pycrypt"> +<META NAME="resource-type" CONTENT="document"> +<META NAME="distribution" CONTENT="global"> + +<META NAME="Generator" CONTENT="LaTeX2HTML v2008"> +<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css"> + +<LINK REL="STYLESHEET" HREF="pycrypt.css"> + +<LINK REL="next" HREF="node17.html"> +<LINK REL="previous" HREF="node15.html"> +<LINK REL="up" HREF="node15.html"> +<LINK REL="next" HREF="node17.html"> +</HEAD> + +<BODY > + +<DIV CLASS="navigation"><!--Navigation Panel--> +<A NAME="tex2html251" + HREF="node17.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> +<A NAME="tex2html247" + HREF="node15.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> +<A NAME="tex2html241" + HREF="node15.html"> +<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> +<A NAME="tex2html249" + HREF="node1.html"> +<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A> +<BR> +<B> Next:</B> <A NAME="tex2html252" + HREF="node17.html">Security Notes for Public-key</A> +<B> Up:</B> <A NAME="tex2html248" + HREF="node15.html">Crypto.PublicKey: Public-Key Algorithms</A> +<B> Previous:</B> <A NAME="tex2html242" + HREF="node15.html">Crypto.PublicKey: Public-Key Algorithms</A> + <B> <A NAME="tex2html250" + HREF="node1.html">Contents</A></B> +<BR> +<BR></DIV> +<!--End of Navigation Panel--> + +<H2><A NAME="SECTION00061000000000000000"> +The ElGamal and DSA algorithms</A> +</H2> +For RSA, the K parameters are unused; if you like, you can just +pass empty strings. The ElGamal and DSA algorithms require a real +K value for technical reasons; see Schneier's book for a detailed +explanation of the respective algorithms. This presents a possible +hazard that can +inadvertently reveal the private key. Without going into the +mathematical details, the danger is as follows. K is never derived +or needed by others; theoretically, it can be thrown away once the +encryption or signing operation is performed. However, revealing +K for a given message would enable others to derive the secret key +data; worse, reusing the same value of K for two different +messages would also enable someone to derive the secret key data. An +adversary could intercept and store every message, and then try deriving +the secret key from each pair of messages. + +<P> +This places implementors on the horns of a dilemma. On the one hand, +you want to store the K values to avoid reusing one; on the other +hand, storing them means they could fall into the hands of an adversary. +One can randomly generate K values of a suitable length such as +128 or 144 bits, and then trust that the random number generator +probably won't produce a duplicate anytime soon. This is an +implementation decision that depends on the desired level of security +and the expected usage lifetime of a private key. I can't choose and +enforce one policy for this, so I've added the K parameter to the +encrypt and sign methods. You must choose K by +generating a string of random data; for ElGamal, when interpreted as a +big-endian number (with the most significant byte being the first byte +of the string), K must be relatively prime to self.p-1; any +size will do, but brute force searches would probably start with small +primes, so it's probably good to choose fairly large numbers. It might be +simplest to generate a prime number of a suitable length using the +Crypto.Util.number module. + +<P> + +<DIV CLASS="navigation"><HR> +<!--Navigation Panel--> +<A NAME="tex2html251" + HREF="node17.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> +<A NAME="tex2html247" + HREF="node15.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> +<A NAME="tex2html241" + HREF="node15.html"> +<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> +<A NAME="tex2html249" + HREF="node1.html"> +<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A> +<BR> +<B> Next:</B> <A NAME="tex2html252" + HREF="node17.html">Security Notes for Public-key</A> +<B> Up:</B> <A NAME="tex2html248" + HREF="node15.html">Crypto.PublicKey: Public-Key Algorithms</A> +<B> Previous:</B> <A NAME="tex2html242" + HREF="node15.html">Crypto.PublicKey: Public-Key Algorithms</A> + <B> <A NAME="tex2html250" + HREF="node1.html">Contents</A></B> </DIV> +<!--End of Navigation Panel--> + +</BODY> +</HTML> |