[PLUG] Notes on Mark's hash table talk at Central

[Walt Mankowski <waltman@pobox.com>]

Mark asked me to forward this to this mailing list.  I don't believe
he's subscribed to the list, so please direct questions about the talk
directly to him.

Walt

----- Forwarded message from Mark Dominus <mjd@plover.com> -----

Date: Thu, 07 Jan 2016 16:59:25 +0000
From: Mark Dominus <mjd@plover.com>
To: Walt Mankowski <waltman@pobox.com>
Subject: Re: Slide corrections
X-Mailer: Perl5 Mail::Internet v2.14

Thanks for corrections!

Would you please forward this note to the PLUG mailing list for me?

	Thanks for inviting me to speak and for being such an engaged
	audience; this was my 13th annual December talk for PLUG, and
	I hope to see you back next year.

	The slides from last night's presentation are at

	    http://perl.plover.com/yak/HashHistory/

        and there are detailed notes at 

	    http://perl.plover.com/classes/HashHistory/samples/NOTES.html

 	In particular, the discussion of SNOBOL tables, which I had to
        omit because I wasted too much time with a long introduction, is at 

	    http://perl.plover.com/classes/HashHistory/samples/NOTES.html#snobol

	Rachel asked a question about the suitability of MD5 as a
	random number generator.  MD5 is no longer considered
	sufficiently secure to be used for cryptographic applications.
	Differential cryptography techniques have resulted in
	successful collision attacks on MD5; this means it is now
	possible to find two inputs that hash to the same output.
	(See https://en.wikipedia.org/wiki/MD5#Collision_vulnerabilities )
	However, as far as I know there is still no effective way to
	predict what the output will be for a given input, so MD5's
	usefulness as a random number generator is unimpaired.
	Disclaimer: Cryptography is difficult and I am not an expert.

	I'll be glad to answer questions by email.

        P.S. At Clarkville I posed the following problem:

            If a right triangle has a hypotenuse with length 10, and
            the perpendicular dropped from the opposite vertex has
            length 6, what is the area of the triangle?

        The obvious answer, 30, is wrong, and the puzzle is to figure out why. 

        The answer, should you want to see it, is at

	    http://math.stackexchange.com/q/1594740/25554


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