[ pycrypto-Bugs-1041588 ] wishlist: DH key agreement

Bugs item #1041588, was opened at 2004-10-06 16:26
Message generated for change (Comment added) made by zooko
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Category: None
Group: None
>Status: Closed
>Resolution: Invalid
Priority: 5
Submitted By: Zooko O'Whielacronx (zooko)
Assigned to: Nobody/Anonymous (nobody)
Summary: wishlist: DH key agreement

Initial Comment:
I need something that is not encryption nor
authentication, but key agreement.  That is: Alice
generates random x, Bob generates random y, Alice
computes g^x mod p, Bob computes g^y mod p, Alice
(given g^y), computes (g^y)^x.

How can I accomplish this?


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>Comment By: Zooko O'Whielacronx (zooko)
Date: 2005-08-04 12:22

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I'm attempting to close this since it turns out DH key
agreement already works.

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Comment By: Zooko O'Whielacronx (zooko)
Date: 2005-06-14 21:27

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Yes, I eventually noticed that Python does this efficiently.
 It was fine.  Not stellar -- I think it was something like
1 second for 4096 bit DH or something -- but fine.

I'm glad to see that AMK is tending to pycrypto again...

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Comment By: Nobody/Anonymous (nobody)
Date: 2005-06-14 21:07

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Umm...The plain DH is rather weak in itself. I'd strongly
recommend that you pick up B. Schneiener's Practical
Cryptography.

-NcF

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Comment By: A.M. Kuchling (akuchling)
Date: 2004-10-20 16:56

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Python supports pow(g,y,p) to compute g**y mod p.

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Comment By: Zooko O'Whielacronx (zooko)
Date: 2004-10-06 16:36

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Well I looked into the source of pycrypto to see what it
would take to add this functionality.  It turns out that the
El Gamal stuff is implemented in 100% Pure Python!  That's
kind of shocking, but at least it answers my question about
how to compute this.  The answer is something that includes
lines like "pow(g, y) % p".  I'll be interested to see how
this performs.


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