I studied RSA and Diffie-Hellman key exchange from a quite old book (Discrete Mathematics by Berardi, Beutelspacher) and so I wonder if the recommended dimensions for the prime p and the secret numbers a and b of the DH key exchange and for the RSA's public key are still valid or not. The dimensions are 1024 for the prime in RSA and the same for the group of DH.

I tried to find an answer online but I found several different opinions. Can anyone share his knowledge and/or experience about it? I would appreciate also references to data from valid online resources.

  • $\begingroup$ What book? What dimensions? $\endgroup$
    – Maarten Bodewes
    Sep 8 '16 at 16:04
  • $\begingroup$ By dimensions, I assume he means size. $\endgroup$
    – poncho
    Sep 8 '16 at 16:07
  • $\begingroup$ "Discrete Mathematics" - Berardi, Beutelspacher. 1024 bit for n=pq in RSA, the same for p in DH key exchange. $\endgroup$
    – M-elman
    Sep 8 '16 at 16:08
  • 3
    $\begingroup$ See http://keylength.com and / or it's links. DH = discrete logarithm. $\endgroup$
    – Maarten Bodewes
    Sep 8 '16 at 17:38
  • 4
    $\begingroup$ I think this is our canonical ressource on this subject (for RSA at least). $\endgroup$
    – SEJPM
    Sep 8 '16 at 18:06

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