Parameters and key dimension for DH and RSA

Asked Sep 08 '16 at 14:31

Active Sep 08 '16 at 23:28

Viewed 199 times

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.

edited Sep 08 '16 at 23:28

Maarten Bodewes

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asked Sep 08 '16 at 14:31

M-elman

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What book? What dimensions? – Maarten Bodewes Sep 08 '16 at 16:04
By dimensions, I assume he means size. – poncho Sep 08 '16 at 16:07
"Discrete Mathematics" - Berardi, Beutelspacher. 1024 bit for n=pq in RSA, the same for p in DH key exchange. – M-elman Sep 08 '16 at 16:08
@M-elman: actually, that advice is rather outdated... – poncho Sep 08 '16 at 16:43
@poncho It's the reason why I asked. I want to know which sizes are considered secure nowadays. – M-elman Sep 08 '16 at 17:14
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See http://keylength.com and / or it's links. DH = discrete logarithm. – Maarten Bodewes Sep 08 '16 at 17:38
This is a useful website, thank you. Is the "key" in the Discrete Logarithm section the recommended lenght of a and b in DH key exchange? – M-elman Sep 08 '16 at 18:06
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I think this is our canonical ressource on this subject (for RSA at least). – SEJPM Sep 08 '16 at 18:06
@M-elman Yes, that's it. Note that - although there are certainly differences between the algorithms - that the group size in DH is generally identical to the size of the RSA modulus/private key when strength is considered. – Maarten Bodewes Sep 08 '16 at 23:24

Parameters and key dimension for DH and RSA

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