Re: [TLS] Comparative cipher suite strengths
Eric Rescorla <ekr@networkresonance.com> Wed, 22 April 2009 13:42 UTC
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Date: Wed, 22 Apr 2009 06:46:27 -0700
From: Eric Rescorla <ekr@networkresonance.com>
To: "Blumenthal, Uri" <uri@ll.mit.edu>
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Subject: Re: [TLS] Comparative cipher suite strengths
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At Wed, 22 Apr 2009 09:24:26 -0400, Blumenthal, Uri wrote: > > Eric, > > I disagree. You're mixing together two orthogonal issues: security > of algorithms and security of implementation. > > NIST recommends that algorithms in a cipher suite are of comparable > strength. That includes relative key length. I appreciate that NIST recommends this. I think it's silly. It doesn't get any less silly because it's typeset in cool FIPS formatting. > The fact that despite of using secure algorithms your implementation > still can have exploitable bugs (that nullify the benefits of > cryptography) is 100% irrelevant to the issue of selecting > algorithms and their parameters. I don't agree that that's true, but in any case it's not what I'm saying. The amount of computational power required to break a 128-bit AES key with current is so outlandishly large that there is plausible scenario that such a key will be broken by brute force. The only plausible situations in which 128-bit AES keys are breakable, then, are non-brute-force attacks such as attacks on the implementation or an analytic attack. In neither case does 2^{128} represent an accurate estimate of the security of the algorithm, nor is there any reason to believe that AES-256 is 2^{128} times more secure under such attacks. Thus, the inference that one ought to use an RSA key that is 2^{128} times stronger with AES-256 than AES-128 also does not follow. -Ekr
- Re: [TLS] Comparative cipher suite strengths Blumenthal, Uri
- [TLS] Comparative cipher suite strengths Carl Young
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths carlyoung
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Simon Josefsson
- Re: [TLS] Comparative cipher suite strengths carlyoung
- Re: [TLS] Comparative cipher suite strengths Steven M. Bellovin
- Re: [TLS] Comparative cipher suite strengths Blumenthal, Uri
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Blumenthal, Uri
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Steven M. Bellovin
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Steven M. Bellovin
- Re: [TLS] Comparative cipher suite strengths Michael.G.Williams
- Re: [TLS] Comparative cipher suite strengths Blumenthal, Uri
- Re: [TLS] Comparative cipher suite strengths Daniel Brown
- Re: [TLS] Comparative cipher suite strengths Nicolas Williams
- Re: [TLS] Comparative cipher suite strengths Peter Gutmann
- Re: [TLS] Comparative cipher suite strengths Blumenthal, Uri
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Daniel Brown
- Re: [TLS] Comparative cipher suite strengths Paul Hoffman
- Re: [TLS] Comparative cipher suite strengths Daniel Brown
- Re: [TLS] Comparative cipher suite strengths Paul Hoffman
- Re: [TLS] Comparative cipher suite strengths Steven M. Bellovin
- Re: [TLS] Comparative cipher suite strengths Nicolas Williams
- Re: [TLS] Comparative cipher suite strengths Dean Anderson
- Re: [TLS] Comparative cipher suite strengths Martin Rex
- Re: [TLS] Comparative cipher suite strengths Dean Anderson
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Michael D'Errico
- Re: [TLS] Comparative cipher suite strengths carlyoung
- Re: [TLS] Comparative cipher suite strengths Florian Weimer
- Re: [TLS] Comparative cipher suite strengths Peter Gutmann
- Re: [TLS] Comparative cipher suite strengths Blumenthal, Uri
- Re: [TLS] Comparative cipher suite strengths Vipul Gupta
- Re: [TLS] Comparative cipher suite strengths Nicolas Williams
- Re: [TLS] Comparative cipher suite strengths Robert Relyea
- Re: [TLS] Comparative cipher suite strengths Peter Gutmann
- Re: [TLS] Comparative cipher suite strengths Bill Frantz
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Peter Gutmann
- Re: [TLS] Comparative cipher suite strengths Blumenthal, Uri
- Re: [TLS] Comparative cipher suite strengths Jeffrey A. Williams
- Re: [TLS] Comparative cipher suite strengths Martin Rex
- Re: [TLS] Comparative cipher suite strengths Eric Rescorla
- Re: [TLS] Comparative cipher suite strengths Peter Gutmann
- Re: [TLS] Comparative cipher suite strengths Dean Anderson
- Re: [TLS] Comparative cipher suite strengths Steven M. Bellovin