[HN Gopher] Breaking supersingular isogeny Diffie-Hellman (SIDH)
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       Breaking supersingular isogeny Diffie-Hellman (SIDH)
        
       Author : hasheddan
       Score  : 9 points
       Date   : 2022-07-31 19:48 UTC (3 hours ago)
        
 (HTM) web link (ellipticnews.wordpress.com)
 (TXT) w3m dump (ellipticnews.wordpress.com)
        
       | zw123456 wrote:
       | Can I get an ELI5 ?
        
         | espadrine wrote:
         | When a browser talks to a server over HTTPS, it needs to have a
         | shared secret key with the server to encrypt its streams.
         | Diffie-Hellman is a protocol that achieves that through a back-
         | and-forth communication with no preexisting secret, but its
         | security relies on the complexity of solving the discrete
         | logarithm problem, which is hard on a classical computer, and
         | thus safe; but is much more tractable on a quantum computer,
         | and thus unsafe. Quantum computers that are big or reliable
         | enough don't exist, but nefarious people can store HTTPS
         | streams on disk until they do, and decrypt them once quantum
         | computers are good enough, which will be a tremendous loss of
         | confidentiality worldwide.
         | 
         | As a result, there is some urgency in getting browsers to use a
         | new algorithm that survives quantum computers. NIST set up a
         | competition: PQC. Various entries adopted different
         | mathematical approaches. One of the entries, SIKE, which is an
         | instance of SIDH, survived cryptanalysis and was a 4th round
         | finalist.
         | 
         | However, this week, a paper was published, describing an
         | algorithm that can recover the shared key from seeing the SIKE
         | Diffie-Hellman exchange. It is not just theoretical: it was
         | implemented and could break keys in less than a day. It is
         | particularly shocking because we came near a situation where it
         | could have been standardized or even implemented in browsers
         | with devastating consequences once the attack was found.
         | Furthermore, it puts into question the use of the whole
         | mathematical approach used for SIKE.
        
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       (page generated 2022-07-31 23:01 UTC)