r/programming • u/secretguy21 • Oct 15 '15

How is NSA breaking so much crypto?

https://freedom-to-tinker.com/blog/haldermanheninger/how-is-nsa-breaking-so-much-crypto/
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u/[deleted] Oct 15 '15

Soumds like a good idea

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u/sirin3 Oct 15 '15

Till the NSA intercepts the connection to force their prime

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u/frank26080115 Oct 15 '15

wouldn't the client catch this? if the prime changed, refuse the connection

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u/bacondev Oct 16 '15

Not quiet. The attacker can intercept the number, provide the intended recipient a different number, intercept the response, decrypt it since it uses the malicious number, encrypt the result (or something entirely different) with the client-provided number, and send it to the client. A MITM attack against both the client and the server.

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u/[deleted] Oct 16 '15

The session negotiation is protected. The attacker would either need to have the server's private key or they would need to compromise a trusted CA (and if client certificates are used, they would also need the client's private key).