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In 2012 CRIME attack effectively killed TLS compression. Has anything changed since 2012 regarding compression in TLS or have modern browsers sacrificed security over performance? If browsers now use TLS compression how does it bypass CRIME/BREACH?

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    $\begingroup$ ‘security over performance’ I’m curious if you’ve ever actually benchmarked TLS compression.The common implementations did not ever really give great performance benefits for web browsers. HTTP compression was almost always better, because it doesn’t scramble the dictionary with the headers, and DEFLATE (the only algorithm widely supported) is honestly not great for streaming data transfers (even with HTTP it’s not great most of the time). $\endgroup$ Oct 3, 2023 at 18:55

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TLS compression is removed in TLS 1.3. And even for lower TLS versions it is no longer available in the browsers and disabled by default in OpenSSL. Note though that compression at the TLS level is only relevant for the CRIME attack, BREACH is instead about compression at the HTTP level. Thus BREACH is not mitigated by disabling TLS compression.

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  • $\begingroup$ btw, did BREACH lead to removing HTTP compression from modern browsers? $\endgroup$
    – pacman
    Oct 10, 2023 at 11:37
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    $\begingroup$ @pacman: no. it's still in there. $\endgroup$ Oct 10, 2023 at 15:33

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