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I understand that anything not using CBC will work, but are there any such modes? I'd also like to avoid weak stuff like RC4/5 and MD5 so preferrably ciphers that use sensible functions.

On a SSL 3.0 only server with several weak functions disabled client-side, Internet Explorer defaults to 3DES keys with SHA1 HMAC in CBC mode, is there anything better I can do?

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  • Isn't TLS_FALLBACK_SCSV sufficient? May 31, 2016 at 15:17
  • In SSL3 (and TLS1.0 and 1.1) the only choices are RC4 (with no mode) and CBC mode with several block ciphers of which only 3DES and AES are both acceptable and common. Any CBC cipher in SSL3 is badly broken by POODLE, but acceptable in 1.0 and 1.1; BEAST in 1.0 proved not very fierce AND practically all stacks implemented (compatible) 1/n fragmentation which totally blocks it anyway. CBC in all (even 1.2) is subject to Lucky13 but for now that's still impractical. Attacks on RC4 apply to all versions but are still relatively costly; SSL3 CBC is broken in seconds versus RC4 in days. ... Aug 2, 2016 at 9:07
  • ... RC5 is not used in SSL/TLS at all. MD5 in HMAC is actually fine (HMAC doesn't need collision resistance of the hash) but all acceptable ciphers combinable with MD5 are also combinable with SHA1. Aug 2, 2016 at 9:07

2 Answers 2

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I don't think so, at least not with IE (per this page on Wikipedia).

Between RC4 and CBC there really aren't any good SSLv3 cipher suites to use.

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If you have clients that require old cipher suites, then make them VPN in to your webserver. The VPN session can mitigate the risks.

If that isn't an option, lock them down by IP address. You can do this with a dedicated server such as legacy.company.com for clients that can't or won't upgrade

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  • I cannot add a layer of anything as this is a router with limited storage and RAM and I've only got a lightweight webserver to work with.
    – Searinox
    May 29, 2016 at 20:21
  • Can you upgrade the server's SSL/TLS library? Usually they're standardised (e.g. openssl)
    – Polynomial
    May 29, 2016 at 23:18

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