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I read that Mozilla uses its own trust certificate store but does "weak encryption" have anything to do with whether the browser trusts the certificate?

Has it got anything to do with the signature algorithm or signature hash algorithm?

Firefox Screenshot 1:

Printscreen 1 of Firefox

Firefox Screenshot 2:

Printscreen 2 of Firefox

Firefox Screenshot 3:

Printscreen 3 of Firefox

Chrome Screenshot 1:

Printscreen 1 of Chrome

Chrome Screenshot 2:

Printscreen 2 of Chrome

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  • 1
    Did you check SSL Labs' test? I'm guessing Firefox either doesn't like TLS 1.0, or doesn't like CBC.
    – forest
    Dec 24 '19 at 8:45
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... does "weak encryption" have anything to do with whether the browser trust the certificate? Has it got anything to do with the signature algorithm or signature hash algorithm?

The weak encryption has nothing to do with the certificate: The hash algorithm used for the certificates signature is SHA-256 which is perfectly fine. The signature is also done with a RSA key of 2048 bit (can be seen in the intermediate CA, which is not shown by you) which is also perfectly fine.

Instead like said in the other answer the weak encryption refers to the use of TLS 1.0 with a CBC cipher. Note that unlike Chrome Firefox does not use RSA key exchange with this site but instead DHE (the cipher is TLS_DHE_RSA_WITH_AES_128_CBC_SHA), so the information regarding the weak key exchange in the other answer does not apply to Firefox.

To determine what exactly Firefox considers weak I was trying the same cipher with the same length of the DH parameters (1024 bit) as used by the original server but changed the TLS version. It looks like with TLS 1.2 Firefox 70.0.1 considers the encryption strong and only when disabling TLS 1.2 it considers the encryption weak since it now has to use TLS 1.1 or TLS 1.0.

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  • TLS_DHE_RSA_WITH_AES_128_CBC_SHA isn't ECDHE, it does fall short in the ways Firefox lists
    – Ben Voigt
    Dec 24 '19 at 17:27
  • @BenVoigt: DHE provides forward secrecy, contrary to RSA key exchange. ".., it does fall short in the ways Firefox lists" - do you have details (preferable with source) on what exactly Firefox considers weak or is this statement just your feeling on how Firefox behaves? Dec 24 '19 at 17:36
  • RSA is still part of that cipher. Firefox is recommending to use Elliptic Curve cryptography instead of modular exponentiation.
    – Ben Voigt
    Dec 24 '19 at 19:08
  • @BenVoigt: "RSA is still part of that cipher" - This "RSA" in the cipher stands for RSA based authentication and relates to the type of public key in the certificate. This is still the predominant form of authentication and still considered secure with the proper key length (at least 2048). Please show me any recommendation by Mozilla or any other reliable source which considers RSA based authentication (i.e. the use of RSA certificates) weak. Dec 24 '19 at 19:56
  • It's the DHE key exchange which is considered weak. DHE uses modular exponentiation in a prime field, aka RSA. See digicert.com/blog/google-plans-to-deprecate-dhe-cipher-suites Diffie-Hellman (DH) and the ephemeral version (DHE) specify the order of operations for key exchange. RSA vs ECC specifies the crypto inside the individual operations.
    – Ben Voigt
    Dec 24 '19 at 20:15
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While Chrome doesn't throw a warning in main the user interface, here are the warnings shown in the developer console:

Connection - obsolete connection settings

The connection to this site is encrypted and authenticated using TLS 1.0, RSA, and AES_128_CBC with HMAC-SHA1.

  • TLS 1.0 is obsolete. Enable TLS 1.2 or later.
  • RSA key exchange is obsolete. Enable an ECDHE-based cipher suite.
  • AES_128_CBC is obsolete. Enable an AES-GCM-based cipher suite.

Being obsolete doesn't mean it's broken, that might be why Chrome doesn't feel the need to tell the user directly about it.

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  • "Being obsolete doesn't mean it's broken" is true, but ignoring the fact that in the screenshot posted, Firefox explicitly says it is broken.
    – Ben Voigt
    Dec 24 '19 at 17:25
  • Thanks, everyone!
    – Neo
    Dec 30 '19 at 8:42

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