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Of the following ciphers for RSA authentication, Firefox and Chrome do not use stronger than ECDHE-RSA-AES128-SHA256.

ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(256) Mac=AEAD
ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(128) Mac=AEAD
ECDHE-RSA-AES256-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(256)  Mac=SHA384
ECDHE-RSA-AES128-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(128)  Mac=SHA256

Why is this?

Isn't ECDHE-RSA-AES128-SHA256 the weakest of those listed above and ECDHE-RSA-AES256-GCM-SHA384 the strongest?

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I tested Chrome and Firefox, both mobile on ssllabs.com:

Chrome

Cipher Suites (in order of preference)

TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 (0xcca9)   Forward Secrecy    256
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 (0xcca8)   Forward Secrecy  256
OLD_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 (0xcc14)   Forward Secrecy    256
OLD_TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 (0xcc13)   Forward Secrecy  256
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (0xc02b)   Forward Secrecy  128
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f)   Forward Secrecy    128
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA (0xc00a)   Forward Secrecy 256
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014)   Forward Secrecy   256
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (0xc009)   Forward Secrecy 128
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013)   Forward Secrecy   128
TLS_RSA_WITH_AES_128_GCM_SHA256 (0x9c)  128
TLS_RSA_WITH_AES_256_CBC_SHA (0x35) 256
TLS_RSA_WITH_AES_128_CBC_SHA (0x2f)

Signature algorithms

SHA512/RSA, SHA512/ECDSA, SHA384/RSA, SHA384/ECDSA, SHA256/RSA, SHA256/ECDSA, SHA224/RSA, SHA224/ECDSA, SHA1/RSA, SHA1/ECDSA

Firefox

Cipher Suites (in order of preference)

TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (0xc02b)   Forward Secrecy  128
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f)   Forward Secrecy    128
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA (0xc00a)   Forward Secrecy     256
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (0xc009)   Forward Secrecy     128
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013)   Forward Secrecy   128
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014)   Forward Secrecy   256
TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x33)   Forward Secrecy   128
TLS_DHE_RSA_WITH_AES_256_CBC_SHA (0x39)   Forward Secrecy   256
TLS_RSA_WITH_AES_128_CBC_SHA (0x2f)     128
TLS_RSA_WITH_AES_256_CBC_SHA (0x35)     256
TLS_RSA_WITH_3DES_EDE_CBC_SHA (0xa)

Signature algorithms

SHA256/RSA,SHA384/RSA, SHA512/RSA, SHA1/RSA, SHA256/ECDSA, SHA384/ECDSA, SHA512/ECDSA, SHA1/ECDSA, SHA256/DSA, SHA1/DSA

SHA384 is seemingly unpopular. Have not seen it in the wild. Firefox (NSS) and Chrome (WebCrypto) have some problems implementing those strong ciphers.

Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=923089

Chrome: https://groups.google.com/a/chromium.org/forum/#!topic/chromium-discuss/ufzO8NhttaA

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  • Thanks for the ssllabs.com link. I wonder why the order of preference is what it is?
    – Geremia
    Commented Mar 14, 2016 at 21:22
  • From here it appears that the recent Safari and IE support TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, but the recent Opera, Firefox, and Chrome versions do not. I wonder why.
    – Geremia
    Commented Mar 17, 2016 at 19:31

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