1

From this I understand that SRP is an algorithm that performs authentication and key exchange between a client and a server.

Consider two cipher suites like the following two, which algorithm would be used for key exchange in the second one, SRP or RSA?

1) rsa-aes-256-cbc-sha
2) srp-rsa-aes-256-cbc-sha

I also understand that even though these two cipher suites have the same encryption algorithm (AES), encryption mode (CBC), key size (256) and Message authentication code (SHA) they are two different cipher suites, correct?

2

The output for openssl ciphers -V for this cipher suite is:

0xC0,0x21 - SRP-RSA-AES-256-CBC-SHA SSLv3 Kx=SRP      Au=RSA  Enc=AES(256)  Mac=SHA1

This means: Key exchange (Kx) is done with SRP while the authentication (Au) is done with RSA. Comparing this with the first cipher suite you have:

0x00,0x35 - AES256-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(256)  Mac=SHA1

As you can see the difference is that this time RSA is used as key exchange too, not SRP.

  • So they are two different cipher suites? – Neofytos Frangos Aug 13 '17 at 13:20
  • @NeofytosFrangos: Since they differ in the key exchange they are obviously different. – Steffen Ullrich Aug 13 '17 at 15:00

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