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You cannot change the hash size without altering TLS: From: Appendix C. Cipher Suite Definitions MAC Algorithm mac_length mac_key_length -------- ----------- ---------- -------------- NULL N/A 0 0 MD5 HMAC-MD5 16 16 SHA HMAC-SHA1 20 20 SHA256 HMAC-SHA256 32 ...

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In TLS 1.2 the GCM and SHA-256 in GCM_SHA256 should be seen separately. GCM is the authenticated mode of operation used for confidentiality and integrity/authenticity of the messages (including the messages containing the data that TLS has been designed to protect). SHA-256 is a parameter for the HMAC function which is used as PRF (pseudo random function) ...

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I'll quickly decompose this cipher suite. TLS - standard starting point ECDHE - elliptic curve version of the Diffie-Hellman key-exchange using ephemeral keys (/exponents), other values for this position include RSA, DH and DHE ECDSA - signature algorithm, used to sign the key-exchange parameters, omitted for RSA, other values include RSA AES_128 - AES ...

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This is what openssl s_client -trace says: Received Record Header: Version = TLS 1.2 (0x303) Content Type = Handshake (22) Length = 333 ServerKeyExchange, Length=329 KeyExchangeAlgorithm=ECDHE named_curve: secp256r1 (P-256) (23) point (len=65): ...

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Let's shortly recall, how HMAC looks like: $HMAC_K(M):=H((K\oplus opad) || H((K \oplus ipad) || M))$ As you may observe here, the calculation of the outer hash is fully independant of the message. So the standard approach into implenting "update" functionality is to store the key and go as follows: Init(Key): Store the Key in K Init two Hash-function ...

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Of course - the whole important question is the one you "left out for another day." If a party in the middle can spoof IP addresses for some poor browser, then the party in the middle can act like a server to the browser, and act like a browser to the server. There will be two "premaster secrets", and how will either the browser or the server know?? ...

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LOL the NSA would have you believe that it is about uncrackable (256). 256 is used for web pages for goodness sake. The real data they care about is topped by at least 240000 bit encryption that is changed very frequently. Lets not forget the public stuff we have that we are appalled by, is what the government has been made far in advance. I done some ...

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TLS has different keys for the two different directions. That is, the server-to-client connection is encrypted with one set of keys, and the client-to-server connection is encrypted with another. Both sets of keys are derived at the same time, however they are distinct. Because the keys are distinct, using the same nonce isn't an issue. Technical point ...

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