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Short answer: yes you are right and you can do this. To be on the safe side however, you must ensure not to lower the HMAC function security by using it properly and not putting wrong expectation on the function used. By design HMAC functions expects one parameter to be a secret key, and the other being a message which could be public (you can find more ...


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I believe U2F changed their specification from using raw USB communication to using USB-HID communication. I am no expert in USB communication, but I believe the Yubikey lack of backward compatibility is either : not being able to implement both USB protocols at once. a hardware limitation.


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The "keyed MD5" described in RFC 1828 can be summarized as follows: for key K and data D, the MAC value is MD5(K||D||K) (in the RFC, K is first padded to a length multiple of 512 bits, but it does not substantially change things here). To my knowledge, there is no known weakness to that construction, but there is not much security analysis either. HMAC has ...


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I'll step by step and then overall crypto system, seems most logical to me. Generate a new AES 256bit/CBC/PKCS7 Master Key (Km) Generate a new 128bit IV (strong PRNG) CBC is fine here as there isn't any sort of oracle the attacker would have access to and bit-flipping attacks are ruled out by the tag. Random IV is correct, 256 bits is more than ...


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Looking at OpenVPN's source code, this appears to be a cosmetic quirk of OpenSSL. When using --show-digests, OpenVPN calls OpenSSL's EVP_get_digestbynid() with, as parameter, all integers from 0 to 999. For some of these values, EVP_get_digestbynid() returns a non-NULL pointer that identifies the corresponding hash function implementation, and then OpenVPN ...


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As pointed out in the comments, ssl/tls will protect your credentials in transit. Encrypting traffic is part of the purpose of the protocol. The other major purpose of the protocol: verifying that you are communicating directly with the party you think you are communicating with. The OP said that ssl proxies are possible and has seen it in action for ...


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Details matter. As @Ricky points out, showing truncated HMAC values won't help the attacker finding the secret key, compared to a similar situation where the HMAC values would not be truncated. This makes sense: the truncation only removes information. However, the attacker is not ultimately after the secret key. What the attacker really wants is to make ...


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Yes. ‚Äč Yes. B interacts with A and the challenger as follows: B forwards all queries from A to the challenger, and gives the same output as A. For each response from the challenger, B truncates the response and sends the truncated response to A. A's view in that interaction is identical to A's view in the interaction for your scenario with the same key, ...



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