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As Steth stated before, using system time as seed in cryptographic implementations is terrible idea for any PRNG because this may be simply very predictable. There are better solutions based on noise generated by device drivers in the system (see man urandom) What you want from PRNG in cryptography is to be uniform and unpredictable, so the entropy would be ...


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I do not know why the OpenSSL implementation specifically does this. However, a branch-less (constant time) implementation of the RSA private key operation, might be slightly more efficient if the parameter $c = q^{-1} \bmod p$ is calculated for $p$ being the greatest prime of the two. Otherwise the value of $J_q = I^{d \bmod q-1} \bmod q$ has to be taken ...


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There's no real difference between $p$ and $q$ in RSA. It looks like OpenSSL just has the agreement "$p$ has to be bigger than $q$" for conveniences. One of the numbers has to be bigger than the other (otherwise they would be the same number, and $p = q$ is very bad in RSA). Just use two examples: $p = 13$ and $q = 11$. $p$ is bigger than $q$, all right. ...


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First, I am assuming, per https://security.stackexchange.com/questions/29172/what-changed-between-tls-and-dtls, that the client handshake protocol in DTLS is not different from that in TLS over TCP. This seems a safe bet since the client/server encrypted handshake protocol in OpenVPN's UDP implementation is the same as in standard TLS over TCP. I am not ...


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To make it easier for humans to read.


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If the application completely trusts the public key (e.g., runs code signed by it), then you could add "master key change" messages that can be signed by it, that make the application change it's hard-coded key. For additional security, you could require that the new key be additionally signed by a key hopefully separated from the now-compromised one - here ...



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