# Tag Info

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Insecure, you just replay $\text{username}$ and $\text{password}$. Password is also sent in clear text. Secure, if the hash function $H$ used is strong enough to resist bruteforcing of the password. However you'll also need to send the timestamp so that the server can check the auth, so this scheme is better portrayed as $\text{username, timestamp, ... 0 Assuming that Alice and Bob have exchanged keys before, when Alice receives the message [R]B, she knows that B has sent that message at some point. Therefore she knows (at most) that B has participated in the protocol. She doesn't know that Bob has ever sent the message [R]B to her, maybe he sent it to Charlie and Charlie or Mallory resent it. There is no ... 2 We don't say this can't happen, we just say it won't happen. The only value that will decrypt to$p_2$under$(e_2,n_2)$is$p_2^{d_2}$, which we can call$s_2$. So, your problem comes down to asking what is the probability that$s_1=s_2$? If we assume that they're random, and that the moduli are similar enough sizes that this is even a realistic ... 2 I can't remember anyone claiming that:$s_1^{e2} \bmod n_2 = p_2$is never true. However, there is a single value$s_2 = p_2^{d_2} \bmod n_2$; it would be a rather strange coincidence if that value just happens to be the value$s_1 = p_1^{d_1} \bmod n_1$1 It is not impossible that a signature be authenticated with respect to the wrong public key. However odds of that are so remote (similar to having a random number less than the public modulus pass as a signature) that we can safely neglect this possibility. 0 We consider a server$S$and a bunch of users$U_1, \dots, U_n$. What you want: Users should be able to send queries to the server and receive replies. The users should be able to register identities with the server. Any reply$m'$that a user accepts as coming from the server in response to a query$m\$ from that user, really came from the server in ...

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The Wikipedia article points out a good reason for using a random challenge value: preventing replay attacks. If the hash was always the same (as the hash of the symmetric key would be), then having listened in on one challenge-response cycle, a malicious listener could pass further handshake tests.

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Some devices I've been working with do indeed update biometric information. The reasons is that there may be additional information: acceptable fingerprint was scanned (required features are found), but the scan shows some area of finger not involved in previous scans. some other additional information helping make more exact scans in the future

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If you can put the entire PGP certificate in a proprietary non-critical extension then you don't need to find the PGP certificate in a store. This solution depends on the condition that you are able to create your own OID and insert the PGP certificate in the extension. Furthermore, the server should accept such a certificate and contain methods of ...

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