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Short key fingerprints are indeed vulnerable. But those are different from the short-authentication-string (SAS) used by ZRTP. A simple SAS based protocol using one-time keys could look like this: Alice sends a (collision resistant) hash of her public key to Bob. Bob sends his public key to Alice Alice sends her public key to Bob The short ...

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I'd say that most of the time the signature is accompanied by the certificate of the signer. This certificate contains the public key. Most container formats such as CMS (used in S/MIME, also known as PKCS#7) or XML digsig contain specific fields that may contain certificates - and usually do. When the certificate is received the Public Key Infrastructure ...

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Your requirements are not terribly precise, so here is what I think you mean: "The result must be trusted by all three participants" ==> Even if Alice & Bob are both malicious & colluding, the output of Carol should be uniform. Also, all 3 should get the same output. "The coin is flipped only by Alice and Bob" ==> Alice & Bob do all the work. ...

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This protocol doesn't authenticate the mote at all. Consider this attack: Mote B sends a 'hello' message to Base. This message contains the ID# of Mote A and a random nonce [R] (HW generated) encrypted by the base's public key. Base decrypts the 'hello' and verifies the ID# against a whitelist. Base sends an 'ack' message. This message contains some ...

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Typically, a message will contain some sort of identifying information of the sender, such as the From header of an e-mail. In any case, if the sender of the message is unknown, what's the point of using signatures at all? The purpose of a signature is to ascertain that the message was written and sent by its purported sender. The only way to be 100% ...

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Normally, yes, the hash algorithm in use is communicated beforehand. For example, sending an algorithm identifier during the TLS/SSL handshake process. However, depending upon the "padding scheme" in use with RSA, it may be possible to determine which hash algorithm was used from the signatures themselves. Some padding schemes encode information ...

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As fgrieu pointed out, Alice and Bob must have somehow come to some kind of agreement before the random beacon is generated. Would either of these techniques work for you? use the random beacon directly They could agree ahead of time that "Alice wins if the first random bit sent by the NIST Randomness Beacon on 2015-11-02 at 11:59 is a 0, and Bob wins if ...

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You are probably aware of the existence of public key certificates. A certificate proves the authenticity of a public key, basically by signing the value of that public key (plus some data on the owner of that key) with a private key of some third party. This third party often is a central Certificate Authority (CA) that is trusted by both the sender and the ...

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The original is completely broken and would be regardless of the insecurity of DES. The ECB encryption of a single block message (with a secure cipher) would be a secure MAC, but XORing the message blocks means that an attacker can modify any block of the message simply by making the same change to another block so that they cancel out. The modified ...

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Yes it proves that $y \ne 1 \pmod{n}$ is not an $e$-th root. That is, no $x$ exists such that $x^e = y \pmod{n}$. In particular, if $e | \phi(n)$ then for any $x$ it holds that $\left( x^{ \frac{\phi(n)} {e}} \right)^e = 1 \ne y$. This probably means one last final conclusion designed as a homework. Regarding GQ protocol: prover will be unable to pick an ...

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Most applications store their private keys for TLS in a cleartext file protected with filesystem permissions. On UNIX-ish systems this location is typically in /etc/ssl/private/mykey.key readable only by root. Windows-based systems store private keys in a special secured portion of the system registry database, which only the SYSTEM account (equivalent to ...

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Yes, it could be done. However, it would work a little different from what you imagine. The government can create a new blockchain operating under zerocoin rules. The government could then distributed one satoshi per citizen. This distribution could happen for example by letting each citizen visit a government office to present their passport and receive ...

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