# Tag Info

## New answers tagged protocol-analysis

4

What does this mean, exactly? The purpose of the environment is to model "everything else happening in the universe" besides the protocol execution. In the UC model, the adversary is allowed to talk to the environment during the execution of the protocol. So UC security means "security no matter what else is going on in the world, even if other things ...

2

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 ...

1

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 ...

2

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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