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Questions tagged [advantage]

11 questions
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Should I normalize adversary's advantage in IND-XXX Game?

The Cryptography made simple (page 207, under Fig 11.12)(Nigel Smart) say that adversary's advantage of IND-PASS Game is $Adv1 = 2\times|Pr[b=b']-\frac{1}{2}|$. The reason for multiplying by 2 is to normalize advantage from $[0,\frac{1}{2}]$ to…
apapapa
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Understanding Adversary's Advantage for Target Key Recovery in Ideal Cipher Model

In the ideal cipher model, a block cipher is modeled by a different, independent random permutation for every key. Let $$ \mathcal{A}_{q}^{\text{IC-EKS}} $$ be a ( q )-query exhaustive key-search adversary in the ideal cipher model. and…
CrypticPotato
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Reduction from Distinguisher to Indishtinguishability

Content and Informal Problem Suppose a protocol $\pi$ doing an arbitrary task between two users A and B. I only know that $\pi$ relies on a IND-CPA symmetric encryption scheme $\mathcal{E} = $(KeyGen, Enc, Dec). In details, A holds a key $k$ in…
gamarcad
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About the definition of distinguishing advantage and computational indistinguishability

Given a polynomial-time adversary $A$ with binary output, the distinguishing advantage of $A$ with respect two games $G, H$ is defined…
AYun
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What is the definition of semantic secure advantage?

I'm doing sequence-of-game formal security analysis for key exchange protocol. It confuses me a lot how to calculate the adversary's semantic secure (SS) advantage. In Shoup's tutorial "sequences of games: a tool for taming complexity in security…
Chandler
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A smaller modulus-to-noise ratio means more security in LWE

Let $\text{Adv}^{\text{DLWE}}_{n,m,q,\sigma}$ be the advantage of an attacker to distinguish LWE samples from uniform ones, where $m$ is the number of samples, $q$ the modulus and $\sigma$ the standard deviation of the error distribution. I can't…
C.S.
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Proving 2-way nesting security

I recently came across the theorem about $n$-way nesting. It states that if $\mathcal{E}=(E, D)$ is semantically secure, then $\mathcal{E}$ is secure for $n$-way nesting. I'm trying to prove the specific case of $n=2$. For the encryption…
libre
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Computing the advantage when checking PRF

I am reading a pdf on pseudorandom function I found here https://www.cs.utexas.edu/~dwu4/courses/sp21/static/reductions.pdf My problem/struggle is with the computation of the distinguisher's $B$ advantage. According to the notes $b=0$ means that $B$…
tonythestark
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How to understand the "Authenticity" and "Privacy" of CCM-mode encryption scheme?

CCM mode refers to CTR+ CBC-MAC encryption mode. Based on this paper, the adversary's advantages against the authenticity of CCM is: Eq(1) Authenticity: it should be infeasible for an adversary to forge a valid ciphertext without knowing the secret…
Chandler
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MAC Security - MAC verification queries

In the applied cryptography book by Boneh and Shoup, Chapter 6 on MACs, it is stated that an adversary that is also capable of requesting the challenger for verification queries (in addition to signing queries) is not stronger than an Adversary that…
Evgeni Vaknin
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On showing an Inequality on a Generalized Decisional Diffie-Hellman Problem

This paper talks about a generalization of the Decisional Diffie-Hellman problem over different polynomial exponents of the base generator to be given and be distinguished from each other. Throughout this question I'll be using jargon and notation…
fifteententwenty
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