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51 views

how to calculate nonlinearity?

I am struggling to understand how to calculate non-linearty of an s-box, could someone show me a detailed example? I found this question which helped a little, but I still didn't get it, if someone ...
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0answers
54 views

Given only RSA public key parameters, what security issues might I be able to detect?

I'm attempting to automate some checks against a large list of .NET assemblies, and want to include a test to see if the RSA parameters used to sign the assemblies are sensible. However, since I don't ...
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0answers
50 views

Statistical saturation attack on block ciphers

I was wondering if anyone around here could give me some explanation on this type of attacks. Pretty much the only thing that I could find is this What I really need is basic explanation of the ...
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0answers
45 views

Encryption with a known plaintext

I'm building an application where users can be a part of groups, and can obtain and distribute URLs from the group page that allow anyone who clicks on them to join said group. Groups should not ...
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0answers
108 views

FileVault AES-XTS decryption with cipher text that's missing a part

My mac was recently upgraded to OS X Yosemite and FileVault2 full disk encryption was turned on. Encryption finished, but things went horribly wrong and key parts of the disk are filled with all 0s ...
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0answers
29 views

What is the difference between any secret sharing scheme and arithmetic secret sharing scheme

It looks like that only difference between two of them the variables. But it does not make sense for me and I could not find exact definition of arithmetic secret sharing scheme. I mean what exactly ...
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0answers
56 views

Can CKM_RSA_PKCS signature be made secure by lowering its maximum input size?

The CKM_RSA_PKCS Mechanism in PKCS#11 v2.20 section 12.1.6 PKCS #1 v1.5 RSA is a signature scheme commonly used to implement RSASSA-PKCS1-v1_5 of PKCS#1 signature of data hashed externally to a ...
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0answers
42 views

Security implications of public nonce

I'm planning to use the crypto_box() functions of Nacl (or, alternatively, the crypto_box_easy() functions of libsodium) to ...
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0answers
48 views

Is the half-homomorphic property of RSA a problem for blind RSA signatures?

For blind RSA signatures, is it problematic that RSA is half-homomorph? Take a scenario where blind RSA signatures are used for something like a voting procedure or this proposal: Lots of people, ...
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0answers
87 views

Zero Knowledge Non Interactive Proof with random oracle

I am trying to write an assay about Non Interactive Zero-Knowledge proofs and would like to take the simple discrete logarithm problem example fallowing the Feige-Fiat-Shamir heuristics. I understand ...
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0answers
47 views

Crypto hash function vs encryption algorithms

Why is a cryptographic hash function generally faster to execute in software than conventional encryption algorithms such as DES?
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0answers
160 views

ECC considered secure in OpenSSL?

this is my first question, please bear with me if it comes across silly. If I openssl ecparam -list_curves on my OpenSSL version (1.0.1f), it spits out the ...
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0answers
35 views

Boneh-Boyen like signature scheme

Full Boneh-Boyen signature scheme defines a pair of secret keys (SK) $a \in \mathbb{Z}_n$ and $b \in \mathbb{Z}_n$ and a pair of public keys (PK) $A = G^a \in \mathbb{G}$ and $B = G^b \in \mathbb{G}$. ...
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0answers
242 views

Trivium example

I started learning cryptography from Understanding Cryptography book of Christof Paar and Jan Pelzl. Here is the problem I have solved but I want to be sure that it is correct. Assume the ...
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0answers
86 views

Existence of encryption schemes where $F_{k}^{-1} \big( F_{k}(A) + R \big) = A + O(R)$

Is there a encryption scheme in literature, where I can do something like $$F_{k_1}^{-1} \big( F_{k_2}(A) + R \big) = A + O(R)$$ where, $A$ is a $m \times n$ real matrix, $R$ is a $m \times n$ real ...
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0answers
24 views

Any ideas on login using Digital Signature PKCS

I am curious to know about possibility to login into web application just by identifying the user based on digital signature in usb token. any reference in this direction?
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0answers
60 views

chacha20-poly1305 padding and length encoding

The AEAD construction for chacha20-poly1305 described in the IETF proposal [1] encodes message lengths into the text that is to be hashed. The newer proposal [2] goes further and pads associated data ...
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0answers
61 views

Epsilon Differential privacy using laplace distribution

Given Database X={x_1 ,x_2 ,...X_n} where x_i represent a bit Let f(x) = Sum x_i for 1 <= i <= n Let Y ~laplace(1/(epsilon)) I succeeded proving that Mechanisms: M1(x)= Y-f(x) and M2(x)= ...
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0answers
67 views

Performing HMAC with random key before MAC comparison

In Laravel (a PHP framework) I can see that they calculate a HMAC with a random key over the final HMAC before comparison. This additional HMAC calculation is of course performed for both the ...
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0answers
71 views

Exploration of Blum Micali Security By Seed Size

I'm new to cryptography and am most intrigued by mathematically based pseudo random number generators. With reference to the Blum Micali algorithm: $X_{i+1} = G^{X_i} \bmod P$ can security be ...
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0answers
77 views

How does bitmessage encryption work?

I have been reading around protocol specification and there is either too much technical detail or too bad articles on various sites. I need you to explain in simple words how encryption in ...
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0answers
49 views

Is there a way to “shorten” a Merkle chain?

If I have a Merkle chain of 3 items, is it possible to create a zero knowledge proof of the existance of a correct chain between hash 1 and hash 3? Editing to clarify (Thanks Ricky), what I mean my a ...
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0answers
58 views

Obliviously computing the Least common multiple of two poylnomials

Consider I have two polynomials $f_1$ and $f_2$ of the same degree. I want to secure them (using any kind of encryption except FHE) and outsource them to an untrusted server. I want him to compute the ...
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0answers
50 views

What is the fixed point attribute of DES (when used with weak-keys)

I've heard in some lecture that the weak keys in DES implies the existence of $2^{32}$ fixed points in the algorithm, i.e. that $DES_k(x)=x$ for $2^{32}$ such $x$'s. I couldn't find anything about ...
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0answers
116 views

How does Schnorr signature actually work?

I'm trying to get a grip on how Schnorr signature works. Suppose Alice sends Trent a tuple $(P, M)$, which contains a payload and a message to be signed by him. She then passes the certificate to Bob ...
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0answers
84 views

CAST-256 (CAST6) versions or S-Boxes

Are there different versions of CAST-256 - also known as CAST6 - available? Are there different S-Boxes available for CAST-256? If there are different versions or S-Boxes what identifier should I use ...
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0answers
131 views

Existential Forgery on textbook RSA signatures

Can an adversary who haven't seen the message before forge the signature of that message? The adversary has seen $σ_1 = (m_1)^d \bmod N$ and $σ_2 = (m_2)^d \bmod N$ He forges $m' = m_1\cdot m_2$ $σ' ...
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0answers
82 views

Less known hash functions producing 128 bit hash

Good day. While reversing a malware I stumbled upon a function producing 16 byte hash. I tried to determine which one is that by checking every function from wiki. Nothing fits. So, there are two ...
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0answers
57 views

Efficient proof of knowledge using Wegman-Carter hash

A verifier wants to ensure, with only little exchange of data with other systems, that a large block of data $M$ that the verifier holds is also available to some other system(s). It is not an ...
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0answers
94 views

Interactive assumptions not falsifiable?

Can someone explain why an interactive assumption is not falsifiable? Maybe I'm misunderstanding what the statement means, but isn't even a non-interactive assumption interactive, but just with a zero ...
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0answers
105 views

How can I start the following crypto project?

(Cryptography: encrypting files before storage in the cloud): The project consists of a software implementation of a method to pre-process a file before storing it on a cloud storage server so that ...
1
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0answers
91 views

Complexity to find an preimage of a hash function

Suppose a hash function based on Merkle-Damguard construction. Its compression function is given as $H_i=E_{m_i}(H_{i-1})$, where $E_{m_i}()$ denotes the encryption of an ideal block cipher with ...
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0answers
33 views

Hybrid fair exchange protocol

A gradual fair exchange (layman term) is a form of fair exchange protocol where Alice will transfer 1 bit to Bob then Bob will transfer 1 bit to Alice. The flaw with this protocol is that the party ...
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0answers
83 views

Opinion on my idea for storing credit cards securely

I've been thinking of ways to store credit cards securely, I thought of this: Take the users credit card info Put the card info in a standard format "Full Name/Card Num/Security Num/Expiry ...
1
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0answers
63 views

Multi-round Transposition/Playfair as a secure hand cipher in the computer age

Given that computers can be easily compromised, there is a need for a hand cipher that can withstand computer attack. Clearly the traditional hand ciphers fail. One time pads work. They also have ...
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0answers
36 views

How good is middle cube method with jumbled digits?

I had to make my own prng for a stream cipher for an inter school science project (I am mentioning that a lot). So I thought of cubing the seed instead of squaring it (like in the middle square ...
1
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0answers
168 views

Brute Force AES Calculations

I have an encryption service in which the user decides the length and the type of key, so I would like to build a tool that educates the user on the brute force times for the key they created if using ...
1
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0answers
121 views

How represent message in Menezes–Vanstone elliptic curve cryptography

I ask about represent message in Menezes–Vanstone elliptic curve cryptography I now encrypt function as follow $C_1 = (M_1 * K_1) mod\ P$ $C_2=(M2 * k_2) mod\ P$ My question is about how much the ...
1
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0answers
60 views

Type of cipher used where ciphertext has no discernible pattern, spaces. Type?

What type of cipher could give ciphertext where for example random ASCII chars between say F-z (symbols and numerals inclusive), but with only a few spaces? Frequency of chars shows some similarities ...
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0answers
68 views

Why is it hard to calculate Logarithm on Diffie Hellman?

i read something about Diffie Hellman. What i don't understand: Alice selects a randomly generated Number, calculates X = g^x mod p and sends X to Bob. If she calculates g^x, she needs to calcluate ...
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0answers
43 views

DLOG in $\mathbb{F}_{p^n}^*$?

Assume that we are given an element $g\in \mathbb{F}_{p^n}^*$ and $g$ does not belong to any of the smaller subfields contained in $\mathbb{F}_{p^n}$. If the degree of $g$ is some number $q$, how much ...
1
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0answers
113 views

About the Algebraic Normal Form (ANF) of S-Box in DES

I've thought up a way to represent the transformation of S-Box in DES by ANF. Let $x_i\;(1\le i\le 6)$ be the input of an S-Box, $y_i\;(1\le i\le 4)$ be the output, for example, then $$y_1= 1\oplus ...
1
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0answers
43 views

Infer encoding mechanism from $n$-grams distance?

I have a series of obfuscated strings which across the set of strings have regions of high variance and regions of low variance – implying some encoding mechanism as opposed to an encryption procedure ...
1
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0answers
88 views

To prove $r_2$ is a uniformly at random value in $Z_n$, where $r_2=r_1 . m$

$m$ is arbitrary value in $Z_n$, where n is RSA modulo. Then we do: $r_2=r_1 . m (modn)$, where $r_1$ is a random value such that $r_1\in Z^*_n$. ** Question(1): is $r_2$ a uniformly at random ...
1
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0answers
72 views

Does the transposition cipher have a network application?

So I'm reading a chapter in my networking book and it talks about substitution and transposition ciphers (Transposition Cipher Wikipedia). I know that most network security uses public key or ...
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0answers
79 views

Does NSS fully implement PKCS 11?

I am looking towards using NSS in a Linux application that makes use of a TPM (HSM). So, I am checking the support of PKCS 11 in NSS, at least for the management of Elliptic Curve keys, signature with ...
1
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0answers
87 views

What does “nonlinear mapping” mean?

Page 15 of the Keccak reference (PDF) explains that the $Chi$ step mapping of the Keccak-f permutation in Keccak is defined to be “nonlinear mapping”. Without this, the complete permutation would be ...
1
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0answers
46 views

FEAL-4 Wrong outputs of Round Functions

On page 2 of this article, there is example of FEAL-4. At round 2, the input to F (Round Function) is 0x80800000. As F accepts only 4 bytes I divide the input by 2 so that (As I assume the result ...
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0answers
84 views

Which mathematical operations does secp256k1 point multiplication use?

To convert a bitcoin private key to a public key, the secp256k1 point multiplication math is used. Could I – theoretically – convert a private key to a public key just using the four arithmetic ...
1
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0answers
169 views

Serpent Cipher 128bits (Example rounds on any plaintext/key)

Is there are any possibility to see trace(example) of Serpent Encryption/Decryption on concrete plaintext/key example, (not code implementation) or at least animation of steps. During reading of ...

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