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0answers
68 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, ...
1
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0answers
150 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
69 views

Encryption - How to find $\sigma$?

Alice communicates with Bill using an encryption system of type Feistel. Specifically, each block has a length of 128 bits, the algorithm has 4 rounds and the common secret key of Alice and Bill is ...
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0answers
76 views

Pseudorandom number generators based on hard problems in mathematics

I know that Dual_EC_DRBG's security is based on the ellitpic curve discrete logarithm problem, Micali-Schnorr is based on the difficulty of factorization, and MQ_DRBG is based on multivariate ...
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0answers
59 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 $B = G^b \in \mathbb{G}$. ...
1
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0answers
91 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 ...
1
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0answers
33 views

Reducing key shares in Damgård-Dupont threshold RSA

I'm working on understanding and implementing Damgård, I., & Dupont, K. (2005). Efficient Threshold RSA Signatures with General Moduli and No Extra Assumptions. Public Key Cryptography-PKC ...
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0answers
29 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
84 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 ...
1
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0answers
56 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 ...
1
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0answers
64 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
90 views

request for data to test deterministic ecdsa signature algorithm for secp256k1

I’m implementing the RFC 6979 procedure to compute a message signature. I want to test my program on the secp256k1 elliptic curve. Note the “k” in secp256k1, i.e. the Koblitz curve. If you have the ...
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0answers
196 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
64 views

PRG variant as a commitment scheme

I would like to use a PRG in order to achieve the commitment properties (i.e. Hiding and Binding), however, if we look at a general PRG we cannot state that it has the Binding property. First I show ...
1
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0answers
150 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 ...
1
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0answers
363 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' ...
1
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0answers
150 views

Find generator for irreducible polynomial over binary field

I read this tutorial and I have following question. How they assume that generator: g = (0010) is correct for this polynomial and how to choose the best generator from all for the field.
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0answers
154 views

Implementing a pseudo random function in practice

Can anyone point me to a C++ crypto library with an implementation of a pseudo random function (PRF)? I don't have much background in crypto theory, but I am in the middle of a graduate course ...
1
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0answers
73 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 ...
1
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0answers
129 views

java.util.Random and Dice Rolls

For this question, a dice roll will be considered two 6 six sided dice, to give a possible output of 2-12. Given a java.util.Random instance r, the output of one roll would be: ...
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0answers
128 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 ...
1
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0answers
106 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 ...
1
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0answers
117 views

CCA security of a system that splits messages and encrypts each packet

Propose a symmetric key based crypto-system for implementing a secure email system. This system is based on AES and CCA secure. Suppose that you have to encrypt a large message and that this message ...
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0answers
36 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
90 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 ...
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0answers
223 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
177 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
132 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
77 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
60 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
180 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
51 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
92 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 ...
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0answers
105 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
113 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
59 views

Forward Secrecy with pseudorandom functions

Let $H_1$, $H_2$ be keyed hash functions (e.g. $H_i(x) = SHA_{256}(s_i||x)$ for pseudorandom $s_1$, $s_2$). Let $s_n = H_1^k(s_0)$, $k_n = H_2(s_n)$, where $s_0$ is a secret (pseudorandomly chosen ...
1
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0answers
323 views

how to find key matrix in hill cipher

I want to solve this problem but there are 3 known plaintext-ciphertext pairs. The key of Hill cipher is a 3*3 matrix as k=[k1,k2,3; k4,k5,k6; k7,k8,k9] where the unknown ...
1
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0answers
91 views

side channel attacks on AES

Say you have a web application that's performing AES encryption. What sorts of side channel attacks should one keep an eye out for? Timing attacks affect RSA more than symmetric ciphers in-so-far as ...
1
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0answers
84 views

advantages of hashing over elliptic curve signatures for a proof of work protocol

I'm trying to create a proof-of-work protocol for a proof-of-concept software, and it's basically something like this: ...
1
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0answers
129 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
54 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
106 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
284 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 ...
1
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0answers
309 views

What is the (uncompressed) x,y-representation of a curve point on the P-256 NIST elliptic curve?

I am trying to understand the FIDO U2F Raw Message Format, especially the format in which a user public key should be provided. The documentation says the following: A user public key [65 bytes]. ...
1
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0answers
37 views

Plaintext-aware encryption for symmetric schemes?

The notion of plaintext-awareness is well-known for asymmetric encryption, but the notion seems to make sense for symmetric encryption as well. Is this a known concept?
1
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0answers
70 views

exchanging private key between service and iPhone app - digital signing

I need to do digital signing of my request data which will be sent to the server. My server sends distinct private keys to her clients after authentication and expects all responses to be digitally ...
1
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0answers
99 views

Does Ciphertext policy ABE support search operation on encrypted data

Basically CP-ABE (or attribute based encryption) allows end-users to encrypt the data with desired access control structure. I was investigating the how to do keyword-search on encrypted data given ...
1
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0answers
98 views

Is it possible (how difficult) to find MORE than one valid RSA signature?

Is it possible (how difficult) to find more than one valid RSA signatures for a given message m (after padded) and a public key ...
1
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0answers
387 views

Chi-Squared Step of Vigenere Cipher Decryption

So, I have been assigned an assignment where I had to solve a Vigenere cipher. Following along with this webpage I managed to get all the way to the chi-squared step. But, that is the problem. Upon ...
1
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0answers
574 views

What does “G2” mean when used with X509 certficates and certificate authorities?

For example "Google Internet Authority G2"?. I thought it was another way of specifying Class 2 (for organizations, for which proof of identity is required) but then see certificates such as "VeriSign ...

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