All Questions

43 views

What info should be signed with a digital signature to provide entity authenticaton for DH?

$i \to r\colon\; g^x\bmod p$ $r \to i\colon\; g^y, \langle g^y,g^x\rangle_r$ $i \to r\colon\; \langle g^x,g^y\rangle_i$ Looking at run 2, I am trying to work out why it is necessary to include $g^x$ ...
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181 views

How does SSL work on the browser

I recently bought an SSL certificate from a website and was able to make it work on my Apache server. As far as I know, it uses asymmetric keys and the private key is stored on the server while the ...
73 views

How to calculate ϕ(n) from n?

I'm trying to fully understand all the steps of the RSA algorithm. I have clear so far that: $n$ comes from the product of two numbers: $p$ and $q$ The public key consists of the pair ($e$, $n$) ...
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Do equivalent RSA keys exist?

If $m^{ed} \bmod n = m$ for message $m$, public key $e$ and private key $d$, then adding any integer multiple of $n$ to $m^{ed}$ still equals $m$ modulo $n$. Supposing it exists, how do I find an ...
662 views

Simplified Fiat-Shamir example generates wrong output

I am trying to implement the Fiat-Shamir identification protocol, however the end results always fail to match. I am using algorithm's description from here. Preparation: Select 2 prime integers ...
158 views

Why do different applications of hash functions demand different properties of the hash function?

A strong cryptographic hash function in general must guarantee several properties, including: Preimage resistance, second preimage resistance and collision resistance. It turns out, however, that ...
59 views

How to do statistical analysis on encrypted / anonimized data

Let's imagine Alice wants to send Bob a table with 2 columns: ...
119 views

K Friedman - two texts explanation

I read the $K$-Friedman test to determine the period of a Vigenère ciphertext, and I understand something like this: $K$-Friedman test tries to find out what period of the cipher by calculating some ...
211 views

Can I use a differential that can be traced through the whole cipher with 100% probability?

I'm trying to attack a very simple cipher using differential cryptanalysis as a way of becoming familiar with this method. The cipher is so simple that I've found a differential which I can trace ...
69 views

Is brainpoolP512r1 safe?

I'm using brainpoolP512r1 elliptic curve for DSA and DH in my application. Recently I've found out on this website that brainpoolP256t1 and brainpoolP384t1 aren't secure. Unfortunately my curve wasn't ...
22 views

Construct new SIS solutions from given ones

Assume we have a lattice SIS problem $A x = 0$, with $\Vert x \Vert < \beta$ and we are given $k$ solutions $x_1, \dots, x_k$ by, say an oracle. Is it then hard or easy to construct from there a ...
393 views

Do all ciphers have equivalent decryption keys?

Do all ciphers suffer from the problem of multiple equivalent decryption keys? Is the existence of equivalent keys an essential property for the security of a cipher? If you could prove that a cipher ...
145 views

Under what conditions did a Bletchley bombe stop?

I am trying to understand the conditions necessary for one of the Bletchley Park bombes to stop. Let me give an example. I have been experimenting with Enigma machine and bombe simulators to try to ...
78 views

How to define order according to domain parameters in elliptic curve pairing groups

According to domain parameters, as an example Type 1 pairing domain parameters are ...
481 views

How to deal with a cipher with addition and XORs combined together?

I am trying to cryptanalyze a cipher where bitwise XOR and addition mod $2^n$ are combined together. I've been working on it for a long time but with no result - the main difficulty, which I am unable ...
15 views

How to set M parameter for frequency test within a block

I am using statistical tests to determine whether a sequence of bit is random, one of them is frequency test within a block. In a nutshell: Within a block of M a number of 1 is counted. A joined ...
28 views

Freely available softwares for simulating/implementing MPC protocols [closed]

I have been designing multiparty computation (MPC) protocols for functions that interest me. Although theoretically I am able to deduce the asymptotic complexity of the protocol, I wish to know as to ...
202 views

What is the point of differential cryptanalysis when the amount of necessary plaintext is unrealistic?

As someone with a non-crypto background, I learned that differential cryptanalysis is mostly weak against ciphers like DES because, being a chosen plaintext attack, for a state of art complexity of \$2^...
44 views

How simple can the PRP used in the Even-Mansour scheme be?

For example, in the question “Is there any reason not to use Single-Key EM with AES and a constant key?” it is proposed to use AES with a fixed key as the permutation in a xor-permute-xor construction....
336 views

Practical implementations of Multiparty computations [closed]

Are there any practical implementations and or software platforms to prototype applications based on MPC ?
19 views

How to prove a key generation protocol based on blind RSA signature?

It seems like that a user may use blind RSA signature to obviously generate a key. My design is as follows. Please correct me if I get anything wrong. (Please refer to WiKi https://en.wikipedia.org/...