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RCON for AES 192 and 256

This is question about how many RCON values are used in AES 192 and 256. I read the NIST Publication introducing AES and in Appendix A.2 and A.3 (Key Expansion for 192 and 256-bit keys), only $rcon_1$ ...
1
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1answer
15 views

Is possible that find numbers where the product of 3 numbers is congruent modulo to 1?

It is possible that find the $a, b, c$ randomly in here? $$ abc \equiv 1{\pmod {\varphi (N)}} $$ Instead of $$ de \equiv 1{\pmod {\varphi (N)}} $$ in the RSA Algorithm.
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0answers
9 views

Setup Geth Node for the first Time. HELP Please!

Hello my Name is Sven and i am from Germany.I need Guidance from someone with advanced knowledge in ethereum. I created December 2017 an ethereum Wallet. On March 2018 i invested in P3D. I forgot this ...
0
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1answer
17 views

Is 50% of bits changed in every round always gives 50% of changed bits in the end?

Let's say we have a cipher with such property, that every round change 50% of bits in every block in average. Is it obvious or it means that after few rounds we will get exactly 50% changed bits? If I ...
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0answers
21 views

How Should Form Input be Encrypted for sending to a Server?

I apologise if this question is a duplicate. I couldn't find any similar questions. I am writing a web app that consists of a series of drop-down style question menus. These generate more drop-downs ...
2
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3answers
59 views

Diffie-Hellman, so what?

I know how the Diffie-Hellman Key Exchange (DHKE) works. But where is it used? And ok, now both have the same key. But how are those keys used anyway? I've heard that HTTPS is using the DHKE. Ok, but ...
0
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0answers
11 views

Need help deciphering [closed]

So i recently was added on an arg type game from a friend and there is a bit of code that im not entirely sure what the cipher is, so i was wondering if anyone could help me on figuring it out. "...
0
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1answer
27 views

Curve25519 base point speed up

In the paper regarding Curve25519 DJB defines the base point to be $P_{base} = (9,y)$. The main reason for choosing it this way is, that $P_{base}$ has a big prime order which gives security ...
2
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0answers
26 views

Are skeleton keys possible for ECCDSA?

As alluded to here (split-key vanity addresses for bitcoin), ECCDSA-keys can be merged such that the sum of two private keys $S=S_1+S_2$ yields a public key which is the sum of the respective public ...
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0answers
17 views

Authenticating and encrypting data for an automated system

I wish to distribute a file from A to an automated system B. The requirements are: Contents are encrypted Contents are tamper proof Contents origin is verified To do this I have devised the ...
2
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1answer
31 views

Is there a way to prove knowledge of a limited resource like a phone number just to the people who already know about it?

For instance, let's say Bob's phone number is X and Alice has somehow identified that Bob's phone number is X. Now she doesn't have a direct way to contact Bob, so she wants to post in a public forum ...
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1answer
76 views

Why discrete logarithm modulo composite moduli not popular and not defined in standards?

The classical discrete logarithm problem is to find $x$ such that $g^x\equiv h\bmod p$ where $p$ is a prime and $g$ is generator of multiplicative group modulo $p$. The demerit of this approach seems ...
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0answers
29 views

What is the maths behind Bitcoin's BIP32?

I've read about BIP32 key derivation functions. I'm trying to understand how, given a secp256k1 key pair, that "child" public keys may be generated from just the public key, and the ...
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0answers
17 views

A zero knowledge protocol with a deterministic verifier

Given a language $L$ and $ZKP$ between $v$ and $p$, when $v$ is deterministic polynomial time algorithm, I wish to obtain a probabilistic-polynomial algorithm which solves $L$. Which, if I am not ...
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0answers
48 views

Frequency Analysis on DES, AES, 3DES using Cryptool2

I am trying to analyze symmetric block ciphers like DES, 3DES and AES, using Cryptool 2. I want to do a frequency analysis on each of these ciphers, in order to comment whether this is an effective ...
0
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1answer
39 views

Why do we add error in the definition of LWE?

One of the various equivalent definitions of the LWE problem is the following: Let $n,q$ be integers ($q$ usually is a prime number), $\chi$ a discrete probability distribution over $\mathbb{Z}$ (...
1
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2answers
341 views

Is it fair to say that MACs use a signing algorithm?

The Wikipedia page on MAC calls the algorithm that is used to generate the MAC as a signing algorithm. Is that a fair use of that term? Can we then say that HMAC-SHA-1 uses SHA-1 as the signing ...
1
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1answer
33 views

Hash into elliptic curves for private set intersection

Would it be insecure to hash a message $m$ to an elliptic curve point by multiplying it to some generator $G$ for the purpose of a private set intersection ? $$ M = hash(m) * G $$ I keep seeing ...
1
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0answers
25 views

Why ideal lattices?

An ideal lattice is a lattice $\mathcal{L}(A)$ generated by a block matrix $A = \left[ A^{(1)} \mid \dots \mid A^{(m/n)} \right]$ whose blocks $A^{(i)}$ are constructed from a vector $a^{(i)}$ and a ...
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0answers
23 views

Is $f_N$ in this hash function is Matyas-Meyer-Oseas scheme?

I propose a hash function as following: H is an Merkle-Damgard hash function with a compression function $f: \{0,1\}^{3n} \to \{0, 1\}^{2n}$. Output function $f_N: \{0,1\}^{3n} \to \{0, 1\}^n$. M is ...
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0answers
10 views

Isogeny-based AKE: what is the difference between Gal 1 and FTTY 1?

What is the difference between (a) the AKE scheme proposed by Galbraith (based on TS2 protocol) in https://eprint.iacr.org/2018/266.pdf (page 9-10); and (b) the AKE scheme proposed by Fujioka et al. ...
3
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1answer
27 views

Lemma KL-Divergence (Differential Privacy)

I am studying differential privacy and I got stuck again in proof of a lemma. Which is: $D_{\infty}^\delta(Y||Z) \leq \epsilon$ if and only if there exists a random variable $Y'$ such that $\Delta(Y,...
1
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0answers
27 views

Do practical blind signature schemes make compromises?

I am fascinated by the idea of blind signatures and their applications introduced by David Chaum for electronic cash and voting and his provided analogy with carbon copy is quite compelling. However ...
1
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0answers
47 views

Post-quantum crypto based on undecidable problems

Usual post-quantum crypto, like the isogeny-based algorithm, has its value lying in that no one yet has found a quick way to break it with quantum computer. This makes me wonder why don't we build ...
0
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1answer
34 views

How to find m so that RSA cipher end with '\x00'+SpesificString , if we freely input the plaintext?

I have an RSA encryption with public key $(3,n)$ with 2048 bits modulus $n$. I want to find the value of the plaintext $m$ so that the ciphertext (in bytes representation) value ends with ...
1
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1answer
40 views

Why is GnuPG changing first two characters of ascii armored public key after downloading it from the key server?

When I look at my public key on the key server, the first two characters of the ASCII-Armored data section (as defined in section 6.2 of RFC 4880, which defines the structure of the ASCII-Armored ...
3
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1answer
57 views

Curve25519 key structure

In the paper regarding Curve25519, the set of public keys $q$ is $\{q : q\in \{ 0,1,2,...,2^{256} - 1\}\}$ and the set of private keys $n$ is $\{n : n\in 2^{254} + 8 \cdot \{ 0,1,2,...,2^{251} - 1\}\}$...
2
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0answers
28 views

What is the fundamental difference between multipartite and multilevel secret sharing?

According to this paper , Multipartite secret sharing scheme is a scheme in which the set of participants is divided into disjoint parts and all participants in the same part play an equivalent role ...
2
votes
1answer
49 views

Is there a way of sharing a key without anyone knowing what the key is initially?

I started learning about key sharing and Shamir secret sharing, I'm wondering whether you need someone who knows the key initially and then distributes it, is this step necessary or not? In my case I ...
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2answers
75 views

Resources for mathematics of cryptology

I am an undergraduate student looking for resources (books or lectures) explaining mathematics involved in cryptography, such as number theory, elliptic curves etc. I found the book 'A Course in ...
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0answers
29 views

How does CL signature work?

I'm studying the CL signature that how can it works. However, I cannot understand how equation (42) is calculated. What is the last three factors? The value T is as follows: $$T \leftarrow(A')^{\...
12
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5answers
5k views

Is it easy to crack a hashed phone number?

I want to SHA256 hash phone numbers in order to hide them. Is this a good idea? Are there any other ways I could make this safe?
0
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0answers
39 views

Security implication of concatenating two hashes using different algorithms

Background Hashing files is an expensive thing for CPU. I am tasked to write a secure digital signature scheme. For that, I decided to check the integrity of files using Hash/Digest. To be more secure,...
3
votes
1answer
90 views

randomness of encrypt

In the paper "Efficient Encryption from Random Quasi-Cyclic Codes" of Gaborit et al. p.14, I read "Encrypt$(pk=(G,Q,s),\mu,\theta)$: uses randomness $\theta$ to generate $\epsilon \...
3
votes
1answer
40 views

Curve25519 extension field

The paper regarding curve25519 presents a theorem in chapter 2 (specification). The extension field $F_{p^2}$ is used in this theorem. I don't understand why this extension field is needed for the ...
2
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1answer
39 views

How do I encrypt a long message using ElGamal encryption correctly?

According to ElGamal encryption, in order to encrypt a message I need to generate a shared secret s and after that I am to calculate ...
0
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0answers
17 views

How to prove properties of pre-image of random oracle in zero-knowledge proof?

A signature Sig is given as input to random oracle H, such that y = H(Sig) and Sig should be hidden from the verifier. How to prove in zero-knowledge to the verifier that y is the correct output from ...
0
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0answers
49 views

RNG randomization strength for PRF seed

Consider a use case that requires the creation of multiple asymmetric key pairs. There are two options for generating random seeds for a PRF: Use a software based RNG and generate a new seed for each ...
1
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1answer
48 views

What papers describe the rationale behind cryptography algorithms

I am trying to introduce myself to cryptographic hashing and encryption. I am looking for original papers of sorts, to describe the inspiration behind why they choose certain numbers, if they are ...
1
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1answer
43 views

Is it possible to create a 128-bit UUID from a weak entropy source?

I am looking at a seemingly popular piece of JavaScript code to generate a UUID which is supposed to be a 128-bit number: ...
7
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2answers
390 views

Calculating RSA Public Modulus from Private Exponent and Public Exponent

If I know the private and public exponents ($d$ and $e$) of an RSA key pair, is it possible to (efficiently) calculate the public modulus $n$?
0
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1answer
25 views

Prior art: SSH key authn over TLS?

I’m developing an application that runs over TLS. In addition to password-based authentication we’d like to be able to use SSH keys. Is there any prior art in using SSH keys for authentication over ...
0
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1answer
42 views

Functional signatures vs homomorphic signatures

I found that homomorphic signatures allows an agency to carry out arbitrary computation $f$ on the signed data $m$ and accordingly gain a signature for the computation result $f(m)$ with respect to $f$...
1
vote
1answer
74 views

Sensible amateur usage of web crypto API

I want to know if my usage of the web crypto API is sensible. I want to use it for symmetric and public-key encryption and decryption, and signatures, but as a non-expert I am scared by the warning on ...
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1answer
55 views

Is storing salts encrypted a good idea?

I've read that storing password hashes in a database, you can store the salt in plaintext alongside the actual hash with no detriment to security. I was thinking that one could derive a key from the ...
1
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0answers
49 views

The Security of AES-N-GCM

In the paper The Security and Performance of the GaloisCounter Mode(GCM) of Operation,it shows the AES GCM SECURITY in Corollary 1. But I can not get the same result (the right corollary) from the ...
0
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1answer
59 views

Can I find a number, such that the its SHA-256 hash is all-0 [duplicate]

I want to find a number, such that the result of its SHA-256 hash is all 0. I don't know if this number exists.
0
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0answers
72 views

Can we defends against RSA Timing attack when we use java.math.BigInteger.modPow?

I think that Montgomery and sliding window techniques are applied within java.math.BigInteger.modPow (and more specifically ...
1
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0answers
30 views

CVC-PKCS#10 Generation and Signing

Good day, I have gotten a task at work which has turned out to be a rather interesting nightmare because of the lack of Information on the topic. My task is as follows: In order to ensure an ...
0
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0answers
43 views

RSA How many value for d

How many value can have a private key with this format? p,q,d = (19, 41, d) where 1< d <18x40? I want know how to calculate that.

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