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How is public key cryptography used for digital signature?

In public key cryptography, there are two different keys used for the encryption and decryption of data . I am wondering how it is used for digital signature
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1answer
1k views

Passing data securely through QR codes?

We have to implement a way to securely transfer data from a POS to a mobile app using QR codes. The mobile app gets the payment parameters (amount, description, purchase_id, store_id) to create the ...
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2answers
225 views

Private Information Retrieval and Writing at the same time possible?

Are there any (possibly multiserver) private information retrieval (PIR) schemes that support private reads and writes (so called PIR Writing) at the same time, while having sublinear (in the database ...
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1answer
56 views

The security of adding random noise many time pad

In may application, I have a series of real number $\{v_1, v_2, \ldots, v_N\}, v_i\in\mathbb{R}$. To protect them, I add a random noise $r\in\mathbb{R}$ to each themselves like one-time-pad encryption ...
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5answers
355 views

Is there any existing cipher capable of scaling from a 1 bit key up to a one-time-pad?

We have ciphers that handle small amounts of entropy, such as a 256 bit key for AES; and we have one time pads for enciphering 1:1 entropy, such as a 1GB key for a 1GB file if you could ever harvest ...
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1answer
71 views

What are some of the new directions of research in Elliptic Curve Cryptography?

I am searching for some new research areas in ECC for my masters' project. My professor suggested me to go for Image Encryption using ECC. But I am clueless as to what are the new directions possible ...
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0answers
29 views

Solve matrix products

This question follows-up from two old questions. Suppose, there are two $n\times n$ non-singular binary matrices $X$ and $Y$. The product $XY$ is given. I guess, we can agree it is not possible to ...
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0answers
20 views

Block slicing operation and side-channel attack

I got block slicing operation in my cipher. I mean after each round we take first $a$ bits and second $b$ bits of 128-bit block and then compute $b+a$. $a$ and $b=128-a$ is computed from key schedule ...
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0answers
38 views

Decomposition of Sbox in three shares x1,x2,x3?

ex: $x| 0|1|2|3|4|5|6|7|8|9|a|b|c|d|e|f|$ $s(x)| 1|a|4|c|6|f|3|9|2|d|b|7|5|0|8|6|$ now how to split $x$ such that $x=x_1+x_2+x_3$
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0answers
48 views

Why are RSA and ECDSA sign and verification time different?

I would like to know why ECDSA signs faster than how it verifies? On the other hand, why RSA verifies faster than how it signs?
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0answers
48 views

A known plaintext attack on Elgamal Cryptosystem where the random is fixed

Let the public key of Alice be $(p, g, h)$, where $p$ is a big prime $g$ is a generator for $\bmod p$ $h=g^a$. The secret key for Alice is $a$. Bob wants to communicate with Alice, so he encrypts ...
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0answers
46 views

Modifying the One-Time Pad so that one key can be used two times

I'm currently working on a modified one time pad and I'm trying to use the encryption scheme such that the key will be used twice. I have written a small pseudo code but I'm stuck. Here is my attempt: ...
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0answers
55 views

Padding requirements for a stream cipher

You are given a stream cipher and a block cipher with a block size of 64 bits. The data input is 32 bits. How many bits do you need to pad before processing the data input using a stream cipher?
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1answer
130 views

Asymmetric encryption that preserves the plaintext size

I'm looking for an asymmetric encryption algorithm that preserves the size of the thong in clear text. The encrypted file must not be longer than the plaintext file and must not contain any special ...
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1answer
72 views

Which is more secure, AES CTR or OTP with generate key?

My idea of the OTP is to generate from 50 letters (5 words, each 10 letters) a new pad of 2000 random letters, then attach user email to the pad end (to make it unique). The keywords and the pad will ...
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1answer
52 views

How to calculate base value in modular exponentiation

If you have $a^b \bmod n = c$, and $b,n,$ and $c$ values are given, is it possible to find a value for $a$ within a given range? So is it possible to find $a$ in $a^{2051} \bmod 3149=636$ knowing a ...
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1answer
128 views

Encryption algorithms that can be used for key exchange and can be eavesdropped

Which algorithms can be used for key exchange between two wireless nodes and are not secured, meaning they can be eavesdropped?
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1answer
49 views

Deterministic procedure for mapping an arbitrary value into a 𝑝,𝑞 pair for public key cryptography

I want public key cryptosystem to used for re-encryption as describe in Can Paillier ,RSA or any other schemes be used for universal re-encryption like elGamal? Now i have little solution for ...
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2answers
908 views

How to find the key of XOR encryption in Java?

I am trying to find the key of an XOR-encrypted string in Java. It is very probable that the key is eight characters long. I have the encrypted string. I do not understand how to go backwards and ...
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1answer
41 views

Rijndaelcipher mix column query

I quote a wikipedi para that says The operation consists in the modular multiplication of two four-term polynomials whose coefficients are elements of ${\displaystyle \operatorname {GF} (2^{8})} $. ...
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1answer
302 views

What is the difference between Forgery and Chosen-Message Attacks?

I did some researches about forgery attack and chosen-message attack. For me, forgery attacks are more focused on the verifiability whereas chosen-message attacks are similar to brute-force attacks. ...
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1answer
101 views

Original papers for hashing functions

I would like to learn how hashing functions are discovered / created. In part of this process I think it would be helpful to see the original works or papers of any authors of cryptographic or non-...
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1answer
55 views

Verification of the NI-ZK Proof

I'm currently learning about ZKP and Non-interactive zero knowledge (NI-ZK) but I'm confused in the process of NI-ZK verification. I have taken the following example to learn about NI-ZK from this ...
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1answer
81 views

Zero Knowledge Interactive Proof vs zero knowledge proof

What is the difference between Zero Knowledge Interactive Proof and zero knowledge proof? Nathan Aw
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1answer
66 views

why Blum-Micali algorithm is deterministic algorithm

Can anyone give me the answer of the following question. Justify why Blum-Micali algorithm is deterministic algorithm ?
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1answer
105 views

What algorithms to use for a secure transport protocol on devices with limited computing power

I am new to cryptography. My questions is this: I process packets on runtime. I do not have time for advanced encryption or decryption techniques that take a long time. As far as I know, going with ...
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1answer
93 views

XOR of users password Scrypt key and Random 32 bit salt?

I am trying to encrypt users private keys with the user password but if a user provides a weak password then the scrypt key generated from it will also be weak and suspectible to attack. Let say the ...
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1answer
564 views

Cube root modulo prime

I make research about big numbers in finite fields and I need to calculate a cube root modulo prime P for the number N: ...
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1answer
136 views

How can I protect AES-256 encrypted data?

In April 2017, Jacob Henning asked "What are the chances that AES-256 encryption is cracked?" and part of his question was how best the transmitted data, now in his web database, a.k.a. "data at rest" ...
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1answer
145 views

Encrypt 2 numbers preserving arithmetic correlation

I want to encrypt 2 numbers using a public key and have the reader know the correlation between those 2 numbers. I can also share the public key. Example: ...
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1answer
82 views

Decide whether a polynomial is invertible mod $q$

When implementing NTRU related cryptosystem, I came across the problem of deciding whether a randomly generated polynomial is invertible mod $q$. How to solve it?
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1answer
764 views

Elliptic curve discrete logarithm problem and mini example

Consider the group E23(9,17), this the group defined by the equation y2 mod 23 = x3 + 9x + 17 mod 23. What is the discrete logarithm k of Q = (4,5) to the base P = (16,5)? the solution is: 2P = (20,...
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1answer
181 views

Rabin Encryption is not CCA secure

Why is Rabin Encryption is considered as not CCA secure and how can I prove it? Any example would be helpful.
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1answer
143 views

What is the result of encryption if Feistel cipher maps every 16 bit input to 0xFFFF regardless of subkey?

Suppose the F function of a 16 round Feistel cipher mapped every 16-bit input R, regardless of the value of the subkey K[r], to 0xFFFF What is the result of running an encryption with this cipher?
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2answers
179 views

A quick way to justify whether $a^m \equiv 1 \pmod{n}$?

Say I would like to justify whether $10^{28} \equiv 1 \pmod{29}$. I know according to Fermat's little theorem that $a^{p-1} \equiv 1 \pmod{p}$ when $a$ is a primitive root modulo $p$. What about ...
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1answer
616 views

how to encrypt the chat message with multiple people public key together and restore the message?

I have a application with two users and one middle man, all of them holding the private and public key, To make the secured chat, two users and one middle man are all sending the public key and ...
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1answer
249 views

Random number generator in a 2p2 Network

for my thesis I am trying to develop a system where nodes from a peer to peer network agree in generate a random number every tot seconds. I am stocked in this problem since almost 1 week anyone can ...
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1answer
241 views

RSA public key verification based on a secret

I'm attempting to develop my messanging app with encryption evolved. For now I came up with algorithm for authorization and message exchange. P.S. conneciton between server and client is over https ...
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1answer
96 views

Question about key establishment protocol and key exchange attack

If an adversary $M$ observes a session of the protocol between $A$ and $B$ and learns the session key $k_{AB}$.How Can the adversary mount a successful impersonation attack and communicate with $B$ on ...
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1answer
73 views

Simple hexadecimal to 2s complement question

From 2.5.1 in this paper, how is $p$ = FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFFFF 00000000 00000000 FFFFFFFF = $2^{384} − 2^{128} − 2^{96} + 2^{32} − 1$ ...
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1answer
200 views

ECDH can be used for Key Agreement(KA) as per ECIES specification?

I want to implement a library to provide ECIES (Elliptical Curve Integrated Encryption Standard). We could see DH can be used as KA function for ECIES. I want to know specifically the ECDH (Elliptic ...
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1answer
99 views

Reversing key exchange algorithm

I'm analyzing some software and finding key exchanging procedure. Its looks like very similar with Diffie–Hellman, but not the same. I can’t understand the purpose of this. The step of algorithm is: ...
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1answer
943 views

RSA : if my key and message are too large , how to do?

I want to send a message consisting of a string of number (e.g: 124124134235235) Then, p:125243 q:56454547 e: 2659043 d: 5261378624675 However, it will be too large...so, is there any solution to ...
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1answer
410 views

GMW Protocol with semi honest adversaries

I know the GMW Protocol is secure in the case of a semi honest adversary which control all the parties except one. However I want to proof that it is also secure in the case the semi honest adversary ...
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1answer
128 views

Classical cryptographic key exchange

I am currently reviewing for my exam and a questions comes to my mind when I read an example about a simple key exchange protocol. In my textbook, the author comes up with an example about a simple ...
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1answer
101 views

Finding greatest integer m satisfying modular relation

I solved (c). I want to know (a) and (b) For (a), what i have done is that p-1=t2^s(t is odd) = 2^s (mod 2^m) And for m=1,2,...s, both sides are 0. So, m is s or more than s. For m= s+1, s+2,... what ...
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1answer
3k views

How to generate sha 256 hash using https url

I want to generate sha256 hash of https url. ex: url "https://www.google.com/" I want sha hash of this url. I have tried extracting public key from ssl certificate and used following command. ...
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2answers
99 views

Table of Curve Paramters

I'm studying Elliptic Cruve Cryptograhpy. When I do a search on Google of ECC, I find some pdf where I see these curve's paramters: $q, h, r, exp1, exp2$. What are these parameters ? Are there tables (...
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1answer
943 views

Can I calculate $d$ given only RSA’s $c$, $n$ and $e$?

The question “Calculating RSA private exponent when given public exponent and the modulus factors using extended euclid” assumes the factors are known. This got me wondering if it is possible to ...
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1answer
982 views

can pdfcrack software crack a 128 bit encrypted pdf file

One day ago,i downloaded a pdf that requires password then i search a software to decrypt the password that's s/w called pdfcrack Then i install pdfcrack and run a cmd in terminal pdfcrack -f ...

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