Questions tagged [algorithm-design]

Design of cryptographic primitives (algorithms), like block ciphers, stream ciphers, random-number generators, hash functions, MACs, key exchanges, public-key encryption or signature schemes. Also tag with the relevant type of primitive. If you ask about a known existing algorithm, also tag with its name.

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25 views

Cryptography — with a semi-priveleged user in the middle — to prevent request-tampering with another server

I'm working on a chat server for a mobile app I am writing. I would like to use a different application server for non-chat related operations and another application for chat operations. I would ...
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302 views

Hash function that is efficient on GPU and poorly suited to ASIC

I have such requirements to the hash function in my project: operating on 32-bit data, not mathematically breakable (built on existing hashes known to be secure), free of branching, as much as ...
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160 views

Does anyone have a copy of the paper describing the HiSeC™ algorithm?

I'm trying to create a remote controller compatible with HiSec algorithm. It's so old that “National Semiconductor” (now “Texas Instruments”) discontinued NM95HS01/02 and docs are unavailable. Does ...
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Are there any bi-bidirectionally indistinguishable Asymmetric Encryption Algorithms

I have been using Asymmetric Encryption for a while, and I have come across an interesting concept, and it would be cool if it could be done. Are there any Asymmetric Encryption Algorithms where the ...
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640 views

Method and explanation for calculating difference in speed between DES and RSA

Our assignment asks us to convert an RSA speed in bytes per second to a DES speed in bytes per second. Our professor's treatment of this ("RSA is 100 times slower than DES") seems insufficient. Could ...
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205 views

Getting the Encryption Function From the Decryption Function + Decryption Key + Encrypted Item

Is it mathematically possible to always be able to get the encryption algorithm used to encrypt a certain item (file, number, text, ...etc.) by knowing the decryption algorithm that will be used to ...
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32 views

Generating traceable passwords

I'm new to cryptography, so please bear with me as I try to explain what's going in my head. I have an idea to write a program to generate one-time passwords for online conferences that are although ...
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Given the anonymity in the blockchain under Mimblewimble - how would you identify whether a transaction had already been spent?

I have searched high and low, but can't see any explanation of an algorithm that could take a Mimblewimble based blockchain and identify the unspent transactions (so if someone tried to spend a ...
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20 views

How does APE: Authenticated Permutation-Based Encryption work?

I am trying to understand the encryption and decryption process of the APE: APE: Authenticated Permutation-Based Encryption for Lightweight Cryptography Full paper The Encryption what is exactly the <...
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49 views

How to design number of rounds in my cipher?

I have specific cipher which is built from permutations. It has or should has few rounds. If we do 2 rounds it is like 2 permutation composition. 3 rounds are like composition of 3 permutations and so ...
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30 views

Are there popular and secure Authenticated Encryption schemes with Salsa20/Sosemanuk in CTR-mode with a Carter-Wegman MAC?

I read that AES/GCM is a good choice for authenticated encryption because: AES has very strong heuristic security Encrypt-then-MAC leaks no information about the plaintext The CW-MAC in GCM can be ...
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35 views

Approach used with XOR cipher in black box scenery

What's the approach used in cryptanalysis to make an decrypter for a simple xor stream cipher in a Black Box scenery with only the output?
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30 views

How to determine the maximum number of times the DES algorithm needs to be run?

I am only a beginner in cryptography and I am getting confused by the following: Question Consider a known-plaintext attack performed on a double-DES cryptosystem. (a) Determine the maximum number ...
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35 views

How to calculate degree of confusion of an encryption algorithm?

I am programming an encryption-decryption model in python 3. I want to check its strength. I found 3 methods to check, they are: 1. Degree of diffusion 2. Degree of confusion 3. Integrity check For ...
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Finding the relationship between generating elements represented by a Hamiltonian cycle of a Cayley graph (like in strong RSA condition)

Consider an undirected Cayley graph of a finite group $\mathbb{Z}_p \times \mathbb{Z}_q$, where $p$ and $q$ are distinct primes. Let the generating set for the Cayley graph be $S=\{g_p, g_q\}$, where $...
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42 views

How could I verify that a contract was actually sent to me from the client as soon as the contract is received?

with the information provided - what would be the best solution - something like document management program like IBM Filenet ? or trusted timestamping? If I want to store electronic contracts for ...
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How to disperse personal data before returning?

I am working on a project that is dealing with personal data. The task is to find a method such that when user makes a query into multiple institutions, the result will contain already scattered/...
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45 views

WPA/WPA password algorithm

I would like to understand the mechanism behind wpa/wpa2 algorithm. Is there any script that can put this theory:(Key = PBKDF2(HMAC−SHA1, passphrase, ssid, 4096, 256)) into action to test it ? I made ...
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67 views

What is meant by the duality and homomorphism of an encryption algorithm?

I am new to the field of cryptography and security so spare me with this question. What is the general idea of duality and homomorphism of an encryption algorithm? And how one may prove those two ...
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150 views

Is there an efficient algorithm that allows to construct a cryptographically secure $n$-bit hash function based on two unkeyed $n$-bit permutations?

Let $f(x)$ and $g(x)$ denote two independent, “ideal”, unkeyed, public $n$-bit permutations (two publicly known bijective functions that produce $n$-bit outputs from $n$-bit inputs), where $n$ is an ...
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Is there a name for encryption which relies on repetitive calculation (=time) instead of a key-value? (e.g. block chain, hash value, block cipher)

Many encryption problems are fast to solve if a key, factor, exponent or something similar is known. Other encryption methods don't have such keys. E.g. a hash value of another value. It's used ...
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40 views

GCD in Montgomery arithmetic

Wikipedia article on Montgomery modular multiplication contains the following statement: Many operations of interest modulo $N$ can be expressed equally well in Montgomery form. Addition, ...
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Do any block cipher encryption functions (or similar functions) exist which are associative to each other and cyclic?

Most block ciphers encrypt a plaintext deterministically into a ciphertext which allows decryption in the opposite direction. Now, instead of encrypting just one plaintext, I'm looking for a cyclic '...
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65 views

Do there exist cryptographic algorithms where the “core” function is 96-to-32-bit?

There exists a FOX family of block ciphers (Wikipedia article: IDEA NXT). This cipher uses a function called "f32" which operates on three 32-bit words and outputs one 32-bit word. This function ...
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Modifying Elliptic Curve Parameters

For context, I was watching this bit of the video: which goes over this source code. The piece is about elliptic curve cryptography and how it works. I want to use some of this knowledge to make my ...
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52 views

Chinese remainder theorem

Z/11Z[X] is the finite field P(2) = 4 P(3) = 3 P(5) = 7 How can I solve my congruence system with polynoms? I made my system of congruence like that : X = 2 [4] X = 3 [3] X = 5 [7] And it gives me ...
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Unique numbers with $P^aQ^bR^c \mod N$ for each combination of $a,b,c$ possible? Would it be safer than separate form (like $T^a \mod P$ for each)?

Main question: Is the computation of $a,b,c$ in $P^aQ^bR^c \mod N$ (much) harder than in $T_p^a \mod P$, $T_q^b \mod Q$, $T_r^c \mod R$ ? (assuming the first form exists) $P^aQ^bR^c \mod N$ With $P^...
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51 views

Proxy decrypt algorithm in Extended Proxy-Assisted Attribute Based Encryption (ABE) Scheme

Context I'm trying to implement the Attribute-Based Encryption (ABE) scheme described in the paper - Extended Proxy-Assisted Approach: Achieving Revocable Fine-Grained Encryption of Cloud Data (Yang ...
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65 views

Dependency of cryptographic protocols on cryptography primitives

To what extent depend cryptographic protocols on cryptographic primitives? Are there cryptographic protocols that can only be implemented with certain cryptographic primitives? If the answer is yes, ...
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278 views

Values of p and q when e = 3 (RSA)?

I am doing a paper on textbook RSA (this is for high school btw) and in my example I need two very large primes, but I want my $e = 3$. Is there a short way to calculate the values of $p$ and $q$ ...
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140 views

Is it possible to have E=D and Ke <> Kd?

Let us consider $E$ an encryption algorithm that encrypts a message $m$ into a ciphertext $c$ using a key $K_e$. i.e $c = E(K_e, m)$. Similarly, decryption is achieved by $m = D(K_d, c)$. Is there ...
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73 views

RC4 via nonlinear mixer — sound?

We implemented a rc4 (ARC4) variant for creating a cryptographic stream - question is: Is this sound? (I'll give an example for 32 bit variant, though 64 bit/larger is possible) Algorithm is as ...
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96 views

How to establish if a string contains a message

If you have a string S, then the string can be composed of four things: cleartext 'random' data encrypted data compressed or otherwise non-encrypted, but modified, cleartext If you want to see if ...
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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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125 views

How to find roots of equation $f(x)=0 \pmod p $, where $p$ is prime number?

$f(x)$is any nth degree equation $n>0$, how to find roots of $f(x)$ over prime modulo.
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401 views

Encryption algorithm designed to be easy to decrypt by machine but impractical to decrypt by hand

I am looking for - or considering the design of a new - encryption algorithm that does not use variable keys, such that it is easy for a computer to encrypt and decrypt any message regardless of its ...

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