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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Algorithmic game theory and protocol design for communication

There is a field of exchanging information that combines cryptography and game theory. I am interested in understanding this field, but it's a little complex for me. To begin with there is a paper of ...
Hunger Learn's user avatar
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Hash function producing cycles with expected max length

Is there a known hash function $H_k: X\to X$ such that: $\forall{x\in{X}},\exists{n\in{\mathbb{N}}}, n<k \land H^n(x)=x$ === EDIT === By hash function I mean ...
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Encryption of data with multiple possible decryption keys

I'm new to the Cryptography Stack Exchange, so my question might be very naive. What encryption algorithms are out there that will allow different decryption keys to decrypt the same piece of ...
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Key stream instead of key schedule

Let's consider a block cipher in CTR mode. And let's consider a keyed PRNG or just a good PRNG with a seed as the key. The PRNG has to be very fast. Is it a good idea to put away the key schedule and ...
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Hashing of variable-length chunked data leading to leakage of secret key from side channel?

Hypothetically, secret data could be hashed in some schemes in one way or another. Could chunking of the data lead to exposure of secret component through side channel? Say converting a randomized ...
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Looking for an algorithm to encrypt with a single key and decrypt with a lot of keys without consuming too much space

Is it possible to have an encryption scheme that could be encrypted with a particular key, then decrypted with a large amount of keys without massively inflating the size of the final result? I am ...
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How does one ensure that a handshake protocol is secure assuming all underlying cryptography used are secure

Suppose one have to design handshake protocol using known secure cryptographic algorithm. The designer of implementer can assume that crypotography is secure but how would they ensure protocol itself ...
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Asymmetric non-interactive proof of work scheme

I'm looking for a non-interactive proof of work scheme. I want for it to (1) be faster to find solutions to if you're in the possession of an arbitrary secret, like a private key, and (2) for the ...
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Generating a MAC on a Polynomial

In the following, all the operations and polynomials are defined over a finite field of prime order, $\mathbb{F}_p$, where $p$ is a sufficiently large prime number. All polynomials and values below ...
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Does a digital signature algorithm exist which has a normal, a blind, an elliptic curve and an elliptic curve blind version?

Q: Does a digital signature algorithm exist which has a normal, a blind, an elliptic curve and an elliptic curve blind version? I am searching for an algorithm where you can see what happens if you ...
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Explaining Berlekamp-Massey Algorithm in simple/layman term?

My foundation in Mathematics is not great. But I would like to understand how Berlekamp-Massey Algorithm works and how it is used in lay-man terms. The only thing I find out there is the emphasis on ...
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Additive homomorphic secret sharing

I am new to cryptography esp, homomorphic encryption. I would like to know if the following is possible using something similiar to additive homomorphic secret sharing. Please apologize me if its too ...
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Is a hash function based on multiple nested iterations of HMAC-SHA-256 cryptographically weaker than SHA-512?

Let $M$ denote a message. Choose (arbitrarily or randomly) five different sequences of bits (their lengths are allowed to be arbitrary, assuming that our HMAC construction will not exceed the ...
lyrically wicked's user avatar
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Are there any pseudo-random permutation algorithms for any number of words in the input independently of the word size (as in MD6 core function)?

I am interested in fixed pseudo-random permutation algorithms that are defined for any number of words in the input (but there might be some minimal number of words, e.g. 8), where the word size may ...
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What cryptographic primitives use AES or its Round function?

I have found the following two block/stream ciphers or Hash Construction that make use of AES or its round functions A New 128-bit Key Stream Cipher LEX 3D: A Three-Dimensional Block Cipher ALE ASC-...
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Cryptographic Tagging of Information over an Insecure Channel

Is there an efficient algorithm for the tagging and location of information over an insecure channel, where two parties (the tagger and the intended recipient for the tag) can recognize a piece of ...
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Distinct keys but value revealing

Suppose we have a trust party $P_A$ that can be used to manage a data transfer from parties $P_I = P_i, \ldots, P_{i+n}$ which do not trust each others to a party $P_R$ which is also not trusted. ...
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How to prove that a perfectly secure cryptographic protocol is not possible in a given scenario?

This question was inspired from the discussion related to this question on security StackExchange. Now I was wondering given a scenario, is there a general approach to prove that a cryptographic ...
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What are the positive consequences for choosing 8 S-boxes for DES vs 1 S-box for AES?

What are the positive consequences for choosing 8 S-boxes for DES vs 1 S-box for AES? I could guess side channel resistance, but I can't find anything on it.
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Issue Factorization Quadratic Sieve

Good evening, I'm about to write my own quadratic sieve implementation in C using GMP library for large numbers. I'm facing an issue while attempting to do the last factorization step for the number: ...
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How to encrypt an image with logistic chaotic map?

I need to encrypt color images, using logistic chaotic map. Could you please recommend an algorithm for this? All the articles that I've found on the Internet are completely unclear.
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Encryption & decryption of integers using modular multiplicative inverse and extended euclidean algorithm

I'm looking for a neat algorithm, which is capable of encrypting an integer to another integer and decrypting it again AND is secure. When I was in university, my professor showed me an awesome way ...
Marcello Mönkemeyer's user avatar
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How to calculate the avalanche effect in aes-256?

I am a beginner in cryptography. I'm testing AES-128 bit key, AES-256 bit key, and Camellia-256 bit key. I'm using AES-256, 9 character salt, CBC mode, PKCS #5 padding, and the ciphertext using ...
Ahmad Amran's user avatar
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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 ...
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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 ...
calico's user avatar
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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 ...
user11909's user avatar
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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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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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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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Does diffusion also include the reducibility inability of the $n$-times appliance of an encryption scheme? Or has this another name? Any proof for it?

With optimal diffusion the change of a single input bit should change every single output bit equally likely with a chance of 50% each (in mean). But this does not necessarily mean it makes it ...
UncleBob's user avatar
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Implementing Secret Sharing Among Multiple Parties

I'm working on a scenario where a safe has a lock code '42', and this code needs to be shared securely among four individuals. The goal is to set up a system where at least two out of these four ...
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Key-dependent cipher generation

Is there any cryptanalysis possible if the cipher itself is deterministically derived from key material? For example, suppose you have n building blocks (ARX primitives, AES ops, other primitives) and ...
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Open-Source Shamir Secret Sharing Hardware Implementations in GF

Is there any hardware implementation of Shamir's secret-sharing method available? I have only go the following two implementations in the existing literature. Paper 1 Paper 2 Anything more in the ...
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What is the AEGIS design rationale for one way rounds and slow diffusion?

The AEGIS reference document doesn't specify why the authors chose a slow diffusion process and a one way round transformation. As you can see the previous state is XORed with AES applied to itself ...
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Lower bound on additive error when releasing vector of values differentially privately

I have a vector of $n$ elements where each entry is a non-negative integer. Neighboring vectors differ in one element where the absolute value difference between the elements that differ is $1$. I ...
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Is combining Elgamal algorithm and RSA algorithm for key generation and AES+RSA algorithm for encryption and decryption a novel approach?

Key generation: Key Generation Firstly, the RSA algorithm will be used to generate a public and a private key. Generate two random prime numbers p, q. Select RSA public key, P k such that gcd(P k, Φ)=...
Srity Ahmed's user avatar
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Does randomization make a big difference in the output of the BKZ algorithm?

We all know that block Korkine-Zolotarev (BKZ) algorithm is essentially a deterministic lattice reduction algorithm. However, in the actual implementation, the BKZ algorithm contains some ...
constantine's user avatar
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Why is decryption algorithm usyally deterministic?

For security against Chosen Plaintext Attack (CPA), we need randomized algorithms for encryption. But in some schemes (maybe almost all of them) take decryption algorithm deterministic. This procedure ...
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Provably secure and Practical ciphers

Are there any ciphers that are provably secure (reducable to a hard problem (including like factorization, not necessarily to NP-Complete or harder) ) are practical (not necessarily for too much ...
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Using PRF as a building block to build other primitives?

I am doing an independent research in cryptography. I have designed a post-quantum secure pseudo random function. Just constructing a PRF will not help me to publish in reputed journals. I was ...
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Difference between WhatsApp and Signal implementation of the Open Whisper Protocol

WhatsApp has taken the step of using the Open Whisper Protocol for their message encryption, borrowed from the Signal application. I was wondering if there was any obvious, high level, difference in ...
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Is it better to XOR rounds or just to make round by round in cipher?

Let's consider we have keyed PRNG's and we want to build a cipher. What is better: to xor let's say ten such generators with some input as a plaintext (every generator got different key, but the same ...
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How can a concatenation of $N$ block-cipher with known keys be more secure?

General problem / Intro: encrypting the (computable) relation in between two random numbers which are members of a as small as possible set while anything except the order of execution is known to the ...
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Test vectors for SIT -encryption algorithm?

Test vectors for SIT -encryption algorithm? I'm looking for Tests Vectors to test my implementation of SIT. Thanks a lot.
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Most popular block ciphers

Which block (cipher) algorithms are the most popular and most used today? What parameter values (block length, key length) are now considered standard (safe).
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Is this really a universal one-way function?

This PDF supposedly gives a construction of a universal one-way function, i.e. a function which is one-way as long as there exists a one-way function: Recall that there are only countably many Turing ...
Keshav Srinivasan's user avatar
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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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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 ...
Tom's user avatar
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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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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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