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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Enigma Questions: Eliminating the can't encode to itself flaw? Maybe not a flaw
I am currently writing a paper in my old age for the fun of it. I feel that the enigma machine had gotten a bad wrap for some of its flaws. I decided to write a machine simulation to see if I can ...
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Is there a type of method where multiple keys are involved, and final key produces invalid results unless all prior keys are used?
I'm looking for a mechanism for a type of cert/key signing, where multiple keys need to sign/encrypt something, and a final key/method does not product a valid confirmation unless all those keys did ...
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Is there a good website to circulate RFCs [closed]
I'm drafing an RFC for a low computation crypto algorithm, intended for low power bluetooth communication. Likely without a connection using advertisements only.
It's going to include raw C code ...
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What is the name of this kind of cipher? (algorithm and description provided)
I have a cipher algorithm that doesn't seem to be one of the "well known" ones I could find. I expect someone has already come up with this and I just don't know the name. Hoping one of you ...
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Given the existence of provably-hard-to-solve problems, why do we routinely rely on conjectured-to-be-hard problems for encryption?
Let $(X, Y, Z)$ be a set of binary strings of length $n$. Let random $X$ be the private key for encoding (or decoding) message random $Y$ as $Z$. Let the encryption algorithm $m$ be a matching ...
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What can make an implementation of a large integer library unsafe for cryptography
Unfortunately, I don't have any references, but I remember people mentioning that some large integer libraries can be unsafe to use for writing cryptographic algorithms such as the RSA.
That made me ...
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Why in authenticated encryptions do we need separate keys for cipher and MAC?
As asked, I suppose this must have been answered before, even if not in the form asked here. The most notable AEAD schemes GCM-AES and ChaCha20-Poly1305 do this. Also, even outside AEAD, ad-hoc ...
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Constant-time decompression on an elliptic curve
Let $E\!: y^2 = f(x)$ be an elliptic curve over a finite field $\mathbb{F}_{q}$ of odd characteristic. Consider an $\mathbb{F}_{q}$-point $P = (x,y)$ on $E$. Suppose that we only have the $x$-...
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Cryptographically obfuscating IP addresses while preserving locality
In an online community, you sometimes have to ban certain IP addresses or even entire IP ranges due to abuse. You may hire moderators to help you with this, but you might not trust them enough to show ...
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Can new decryption keys be issued without modifying the encrypted contents? [closed]
I'm curious if there's an encryption scheme where content may be encrypted to a public key where the associated private key can generate new decryption keys for the same content. The goal is to ...
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Conceal time-based GUIDs with an affine-cipher?
I'd like to create a custom type of sortable GUID by concatenating an 8-byte nanosecond timestamp, 6 random bytes, a 1-byte node number, and a 1-byte counter. But, such a precise timestamp can be used ...
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Is finding an encryption (or hash) algorithm science, or is it art? [closed]
I'm not into cryptography, but I read a bit about it.
I wonder:
AFAIK all encryption (decryption) and hashing routines are built using some very primitive functions (let's name them "atoms" ...
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Which encryption algorithm should I use for encrypting a string [closed]
I have a very important string it's of around 20-40 words. I want to encrypt this string and store it online . Which encryption algorithm will be useful for me.
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Can we find pairs $(c,m)$ with $f(c)=f(m)=true$ in $c = AES(m,K)$ with a fixed known Key $K$ significantly faster than brute force?
Different to the usual adversary use case we do not want to find the hidden key but instead pairs of $(m,c)$ which each fulfill a certain property $f(x)=true$
An example property could be e.g. 42 ...
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What exactly is a "pass" when talking about hashing, ciphers and MAC algorithms?
I was very surprised when I said that hashing the same data twice was "double pass" and a comment came in that this wasn't the case if the hashing could be performed in parallel. This would ...
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blake3 keyed hash compression output xor'ed with key secure?
I'm currently trying to write the blake3 algorithm in JS using the official whitepaper or what it's called.
If I understand correctly then... after the 7 round keyed permutation (at the end of the ...
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What does it mean that DES algorithm was meant to run on hardware?
According to sources that I've read, it says that DES is not suited to a software implementation and that it is better suited to hardware, what does this mean?
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How fast does revealing parity bits leak information?
I've got a scheme where I XOR a secret key value with a public (but random) value, XOR together all the bits of the result, and publish that bit (0 or 1), which is the parity of the result of the XOR. ...
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Keyspace in Encryption using Chaotic Maps
I wish to encrypt an image using Logistic map. A Logistic map can be specified with the Equation:
$$x_{n+1} = r\,x_n (1-x_n).$$
Now, according to the Kerckhoff principle, the entire system's security ...
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Identifying an encryption algorithm and/or writing an encryption function
I am currently trying to reverse engineer a piece of software that uses a seemingly-custom encryption algorithm.
After disassembling the decryption part of the code, I've come up with the following ...
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What is the standard checklist for designing a Key Derivation Function?
What kinds of properties does a KDF need to have in order to be considered secure? What steps should be taken during analysis to test for flaws?
In particular, I mean a KDF that is going to be used as ...
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Can ML be used to overcome cryptography
I saw some recent papers(e.g Encrypted DNS --> Privacy? A Traffic Analysis Perspective) about adopting ML technology to overcome cryptography implemented to ensure network security. Network packets ...
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How to choose Kangaroo algorithm parameters?
I am implementing pollard kangaroo to compute the discrete logarithm of a group element $G$ of generator $g$. $G$ is a$\mod p$ multiplicative group ($p$ a prime number). So, I want to solve $g^a=h$ ...
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Is a simple KMAC-128 or KMAC-256 hash secure as a KDF?
Context
I am trying to build a simple protocol for key derivation. I want to use SHA-3 family hash functions, which (as far as I understand) should not be combined with HMAC because their security ...
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Should we classify things such as LIONESS and Tor as cryptographic primitives?
Presuming (if we ought to?) that we classify instantiations of algorithms as primitives,
https://cwe.mitre.org/data/definitions/1240.html
Colloquially, one would say that AES (and sometimes AES-256) ...
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SHA256 - alternative algorithm to receive same hash?
My question is whether it is possible to use "another" algorithm than the sha256 to hash data but end up with the identical sha256 hash (obviously without using the sha256 algorithm)?
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Seeking name of encryption algorithm
I found an algorithm described in my old math notes that I wanted to dive into further, but the name I noted is apparently completely wrong ("Bolson Adding"), so now I am trying to find the ...
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Are there any "hard lower bounds" to zero-knowledge proving space/time/commmunication complexity?
There is a lot of "retail investor" hype implying a zk revolution in the future where we have circuits for common instruction sets and many software backends are zk-proven.
I'm wondering, ...
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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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Montgomery algorithms for Lattice based schemes [closed]
Why most of Lattice based scheme use Montgomery Multiplication algorithm?
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Something like restricted multikey system?
Imagine there are $n$ parties and me. I want to give them each their own secret $b$ bits. So, $nb$ bits in total. They are not supposed to share their secrets. I want them to be able to reconstruct (...
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RSA Big prime picking [closed]
Is the random picking of big n-bits random numbers for primality test a time sensitive operation?
If so, would an heuristic for limiting the search space (about 5-10x) without missing out on any prime ...
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What non-trivial benefit does including a "context"/"signer info" provide in SM2-DSS and EdDSA?
While implementing SM2 DSS and reading RFC-8032 for EdDSA, I noticed that, both families of schemes provide provisions for including a "context" (in EdDSA) or "signer info" (in SM2 ...
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What is the methodology for selecting symbol bit length and window size when performing Shannon Entropy Analysis?
When performing Shannon Entropy analysis on something like an RNG or a file, you must:
Select a symbol bit length and number of samples would will perform analysis on at a time (IE: windows size)
...
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Which is the smallest, cyclic in 3 directions, consistent structure of random values which can be hidden at the adversaries machine? (some comparison)
Or more general each member can be part of up to three 2D locally euclidean planes of 2 different dimensions each.
(each of those planes is cyclic in two orthogonal directions, like a torus)
Given ...
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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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Algorithm that solves a system of linear equations over finite fields when a parameter is needed
I was reading Kipnis' and Shamir's paper on Cryptanalysis of the HFE Public Key Cryptosystem by Relinearisation and I wanted to implement the example at the end in Octave without using any additional ...
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Difference between FFT and NTT
What are the main differences between the Fast Fourier Transform (FFT) and the Number Theoretical Transform (NTT)?
Why do we use the NTT and not the FFT in cryptographic applications?
Which one is a ...
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Is there something like a node network with more than 2 edges/neighbors in cryptography/encryption?
Many types of encryption can be generalized as using a message $m$ and a key $k$ as input of an encryption function $f$ with a cipher $c$ as output.
$$f(m,k)=c$$
As a node graph this could look like ...
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Questions on LWE with a repeated secret matrix S
Consider a formulation of LWE where we are given either $(x,S x+e)$ or $(x,u)$ --- where $S$ is an $m \times n$ secret/hidden matrix, $x$ is a randomly sampled $n \times 1$ vector, $e$ is an $m \times ...
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Does generic group black box model prohibit MSB of discrete logarithm?
Black box generic models prohibit calculation of discrete logarithm in groups of order $q=2p+1$ where $p,q$ are random primes to $\Omega(\sqrt{p})$ steps (refer Discrete Logarithm in the generic group ...
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Are there crypt. methods $f,g,h$ which commute and finding $x$ for given $c=f^ig^jh^k(x)$ is harder than $O(i+j+k)$ but with only $<2^{256}$ values?
Are there any cryptographic methods $f,g,h$ which can be applied in any order to an input $x$ while still resulting in the same result $r$:
$$f(g(h(x)))=h(g(f(x)))=ghf(x)=fhg(x)=hfg(x)=gfh(x) = r$$
...
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How did the developers of SHA-2 algorithm come to what we have now?
After a bit of research, I finally understand what's the step by step algorithm of SHA-2 (however, of course, I won't remember it myself).
But I don't understand what's the idea behind it. Did the ...
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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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Are there any cryptographic methods $f,g,h$ with $f(g(h(x)))=h(g(f(x)))=g(h(f(x)))$ and finding $x$ for given $c=f^ig^jh^k(x)$ harder than $O(i+j+k)$?
Are there any cryptographic methods $f,g,h$ which can be applied in any order to an input $x$ while still resulting in the same result $r$:
$$f(g(h(x)))=h(g(f(x)))=ghf(x)=fhg(x)=hfg(x)=gfh(x) = r$$
...
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Distinguishing points in elliptic curves over binary extension fields using Trace
Let $E$ be an elliptic curve curve $𝑦^2 + xy ≡ 𝑥^3+𝑎𝑥^2+𝑏$ (a Weierstrass curve) (in this case, with characteristic 2) over a binary extension field $𝐺𝐹(2^{m})$ with constructing polynomial $𝑓(...
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Single-party encryption, multi-party and single-party decryption
Let’s say person A encrypts a message. Now I want both person A and persons B, C, D – A as a single individual – and B, C, D only as a group, to be able to decrypt the encrypted message. The ...
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Cryptographically safe lookup of value in a set
I'm looking for an elegant solution to the might-seem-trivial problem of looking up for specific value in a known set of values without disclosing what value we look for. Let me describe it in a ...
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Understanding the algebra behind GCM's security
I would like to understand the algebra behind GCM's security. Before I ask my questions, let me state my understanding of the math behind GCM. If correct, my questions are at the end; if incorrect, ...
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Converting a 32-bit ARX cipher to a 64-bit one, should the rounds be increased?
I read about using 64-bit words in PRF functions.
I want to convert the 32-bit ARX cipher Chacha into a 64-bit version, with key/block size of 1024-bits (512*2=1024-bits)
My question is:
Should I add ...
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