Questions tagged [symmetric]
Symmetric cryptosystems assume two communicating entities share a pre-established secret key.
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Are there any symmetric Partial Homomorphic Encryption Schemes?
Note that I am asking specifically for Partial Homomorphic Encryption (PHE) schemes and not Somewhat Homomorphic Encryption (SME) schemes. I believe there are several SHE schemes that are symmetric ...
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How strong is XooDoo vs AES?
What is Gimli, and how does XooDoo compare to symmetric ciphers such as AES or ChaCha?
I am looking at this library, called charm.
Interesting paper here.
I also ...
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Is it possible to enhance white-box cryptography security by homomorphic encryption?
Background:
Let's discussed based on published symmetric white-box crypto only, such as Chow's white-box AES.
I only know basic concepts/objectives of homomorphic encryption, such as PHE and FHE. ...
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546 views
When encrypting twice with two separate keys, can a single key decrypt both steps?
Is it possible that if a plaintext is encrypted first with a key, $n_1$, and then this ciphertext is again encrypted using the same algorithm but a different key, $n_2$ that the resulting ciphertext ...
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Very short block ciphers for equally-short plaintexts
I'm trying to develop an encryption technique for encrypting short phrases (such as reversibly-anonymized names) in text. The key-generation and ciphertext-representation details are fungible, but ...
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Authenticating without sending password to the server, and store data encrypted with password derived key on server
I am trying to think of a scheme that would allow a user to authenticate to a server, whithout sending the password to the server, and to also derive a symetric key on the client (that also never gets ...
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1answer
193 views
Are “non-mathematical” encryption algorithms comparably secure against brute force key recovery?
I recently learned about a desktop encryption application called ALKEMI, which does not use mathematical encryption according to the website, which I understand to be a misnomer, at best:
The ...
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1answer
137 views
Does anyone sell a proprietary symmetric encryption alogirthm?
I know that the majority of people use standardized encryption ciphers such as AES-256, and for good reason. But what I want to know is if anyone has come across a company or organization that is ...
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1answer
115 views
Single Ciphertext which can decrypt with multiple keys
Say we have a public key system where we have 2 users, Alice, and Bob each has a public and private key. We also have a publicly available server which stores a message.
I want to encrypt this ...
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Term for non-ARX symmetric-key cryptographic primitive design strategy
What's the term for describing designing symmetric-key cryptography primitive out of bitwise operations and shifts and rotations?
The closest thing I've found is this Keccek team's page calling it ...
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1answer
61 views
Reversible Decryption in Symmetric Key Algorithms
I am currently learning the Internal Working of Symmetric Key Algorithms, like DES, AES, BlowFish, IDEA just to name a few.
These are all quite complex Encryption alogrithms, which requires a lot of ...
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Is lattice-based cryptography relevant in symmetric cryptography?
I've seen that lattice-based cryptography works well with public key cryptography as well as cryptographic hashing algorithms, but does it apply to symmetric key cryptography?
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how are variable key sizes produced?
I am current learning the internal working of several Symmetric key Cryptographic algorithms, and came across DES and AES.
DES takes in input a 64 bit key and AES-128 takes in input a 128 bit key
...
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AES encryption question
If we consider the generation of keys as
$$\begin{aligned}
K_0 &= E_K(IV); \\
K_{i+1} &= E_{K_i}(A)
\end{aligned}$$
Where A is a block of zeroes, and the ciphertext blocks are computed as
...
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1answer
115 views
In GnuPG, what's the difference between --s2k-cipher-algo and --cipher-algo? [duplicate]
I want to change some encryption options while using GnuPG to encrypt a file symmetrically.
1) However, for choosing the cipher algorithm, GnuPG has two commands and I don't know which one to use.
...
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1answer
107 views
Best practices when encrypting a file with three different ciphers [closed]
I have some files that contain important information, so I want to encrypt them by the most secure encryption method possible.
I've read countless StackExchange answers on similar questions and some ...
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2answers
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Does ChaCha20/Salsa have the same Bit Strength as AES for identical key sizes?
i.e. does ChaCha20 with a 128bit key, require 2^128 attempts to brute force, as with AES-128, theoretically?
Ps. notwithstanding that ChaCha is a stream cipher.
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1answer
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Symmetric property of DDT of inverse function
Given a bijective function $F: \mathbb{F}_2^n \rightarrow \mathbb{F}_2^n$.
The entry of the Difference Distribution Table (DDT) at row $\alpha$ and column $\beta$ is defined as
$$DDT_{F}(\alpha,\...
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2answers
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Symmetric Encryption in the P=NP world [duplicate]
I expected to find answers along the lines of quantum-computing insight into attacking AES; however, answers on this question aren't applicable because "Quantum computers give a quadratic speedup on a ...
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2answers
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Is there a maximum amount of data which can be encrypted using a symmetric (AES256) key?
I am working on an application where we will be encrypting billions of small (< 2,000 bytes) records. Combined, we are facing many TB of data. Each record will be encrypted independently, using a ...
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3answers
614 views
Are there any symmetric cryptosystems based on computational complexity assumptions?
Are there any symmetric cryptosystems which are provably secure in the sense that there exists a reduction from their security to the hardness of some underlying hard problem such as integer ...
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1answer
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Key rotation (or other measures) for PASETO v2 “local”
I was looking at using PASETO's v2 "local" encryption (XChaCha20-Poly1305) to implement short-lived tokens to share claims between microservices via an untrusted client. PASETO's documentation is ...
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1answer
51 views
Generate $4\times 4$ Sboxes with a given branch number
Say, I want to generate a lot of $4\times4$ Sboxes with linear (or differential) branch numbre of $3$. One idea is to take all the $302$ affine classes, expand each of those classes and check if any ...
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1answer
70 views
How to symmetrically encrypt 64bit values?
I'm curious about an algorithm that would be good for the following scenario:
32-bit "plaintext" input, taken from a counter
32 or 64-bit "ciphertext" output
It should be possible to decrypt the ...
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Symmetric Key Encryption with the key a seed
Would it be feasible to give two parties a seed to generate random numbers? So that when they want to send data to each other they send the correction on the random number generated?
The random ...
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2answers
212 views
Is it possible to determine the symmetric encryption method used by output size?
I'm attempting to identify the method of encryption for a black-box symmetric encryptor that produces blocks of output that are 4 bytes in length (e.g. small inputs fit in 16 bytes, then 20 bytes and ...
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1answer
109 views
How does the key agreement process take place in Virgil E3Kit SDK for end to end encryption?
I'm using Virgil E3Kit SDK to implement end-to-end encryption in my App. Their E3Kit SDK is very effective and not too hard to understand, but I still don't understand how does the key agreement ...
3
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1answer
120 views
Zero-knowledge proof with only a ciphertext
Suppose there is a plaintext p, which is encrypted with a symmetric cipher using a key k, resulting in a ciphertext c. Bob knows both c and k, but Alice knows only c. Is there any protocol by which ...
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1answer
75 views
What does it mean : “Canonical representative of Sbox is 0123468A5BCF79DE”? and How can we calculate this representative for Sbox?
In paper :Cryptographic Analysis of All 4 × 4-Bit S-Boxes Saarinen has classified $4 \times 4$ S-Boxes and defined Canonical representative for each class of S-Boxes.
What does "Canonical ...
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1answer
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AES: Why is it a good practice to use only the first 16 bytes of a hash for encryption?
I'd like to encrypt Text with AES/CTR and a password defined by the user in java. I already checked the internet (and stackoverflow) for answers. The most used version is to hash the user password ...
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What is the inverse function of the finite field GF($2^3$) and GF($2^4$)?
I am currently reading a paper Cryptanalysis of a Theorem Decomposing the Only Known Solution to the Big APN Problem. In this paper, they mention that they used $I$ which is the inverse of the finite ...
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1answer
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What does $x^{1/e}$ mean in cryptography in this open butterfly structure?
I am currently reading a research paper that introduces this thing called a butterfly structure.
I am confused about the structure of the open butterfly in this paper which has the equation $H^{\...
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2answers
133 views
Reed Solomon secret sharing and as a one-time symmetric key?
Shamir's Secret Sharing is just a special case of Reed-Solomon where only one coefficient is used to store the secret instead of the entire polynomial.
Sarwate however, suggests that the latter can ...
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1answer
35 views
Randomly initialised global counter used to encrypt the kth message with IV = IV + k mod 2^n
The use of an increasing IV is not secure for a block cipher. That is, using a random IV for the first message then IV + 1 for the second , IV + 2 for the 3rd etc. How can I construct an attack to ...
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1answer
356 views
Is there a symmetric-key algorithm which we can use for creating a signature?
I know that in the asymmetric-key algorithm the RSA signature exists but what about the symmetrical ones?
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How can a node establish pairwise shared key with other nodes using its own polynomial share together with other's public values?
A server has a symmetric bivariate polynomial $ F(x, y) = \sum_{{i,j}=0}^{t-1}a_{i,j}x^iy^j$ $\in GF(p)[X, Y] $ of degree $t-1$. For simpliciy, $ F(x, y) = a_{0,0}+a_{1,0} x+a_{0,1}y+ a_{1,1}xy$ mod ...
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Find encryption algorithm knowing input, output and secret
Today on my PC I found some old backups; they contain also some pictures I encrypted years ago with a smartphone running Windows Mobile but I don't remember the application I used to cipher them.
I'm ...
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CAESAR finalists: Lightweight case (Ascon vs ACORN)
The Ascon cipher has been selected as the first choice in lightweight case and ACORN as the second. However according to Face-off between the CAESAR Lightweight Finalists: ACORN vs. Ascon paper, the ...
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1answer
79 views
OAEP security with variable length hash function
I'm implementing a hobby cryptosystem for fun and to increase my knowledge on the subject, and I was wondering if the OAEP construct was still sufficient as an all-or-nothing-transform if variable ...
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2answers
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Insecure private-key encryption
I am learning about crytography and the differences between the public and private keys encryption examples and I was wondering if it is possible to have a private key encryption scheme that is ...
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1answer
84 views
Definition of symmetric cipher and definition of asymmetric cipher
So I'm currently taking a cryptography class right now and my professor has told the class that she can't even define symmetric cipher for us without getting into asymmetric ciphers and the textbook ...
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How does an S-box introduce confusion
I'm trying to find the logic for introducing the S-box, but having trouble understanding why. In a simple cipher, e.g.
c = pt xor key
I understand that I can ...
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0answers
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What are dual codes and the codewords denoted by these dual codes in terms of trace?
I am currently reading a research paper (linked below) that mentions "Consider only maps that vanish at 0, their short codes $C_f$ and their duals $C_f^\perp$. The duals can be written as $C_f^\perp = ...
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1answer
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What is the link between the parity check matrix, double-error-correcting codes and APN permutations?
I am currently reading a research paper (linked below) which mentions that a map $f:V:=GF(2^{m}) \rightarrow V$ which vanishes at 0 is APN if it satisfies the condition that it is a binary code $C_{f}$...
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1answer
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What does 2-flat mean when discussing APN permutations?
I am currently reading a research paper that uses the term 2-flat. However, I don't understand what this term means.
For example, the paper mentions in its definition of APN that for all distinct $a$,...
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Are all block and stream ciphers symmetric?
I'm trying to categorize my knowledge. Can I place block ciphers and stream ciphers under symmetric with RSA/DH under asymmetric?
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Generate one-time-pad with pre-shared key and public randomness
I know very little about cryptography, so I apologize if the question does not make sense.
Let's say we design a function $F(P, X) \rightarrow K$ that takes in a pre-shared private key $P$ and a ...
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1answer
75 views
How to compare one time pad security and efficiency with AES?
It seems that the minimal size of Pseudorandom permutation (PRP) output is $128$ bits. In general, I'd like to see if there's any minimal size of the output of pseudorandom function (PRF) as well? for ...
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1answer
85 views
Can POS devices really generate random numbers?
I am doing an implementation of a system designed by a payment company and I am a little skeptical about the way they have designed the end to end cryptography.
The system is as follows:
There are ...
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2answers
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How many keys in a Hybrid Cryptosystem?
If symmetric cryptosystems have $C^2_n$ keys, and asymmetric systems have $2n$ keys, how many does a hybrid system have? This was in an online quiz from school
Company A is considering to adopt ...
