Questions tagged [symmetric]
Symmetric cryptosystems assume two communicating entities share a pre-established secret key.
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Is it possible to narrow down the possible keys used for AES CBC encryption, knowing a given plaintext and its ciphertext, where IV=0? [duplicate]
I'm brute forcing a ciphertext with a given dictionary to figure out which key was used. However, it's been hinted at that there is a way to narrow down the dictionary to a smaller subset of ...
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Implementing ChaCha20 in Rust, encrypted output isn't matching test vector, why? [migrated]
I'm trying to implement ChaCha20 from RFC 7539 For some reason my chacha20_encrypt function's output isn't the same as expected. And I'm not quite sure what I'm ...
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4answers
868 views
Why do one-time pads not provide message authentication?
It is often said that one-time pads do not provide message authentication. But, if you and I have a one-time symmetric key, and I send you a message, and it is not complete gibberish, is that itself ...
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646 views
Is it possible to identify a Serpent encryption key in memory?
It has been shown that AES keys that are in use can be identified in memory. This identification relies on discovering expected round keys in memory that are contained within the key schedule.
My ...
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49 views
Extracting RC4 and 3DES keys from system memory
I have read papers [1], [2] that have presented techniques on extracting symmetric encryption keys from memory during the process of encryption. There are tools [3] that can extract AES keys from ...
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1answer
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Key derivation for AES-GCM using HKDF?
I have a system comprising N >1000 nodes. At each node I would like to use HKDF to derive a unique 256-bit key, Kn (for the nth node), from a pre-shared master key, K0, and a locally-generated random ...
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1answer
63 views
How does gpg know what cipher algorithm is needed for decryption?
I am using gpg to make encrypt a tar.gz.
My first try uses --verbose --symmetric and then the decryption is done with ...
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statistical distance in symmetric-key encryption
Prove that for any symmetric-key encrytion scheme $\Pi=(Gen, Enc, Dec)$ with message space $M$ and key space $K$, there exist $m_0, m_1 \in M$ such that $\Delta(Enc(K, m_0), Enc(K, m_1))\ge 1-\frac{|K|...
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Why algorithmic symmetry is important in hardware implementation?
In AES, the encryption and decryption functions ordered in a symmetric way, I mean the same order of functions are used inside the round structure of both encryption and decryption (subbytes, ...
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1answer
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Can I change the S-box and P-box in DES?
I am a newbie to crypto and just one quick question on the s-box and p-box of DES. I understood that the s-box is where the security comes from and NSA has somehow decided how it should be filled in.
...
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2answers
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Can frequency attack be successful on Vigenère cipher?
Here is my question when learning Vigenère cipher, can we perform frequency analysis attack toward this cipher?
My first impression is no, because each column of its matrix has exactly 26 English ...
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Are slide attacks effective if the primitive is sandwiched? And key schedule vs. Even-Mansour
Suppose you have a cryptographic permutation consisting of identical rounds, that makes it vulnerable to a slide attack. But if you sandwich it between two XORs of key material. Is it still vulnerable?...
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What is the intuition behind the strength of unstructured symmetric cryptography?
Consider a single round of a cryptographic permutation, what is so special about it that lacking some bits of information that either get mixed into it as a subkey or omitted at the end (sponge ...
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1answer
45 views
Is a symmetric encryption key derivable using the input and the output?
I am looking for a python library for encrypting a string with a single key. I do not want the key to derivable by knowing the input and the output. I have came to ...
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How do I calculate key rotation schedules?
tl;dr: How do I formulaically determine key rotation schedules for different kinds of keys and use cases?
The organization I'm a part of for utilizes both symmetric and public/private key encryption ...
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1answer
62 views
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 (SHE) schemes. I believe there are several SHE schemes that are symmetric ...
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1answer
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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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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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2answers
58 views
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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35 views
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
212 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
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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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148 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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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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2answers
112 views
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
183 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
119 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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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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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
142 views
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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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
53 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
71 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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0answers
41 views
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
222 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
124 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 ...
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1answer
133 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
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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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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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1answer
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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
141 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
42 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
391 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?
