Skip to main content
New
Stack Overflow Jobs powered by Indeed: A job site that puts thousands of tech jobs at your fingertips (U.S. only). Search jobs

Questions tagged [symmetric]

Symmetric cryptosystems assume two communicating entities share a pre-established secret key.

Filter by
Sorted by
Tagged with
1 vote
1 answer
65 views

Is there any notion of key-recovery attacks security (perhaphs using games) that is equivalent to IND-CPA?

I am talking about Symmetric Cryptography only in the following. We know that Semantic Security (in the presence of eavesdropper) implies security against message recovery (in the presence of ...
2 votes
3 answers
1k views

Why can a symmetric encryption algorithm be considered a pseudo-random number generation algorithm?

I have a question from my teacher: "Why can a symmetric encryption algorithm be considered a pseudo-random number generation algorithm? Can anyone explain it to me? And sorry if my english is not ...
2 votes
1 answer
45 views

Is AES-CTR mode with predictable IV vulnerable to CPA attacks?

I'm just confused about this topic problem. I know that the CBC mode will be vulnerable to CPA attacks if the IV is predictable, but what about the CTR mode?
0 votes
1 answer
68 views

Asymmetric encryption of the AES key made available along with the ciphertext

I know there are much more sophisticated encryption schemes than this one that achieve the same goal but I would like to understand any weaknesses in this basic, and probably typical, process: ...
1 vote
1 answer
77 views

Shannon's Perfect Security for Asymmetric Encryption

I have the following definition of Shannon's Perfect Security. Assuming messages and keys are drawn randomly from some distribution then: The probability of guessing plaintext m is not enhanced by ...
2 votes
1 answer
555 views

Proving equivalency of two security definitions of symmetric encryption schemes

how to prove definition 3.8 and 3.9 are equivalence ? picture is from book an introduction to modern cryptography (2nd edition) by j. katz and y. lindell pdf and https://repo.zenk-security.com/...
0 votes
1 answer
94 views

Security of key bits under indistinguishability for randomized encryption

My question is about symmetric randomized encryption. Let $c = \mathsf{E}(k,m;r)$ be a randomized block encryption function where $r$ denotes a random input chosen for each message block $m$. $k$ and $...
2 votes
0 answers
44 views

Design criteria of block ciphers in quantum setting

Some design criteria of block ciphers are already known for the resistance against known attacks like differential, linear , boomerang, etc. Does there already exist any study of design criteria of ...
1 vote
1 answer
49 views

Differential uniformity of vectorial Boolean function

What could we say about differential uniformity of (a vectorial Boolean function) $F = f+g \pmod 2$ (i.e. XOR) in terms of differential uniformity of $f$ and $g$?
4 votes
11 answers
9k views

For Symmetric Cryptography, why is it considered more important to safeguard a key than the function/algorithm for encrypting/decrypting a message?

As stated for the question above here's an analogy: You are a robber looking for a house to rob with two different scenarios that might occur. 1. You have a key that you know belongs to a house and ...
1 vote
0 answers
40 views

How Helpful is NXP's LRP Encryption Protocol vs AES for short keys?

NXP has a custom (I think) encryption protocol known as "Leakage-Resistant Primitive", or LRP, built on top of AES. I think the goal of this is to basically "expand" the length of ...
1 vote
1 answer
70 views

Is it possible to use Diffie-Hellman protocol for symmetric group?

I was asked this question during one of my first cryptography classes, and I'm not sure if I understand it correctly. To begin, I know that after using the Diffie-Hellman protocol (which itself is ...
2 votes
3 answers
4k views

What is the advantage of CFB over OFB?

I was wondering if CFB can be better than OFB in any ways. I would like to know in what cases one would use CFB over OFB.
1 vote
0 answers
189 views

Mathematical approach to symmetric cryptography

I'm no mathematician but when thinking about block ciphers such as AES I find it much easier to think of them as a mathematical function $f$ (rather than an 'algorithm') such that $c=f(m,k)$ with $c$ ...
1 vote
1 answer
77 views

Is a Shift Cipher with Random Insertions Unbreakable?

Imagine an Encryption Algorithm which applies a classic Shift Cipher (also called Caesar or ROT-X) to a text (with only lowercase [a-z] and the space ...
2 votes
2 answers
106 views

Can you use ChaCha20 as one-time pad?

My knowledge of cryptography nothing beyond basic so I am by no means an expert, but I do know a bit of undergraduate mathematics including number theory. I know that stream ciphers like ChaCha20 is ...
3 votes
1 answer
194 views

Is DES/2DES/3DES still used?

I checked a related question, but I still did not find the answer I was looking for. Specifically, do we have any statistics on the usage of DES/2DES/3DES? It seems from here that credit card systems ...
3 votes
1 answer
224 views

Key Encryption: Does it need to be Authenticated?

Alice wants to store files $m_i$ on Bob's untrusted cloud storage platform, with the additional restriction that she can only store one master key $k$ herself. She encrypts the files with keys $k_i$ ...
0 votes
0 answers
32 views

Does Qrypt's BLAST protocol based on "Doubly-Affine Extractors" use public-key or symmetric-key cryptography?

The company Qrypt states that "Key distribution based on asymmetric algorithms is a weak link for cryptography" and claims to "enable encryption without distributing encryption keys&...
0 votes
1 answer
98 views

Do I need to use unique IVs if all encrypted data is unique?

I am designing a service where each user has both a unique 256-bit private and public ID. These IDs should be derivable from one another, but only within the backend of my service (as to not expose ...
0 votes
1 answer
57 views

Shared Key message-encryption multiple receiver communication

Say there are 5 parties. 1 is the sender, and 4 are the receivers. The sender has a unique shared key with each receiver. k1 - between sender and receiver1 k2 - between sender and receiver2 k3 - ...
1 vote
0 answers
42 views

Are semantic security and indistinguishability equivalent for symmetric key cryptosystems?

I've seen a lot written about how, in the context of public key cryptosystems, these definitions are equivalent. Is the same true of symmetric key cryptosystems? If so, what are the precise statements ...
0 votes
0 answers
58 views

Does this protocol description and design look sound?

I am working on a tool that uses password derived keys for AES and a selectable modes of operation to encrypt (and later decrypt) text for storage on an insecure media. The tool is constrained to ...
0 votes
0 answers
17 views

Web app server side encryption scheme

I'm asking if this encryption scheme would increase the security of the user's data. Here's how it would work: The user would create an account (username + password). An encryption key (symmetric) is ...
1 vote
0 answers
180 views

In Symmetric encryption where Alice and Bob message each other, how can both decrypt the same data?

I first posted this question on StackOverflow but they told me it belongs here instead: https://stackoverflow.com/questions/77856486/in-symmetric-encryption-where-alice-and-bob-message-each-other-how-...
2 votes
1 answer
298 views

How does SMB authentication work?

When I learned about the inner workings of the TLS protocol and what exactly it protects a connection against, I was surprised to learn that even asymmetric encryption can be defeated by a MITM attack ...
0 votes
0 answers
66 views

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 ...
1 vote
1 answer
81 views

Security of this MAC scheme

I'm studying for a cryptography exam, I have this question from a past exam: Consider the MAC with key $k$, based on a block cipher $E_{(k)}$ with block size $n$, and a collision-resistant hash ...
11 votes
3 answers
15k views

Digital Signature using symmetric key cryptography

Generally digital signature is a public key cryptography concept.But it needs high overhead. So is there any publication or link available where 'digital signature using symmetric key' has been ...
-1 votes
1 answer
82 views

Is plaintext and ciphertext absolutely one-to-one in symmetric encryption algorithms? [closed]

Known conditions: The block size of this algorithm is 16 bytes. If there are multiple encryption modes, then it is limited to ECB mode. Always use only one immutable key. Since only ECB encryption ...
0 votes
0 answers
60 views

The security of cyclic affine key schedules

Suppose that $k$ is the key for a block cipher. I am interested in the security of key schedules of the form $(k_0,\dots,k_n)$ where $k=k_0$ and $k_{j+1}=A_jk_j+b_j$ where each $A_j$ is some constant ...
1 vote
1 answer
2k views

How to do statistical analysis on encrypted / anonimized data

Let's imagine Alice wants to send Bob a table with 2 columns: ...
1 vote
0 answers
82 views

Can the requirement to increase rounds with key size be bypassed?

When taking AES for example, the number of rounds increases as the key size increases. This is done in order to adequately diffuse key bits into the state of the cipher. Suppose you replace the AES ...
0 votes
1 answer
100 views

How to evaluate the minimum complexity of the key recovery when the success probability p is given?

Since the practical security of a symmetric-key primitive is determined by evaluating its resistance against an almost exhaustive list of known cryptanalytic techniques. My problem is that could we ...
0 votes
0 answers
78 views

Does something like Symmetric reencryption exist?

I'm an amateur so bear with me. I was thinking about an E2E solution for data-at-rest proxy scenarios (like cloud storage provider) that allows you to issue and revoke users via symmetric keys. I'm ...
0 votes
1 answer
516 views

Why does symmetric encryption not provide authentication and integrity? Is it only this type of encryption or cryptology in general have this issue?

Studying for Cryptology and came across a presentation regarding on "Integrity vs Authenticity" where the discussion briefly mentions how Encryption "does not provide integrity or ...
2 votes
0 answers
105 views

Why KeePassXC is deriving (stretching) the key again before saving changes to the database?

KeePassXC supports Argon2, which is great for security. However, there's a quirk that's been bothering me. Every time I save modifications to the database, it seems to stretch (derive) the key again, ...
8 votes
2 answers
406 views

Lack of response to CAESAR competition

Why is there so little response (e.g. implementation in crypto libraries, programs...) after the end of the CAESAR competition? As far as I can see, there is no shift from AES-GCM to any of the CAESAR ...
0 votes
1 answer
92 views

Does ISAAC really guarantee a cycle length of at least 2**40?

I just noticed that the FSE 1996 conference paper which defines ISAAC mentions a counter variable cc. This variable is said to be the reason why ISAAC has a ...
2 votes
0 answers
69 views

Is ISAAC+ actually an improvement over ISAAC?

I just tried to implement ISAAC from scratch, using the Jean-Philippe Aumasson paper from 2007 as a reference. This paper gives a definition of the original ISAAC algorithm as well as the improved ...
19 votes
4 answers
35k views

Is password-based AES encryption secure at all?

For a few years I have put all my passwords in a text file and encrypted that file with a password using a software solution (Axcrypt) which uses AES-128. The password is not really strong, but I ...
0 votes
1 answer
202 views

How secure is a file encrypted with GnuPG, a strong passphrase, and the symmetric option?

Suppose I encrypt a file, of, say, 10 MB, with a secure, suitable passphrase, and the command: gpg --symmetric my_file.txt What level of expertise and hardware ...
1 vote
1 answer
315 views

symmetric key generation - random number vs pbkdf2

I am working on improving my grasp on applied cryptography. Following question is just for learning/understanding purposes.. Lets say I want to generate a 16 byte key that I want to use for some ...
0 votes
1 answer
74 views

Safe implicit value validation: $H_k(k \oplus m) \sim H_k(m)$?

$H_k$ is a cryptographic hash function that's keyed using a section of key material $k$ (for whatever definition of "keyed" that's appropriate for the given hash function $H$). Are the ...
1 vote
1 answer
50 views

Does any encryption/decryption algorithm supports linear decomposition?

I am not sure whether "linear decomposition" is appropriate to summary my question: We know that the traditional symmetric encryption/decryption algorithm (like AES, TDES) can be written as: ...
1 vote
2 answers
83 views

Given $i$ keyed-$PRP$ labels $\ell_{i,x}$ from a $2^{256} \times 2^{256}$ Sudoku (Latin-square), how difficult is it for an adversary to solve?

There's a keyed-permutation I'm playing with, $\ell_{i,x} = \pi_i(x_i)$, which is a bijection $X \leftrightarrow X$, where $|X| = 2^{256}$, and whose evaluations on plaintext inputs $x_i$ perfectly ...
2 votes
1 answer
230 views

Can I predict CryptGenRandom on my own device?

I have a Windows 10 laptop with an algorithm that creates a random number using the PRNG CryptGenRandom. According to Wikipedia: Because CryptGenRandom is the de facto standard CSPRNG in Win32 ...
7 votes
3 answers
2k views

Are there any quantum-resistant symmetric encryption schemes?

It seems that quite a few currently available encryption schemes will possibly be broken by quantum computing. Are there any symmetric encryption schemes that will remain unbroken (either because of ...
0 votes
0 answers
47 views

Securing symmetric ciphers with 56-bit keys

Under the Wassenaar Arrangement and applicable export control law, symmetric cryptography of an (effective) key size of 56 bits or less is (generally) exempted from export control. I am forced to work ...
1 vote
1 answer
202 views

How to obtain inverse key stream efficiently on Present cipher?

I was taking a look at the PRESENT lightweight cipher presented here. You can see an implementation of it in Python here. It is basically a Substitution-Permutation (SP) cipher with ultra-lightweight ...

1
2 3 4 5
17