Questions tagged [symmetric]

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

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would compressing encrypted data and compressing digital signatures bad for security?

I understand that compressing encrypted data and compressing digital signatures are not efficient because they are most likely incompressible. But in my application encrypted data and digital ...
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Security Strength of Symmetric vs Asymmetric Ciphers

NIST SP 800-57 Part 1 rev 5 section 5.6.1.1 gives following comparison between different encryption types. For example, it shows that 3TDEA, RSA-2048, ECC224 provides security strength of 112 bits. ...
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In a PGP like Application , would compress and encrypt leak information

would compress and encrypt on data comromise security for PGP like application, would it be secure for use in Encrypted Messaging? I have heard its safe for data at rest encryption , i have heard ...
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Is there any way to break the AES encryption mechanism? If yes, what is the most secure encryption mechanism? [closed]

I've been studying cryptography recently and from what I've seen, AES-256 and AES-128 seem like some of the best encryption mechanisms. Are these encryption mechanisms not secure compared to others ...
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Confirming understanding of security protocol modelled in Scyther

In university, I'm currently learning how to use Scyther to model security protocols. Currently I am trying to understand what is happening in an example protocol given to me which is: ...
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Does symmetric key cryptography usually include hash function?

This may be a very basic question. I know that symmetric key algorithms use the same key to encrypt and decrypt plaintext and ciphertext. However, it seems that hash functions are often classified as ...
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What are the best known cryptanalytic attacks against AES-128 with 9 rounds?

What are the best known cryptanalytic attacks against AES-128 with 9 rounds? I found many such attacks on AES-192 and AES-256 with 9 rounds, but not for AES-128 with 9 rounds. Are there any ...
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What is the status of the NIST Lightweight Cryptography Standardisation Process?

The NIST Computer Security Resource Center called for nominations for a process to standardise lightweight symmetric primitives in August 2018. In the update talk in the 2019 Lightweight Cryptography ...
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Best attack estimates on AES

The wikipedia article on the Advanced Encryption Standard claims an attack against AES-128 with complexity $2^{126.1}$. The NIST call for proposals for post-quantum cryptography (table on page 18) ...
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How to formalize part of a protocol in ProVerif?

I'm trying to formalize the following protocol in $\mathsf{ProVerif}$, where $m$, $p$ are messages, $j$, $k$, $h$ are private keys, and $\{m\}_k$ is the ciphertext obtained by encrypting $m$ with $k$. ...
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What schemas are possible for the following encryption algorithms?

I'm trying to practice and to understand possible scenarios and the basics of symmetric encryption schemes. For the scenarios I listed below, I am not 100% sure of scenarios 1 and 3. A symmetric ...
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Is AES-128 quantum safe?

I've been reading lately some contradicting messages with regards to the quantum-safe resistance of AES128. First, there are blog posts by Ericsson people like these ones: Can quantum attackers break ...
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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 ...
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What are the performance reasons behind "xor-a-rotated-sum" instead of "add-a-rotated-xor" in Salsa20?

I'm currently reading the specification of Salsa20 (link). DJB on whether he chooses "xor-a-rotated-sum" instead of "add-a-rotated-xor" states the following : Should there be ...
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Reversing an XOR encryption/decryption function

I have a help recommended high-school project that I'm stuck with. To basically explain the problem: I have an encryption function that is used as the decryption function and I need to reverse it to ...
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Password encryption in database

I want to store passwords in a database in a way I can reuse them to authenticate users (symmetrical encryption). I read some good information here: https://cheatsheetseries.owasp.org/cheatsheets/...
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Difference between the eavesdropping and the CPA experiment in the case of multiple messages

while reading Introduction to modern cryptography by Katz and Lindell, I came across these two experiments: For me, they look like it's the same thing. Can you please explain me the difference? ...
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Exchange key and input in GGM tree

In the GGM tree construction for constructing a PRF from a PRG, the secret key is used at the root of the tree and the input is used to trace a path through the tree. Consider a construction that does ...
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Why do web-services tend to use preshared secret keys for client authentication instead of public keys?

Every API that I have ever signed up with gives you a secret key that you can then paste into your application. They know the key, and so do you. (The one exception may be VAPID for Web Push). Why is ...
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Do symmetric and skew symmetric key schedules have any known weaknesses?

A symmetric key schedule is a key schedule of the form $(k_1,\dots,k_{n-1},k_n,k_{n-1},\dots,k_1)$ or of the form $(k_1,\dots,k_{n-1},k_n,k_n,k_{n-1},\dots,k_1)$. A skew symmetric key schedule is a ...
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How LastPass decrypts database on web browser?

According to video from Dr. Pound, password managers (LastPass in particular) holds encrypted image of your data on their servers and then with master password you authenticate to get encrypted image ...
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How to destroy a randomly generated key after using it?

for example, I have an encryption program like this: Input: a message, M; my public key Kpub Step 1: randomly generate a ...
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AES vs Kuznechik (GOST R 34.12-2015) comparsion [closed]

Which algorithm is more crypto-resistant: AES or Kuznechik (GOST R 34.12-2015)?
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Encrypting a document with 2 different keys

Is there a way to encrypt a file with 2 (or more) keys and then access it with only 1? Scenario: Bob and Alice have a tight memory and can only remember ONE key. Bob and Alice encrypt a file with ...
2 votes
1 answer
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Can raw hash be used as secret key

I am trying to use argon2 hash to derive secret key to be used for AES-GCM , in package argon2-cffi in python there is a function argon2.low_level.hash_secret_raw(secret: bytes, salt: bytes, time_cost:...
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Can cryptographically secure randomness be used to implement one time pad?

if I use an one time pad key generated using a cryptographically secure random source like python's secret module , to encrypt a message, will the one time pad scheme be secure? I think the entire ...
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What happens if the number of message queries are restricted?

In this thread, we only consider symmetric key encryption. I am not familiar with this field, so I am somewhat of an idiot myself. The usual symmetric key encryption allows unbounded queries of ...
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is HMAC required if i am using AES-CFB and using Digital signatures for Authentication

I researched online and found AES-GCM and ChaCha20Poly1305 aren't post quantum secure. So I am planning to use symmetric AES256 cipher in CFB mode do I need to implement MAC using HMAC like HMAC-...
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Use blake2 permutation as a block cipher

Blake2(1024 bit state) permutation (compression function core) is basically a modified ChaCha permutation. One of the modifications is to mix in message bits (key schedule?). Given that blake2 is a ...
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Is a static IV really less secure than an IV generated from a master key?

As an example, let's take a simple situation where AES-256-CBC with IV + MAC is used to encrypt a given plainText and offer authentication. ...
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When would we need a bigger IV than 2 bytes when the IV is derived of a master key?

As an example, let's take a simple situation where AES-256-CBC with IV + MAC is used to encrypt a given plainText to offer both authentication and prevent identical cipherTexts. ...
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Whats a practical and safe encryption to use today? [duplicate]

I'm new to making applications that encrypt sensitive data and so don't know where to start. My question is what is a good encryption scheme that can be run in a good time for normal application and ...
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Distinguishing key reuse in encryption algorithms

Let $E$ be any encryption algorithm, and consider the following game capturing key reuse. Alice samples a key $k$ Bob sends a set of messages $\{m_1, ...,m_n\}$ to Alice Alice flips a coin if heads ...
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Sponge Duplex authenticated encryption with nonce reuse or no nonce

With a Sponge permutation in a Duplex construction for authenticated encryption. illustration example: ascon; actual interest if relevant: keccak Suppose there is no associated data and there is no ...
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Encrypting two messages with the same content with different keys/IVs still secure if attacker knows they are the same?

I want to store two ciphertexts inside the same file. The data stored in each ciphertext is the same (except for padding), but the data was encrypted with different keys and IVs. Both ciphertexts were ...
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Simon's quantum algorithm for symmetric encryption

Though there are many papers available on application of Simon's algorithm for symmetric encryption, nothing is clear on implementation - like how to build the oracle, how many PT-CT combinations are ...
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Private key encryption based on NP-complete problem

Over a decade ago, a question was asked on Stack Overflow, which basically asked if there were any encryption schemes that are reducible to an NP-complete problem, in the sense that breaking the ...
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Do we want to allow/Have we allowed parallelization (e.g GPU programming) to enter the cryptographic field? What are the consequences?

With the term GPU programming, I'm referring to highly parallelizable computing in general. Lastly, I have built a bit of a background in cryptography. So I have started to wonder if/where GPU ...
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Asymmetrical scheme: insecurity concerns of saving a hash of a hash of a password

please verify or explain how to do this properly. I'm letting a user create keys from the client through a secure server. I ask the user for a password on the client, then send the hashed password to ...
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Why do we need to use Asymmetric cryptography if Diffie-Hellman solves the key exchange problem of symmetric cryptography?

I am new to cryptography and I cant get my head around this issue: If symmetric cryptography is faster then asymmetric and given that Diffie-Hellman key exchange algorithm allows you to exchange keys ...
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Sending encrypted message without public key from recipient (elgamal)

assume Bob and Alice use Elgamal encryption scheme. Alice wants to send Bob a message, but does not know Bobs public key. Is there a way for Alice to find out Bobs public key by receiving multiple ...
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How to use symmetric encryption on 1on1 and group chat messenger?

Hi everyone so currently I'm trying to learn about encryption to build secure messaging app (Mobile-app, flutter based). I want the app to have 2 messaging features which are 1 on 1 messaging and ...
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Symmetric encryption algorithm based on multiplication

I've been wondering about this paragraph for some time: Multiplication is a great mixing function. If you work out what multiplication looks like in terms of ANDs and XORs it becomes apparent how ...
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Can a digital signature be used to generate a key for AES encryption?

I am looking to see if using a digital signature is a secure and reasonable way to generate a key for AES encryption. To flow would be as follows: A user signs a message ...
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Encrypting with one key and decrypting with a related key

Given $n$-bit block cipher $E$ (and its inverse $E^{-1}$), define block cipher $E^\prime_k(m) = E_k(E_{f(k)}^{-1}(m))$ where $k,f(k) \in \{0,1\}^n$ and $\forall k:f(k) \ne k$. Under the ideal block ...
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$t'$ parameter in XSL Attack

In XSL Attack, $t'$ parameter can be defined as "the number of monomials in the S-Box equations to be used in $T'$ method" Without taking into account the arguments about the attack, how can ...
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Why some people said we should use Asymmetric key to cipher the weak Symmetric key?

I heard from some people that create a software licensing. They need to generate a short license number format. So if they use RSA (Asymmetric) they will got long key. Also if they use AES (Symmetric)....
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Connecting, joining or merging Substitution Permutation layer

I am trying to identify how the SP Network is constructed. I am looking for plausible solutions that help to connect these layers together and what are the ways that exist in literature other than Kam ...
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Security analysis of North Korean block cipher Jipsam1

The cipher is a modification to AES and is described on this website: The only difference between Jipsam1 and AES-256 is the S-box. Whereas in AES the S-box is public and constant, namely $$ \begin{...
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gpg symmetric encryption decrypts without asking for the symmetric key when --decrypt option is used

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