Questions tagged [symmetric]

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

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The magic box puzzle: How to implement a verifiable self-contained secret system?

Imagine we have a magic box that will open only if we pronounce the secret words. Everybody at the beginning of the game have some verifiable proof of the correct secret words. During the first phase ...
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How can I make a new public cryptosystem using given public and private key cryptosystem?

Given a Public key cryptosystem with (Gen1, Enc1, Dec1) and Private key cryptosystem with (Gen2, Enc2, Dec2) I want to construct a new Public key cryptosystem (Gen3, Enc3, Dec3)?
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Is there any encryption system where the sender cannot prove that a specific ciphertext belongs to a specific plaintext

I'm trying to create a message-transfer system where The encrypted messages are stored in a public database. It is possible to verify who is the sender of this message. The sender cannot prove to ...
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State of the Twofish encryption cipher - is it broken? [closed]

Twofish was one of the finalists in the last cipher competition together with Serpent and AES, where AES won. Do you know of any cryptanalysis on Twofish and if its considered "broken" or still ...
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Is 128-bit security still considered strong in 2020, within the context of both ECC Asym & Sym ciphers

Given that much of our ECC crypto primitives provide “only” 128-bit security when defined over a 256-bit curve due to pollard-rho, is it then still safe in 2020 to consider 128-bit security safe for ...
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I need two types of easily crackable asymmetric and symmetric encryption

I have a school project in which I'm comparing asymmetric and symmetric encryption. I need two different types of easily crackable encryption, one symmetric and one asymmetric. I am planning on ...
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Is there any vulnerability in this scheme?

We want to design a symmetric encryption scheme. Note that the following things are true for our system: The plaintext P will change every time for a given user. A user will choose a password which ...
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What's the utility of the last two messages of Needham Schroeder Symmetric key protocol

The protocol works like this But I can't understand what's the utility of message 4 and 5, what do they protect from? They do not protect from replay attack if Ks gets compromised because B won't be ...
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WEP - shared symmetric keys

I know that WEP uses stream cipher encryption. The key stream = RC4(IV, K). My question is: The shared symmetric key is the same for all users? Or each user has it's own symmetric key. Also, how can ...
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Is Googles Envelope Encryption the same as Hybrid Encryption?

Google is advertising the use of Envelope Encryption in their products with their KMS. By the description, it sounds very much like Hybrid Encryption. But since I could not find any reference to ...
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Does encrypting the key with itself make it easier to crack the ciphertext? [duplicate]

As the title states; Is there any risk from encrypting the key with itself? EG. $C = AES(K=K, M=K)$ I'd assume not; after all, how does having the key for a safe inside the safe make it easier to ...
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Why isn't there a final permutation on SPN-based ciphers?

I am doing some research on differential cryptanalysis. Most people who are familiar with that cryptanalysis technique do know the tutorial from Heys (Heys Tutorial). I came currently to the question, ...
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Symmetric key crypto secure communication infrastructure

Imagine that public-key crypto stops working. Are there any academic proposals out there that would explain how we could implement commercially viable secure communication based on the current ...
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How does a key actually work in symmetric ciphers

My sky-high level understanding of modern cryptography is as follows: There is an algorithm and a key. The key or key pair is a randomly generated number (I think). The algorithm describes ...
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Security reason for introduction of PCI Key Blocks [closed]

MAC and encryption keys used in financial transactions have always been stored encrypted as cryptograms (of same length) on ostensibly unassailable hardware devices using 3DES. Now the requirement is ...
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Two possible plaintext's using OTP decryption

I am using this cipher-text c = 04 10 12 00 01 08 67 0A 19 65 0F 03 0A 00 with two possible keys ...
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Why use symmetric encryption with Public Key?

A. From what I heard (and I am beginner at a security/cryptography), if you have a payload that is very large, asymmetric is a no-go. B. Also, if you do have secret symmetric (e.g. AES) keys, you ...
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Commitment based on authencticated encryption

Let $(E,D)$ be the encryption/decryption of an authenticated encryption scheme. Consider the following commitment scheme. Generate a random key $k$. Commit to $m$ by sending $c=E_k(m)$. Reveal $m$ by ...
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Is it possible to execute elliptic curve encryption on small sensor-tags CC2650?

I am working on a project wherein ECC needs to be implemented on small devices, namely, CC2650 sensor-tags for authentication. The ECC implementation should be on Contiki OS. I have read some articles ...
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Encrypting multiple small messages with a single reused symmetric key

What is a good way of doing this? Practical and Secure. This is for a browser environment. For example, let's say there are a few 100 independent messages of about 100 characters each that you want ...
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Lightweight provably secure design [closed]

Is it possible to device lightweight (i.e. without asymmetric crypto and PKI; and without third party Trent) provably secure (in the exact security sense) scheme? Were there any attempts? Is it ...
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Security of key bits under indistinguishability for randomized encryption

My question is about symmetric randomized encryption. Let c=E(k,m,r) be a randomized block encryption function where r denotes a random input chosen for each message block m. k and c denote the ...
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How is Shamir's Secret Sharing better than this simple 2-password technique?

I'm looking for a solution to protect a message, such that both password1 (usually given to trusted person #1) and password2 (...
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Are there any other highly trusted and secure symmetric encryption algorithms besides AES?

AES is the gold standard for symmetric encryption. It is highly trusted and highly secure. Do any other symmetric ciphers - besides OTP - come close to AES's usability, security, trust-ability?
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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?