Questions tagged [symmetric]
Symmetric cryptosystems assume two communicating entities share a pre-established secret key.
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How can we convert public key system to private key? [closed]
I have a public key scheme (Gen,Enc,Dec) and I want to construct a secure private key scheme (Gen',Enc',Dec').
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1answer
36 views
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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Substitution cipher with diffusion [closed]
If we see the classical substitution ciphers, we will see in most of the cases either there was one to one substitution(Caesar cipher and also the same family with random substitution mapping) or ...
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1answer
55 views
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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53 views
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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3answers
6k views
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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48 views
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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2answers
71 views
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 ...
0
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1answer
45 views
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 ...
2
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1answer
34 views
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 ...
2
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1answer
52 views
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 ...
2
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0answers
871 views
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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1answer
55 views
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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0answers
27 views
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 ...
2
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2answers
198 views
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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0answers
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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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2answers
88 views
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
...
2
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4answers
122 views
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 ...
1
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1answer
40 views
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 ...
0
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1answer
34 views
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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1answer
67 views
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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0answers
36 views
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 ...
0
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1answer
36 views
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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1answer
75 views
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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1answer
200 views
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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1answer
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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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4answers
928 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 ...
3
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2answers
672 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 ...
2
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0answers
61 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 ...
2
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1answer
108 views
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 ...
2
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1answer
76 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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0answers
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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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1answer
62 views
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
55 views
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.
...
3
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2answers
224 views
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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0answers
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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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0answers
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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
56 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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0answers
34 views
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 ...
2
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1answer
80 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 ...
2
votes
1answer
180 views
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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0answers
41 views
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. ...
7
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2answers
623 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 ...
1
vote
2answers
90 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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0answers
46 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 ...
3
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1answer
235 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 ...
3
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1answer
165 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 ...
7
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1answer
164 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 ...
0
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0answers
33 views
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 ...
