Questions tagged [symmetric]

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

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Can I use the secret part of a asymmetric encryption keypair as a symmetric encryption key?

Background I'm working on a framework for crypto-based authentication and authorization that is largely inspired by the way Keybase's Teams product works. Keybase uses the same process to generate ...
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RFC 4493 (AES-CMAC) algorithm with 256 bit key

I apologize for the newbie question. If I were to use a 256-bit key and AES256 (assuming I had the function instead of AES128, the length of the for loops in the functions xor_128, leftshift_bit, ...
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Are there any known problems performing a One-time pad with 2 keys stored separately - AKA 2 part Symmetric key exchange over TLS

If this is something that already has a name, please tell me to look at that, but I have not been able to find one yet. I am considering this process for storing some data securely. I want to ...
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Symmetric Or Asymetric- When to use?

In block chain, we use asymmetric cryptography to generate public key which we send to receiver so he can unlock the funds. All other type of hashing for creating nonce, block id, merkel route, ...
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Is the password based key exchange secure even if the public key is known to adversary?

I am assuming the answer for part 1 to be a "NO" as the adversary knows the public key he can get the password by offline attack IN part 2 : the answer is "yes" as the public key is freshly generated ...
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What makes AES look like an ideal cipher?

There are 2128! permutations on 128-bit inputs. AES supports a maximum key length of 256 bits, therefore offers at most 2256 permutations. The total number of 128-bit permutations is much larger than ...
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Using Diffie Hellman with a shared secret

For a crypto course I need to realize a small software project where a client and a server want to communicate over a unsecured network. They both have the same secret. So I bascially have to secure ...
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Use Pohlig-Hellman to encrypt large files

I have an application that needs to combine two cascaded (symmetric) encryption keys using the Pohlig-Hellman cipher. For example: The system needs two keys for encryption $c = E_a(E_b(x))$ while ...
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Weakness in a CBC-like XOR cipher

A simple symmetric encryption algorithm can be written as follows: Input message M and 64 bit key $K$ Divide M into 64 bit size blocks $B_1...B_n$ Get first block $B_1$ and perform bit-wise $\oplus$ ...
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Which algorithm is the simplest reversible fixed-size length-preserving symmetric “cryptographic” with low probability of collision?

I am not a mathematician/cryptographer, so I could not take much advantage of this other question, and it seems (?) to have more requirements than me (SAC). I say simple, because I need it to be have ...
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How to measure brute force speed of a computer for a give cipher with given number of keys for second for a given key space

As I understood brute force attack is measured in number of keys which in turns give time required based on speed of computer It is quite interesting find out how effective an arbitrary computer is ...
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What happens if the first input block is identical to the key in DES?

In Data Encryption Standard (DES), M is the input message and K is the key of 64 bits size. M is divided into n 64 sized blocks (B1,B2,B3...Bn).
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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/...
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Why isn't data encrypted with mutiple ciphers?

Why isn't data encrypted with multiple uncompromised (so far) ciphers? Feel free to answer for a single private key for both and separate private keys. For example, encrypting data with TwoFish and ...
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Concrete Example of AND Gate Using Garbled Circuit

Most of the resources online like the wiki presents the beautiful idea of Garbled circuit in a rather unnecessarily abstract manner. This is the screenshot of Wiki's protocol: What would be an ...
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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 ...
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Testing speed of symmetric vs asymmetric encryption and decryption using gpg

I'm aware that symmetric is faster than asymmetric. I want to test this, but my (obviously incorrect) tests show the reverse. Symmetric test: ...
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Encrypt symmetric session key with asymmetric or symmetric master key?

Every day, I must backup my server's files, encrypt the backup, and upload it to untrusted cloud storage (dropbox, s3, etc.) I've spent time on security.stackexchange where I discovered the typical ...
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Which is the best algorithm for large scale file encryption other than AES?

I've been looking for a fast, powerful and robust algorithm for encrypting large files with authentication . I would like to implement the algorithm on my own without using third party software. I've ...
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Encryption with 2 symmetric keys and decryption with one key

Here is my use case: I need to keep encrypted data in Hadoop. The data is encrypted with symmetric key that is being changed every half a year. When data is retrieved it should be decrypted. Lets ...
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Symmetric versus asymmetric self encryption

I can encrypt my files with a symmetric encryption algorithm like AES, or with an asymmetric encryption algorithm like RSA or ECC (I encrypt my files with my own public key). No communication is ...
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Research Question (Part 2): new symmetric key cryptosystem

A few weeks ago I asked about a new symmetric cryptosystem discovered as consequence of some new mathematics work (link here). As per suggestion of commenters, I spoke with a cryptography professor, a ...
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Estimating the probability of success of a Turing-Welchman attack on an enigma machine as a function of the length of the crib (known plaintext)?

Could anyone please tell me how to to Estimate the probability of success of a Turing-Welchman attack as a function of the length of a crib (known plaintext)?? for example we have the : plain text=...
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Comparison of end-to-end encryption and TLS

I am writing a comparison paper about security of electronic communication and I want to compare end-to-end encryption and TLS by giving two examples such as Whatsapp and Facebook Messenger. However, ...
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Another cut-and-paste attack on CBC mode

I am trying to see specific cases of attacks in the CBC mode, in particular, I am investigating some attacks such as Example of a cut-and-paste attack on CBC. Here I have posted something similar and ...
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Are the signcryption and the authenticated encryption same?

The signcryption and the authenticated encryption are both the combine of encryption and authentication with three natural composition (i.e., EtS, StE, E&S). I am not sure that if they are the ...
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Can symmetric crypto system with counteably infinite message space be perfectly secret?

lets say we have a countable message space for example set of natural numbers then can we have a cryptography system that information-theoretically (Shannon or other equivalence definition) be ...
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Research question: usefulness of newly discovered symmetric key cryptosystem

both myself and my collaborators are pure mathematicians with only tangential experience in the study of cryptographic systems, so if this question is unclear or does not belong here, please do let me ...
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Decrypting data on client side for use inside program

So I am developing a python program and encrypting the trained machine learning models which need to be decrypted when loading them on client side. My program will deployed on the client's machine ...
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Why encrypt symmetric keys first with RSA and then the private-key with a PW?

In for example the Microsoft Encrypting File System, the SYM-Key is first encrypted with a RSA-Pub-key and its corresponding private-key is then encrypted using a users password. Why not encrypt the ...
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Is the encryption more secure if we apply Pohlig-Hellman cipher twice with different keys but with the same modulus?

To encrypt a message $M$, we compute $C=M^k \bmod p$ and to decrypt a Cipher-text we compute $M=C^{k^{−1} \bmod (p−1)} \bmod p$ But if we use Pohlig Hellman twice like $C_1=M^k \bmod p$, and then $...
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Can a message and one time pad each encrypted with separate ciphers be weaker than the stronger of either cipher?

Assume you have: A truly random one time pad, $P$ A plain text message, $M$ Two symmetric ciphers, $C_S$ and $C_W$, where $C_S$ is always more secure than $C_W$ Assume the keys have already been ...
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I have a new cryptography algorithm, what should I do?

I created a new, unknown symmetric encryption algorithm. It looks like it's very fast and can be useful. I'm kind of independent researcher, hobbyist. Since years I'm interesting in Collatz problem ...
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Why is it difficult to encrypt large amounts of information using quantum key distribution?

An article last month claimed that Toshiba Corp. and Tohoku University recently broke the record for the amount of data encrypted using quantum key distribution by transmitting "a few hundred ...
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Forward Security of Symmetric Encryption Schemes with LFSR based PRNG

Forward security can be achieved using symmetric encryption schemes by combining with a pseudo-random number generator (PRNG). Does LFSR based PRNG provide forward security in this case?
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Advantages of encrypting a symmetric key with a public key vs using a fixed symmetric key

I am new to cryptography concepts. I am trying to protect some firmware download. Reading some Wikipedia pages, I understand that asymmetric cryptography is time consuming, so, if I want to protect ...
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Why probabilistic syntax for encryption schemes?

In Foundations of Cryptography II, Goldreich, the basic mechanism of encryption schemes is written as follows: Definition 5.1.1 (encryption scheme): An encryption scheme is a triple, $(G,E,D)$, of ...
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Example of a cut-and-paste attack on CBC

I am reading the cryptography book by Stamp and there is a cut-and-paste attack on $ECB$ and this is easy to follow because $ECB$ is relatively simple, the problem is that I would like to see an ...
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PCI - Limit Key Injection Capabiltiy 3DES + DUKPT

Current Context: I'm using a Triple DES with a DUKPT Key Management Approach. I have two organization which have access to the BDK Key: Orgzanization 1 which acts as the Secure Decryption ...
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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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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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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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