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Questions tagged [symmetric]

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

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1answer
111 views

How to find the type of symmetric cipher? [closed]

How to find the type of symmetric cipher that was encrypted. I have ciphertext, plaintext, key. there is a command in openssl?
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1answer
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What is the general purpose of concealment algorithms introduced in…? [closed]

What is the general purpose of concealment algorithms introduced in https://eprint.iacr.org/2003/050.pdf?
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1answer
70 views

Do I need to use HMAC in this crypto wallet backup application?

I'm building an application for securely backing up cryptocurrency private keys or 12-word backup phrases that crypto wallets use as a seed to generate private keys. For the purpose of this question, ...
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1answer
941 views

How can an all-zero encryption key result in plaintext ?

In the Krack-attack paper, the section 6.3 says that a vulnerability on Android devices involves installing an all-zero encryption key when the message 3 is re-sent. In his demonstration, he shows ...
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2answers
90 views

Shortest key in symmetric algorithm used only once is unsecured?

Considering a message of n bits, one ridiculously short key of 1 bit and using this cryptographic function which performs the <...
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1answer
579 views

How does Permutation and Substitution work?

I'm a little confused on how permutation and substitution works, I've been reading about S-DES and how it goes through P-Boxes and S-Boxes but what goes on inside P or S in the algorithm? Are these p ...
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1answer
3k views

Why do we use multiple rounds of encryption?

I understand that DES and AES use multiple rounds of encryption to secure the cipher text output, what is the real reason this is carried out? Is there a certain point performing multiple rounds ...
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2answers
298 views

Is it enough to encrypt then sign when using symmetric-key encryption?

I'm doing some tests in Java, encrypting messages exchanged between two entities. I'm using a symmetric key to encrypt the messages. Right now I've stumbled upon a question. Is it enough to encrypt ...
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3answers
295 views

Encrypt password for oneself on paper

Assume the following: You have to encrypt a file (ZIP-file) containing import information. This file should be password-protected and you want to leave yourself the password encrypted (on paper, ...
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1answer
128 views

Why does the Gameboy Advance serial encryption include the destination byte address?

The Gameboy Advance encrypts data sent over its serial port. It assembles a random number to seed a linear congruential generator. Then, it xors this PRN, the data, a symmetric key, and the byte ...
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4answers
960 views

Can I encrypt data with multiple keys and decrypt with one? [closed]

Can I encrypt data with multiple keys and decrypt with one? To be clear, I am not saying encrypt a file, decrypt it, then encrypt it again with a different key. I want to encrypt it, then encrypt it ...
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2answers
390 views

Use of symmetric keys rather than asymmetric keys for transport security

Alice has an asymmetric key pair and it also has Bob. They want to encrypt traffic between each other. It would be simple to encrypt the traffic with their public keys, but instead they use key pairs ...
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1answer
1k views

When is public-key crypto used / when is symmetric crypto used?

I read in the book "Cryptography & Network Security" that it has almost been universally accepted that public-key cryptography is restricted to only being used for key management (Does this mean ...
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1answer
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Is libsodium's `box` construct secure without additional manual padding of the plaintext before encryption?

I have read the following questions and answers: How safe are Libsodium Crypto Boxes? What can be learned from the ciphertext of LibSodium's crypto_box_detached()? However, neither of these ...
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0answers
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an asymmetric encryption scheme with multiple distinct private keys [duplicate]

Is there a asymmetric encryption scheme that allows for multiple private decryption keys? where m= plaintext message and c= cyphertext message c = Ek(m) where K is the public encryption key. and ...
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1answer
461 views

symmetric encryption with fixed size

What I basically need is a way to encrypt and decrypt symmetrically an ID which is a string. Both version of the ID will live and work in different domain and I need a way to switch domain without ...
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2answers
538 views

Why does DESX break if one removed post whitening?

DESX uses whitening to strengthen against brute force attacks. What is an attack one could use to recover DESX's pre-whitening key with only two known ciphertext/plaintext pairs, given that the ...
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1answer
258 views

Is ciphertext stealing important in relation to Blowfish?

I am writing a simple messenger (as a proof of concept not for production), and I came across Blowfish as being as being an interesting alternative to AES. As it is not meant to be an actual ...
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1answer
267 views

Crypto algorithm identification (reverse engineering)

I'm trying to identify a certain cryptographic algorithm used in a program. From examining the executable, it appears it Has 16 rounds (plus 2 "rounds" for pre/post processing) Pads the input ...
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2answers
162 views

Existence of 99% successful unbounded adversary against randomized secret key encryption scheme with short keys

It can be shown that if $E$ is a deterministic encryption with key of length $n$ and messages of length $l\geq n + 10$ then there exist two messages $m_0$, $m_1$ and a strategy for Eve so that given ...
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1answer
64 views

Best way to go about understanding proofs and cryptography in general? [closed]

Studying both symmetric and asymmetric cryptography and having the hardest time doing so. I wanted to ask what is the best way to go about learning proofs? I don't have a strong mathematical ...
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1answer
262 views

Is the nonce in GCM mode used as key for HMAC? And how to send it?

So, my believe is that, in some way, GCM mode or any other authenticated encryption mode is useful to provide encryption and integrity for the ciphertext altogether instead of having to handle the ...
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2answers
563 views

AES-GCM for Securing Bluetooth Low Energy Application

I have a task at hand on designing security on Bluetooth Low Energy application layer. The system is created so that only smartphones with symmetric key (long term) could communicate and control my ...
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1answer
76 views

Pad ciphertext with arbitrary number of bits

I have a symmetric-key encryption scheme. I think the output from this scheme (MAC + IV + CBC ciphertext) should already be practically indistinguishable from random, but I would like to pad the ...
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1answer
518 views

AES-encrypted 128-bit null block: lookup table?

Let's say a 1MB file has many many consecutive null-bytes 128-bit blocks. Then, as AES works with blocks, the encrypted file will also have recurrent 128-bit-long patterns of ...
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1answer
81 views

Increasing rounds in DES, increases or decreases the security?

I was wondering whether in DES, if we used more than 16 rounds, the security of the message was increased or actually decreased? (disregarding the decreased speed ...
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3answers
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What's the difference between block ciphers and symmetric-key encryption?

Both block ciphers and symmetric-key encryption use a secret key to transform plaintext into ciphertext, and do so in a reversible manner. Are they the same? Or does symmetric-key encryption also ...
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1answer
267 views

Searchable Symmetric Encryption VS Deterministic encryption?

I am a beginner learning about encryption. The Searchable Symmetric Encryption is better than Deterministic encryption? When I say better I mean smaller leakage.
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4answers
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Transferring Encrypted One-time pad over the internet

I was working with one-time pad, and as I understand , for one time pad to be 100% secure a key shouldn't be repeated. So assuming Alice and Bob have to exchange messages over the network secured over ...
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2answers
208 views

Which element produces randomness in symmetric block ciphers encryption

Talking about symmetric encryption, I have 3 elements which I keep trying to puzzle together: IV, encryption mode, and padding. My question really is which of these elements makes the ciphertext be ...
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2answers
587 views

OTP stream cipher

I am new to cryptography, and there is one thing that is bothering me. I hope you can kindly help me to understand. Let's imagine an attacker harvests the plaintext as well the ciphertext from a ...
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3answers
739 views

Is a message digest useful with symmetric encryption to check for integrity?

I have some confusion that concerns the message digest. I know that the message digest is the real message hashed with function and we use it to verify the integrity of the message. I understand the ...
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2answers
81 views

Property that prevents determining key from ciphertext and plaintext

What is the property (if it is not Forward Secrecy) that prevents (good) symmetrical encryption algorithms from being vulnerable to an attack vector that requires only decrypted data, and the ...
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1answer
142 views

Whats the most secure way to encrypt a string without the use of a computer? [duplicate]

I want to decrease attack surface by preventing the plaintext string or encryption key from ever being typed or otherwise entered into a computer. Ideally the decryption key would be something that ...
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1answer
3k views

AES key expansion for 192-bit

In AES-192 key expansion there are 12 rounds and 52 keys. I am not sure why 52 keys are derived since each block consist of 4 rows and 6 columns (192 bit keys). So if the block is 4 x 4 then we ...
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2answers
623 views

Java - AES with 20 byte packet

I have 20 bytes of data that I need to encrypt and send to a bluetooth node. The main issue being that the receiving node only accepts 20 byte packets. Further, I cannot send multiple packets, one ...
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1answer
982 views

What Is The Weakest Possible Encryption Algorithm [closed]

I've been creating a Capture The Flag site and for one of the challenges I wanted you to have to break an encryption algorithm. Granted I want it to be a weak one, so I want the weakest out there. One ...
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1answer
331 views

Is this MAC-then-encrypt scheme secure?

I have the following requirements: 64 bits (8 bytes) of data ($D$) that requires confidentiality and integrity; the data itself is a nonce, never need to authenticate/encrypt the same value twice (e....
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3answers
1k views

Why is Symmetric encryption classed as Private Key?

I am going for my ethical hacking exam soon and I still can't get my head around why symmetric key encryption is classed as "Private/Secret Key encryption" when symmetric encryption uses the same key ...
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2answers
276 views

Suitable Symmetric Algorithm for Encryption

Please, I would like to encrypt word not more than 5 letters such as (GO, HI, APPLE, EYES) and my key length just (40 bits only), please I am looking for a suitable symmetric algorithm that it can be ...
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1answer
741 views

Simple secret key encryption with PyNaCl [closed]

I am playing around with PyNaCl to get a bit into cryptography atm. Now I wrote two scripts to encrypt a file with a secret key and then decrypt it again using that key. The encryption part works ...
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1answer
72 views

compact hardware implementation of inversion based 8-bit s-boxes

$\DeclareMathOperator{\GF}{GF}$ I cannot figure out how should I determine the matrix for transmission over $\GF(2^8)$ to $\GF(((2^2)^2)^2)$ in compact hardware implementation of inversion based 8-bit ...
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2answers
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Using symmetric-key cryptography

A group of 30 people who wish to establish pair-wise secure communications using symmetric-key cryptography. How many KEYS need to be exchanged in total?
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2answers
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Rubik's Cube as Encryption

Consider this scenario: Alice gets a Rubik's Cube and peels off the colors from each piece. She then writes a small message on one of the faces of the cube and fills the remaining pieces with random ...
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1answer
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Does key-length recommendation provided by NIST consider quantum computer?

Here we can see the suggested key-length by NIST in a few decades: https://www.keylength.com/en/4/#Biblio10 Does this consider quantum-computer?
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1answer
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For a typical n-bit symmetric key, how many keys would be considered too weak to use?

I understand that all zeros or all ones would be weak for any cipher. And certain ciphers, e.g. DES, have a list of weak keys. But I assume that there would many 'patterns' that would be detected (if ...
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1answer
578 views

How to build disk encryption system using forward permutations like Gimli?

First of all, this is purely a thought experiment. The width of Gimli isn't even a power of two (384 bits), and secondary storage bus speeds aren't even worth using a high performance permutation like ...
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1answer
167 views

Indistinguishability in the presence of an eavesdropper attack scenario

The property of Indistinguishability in the presence of an eavesdropper as described in the following experiment: (tract from: Introduction to Modern Cryptography) It must be interpreted as a ...
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0answers
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Difficulty of finding partially matching ciphertexts for a given plaintext when encrypted with two different keys

I'm trying to find a simple, practical proof-of-work scheme based purely on encryption (due to wide availability of optimized, hardware accelerated AES execution on most platforms, including modern ...
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2answers
599 views

How to recognize Authenticated Encryption with Associated Data ciphersuites

I have some doubts regarding AEAD ciphersuites and I need some clarification. In the following ciphersuites list: ...