Questions tagged [aes]

AES (Advanced Encryption Standard) is a symmetrical block-cipher algorithm with a 128-bit block size, and key sizes of 128, 192 or 256 bits.

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What would be the requirements for a new-age cipher standard?

While nowhere near being broken, AES has known attacks like reading from the substitution table, memory-based attacks, etc. If we keep getting better at breaking ciphers and we eventually get close to ...
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does OFB mode has diffusion on the plaintext?

In some block modes, if we change one bit (or more) in the plaintext, the whole block\ciphertext will be changed (i.e ecb: block will be different. cbc: whole ciphertext will be different) Does ...
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RC6 Integer operations in modulo 32 between two 32-bit blocks

I am new to cryptography and I am trying to code the RC6 (Rivest cipher 6) algorithm. The algorithm requires addition, subtraction and multiplication in modulo 232. If I am performing these operations ...
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How is WinZip AES different from normal AES

I'm trying to write a function in dart that can can decrypt a file inside a zip that is encrypted using the WinZip AES-256 standard. Documentation I have found here: https://www.winzip.com/en/support/...
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Safety of AES-256/CBC/PKCS#7 + randomization and reusage of IV

As a start, I'm by any means no expert or anything near that in cryptography. I know the very basic about this, enough to more or less choose a method to implement and then read about it so I knew ...
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Changing Field of MDS Matrix Multiplication

Assume we have an $n \times n$ MDS matrix, whose entries are among $m \times m$ binary matrices. Can we see this matrix as a $n \times n$ matrix with entries from $GF(2^m)$? How can we replace this ...
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layout scheme to store encrypted files

I'm working on a little hobby project to better understand crypto. https://app.gitbook.com/@noojee/s/dvault/ The aim is to make it easy to encrypt a set of files into a 'vault' and decrypt them at a ...
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Reconstructing the AES-192 key out of the last roundkey

Lets assume we know the last-round key of AES. For AES-128, the whole key can be reconstructed using the last-round key since every WORD in the key schedule is based on the previous 128-bit entry. For ...
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Encryption using ASCII instead of bits and bytes (clarification in the body)

I am new to cryptography and I am trying to understand something. I searched it on the internet, though the question is probably a simple one, couldn't find an answer. So, please don't judge me by ...
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Security level of Poly1305 and GMAC

The Libsodium docs list the AEAD forgery limits for ChaCha20Poly1305 and AES-GCM which seems like a < 128-bit security level but says that it's not a practical concern. I've seen other people say ...
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Can AES fail PractRand?

Mellisa O'Neil tested Xoroshiro128+ with 512 terabytes (2^49 bytes) of data. And finally it failed. Would AES fail PractRand with enough data? When we can expect that AES will fail? Maybe with $2^{64}$...
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What is the best attack on AES with a half known key?

If I have a 16 bytes key and I encrypt a text block (1KB) with AES, and the attacker knows half of the key (let's say the first half), how does it weakens the encryption?
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FOR AES GCM decrypt function, Does the output(PT) depend on Tag value(T)?

According to spec, FOR GCM decrypt function input is IV, A, C, and T. As mentioned below: 5.2.2 Authenticated Decryption Function Given the selection of an approved block cipher, key, and an ...
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Can we determine the size of n-bytes before encryption by AES-128?

I am writing a program in python to encrypt files. This program takes subsequent 1024*1024 (1 mebibyte) chunks of data from a file and encrypts it using AES-128. This is performed in a loop until all ...
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Necessity of PBKDF2 in current Setup?

I have a single password which is random bytes that encrypts a database. Right now I am using an encryption scheme of https://gist.github.com/jbtule/4336842. To summarize, we take our one password, ...
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Designing a CRAM protocol for mutual authentication in constrained devices

We are currently designing a simple Challenge-Response Authentication Mechanism (CRAM) protocol based on symmetric cryptography that would be used on the constrained embedded devices that would ...
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What are the minimum mathematics and computer science subjects that I need to understand DES and AES?

I want to study the DES and AES algorithms The question: What are the minimum mathematics and computer science subjects that I need to understand DES and AES? Edit: I mean how they work internally.
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AES and the Feistel Structure Used Together?

In Dual Watermarking in Tele-radiology using DWT for Data Authentication and Security, the authors wrote: The encryption process uses the Feistel structure consisting multiple rounds for processing ...
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Using shared secret as Out-Of-Band authentication data in Bluetooth pairing

According to the Bluetooth Specification, the pairing process starts with Slave sending a connectable advertising packet and then the Master initiates the connection. In LE Legacy OOB authentication a ...
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Are there any block ciphers (like AES) which are (or can be) commutative under composition for different keys?

Let $BC$ be a block cipher with similar security as AES (in ECB mode). This $BC$ is applied to a message $m$ of same bit size. The result is a cipher $c$. e.g.; $$BC(key_A,m) = c_A$$ $$BC(key_B,m) = ...
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ε-close to t-wise inependence of SPN (AES)

According to theorem 3.13, the 6 rounds of AES is 0.472-close to pairwise independence. It is also mentioned t-wise independence used to analyze higher order derivates attacks. it is also mentioned 3-...
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Encryption of small data with fixed key and incremental IV

I have a Bluetooth device that sends a small package periodically (without receiving). I want to encrypt and authenticate the data using AES-128. It has an embedded random and unique key which is ...
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MS CryptoAPI RC4-1024 vs AES-128?

I'm trying to figure out MS CryptoAPI to generate a symmetric key on one computer then an RSA key on another, send over that public key to use to export the symmetric key to that other computer. I'm ...
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Why using same nonce (IV) twice voids confidentiality of plain text or even key?

I understand roughly (without details of GF algebra) the scheme of GCS/GMAC: IV is to be put into Counter-0, so initializing counters. It is known, that using a IV twice can not only reveal the plain ...
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Does reusing IV in AES-CBC weaken it?

Rsynccrypto allegedly uses AES-CBC with a twist: If the last few bytes of plaintext meet a condition*, then stop, pad the current block and start encrypting new block from the current position in file ...
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CTR mode calculate messages before new key is required

I am studying a cryptography video on Coursera here titled: Modes of Operation: Many Time Key (CTR). I have just two simple questions: At around 4:30 in the video they show 2^48 without saying where ...
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Splitting an AES-256 key into two?

I understand there are already few question here which are similar but mine is a bit different in that I want to split AES 256 bit into two 128 bit key and then use a different AES key of 128bit to ...
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Cyclicity of AES [duplicate]

It is known that AES is extremely secure, with its highest standard(AES-256) being able to protect the national secrets of most governments. Due to the nature of its steps, there's the question about ...
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So is AES-256 more secure or less secure than AES-128 after all?

It seems there are attacks that work more effectively on AES-256 than AES-128, which makes it less secure in some cases. But the bigger key size should add some safety margin on the other hand, for ...
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How does encrypting a file with AES affect file size? [duplicate]

I am wondering if encrypting a file with AES will reduce or increase its file size and generally by how much. Thanks for any tips or advice.
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End to end encrypted chat design

I am in the process of creating a flutter application that will include direct messaging. You can message 1 person or a group of people. I want this to all be encrypted for privacy. The method I was ...
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Proper implementation AES-256 for single block E_k then being used on AES-GCM

My first objective is to implement AES-GCM in PowerShell 5.1 since there is not an implementation that not use external dll libraries. According to the GCM schema of encryption: the E_k block should ...
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PRNG For RSA (ANSI_X9.31)

I have a query please , I want to know how to generate random numbers using ANSI_X9.31 algorithm for RSA Algorithm please . Thank u
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¿Can it be proved that both AES's ShiftRows and MixColumns are linear transformation? (if we leave out subBytes and key addition)

I've been researching a bit and found that the mixColumns step could be expressed as matrix multiplication like this: But I'm not sure what's the mathematical proof for it and I can't find an example ...
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Securing counter value for OTP [closed]

I'm working on a project that needs an OTP based on counter value and needs some advice. Suppose we encrypt the counter value C in this way and let's say our sending packet is P = AES(key,C). If ...
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How secure is AES 256bitkey generated from PBKDF2

I am using CryptoJS AES 256 encryption: CryptoJS.AES.encrypt(realData, generateKey(passphrase), {iv: iv}); The secret is generated through: ...
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Crack AES encryption via passphrase dictionary attack?

How easy would it be to crack a AES-256 encrypted file, that is protected by a passphrase? I understand that the trying to brute force a AES-256 encryption key would be on the unfeasible side, even ...
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Why is it not possible to attack an AES by creating a function to model the substitution that occurs in a s-box?

I realise that s boxes are able to make the transformations done in AES non-linear. However I am unsure how this makes AES secure. For instance if we had no s box then it is possible to calculate the ...
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Deterministic data masking

We are building out data masking framework mainly to mask PIIs. Our scale is pretty large, and masking will be done at ingest time, so we want the masking to be done in a very performant manner. Some ...
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Does my asymmetric/symmetric mixed file encryption pseudo code pass sanity check?

I realize this depends on my implementation and the implementation of the libraries I use. I am asking about my process assuming that the encryption libraries and my code are not flawed/compromised, ...
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A few questions regarding the 4-Round AES-Distinguisher (by Gilbert and Minier) and DS-MITM

I am struggling to understand the DS-MITM attack on AES (Original Paper). Especially the 4-rounds distinguisher by Gilbert and Minier (section 3). I get the basic idea that we check exactly on which ...
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Online AES Calculator

I am currently looking into how AES works and found a calculator online: http://testprotect.com/appendix/AEScalc I understand that the AES process has 10 rounds of calculations. Does this mean that ...
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How to minimize AES output size?

I work on a project about CAN bus and I want to encrypt the data among nodes but I have have a problem because CAN bus nodes receive and send 8 bytes among each others and I know the size of AES ...
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Is OpenSSL enc using AES-256-CBC to encrypt large files safe?

I first generate a keyfile with openssl rand -hex 64 -out keyfile. I then encrypt the file with ...
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Decrypt encryptedKey session key using - AES-128 - PKCS-1#rsaes-kem-kdf2-kw-aes128

I have basic knowledge about how encryption algorithms work such as RSA, AES and so on. I have an XML response encrypted with both AES and RSA. I tried using OpenSSL to decrypt with several steps but ...
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AES-GCM can IV be stored alongside in DB?

I'm trying to encrypt and store strings in PHP as per example #1 on the PHP openssl_encrypt documentation. ...
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How to use nonce, counter, and IV in AES-256-CTR?

preface: i am not cryptographically savvy. there are similar questions on this board but they do not give the answer i need. how do i construct a valid IV, given a nonce? What does this have to do ...
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Is this a valid AES instruction reordering?

I'm trying to understand a verilog AES implementation. I know the order of the AES encryption steps to be as shown: However the code I see doesn't do this. They do the following flow graph: at the ...
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in what condition, 2 different AES 128-bit Keys generate at least 6 bytes identical ciphertext on same plaintext

as mentioned in the title, and read some past discusstion on AES collison here. it shows it's possible that, AES(k1, m1)=AES(k2, m1) just wondering what condition those 2 keys need to meet. Thanks.
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Is it possible to crack AES-256 ECB when provided with the ciphertext and a portion of the corresponding plaintext? [duplicate]

AES-ECB encrypts the message by breaking it into blocks and encrypting them one by one. Provided the knowledge of the ciphertext, a portion of the plaintext that corresponds to a block in the message, ...

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