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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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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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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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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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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Use Initialization Vector as Additional Authenticated Data

Cipher is GCM-AES. Is it acceptable/recommended to store the IV as AAD? Any popular examples?
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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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Will OTP provide quantum resistance under 5 conditions?

We already have quantum computing, but when quantum computing becomes commercially available there is a problem for many but not all encryption algorithm. The One-Time-Pad or OTP is the one and only ...
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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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AES Password Based Key Derivation Iterations

I have been writing my own implementation of the Advanced Encryption Standard with cipher block chaining in python3 for the last several months, mimicking the OpenSSL command line interface. I can ...
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7zip : Why does encrypting the same file with AES-256 not give the same output?

Using 7-zip 19.00, on Windows 10 1909, build 18363.592, I encrypted a text file with the contents "hello there" using AES-256 and the password "123". I did this two times, the exact same procedure, ...
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In a hybrid cryptosystem is safe to send the encrypted key together with the encrypted message?

I am encrypting a message using an hybrid cryptosystem: I encrypt my message using AES-256 and I encrypt the symmetric cipher key using RSA. The following questions come to my mind: I want to know if ...
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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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I need help determining the best encryption options based on System.Security.Cryptography in .NET

I asked a question on Code Review Stack Exchange, and received a great summary but was redirected here. Covering the answers of the post, it was noted and suggested that: Use of plain (CBC) mode. ...
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AES/GCM/PKCS5Padding giving issues while AES/CBC/PKCS5Padding works fine for my use case

I have a requirement to read-encypt-save plus its reverse i.e. read-decypt-save files through chunk/block mechanism (single operation not feasible because of huge(GBs) file sizes). So essentially the ...
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Is it true that AES initialization constants, which are supposed to be random numbers, were in fact chosen by the NSA?

Is it true that AES initialization constants, which are supposed to be random numbers, were in fact chosen by the NSA? I mean, it's said it was done before algorithm standardization when it was still ...
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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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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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OCB-AES: Ambiguous definition of "Encipher" in RFC document

I'm implementing an OCB-AES cipher (which is described in RFC 7253), now I have to call the AES encipher function (I'll refer to that as AES-256, described in FIPS 197) Pre-summary: I'm not sure ...
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Can we design a block cipher based on SP-network without loss of E/D similarity theoretically?

I understand what SP-network (Substitution-Permutation Network) and Feistel Network look like. And those ciphers based on Feistel (e.g. DES) often achieve so called E/D similarity, which indicates ...
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Encryption and decryption of Request and response for REST API

I am working on encryption/decryption for the rest of the API. The client here can be mobile, desktop, web browsers, etc and all the requests will be made to an https endpoint. The main goal here is ...
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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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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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Why does AES use a Binary Field?

The key idea in AES is the use of matrix multiplication and the corresponding inverse (as opposed to Feistel). But the algorithm does that using a GF instead of simple modular arithmetic. Is there ...
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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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AES MixColumns, Predefined Lookup 2D Tables, and Rcon Predefined Lookup 2D Table

I need a copy of the predefined 2D table lookup for AES MixColumns when the state is multiplied by 2 and 3, 9,11,13,14, and the Rcon predefined table. I have searched for them everywhere with no luck. ...
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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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Which encryption technique should be adopted to keep the search functionalities?

I am in exactly the same situation as described in this post. I must be able to encrypt data from a client workstation then send it to an untrusted server (encrypted at rest), then decrypt it only on ...
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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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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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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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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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Verification of data on an untrusted remote storage server

I was looking at tahoe-lafs which accepts a file, encrypts it, does erasure coding on it which generates n shares and then distributes it over the storage servers. The distribution is Share 1 = Server ...
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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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Figure out chosen-plaintext-attack in Zerologon attack

Actually, I'm reading the description about Zerologon attack from the original whitepaper document. In there, Tom Tervoort mention these sentences: "So I tried to come up with some chosen-...
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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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What are the popular modes-of-operation (AES-GCM, AES-SIV, AES-GCM-SIV, etc.) geared for?

I'm interested in developing software capable of encrypting personal files (which will ultimately be backed up to the cloud) and have been doing my best to follow best practices. There are many forms ...

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