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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Create MAC and IV given known IV and MAC for previous message

I've been given a AES-CBC-MAC, a message and the IV. I don't know the key. Given a second message I am supposed to derive the IV and create a valid MAC. I believe I've successfully created the ...
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initial addround key process in AES

how sub key generated in initial round process.What is the process involved in generation of key in addround step in initial stage. how we are getting [k0,k4,k8,k12 k1,k5,k9,k13 k2,k6,k10,k14 k3,...
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Is it ever worse to add more rounds?

As my understanding goes, it is generally more secure to add more rounds to an algorithm (though it may increase processing time). Is there any exceptions to this rule? Theoretically - if your ...
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Is it possible to recover password having ZIP/AES file and unpacked file?

Is it possible to recover password having ZIP/AES file and unpacked file? Or unpack other files with the same password?
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Handling key invalidation

I'm writing an Android app which will need to store some data for the user as a byte array of unknown length. The data must be encrypted. I have gone down the path of the hardware-backed keystore and ...
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158 views

Dangers of using AES CTR without authentication - can you recover the plain text?

I understand that if a system uses AES in CTR mode (or other modes) without authentication that an attacker can flip bits to try to get the system to do something it wasn't intended to do (or wasn't ...
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What are the positive consequences for choosing 8 S-boxes for DES vs 1 S-box for AES?

What are the positive consequences for choosing 8 S-boxes for DES vs 1 S-box for AES? I could guess side channel resistance, but I can't find anything on it.
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675 views

How to use OpenSSL command line utility to encrypt data with encrypted key from public key?

I may not be asking the right question. I am fairly new to data encryption. I am currently being sent encrypted data that's stored as follows: [ [keysize] [key encrypted with public key] [ivsize] [...
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361 views

Is parallel, vectorized NORX nearly as fast as hardware-accelerated AES-GCM?

As I understand it, NORX gets 3.5 CPB in an unoptimized implementation. But NORX can be parallelized. With 4-way SIMD, I would expect about 7/8 CPB performance. This is nearly as good as AES-GCM in ...
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Why need mapping to slots to embed bytes in AES-homomorphic encryption?

The encoding of each AES bytes $𝛼_𝑖$ is using CRT(Chinese remainder theorem). It means that there is an aggregate plaintext $H$ such that: $H \mod F_0 =𝛼_0(MappingData[0])$ $H \mod F_1 =𝛼_1(...
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582 views

Difference between AES-CCM and AES-CCM*

I'm trying to understand the different between AES-CCM and AES-CCM* (as defined in IEEE Std 802.15.4™‐2011, Annex B). I see that there are more restrictions on L and M and also M=0 is allowed: L = 2 ...
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247 views

AES-GCM Hash sub key parameter in Intel's IPsec library

I am trying to use Intel's optimized AES-128-GCM implementation (from the Intel white paper “Fast Multi-buffer IPsec Implementations on Intel Architecture Processors”, you can find the code here). ...
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636 views

File encryption using per-user-encrypted shared key

So I'm looking to encrypt files using AES CTR, using a shared key that would be accessed via a per-user password. My two main concerns are: making sure that the algorithms in use are appropriate for ...
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199 views

What is the 'identity function' in AES?

I'm trying to understand how AES works. I got as far as knowing how a password is converted to an unifinished key with the PBKDF2 function. After that RFC3962 says that an AES useable key most be ...
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Designing an AES-based protocol for controlling and acessing ioT boards via RF

I'm designing an open ioT protocol to be used on ioT boards based on Texas Instruments RF-based MCUs. These MCUs have an AES module to easily encrypt and decrypt AES content, so that's why I choose a ...
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How to calculate the avalanche effect in aes-256?

I am a beginner in cryptography. I'm testing AES-128 bit key, AES-256 bit key, and Camellia-256 bit key. I'm using AES-256, 9 character salt, CBC mode, PKCS #5 padding, and the ciphertext using ...
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647 views

Unicity Distance - AES

I am quite confused calculating the unicity distance and I was hoping that someone can clarify some things for me. My main issue comes from somewhat a difference of the calculation given by our ...
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FileVault AES-XTS decryption with cipher text that's missing a part

My mac was recently upgraded to OS X Yosemite and FileVault2 full disk encryption was turned on. Encryption finished, but things went horribly wrong and key parts of the disk are filled with all 0s (...
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218 views

CCA security of a system that splits messages and encrypts each packet

Propose a symmetric key based crypto-system for implementing a secure email system. This system is based on AES and CCA secure. Suppose that you have to encrypt a large message and that this message ...
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356 views

How does AES-CCM work in BitLocker?

I'm studying this white-paper: http://jessekornblum.com/publications/di09.pdf The author says that using AES-CCM with the external key (highlighted in green at page 9, figure 4) and with the nonce at ...
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Cryptography — with a semi-priveleged user in the middle — to prevent request-tampering with another server

I'm working on a chat server for a mobile app I am writing. I would like to use a different application server for non-chat related operations and another application for chat operations. I would ...
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429 views

How we transfer 128bits cipher to a 4x4 matrix for AES input?

Why the input cipher for AES encryption, can write in 4x4 matrix with 8 bits entires, and can said is 128bits? if each cell is 8bits in binary, how we said this matrix is represent 128bits?
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Security of .net AES implementation and security of a hash MAC

My question rather splits into two sections: Is AES correctly and security implemented in the .net Framework? Are there any reviews of implementation mistakes that would weaken the security of AES (...
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How to know which key was used for an AES encryption?

I am starting a project where several categories of sensitive data have to be accessed within a table. Based on his role, a user can see clear text columns (not encrypted), accessible columns (...
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307 views

Recovering plaintext from AES-128 given round key 10 and ciphertext

I'm working on an old CTF challenge where AES-128 was used on a 16 byte block. I have the round 10 key and the ciphertext. What techniques exist for obtaining the plaintext?
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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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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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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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¿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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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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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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32 views

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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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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Security of generating one long hash and using half as a secret key and half as a “public” hash vs generating two hash values?

My question is what would be more secure, generating 2 hashes (one key and one hash) with the same password and two different salt values, or generating one long hash with a single salt, taking the ...
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Where to get AES GCM NIST-like test cases

I'm implementing AES GCM 256 bit at the moment. Now I'm finished with copying the content of the standard as a program and now have to make it actually work. With the test cases in the official NIST ...
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Is AES/CBC/PKCS5Padding vulnerable if used for store data on a db

Is padding oracle attack applicable to data stored on a DB in AES/CBC/PKCS5Padding? Specifically I would like to be able to use Postgres with pgcrypto https://www.postgresql.org/docs/13/pgcrypto.html#...
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Number of false keys in exhaustive key search for block ciphers

I'm doing a self study through Understanding Cryptography by Christof Paar and I have a question about Theorem 5.2.1 in the book: Given a block cipher with a key length of $k$ bits and block size of $...
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CNG/BCrypt/NCrypt Import an ephemeral AES key wrapped with a persistent RSA key

I will write some kind of security client/server pair: The server part provides wrapped AES keys. The client part, based on CNG win32 API (ncrypt.h+...
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50 views

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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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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49 views

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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Conditional probability being Constant in Threshold Cryptography

I am working on Threshold implementation of algorithms to prevent side channel attacks. I am not that much proficient in Statistics and Probability theory. I want to know what is the significance of ...
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Using pin code as a lockscreen for a mobile application

So I am developing an iOS & Android Application where a lock screen is used for authenticate a user. There are 4 options to unlock the screen: Password, biometric, pin code and nothing. I wanted ...
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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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Best model for client software encryption / decryption

I would like to develop a small solution (c#) that must secure data exchange with an untrusted server. The model is that this software will run on a Windows client then Encrypt data before pushing it ...
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Web Cryptography API and low level AES APIs

Does anyone know why https://www.w3.org/TR/WebCryptoAPI/ does not offer also low level AES APIs like: AES block encryption with several allowed block sizes (like for example the one offered in golang,...
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Suitable hybrid encryption approach?

I need help for my bachelor thesis. I have a general question regarding hybrid encryption in different ransomware. The hybrid encryption often uses symmetric and asymmetric encryption techniques. ...
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Modifying SubBytes Operation In AES

Let us assume the SubBytes operation changed to just shift right operation. for example - f(00011101) = 10001110 How we perform a Known/ Chosen Plaintext Attack and find the key? How much time does it ...
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Matrix multiplicative inverse

How to determine the inverse multiplicative matrix of the following two irreducible polynomials GF(2^8) x^8 + x^5 + x^3 + x^2 + 1 and x^8 + x^5 + x^4 + x^3 + x^2 + x +1
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Mathematical and empirical analysis of AES

Hello everyone and happy new year in advance. I'm doing a work about the analysis of the AES algorithm, and I have some doubts about this. First, I need to do the mathematical analysis of the ...