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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AES GCM : is it acceptable to return the wrong plaintext if the tag is incorrect?

Let's start by saying I'm no crypto expert, I'm just a dev, so feel free to correct me (using words, not downvotes) if what I'm saying is non-sense. Context : I'm doing some crypto as a service for ...
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Generation of keys in AES using Matlab?

What is the recommended way of generating a secure, random aes key in Matlab? How to generate the keys using random key generator? Is it possible to generate a 256 bit random key in Matlab using any ...
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find master key given all but last decryption round keys

I have all but the last round key in AES-256 CBC decryption, and would like to build the master key, but I am unsure how to go about it. I have read I can convert decryption roundkeys to encryption ...
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Custom Pmac forgery challenge

I'm trying to solve a crypto challenge which realy looks like the one describe by "nobody" in this thread : Here is the problem as I analysed it : we are in the finite field GF(2^128) L(0) =...
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AES plaintext is smaller than 128 bits

I'm currently developing a AES implementation in a graduation project at university. As far as I know, AES uses a 128 bit block length as input . if the entered string to encrypt is not 128 bits such ...
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what is auth data in AES-GCM

I am trying to understand AES-GCM and I do not understand what I should transmit to Auth Data during encryption. What kind of data is that?
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How to do unmasked addition on SSS masked shares?

I'm trying to understand how Shamir's Secret Sharing algorithm is applied to AES when doing threshold masking. I understand how the secrets are created and the secret is calculated and I'm now trying ...
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Is a random string good for an AES-256 instance

I have a randomly generated string of about 256 characters long. This string is hashed to for a key and initialization vector for a program running on the .NET framework 4.8. Is this method secure ...
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Number of plaintext–ciphertext pairs needed to rule out false keys with a reasonable likelihood in AES

I am new to cryptography and I've got the following question from Understanding Cryptography: Imagine that aliens — rather than abducting earthlings and performing strange experiments on them — drop a ...
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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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AES or One-time-pad for encrypting a single 128bit block?

I just started my network security course and came across the below question. Could some one help me here. User A wish to send a 128-bit secret message, S, to user B. As the preliminary step, both A ...
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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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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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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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How much data can we encrypt using AES 256 before changing the key?

Although this question has been answered in this link (After How Much Data Encryption (AES-256) we should change key?), I am not satisfied with the answers because the Recommendation for Block Cipher ...
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How does AES bit security increase by round?

As AES progresses through multiple rounds, approximately how does it security increase round by round up to its maximum? I'm curious about the shape of the curve. Is it linear, some kind of ...
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Decrypt message in swift encrypted in java using AES/GCM/NoPadding [migrated]

I want to create secretKey(symmetricKey) using my EC privateKey and publicKey from backend(Java) and decrypt message using that secretKey. How to achieve this? Here is implementation: This is how ...
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Can Stream Cipher be Used to Encrypt & Decrypt a File (Eg: .txt .docx .exe .zip)?

I was new to cryptography. And I know that in the world of cryptography there are two types of Symmetric Algorithms: Stream Cipher (RC4, Salsa & Chacha) Block Cipher (DES, AES) And when doing ...
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Is there any correlation in between two AES with a key differ only by one bit? (ECB mode)

Given two AES (128bit, ECB mode) with almost equal keys $k_1,k_2$: 127 of the 128 key bits are equal. Is there any correlation in between the ciphers they build? $$AES_1(m_i) = c_i$$ $$AES_2(m_i) = ...
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AES Implementation for Image Encryption

I've been delving into cryptography for fun and trying to implement a visualization for AES using image encryption. So far, represented each pixel's RGB values as hexadecimal numbers, then split it ...
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How to create the ciphertext that generates a desired plaintext in CBC (previous cipher- and plaintext are known)

I'm struggling with understanding this part of the literature: It can be assumed that the entire ciphertext AND plaintext is known. Considering the encryption method is $C_i = enc_k ( P_i \oplus C_{...
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Low Encrypted Entropy on PDF File

Thank you for the answers, I have edited my questions. It is a known fact that encrypting the files increases the file entropy. You can see the average entropy values of encrypted and non-encrypted ...
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CTR block generation

From what I understand, CTR works by taking a counter, concatenating it with a nonce, and encrypting the result, which gets XORed to the ciphertext. For a 128-bit block cipher (ie. AES), my ...
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How to implement AES in crypto++ which is applied multiple times to an input? which AES mode? [migrated]

For my target application I want to use AES multiple times in a row for a given input. After encrypting it $i$ times in a row it should result in same starting input if decrypting it $i$ times ...
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Changing an Encryption scheme from AES to ChaCha20

I am using the AES cipher for my OTT platform. Almost all Chip vendors (ARM, Intel, etc) have built-in AES for faster and secure processing. Now, how feasible it is to move from AES to ChaCha20? ...
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Combining ECC And RSA for a Web Based Chat system

I'm a building a Web application chat message system(Over TLS) and i would like to know if the following theory is correct. Sender I'm generating keyPairs using RSA and another KeyPairs using ECC. By ...
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Exploitability of AES in CBC Mode For Recovery of Plain Text

I'm aware of existing literature that shows in a comprehensive manner just how simple it is to tweak the ciphertext of AES-CBC such that the decrypted message ends up being entirely different than ...
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1answer
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Is AES strictly speaking a SP network?

Forgive me if this seems like a trivial question. I've read that AES is a SP network. However, when reading about P-boxes in SPNs they say that they simply shuffle bits around. In AES the ShiftRows ...
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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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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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Finding the IV of AES CBC (CTF)

We have a python program that encrypts/decrypts plaintext given in hex to a cipher using AES CBC. We know that the IV is the same and is not going to change (it is stored in a file). How can we ...
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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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Is it safe to reuse an IV 100 times to a single key with AES CBC? [duplicate]

I have a unique 6 digit number that I am generating a IV from. I am trying to make it as unique as possible. From my programming, I am able to get it down to only have 100 duplicate IVs per unique 6 ...
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Triple AES-128 encryption with 2 keys

We have a system where two devices communicate. Due to restrictions on one of them, we can only use AES-128 (so no AES-256) for encrypting the communication. However, new requirements on these kinds ...
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AES MixColumn Polynomial Transformation [duplicate]

I just read about the AES MixColumn step, which can be calculated as: $$b(x)=c(x)a(x) \pmod{X^4 +1}$$ $a(x)$ is the column to encode and $c(x)=3x^3+x^2+x+2$ My question is: how did they calculate $c(x)...
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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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IV in RSA Encrypted Private Key

I have been provided an RSA encrypted private key which was generated in NodeJS (crypto) using the following: ...
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Cipher Text generated is different if nonce is greater than 12 bytes

I wrote a library which uses AES-GCM-128 to perform encrypt and decrypt operations. This library uses EVP functions that provide a high level interface to OpenSSL cryptographic functions. To verify my ...
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AES-CBC decrypts to wrong output?

Someone I know showed this to me, and I can't put a finger to why it's happening. Am I missing something? They encrypt the text, and the output is really guessable. $u\to t$, $i\to h$ (it's one letter ...
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Where is the SIV in AES-GCM-SIV?

This is my understanding of Synthentic IVs You have 2 keys $K_1$ & $K_2$. $F$ is a PRF Instead of choosing a separate IV, you instead generate the IV from the PlainText. $IV = F(K_1, m)$ $c = E(...
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AES-ECB Reverse attack CTF [closed]

We have a key representing an SHA-256 hash in HEX, and we have the key in AES-ECB. We also have a file with plaintext to cipher messages that were encrypted with our key. How could we find this key? <...
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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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Does Terra Quantum AG break AES and Hash Algorithms?

According to this Bloomberg article: A Swiss Company Says It Found Weakness That Imperils Encryption Terra Quantum AG has a team of about 80 quantum physicists, cryptographers and mathematicians, who ...
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E2E Encryption w/ PBKDF2 + AES-GCM

I'm currently developing a product that requires user data to be encrypted on the client side. The product is a web app + a browser extension, so the focus is encrypting user data with Javascript. The ...
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AES GCM SIV implementation

I have a library which implements AES GCM algorithm. However, as you know even a single nonce reuse can have catastrophic results. As we can't guarantee a unique IV every time, I would like to run the ...
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Security of ChaCha compared to AES and Serpent

I'm trying to understand how secure XChaCha20 is in comparison with other ciphers. From what I know, ChaCha is more secure than AES, but less secure than Serpent. My question is how much more "...
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1answer
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What encryption mode should I use to protect CAN bus communication?

I have a CAN bus project and I should encrypt the communication between nodes using the AES algorithm. Which encryption mode should I use?
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AES-128/CTR/NoPadding HMAC vs Signature

Is there a semantic difference between tagging AES_128/CTR/NoPadding ciphertext with a MAC (HmacSHA256) or Digital Signature (<...
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Byte At A time ECB Attack

This is my first post on stack overflow/stack exchange so please excuse me if I asked the question in a bad way or the format is bad. I am currently working through the cryptopals challenges and I got ...
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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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