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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Random salt and PBKDF2 key

Suppose I wrote a function key_iv_generator(passwd) which generates a random salt (32-bytes) and a random iv(initialisation vector)(16-bytes) and use a KDF(key ...
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Using an encrypted packet counter as a counter value in AES-CTR

I am designing a networking protocol meant to be layered on top on UDP, where all data, including packet headers, is encrypted after initial public key exchange. This protocol is not really meant to ...
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Can I derive IV, if I know Encrypted Txt, Key and Encryption Method?

I want to know is there any way to derive the initialization vector, if I know all the other details. AES SHA 256bits CBC pkcs5padding Input: Hello Key: 123 Output: xORGCDL88sa8cUrK8JNSCQ== Now, how ...
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Is it possible to use an S-box similar to the one used in DES in AES? How would this work?

I'm reviewing some questions given to me by a professor and am stumped on this one. My initial guess is that yes, this is possible, but I do not know how to explain it, specifically for a function $\{...
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AES attack 4 rounds

I have currently a problem which I am unable to solve. I want to implement an attack on AES after 3 rounds without the mix columns on the 3rd. The goal is from the last round to guess the value of ...
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Need help understanding math behind Rijndael S-Box

in Rijndael SubBytes() step all bytes of input block are substituted based on a lookup table S-Box. S-Box is initialized by taking all elements of $GF(2^8)$, ...
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AES confused about how ShiftRows() step works

Advanced Encryption Standard has a ShiftRows() operation that cyclically shifts last three rows of 16 byte block as shown here. This process is explained here in ...
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1answer
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AES 128-bit encryption - not getting expected results

I am trying to implement AES encryption on my own (128 bit key and ECB mode for now) and I can't seem to get expected results. From what I understand about AES algorithm is that it divides message in ...
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Is AES-GCM-SIV with fixed IV deterministic authenticated encryption?

Is there any functional or strong security difference beyond speed between AES-GCM-SIV with implicit fixed public IV and no additional data AES-CTR (or AES-OFB) with 128-bit IV computed per HMAC-SHA-...
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Is CMC/EME mode invulnerable?

I am looking for cipher mode to encrypt disk at a sector level 512B/4K Performance-wise CMC is not a problem here. There is no possibility to store additional data. Is there any other option without ...
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Create a TOTP for machines using HMAC or AES

I'm trying to create a sort of Time-based One Time Password (TOTP) where machines are involved (not humans). In this kind of TOTP the step is 15 minutes between one code to the next one and both ...
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Is there any real attack deployed on the CTR mode over history?

The CTR mode, with its CPA security, is one of the malleable block cipher mode of operations. An attacker can simply modify the bits of the ciphertext stream in their advance. This is due to the lack ...
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How can i found the first and second round subkey in AES 128-bit by using python [closed]

How can i found the first and second round subkey in AES 128-bit by using python if the key is all zeros
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Disadvantages of AES-CTR?

On paper, it sounds *very* good to me: secure fast (in my tests it's somewhat slower than ECB (but without most of the weaknesses, more on that below) but faster than every other alternative I tested,...
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AES in terms of Diffusion and confusion [duplicate]

I will like to get a better explanation if anyone can give on the roles of matrix multiplication (mixColumn) and S-box operations in AES regarding the diffusion-confusion properties. I know that if a ...
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Is it dangerous to encrypt lots of small files with the same key?

I want to encrypt 1000s of old files on old hard drives before uploading them to the cloud. I'm planning to use AES-GCM with only one or a few keys. (I'm using Apple's CryptoKit library which provides ...
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AES-GCM ciphertext that deciphers under two keys

How can we exhibit an AES-GCM ciphertext, including IV and 128-bit authentication tag, and distinct keys $K_0$ and $K_1$, so that decryption succeeds for both keys? What degree of control do we have ...
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what are the things that aes cbc-mac , aes cmac guarantees?

does aes-cbc-mac guarantees integrity, authenticity and confidentiality? does aes-cmac guarantees integrity, authenticity and confidentiality? because I only know that aes-ccm guarantees all i.e. ...
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What will be the MAC size of AES CBC-MAC if there are suppose 10 blocks in the AES CBC-MAC?

What will be the mac size of AES CBC-MAC if there are suppose 10 blocks in the AES CBC-MAC? Will it always be 128 bits MAC size for no matter how many numbers of blocks?
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Formula for bits of entropy per bit, when combining bits with XOR

Assume that bits $A$ and $B$ each have .5 bits of entropy per bit. The two-bit result of the concatenation $A‖B$ has 1 bit of entropy total, and it retains the entropy density of .5 bits of entropy ...
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Why random number used in RSA padding but not in AES?

I noticed that people use a random number in the RSA-OAEP padding scheme to avoid deterministic encryption. But in pkcs#7 people just use the padding size rather than some random bits. Doesn't it make ...
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Consequences of AES-GCM always encrypting the same plaintext

I am analysing an authentication protocol. In this protocol AES-GCM is used to encrypt part of the messages. Regarding the authentication protocol, I made the following observations: The plaintext ...
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The Rationale behind NIST's counter/LFSR recommendation on deterministic IV constructions on SP 800-38D

The NIST has a "SP 800-38D: Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC". This guideline is a base for AES-GCM from definition to security ...
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What are the rules for using AES-GCM correctly?

When using AES-GCM I know that I am supposed to use a new initialization vector every time I call the AES-GCM algorithm with the same key. What are other rules must be followed to use AES-GCM ...
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Can AES GCM mode detect an incorrect key and refuse to decrypt?

I understand that AES in GCM mode produces an authentication tag that is used to ensure that a tampered with cipher text is not decrypted. However, if I pass the wrong key will AES in GCM mode detect ...
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Reusing encrypted message on MITM attack?

I'm using RSA public key private key for sending AES key from each client to server application. then i'm using this AES key and IV for communicating between client and server. what should i do for ...
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AES Padding (Nullbytes vs PKCS7)

I currently implement the AES(128,192,256)(ECB,CBC). Does the type of padding affect security? I just want to fill the blocks with null bytes.
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Can I use different IVs when encrypting identical plaintexts with identical keys with AES-CTR?

I would like to use AES-CTR to encrypt the same plaintext with the same key more than once (on different machines). I'm wondering whether I should try to use the same IV each time, or whether it's ...
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What can be deduced/extracted from this local hash extracted from Windows Machine?

I'm new to cryptography. I've been experimenting with getting Windows hashes to see whether it's possible to reverse engineer. The following hash is what I got from my test laptop. What can you ...
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How to perform encryption/decryption in a RESTful system? [migrated]

I'm not a crypto/security expert and have designed an architecture for encryption/decryption. I'm not sure if its full proof and want to know what people use as industry standard? I'm trying to ...
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Can I and How Decrypt this Online

Although I had a security course in school a long time ago, I am effectively new to cryptography. I have an encrypted text, the encryption key of 44 characters, the encryption method, (Fernet, which ...
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Decrypting an AES string

I'm dealing with a website that loads a javascript file which eventually sets an AES hash/value (whatever it's called) as a cookie. The file is heavily obfuscated making it hard to understand certain ...
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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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Security of a custom AES-based attack model

Provided that: $AES(plaintext, key)$ is the standard AES block cipher for a 128 bits block. $\oplus$ is the standard XOR operation. $K$ is a constant 128 bits pseudorandom value, which is used as the ...
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Best suitable column type for openssl $tag,$iv,$key,$encrypted?

Which column type is best for storing $tag, $iv, $key, $encryptedData generated by openssl_encryption, and in which format I should save these values? I am using &...
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How to securely design REST API for Password Manager app? [migrated]

I want to create Password Manager where users can create their accounts and store website passwords. For the frontend, it will be a mobile app, but I need REST API as the backend data where the data ...
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What is Associated Data in AEAD?

I am trying to understand what is AEAD exactly. I am application developer not a cryptographer. I have been searching online for a while watched a bunch of Youtube videos, read through a couple of ...
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Number message limits of Galois/Counter Mode (GCM) per key

In https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf page 27, it is said that ...the total number of blocks of plaintext and AAD that are protected by invocations of the ...
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Java large file AES Encryption is very slow [migrated]

I'm trying to encrypt a 512 Mb file with AES/CBC algorithm. It is taking around 7 sec which is too much. How to reduce the encryption time and make it faster. I'm using a fixed key and tried using ...
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How to check that an $km \times km$ block-binary matrix is an MDS matrix in $k$-bit words over $\operatorname{GF}(2)$

I have been reading about MDS matrices. It is defined as (paraphrased from Section 2.1) An $n \times n$ matrix $M$ is MDS if and only if $bn(M) = n + 1$ where $bn$ (branch number) is defined as: $bn(...
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AES homomorphic updates

I am looking for some help regarding something I am trying to do and I think to solution might be in Homomorphic encryption. Person A and B encrypt the same number(unsinged long) N using AES with ...
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Should I be worried about XTS tampering when encrypting backups using VeraCrypt?

From Wikipedia: XTS mode is susceptible to data manipulation and tampering, and applications must employ measures to detect modifications of data if manipulation and tampering is a concern: "......
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Encryption and decryption of Request and response for REST API

I am working on encryption/decryption for the rest API. The client here can be mobile,desktop,web browsers,etc and all the requests will be made to a https endpoint. The main goal here is that the ...
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Find first two blocks of plaintext given a final plaintext block, the IV and ciphertext for CBC?

I have the following: complete ciphertext; iv; last block of plaintext including the padding which is 04040404. The encryption was made using AES-CBC-256. I can ...
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1answer
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Pipelined architecture for secret key block ciphers

I want to implement a pipelined architecture of AES128; and I couldn't figure out the number of the pipline stages. As I undestand, it is possible to make the piepline stages inside the round, or ...
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What is the proper way to implement AES CTR with 128 bit nonce and 64 bit counter?

While encrypting AES in CTR mode, the input to the AES encryption function is the either a combination of IV + $m$ bit counter or is either $0$ IV bits with an $m$ bit counter. It is however rare to ...
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Will Fernet’s key function at any timeframe?

I’m very new to cryptography and I need to use a symmetric cryptography approach. My simple question is, will the key always at any time be able to decrypt the encrypted text? The encrypted text may ...
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Issue with decrypting self-coded AES

Summary: As a trainee, I got the task to extract encrypted passwords of our external password manager (Zoho Vault) and decrypt them. The documentation regarding how to decrpyt them is...none. I ask ...
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Encrypting Sectors of MiFare Plus SE

I am trying to have some MiFare Plus SE cards manufactured but I was told that I need to give instructions on the HMAC encoding method, as shown in the image, which I understand and have done, but ...
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Problems with calculating inverse of finite field $GF(2^8)$ of AES

I know this question is being asked to death here but please hear me out. I was learning how to encrypt using AES and in one of the methods, we have to calculate multiplicative inverse in the finite ...

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