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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DFA on aes Giraud's attack on 10 th round

I am trying to implement an attack on aes using Giraud's attack on the last round of aes using a fault injection of one bytes here is the situation normal byte in the 10th position (1,2) of the 4x4 ...
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Encrypting multiple groups of data with separate keys in a single encrypted column

I will write this question using a database example, but please note this detail may be irrelevant. Let's say I have data belonging to N clients stored in a single column of a database table. Each ...
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25 views

Calculating equivalent substitutions to AES operations(MixColumn/ ARK)

When the AES algorithm is implemented in a table lookup(SubByte, MixColumn) fashion, how many substitutions required in full round encryption? When AES is encrypted without using the table lookup(only ...
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Known plaintext attack on AES with CBC

Assume I have a plaintext and a ciphertext, encrypted using some key and AES with CBC mode. I don't have a service, that I can send something to, so I can't use the Padding Oracle attack. Are there ...
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39 views

Using AES to create a secured MAC

Considering public message M and private key K, would it be safe to create the MAC tag this way: $$MAC(M,K) = AES(m_1) \oplus AES(m_2) \oplus \cdots \oplus AES(m_n)$$ when $m_1,m_2,\ldots,m_n$ are n ...
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Symmetric Crypto Primitives derived from Rijndael Block Cipher

Rijndael Block Cipher supports multiple block/ key lengths and a subset of these was selected as AES. What other cryptographic primitives are derived from Rijndael or make use of its round function/ ...
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68 views

CMAC operation on HSM

I have generated an AES key on HSM and I need to calculate the CMAC between this key with an input value. Is it possible to do this on HSM? What is the mechanism to invoke?
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54 views

AES MDS D-XOR and S-XOR count

I am trying to implement the D-XOR and S-XOR count in python but despite reading multiple articles on how to perform the calculation I have failed to understand the process used. I would appreciate it ...
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50 views

Encryption for data tokenization

Somewhat of a crypto noob here. I've been doing a lot of reading and think I have something but would appreciate any feedback, including "you are full of it". I'm looking for a way to ...
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32 views

What security vulnerabilities exists when encrypting then hashing to be able to search values in database?

im trying to find a good way to allow searches against encrypted data in the database. Lets say i want to encrypt phone numbers, if its encrypted securely i cant search against phone numbers directly ...
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190 views

Converting a plaintext to hex for AES encryption

Looking through AES process I see it uses a substitution table which need the input in the form of hex. Im wondering if i have a plaintext of 16 bytes such as 'j±…<Ãà!Dȶ;5˜‰*', how can I convert ...
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39 views

Issue with only applying key addition layer before first round of AES

What would be the issue if AES only applied the key addition layer once, before the first round? As in, how would this make the algorithm vulnerable to attack?
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Re-encrypt modified file section with AES-CTR

I am trying to encrypt a file using AES/CTR/NoPadding. The goal is to re-encrypt the new/changed blocks and leave the old ones unchanged then generate a new MAC. My thinking is that when the file ...
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50 views

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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46 views

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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70 views

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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62 views

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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1answer
88 views

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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75 views

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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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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85 views

Client-Side Encryption for a small app

I'm designing a small personal journal web application for my wife. I'm a crypto newb, but I want her to feel secure knowing only she will have access to her journal entries. I am thinking of the ...
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84 views

Which cryptographic attacks can AES 128-bit withstand?

Most of the articles and forums are stating that the Brute Force attack can test the strength of an encryption algorithm. However, I am looking for those attacks that AES can withstand for the testing ...
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24 views

Authenticating and encrypting data for an automated system

I wish to distribute a file from A to an automated system B. The requirements are: Contents are encrypted Contents are tamper proof Contents origin is verified To do this I have devised the ...
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Why cant we use AES to hash a password, instead of a hash function?

AES needs a key in order to work, hashing-algorithms do not. Suppose we have a fixed key for AES, why don't we simply hash our keys with that? As with hash functions, AES has arbitrary input size, ...
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120 views

Are My Answers to This AES Question Correct?

Question I am extremely new to cryptography and AES and so I am not confident that I did this question orrectly. Please can you check my answers and let me know if anything jumps out as incorrect, ...
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How to prevent cache timing attack on table lookup AES implementation?

I've been trying to find a solid method to prevent cache timing or other possible side channel attacks on an AES implementation, that uses lookup tables for S-box substitution. I realize that there ...
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248 views

Is there a more efficient C# CryptoStream implementation for streaming decryption of large files

I am using LibVLC and Unity to playback locally stored encrypted 360 videos. VLC's Unity package has a feature to play content via a C# stream. I am using a FileStream wrapped in a CryptoStream to get ...
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63 views

How does a cache timing attack work on AES with lookup tables?

I was trying to make a software only implementation of AES (Rijndael). At first I was able to implement it using table lookups for the Galois field multiplication and also for the SBox, but, I really ...
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Clarification on polynomial used in Rijndael MixColumns implementation

I'm seeing the fundamental function in open source code for Rijndael MixColumns implementation. (Picture below) If i translate the 8'h1b correctly, it is represent the polynomial of $x^4+x^3+x+1$. ...
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96 views

How to use Whitebox aes

There are server programs and client programs. Prepare two keys (A, B) for AES. The A key creates an encryption table in advance with WhiteboxAes. The B key creates a decryption table in advance with ...
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36 views

AES S_BOX Generator additive constants

I try to generate other S_BOX for AES but I don't realize how to choose additive constants for S_BOX from decryption if for encryption it is 0x63 why is ...
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59 views

Can I use aes-gcm to authenticate a user based on his ability to decrypt a payload?

I'd like to authenticate my users without storing their password, even in a derived form with scrypt/pbkdf or other derivation methods. I'm exploring the idea of encrypting a random payload with AES ...
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83 views

Is encrypting data with AES-CTR-128 and keys with RSA-2048 secure?

Here's a question. I have a file that have to be encrypted with strong cipher (I've choosen AES-CTR-128). I'm using MVC 2019 to compile C++ program. Firstly, I create RSA-2048 key pair (public and ...
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Server stored, encypted messaging app

For my personal research, I have to create a messaging app, but security is only important part of application, security from MITM (man in the middle attack), at device end, and at server level. (note:...
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If we have chunk encryption for AES-Rijndael-CBC, should we hash Authenticate/tag each single chunk with a hash vs whole file?

was frustrated by which one to pick and my brain could not guess which one is better Authenticate the whole file as one with a hash vs authenticating each ciphered text. So very quickly: i have super ...
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recommended encryption algorithms to create an encrypted communication application

I have just turned 17 and I have been developing in Java for a few years. Recently I have been interested in a language called rust, I have also been made aware of privacy issues by some of my friends....
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174 views

AES-MixColumn layer in the last round

In the "Introduction to Cryptography: With Coding Theory" by Trappe and Washington, in the chapter about AES algorithm the authors say that in the last round of the encryption algorithm the MixColumn ...
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AES - Non-linearity hinders differential cryptoanalysis

Can you explain me, in simple terms if possible (I'm not a mathematician :( ), why the non-linearity introduced by the AES s-boxes hinder the differential cryptoanalysis ?
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500 views

Encrypting data on both iOS and Android without external dependencies (can I use AES-CBC?)

I am trying to achieve AWS KMS envelope encryption on both iOS and Android. From the KMS API I get a 256 bit data key in both plaintext and encrypted forms (encrypted by a master key held only on KMS ...
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Are there any specific weakness in this crypto implementation?

I am reverse engineering the firmware of a particular router/modem. I am focusing on the functionality to export the router configuration. I an searching for a way to decrypt the configuration backup ...
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185 views

Generating the Backup Exec AES-256 GCM key used to encrypt/decrypt LTO5 tape drive data

I've got an LTO5 tape that was backed up using Backup Exec (BE), which used hardware compression when writing to the tape. I've been given the passphrase that BE used to create the actual encryption ...
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How many AES 128-bit keys does a MIFARE PLUS tag have?

I know that the question is a bit silly but I dont know how many keys can a MIFARE PLUS tag store in it. Provided that I have a MIFARE PLUS S tag with 4k memory room and the key length is 128 bit, ...
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how to compute Bit Independence criterion of SBOX?

I want to compute BIC's of my Sboxes, I found out some theses for that but I could not understand how to do it. Can someone help me?
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AES encryption question

If we consider the generation of keys as $$\begin{aligned} K_0 &= E_K(IV); \\ K_{i+1} &= E_{K_i}(A) \end{aligned}$$ Where A is a block of zeroes, and the ciphertext blocks are computed as ...
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229 views

How the counter of AES-CTR in SSH is used

I am currently trying to decrypt an SSH session using memory derived keys and IVs. My current problem is that the counter value seems to be the IV plus some value < 256. My question is now why the ...
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How to change the known ciphertext so the known plaintext is changed in AES CBC mode?

I already read a blog about the padding oracle and also some posts about how to change the plaintext but it didn't work out. So I have the encrypted cookie (AES_CBC): ...
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XORing with 1B in MixColumn transformations for AES encyption

In MixColumn transformations in AES encryption, do we have to Xor the shifted input with 1B only when the leftmost bit is high or is it like the number of times we shift it, and then when a one ...
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222 views

Sharing secret content with multiple recipients

I have a sender and N recipients, and am thinking of using the following scheme to send secret content to those recipients. This is similar context to a group chat or email. I am no expert in crypto ...
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137 views

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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Why Diaspora Federation pod communication protocol shares AES keys over asymmetric encrypted channels?

As I was looking over the diaspora federation Magic Envelope documentation, I noticed something weird: { "aes_key": "...", "encrypted_magic_envelope": "..." } ...