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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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Why is ShiftRow important in AES?

I came across a comment about AES 128 without ShiftRow. I want to use this weakness to perform an attack. So far, I get that It possible to divide in 4 independent blocks of 32 bits. So we can launch ...
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Linear cryptanalysis resistance of AES Sbox

If you look at the AES Linear Approximation Table (computed for example with Sage) you will see there are many entries with what looks like a high bias of -16 ("absolute bias" scale). I ...
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99 in AES s-box, where it came from?

The multiplicative inverse in AES s-box is transformed using the following affine transformation: $s = b \oplus (b \lll 1) \oplus (b \lll 2) \oplus (b \lll 3) \oplus (b \lll 4) \oplus 99_{10}$ Where ...
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Does deriving a key from a master key and then encrypting with AES-GCM increase the lifetime of the master key?

Suppose that we have a symmetric 256-bit master key, and we want to encrypt using AES-GCM with random IVs. I understand that with random IVs, the lifetime of the master key is 2^32 in order to conform ...
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How to create a key for AES in a 192 bit key length from a password?

Let's say that I have a password. And it's secure. But it's a 10-character string. So If I wanted to create an AES key for the 128-bit version of the algorithm I would just hash it using MD5. Or If I ...
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AES CBC: When to use new IV

I am trying to figure out when to use a new IV for an AES-CBC communication and whether my approach is safe. Here is a quote from Thomas Pornin from a similar question: So, to sum up: you must choose ...
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What is the difference between AES-CCM8 mode and AES-CCM mode?

I know AES-GCM and AES-CCM but what is the difference between AES-CCM8 mode and AES-CCM mode ? Is it the length of the cipher?
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Generalizing AES s-box circular shifts in bigger GF

According to wikipedia: https://en.wikipedia.org/wiki/Rijndael_S-box AES is doing interesting thing (where $<<<$ is circular shift): $s = b \oplus (b \lll 1) \oplus (b \lll 2) \oplus (b \lll ...
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Validating AES GCM authentication tag between two different implementations

I'm a bit confused on how to validate the authentication tag between two different AES GCM implementations. One implementation (on my part) is in Java. The other, I don't know. In my implementation, ...
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How to use symmetric encryption on 1on1 and group chat messenger?

Hi everyone so currently I'm trying to learn about encryption to build secure messaging app (Mobile-app, flutter based). I want the app to have 2 messaging features which are 1 on 1 messaging and ...
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On what Galois field AES really works?

I'm trying to understand the GF theory, but every time I come across information about AES it all makes no sense. In my opinion $GF(2^8)$ defines any polynomial of the form: $a_{7} x^7 + a_{6} x^6 + ...
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Is this AES GCM + asymmetric schema secure?

I want to use the asymmetric encription offered by a tool to encrypt my files and I would like to know if the following encryption process works, regardless of perhaps not optimal use. Generate a <...
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How to Remove Encryption Key from Python Code

I am trying to remove the encryption (AES) from the improved LSB which is in Python: I want to do comparison on LSB with AES and LSB without AES. The AES is connected to LSB.py, PLShandler.py, main.py....
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Is AES GCM with PBKDF2 100k iterations still ok as of 2022?

Is using AES GCM with PBKDF2 and 100 000 iterations still considered secure as of 2022? In our threat model, if we ignore the risks linked to quantum computing, is this secure? Here is an example ...
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How do I find an equivalent permutation of AES S-box which sends $0$ in $0$?

I am testing the quality of AES S-box and using the lookup table I built a function from GF($2^8$) to GF($2^8$) seen as vector spaces. I was wondering if there is a transformation that I can use to ...
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What's the deal with Belgian cryptographers? [closed]

Some of the most widely-used/advanced cryptography products these days - AES and SHA3 - were invented by Belgians. It seems that fact is hardly a coincidence. Since I'm a complete layman, I can make ...
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Decryption considering AES OFB and ECB

I have the following pseudo code considering a ransomware methodology to encrypt files: cFile = AESEncrypt(sessionKey, pFile, OFB, iv) keyBlob = AESEncrypt(masterKey, sessionKey, OFB, iv) ivBlob = ...
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What can an attacker do with this in-secure usage of AES-CFB8?

I believe I have found insecure usage of AES-CFB8 in an application I am working on and would hope someone could explain how and why this is insecure and what an attacker could do such as key recovery ...
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Can I decrypt AES-CBC ciphertext if I have the key without IV? [duplicate]

Can I decrypt ciphertext from AES-CBC encryption, if I have the key and ciphertext only?
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AES-GCM Encryption of 1 byte

AES is known to be resistant against the plain text attack. However, any idea what is the possibilities of breaking it if the input data is just the one byte, with known and unknown IV?
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Can I use half of 256 bit key as AES 256 IV?

After some google research, I have found out the IV used in AES 256 bit encryption must be a 128 bit key. My AES256 encryption is processed with key of random 256 bit key and IV generated of text ...
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RSA / AES issue : Decryption

I perform the following commands because I need to decrypt a file -encryption key file- (which is longer than module): cat key.enc | base64 -d > encryptedrawfile.txt openssl rsautl -decrypt -inkey ...
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AES output lengths are not always a multiple of 16

I have a C# solution that encrypts a bunch of small data chunks using AES. ...
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Can a digital signature be used to generate a key for AES encryption?

I am looking to see if using a digital signature is a secure and reasonable way to generate a key for AES encryption. To flow would be as follows: A user signs a message ...
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AES XEX Mode: Cache-attacks demonstrated?

Assume AES in XEX mode, so we encrypt a plaintext $x$ as $E_K[x \oplus k_1] \oplus k_2$ where $E_K$ is the usual AES Block cipher (assume $x$ is of block size). Assume the implementation of AES is ...
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If keeping the S-Boxes secret in SPN ciphers increase they security, does using one different S-Box set per round in them increases even more? [duplicate]

I read in this paper that keeping the S-boxes secret in AES raise its security from 128-256-bits to 1812-1940-bits. Let's suppose I use one different S-Boxes set per single round. /\ Does this ...
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AES and quantum computing

I am trying to understand the AES-256 encryption algorithm as it would be implemented on a gated quantum computer (actually, a simulator), and I am having some trouble understanding the theory behind ...
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Generating Alternative Initial Value while wrapping keys with AES

Am following the instructions on https://datatracker.ietf.org/doc/html/rfc5649#section-3 ("AES Key Wrap with Padding Algorithm") and I have gotten to a point where I need to generate the <...
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Why some people said we should use Asymmetric key to cipher the weak Symmetric key?

I heard from some people that create a software licensing. They need to generate a short license number format. So if they use RSA (Asymmetric) they will got long key. Also if they use AES (Symmetric)....
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What encryption system to use if the parts of the message are known?

I want to encrypt a system firmware, and future firmware updates will use the same encryption system. Because this firmware isn't fully from scratch but rather is based on an existing framework, it is ...
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What is the Diffie Hellman session key used for in IPsec protocol?

Let's say we choose AES as cryptographic algorithm for IPsec. My question is the following Is the key produced by Diffie-Hellman algorithm used as INPUT to the AES algorithm so AES does the ...
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What would be the benefit of using a Stream Cipher which achieves encryption performance of 0.01 cpb using 1 CPU thread?

If such throughput could be achieved what would the benefits for a data center or IoT devices in terms of power saving. Also I was wondering if such speed was possible to be realized by a cipher, ...
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AES in binary-circuit-based 2PC

No matter AES with CBC or EBC etc, the inputs for AES i.e, plaintext, key, IV, are always provided by one party. In other words, there is no need for AES in a 2PC scenario since one party can already ...
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Protection (nonce addition?) against key discovery in AES 256

I've got a situation where I need to send message ciphered with AES-256. However the content, and therefore length, of the message may be intercepted before (don't ask;)) and the question I was asked ...
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Security analysis of North Korean block cipher Jipsam1

The cipher is a modification to AES and is described on this website: The only difference between Jipsam1 and AES-256 is the S-box. Whereas in AES the S-box is public and constant, namely $$ \begin{...
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Can cryptographic accelerators along with side channel attack be used for GPS spoofing?

While having a discussion with someone on a forum about GPS spoofing, he mentioned that GPS signal can be spoofed for a cruising missile and make it land somewhere else using side-channel attack along ...
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3 votes
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Is there a way to calculate the global energy footprint of AES?

Something that's puzzling me for a while is how we could calculate approximately the energy cost of using AES, for a company like Amazon or Google. How likely it is due to the nature of their business ...
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AES-128-CFB repeated IV and KPA

I'm doing reverse-engineering a product and identified a critical issue with it. The work is done and the developer was notified, but for my own personal curiosity, I'd like to learn how to exploit it ...
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Double AES Encryption [duplicate]

Let's say we have the following encryption: $AES^2_k(x) =AES_{k1}(AES_{k2}(x))$ with k = k1 || k2 and k1, k2 are 256 bit keys. $AES_{k2}(x)$ means that we use AES encryption to encrypt message x with ...
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Multiple Encryption Using GCM For Multi-Key Security

Multiple Encryption For Multi-Key Security I have a hypothetical question about multiple encryption after reading Matthew Green’s blog on multiple encryption. For those who are familiar with GCM…I ...
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what will be the impact of a 2-bit error in a ciphertext block for decryption if AES is used in ECB, CBC and CTR mode?

So I was reading about 1-bit error propagation for AES mode and how it propagates in various modes. I was wondering how error would propagate in ECB, CBC and CTR modes if it was a 2-bit or a 3-bit ...
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Is it possible to find an AES key given part of the key, the ciphertext, initialization vector and mode of encryption?

The following details are given: Partial Key: ...
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How is TLS 1.3 application data encrypted with AES-GCM sent 'over the wire'?

I've been trying to manually decrypt some TLS 1.3 traffic for educational reasons, and have stumbled across a roadblock. So far, I've been able to complete most of the key schedule, including deriving ...
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AES key expansion question

I'm reading about the key expansion for AES but I can't seem to find the answer to this question yet. The book refers to a cipher key and the expanded key (or key schedule). This is the algorithm from ...
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Is this a scenario where reuse of a One Time Pad is acceptable?

I require an encryption algorithm that requires two parties with two different keys to be able to decrypt it. I could double AES encrypt, but I am instead considering AES encryption followed by a OTP ...
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AES substitution box and key expansion question

I'm reading FIPS 197 (AES) to try and understand how the algorithm works but I don't yet have answer for are these two questions: I see the 256 byte s-box for substituting during the rounds. Do the ...
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Evaluation of prediction of probability is a DES structure

Suppose you are given $DES_k(m)$ for some unknown $k$ and $m$, where DES() is the usual DES scheme. With what probability can you predict, for example, the 12-th bit in the output of $DES_{\bar{k}}(\...
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Performance of AES CTR + HMAC SHA1

I'm doing a performance test on AES with CTR mode and HMAC SHA1 for message authentication and found the openssl speed tool for that. I run multiple tests with <...
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CTR HMAC SHA1 vs GCM Key management

The protocol SRTP uses by default AES in CTR mode with HMAC-SHA1. For my thesis I want to research if GCM would be a better option. Therefore I read following discussion. There the answer was that GCM ...
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Is it possible to prove possession of AES-128 key?

My question is kind of related to this topic: Can we prove possession of an AES-256 key without showing it? But I couldn't figure out how to apply it to my problem. Description: Lets say I have a ...
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