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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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How to generate 24 bytes CMAC using AES-192 or AES-256

Is it possible to generate a 24 bytes CMAC using AES-192 or AES-256 and if so, how? According to AN10922AN10922.0df,looks like we can generate 24 bytes and 32 bytes key using div constant ?
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Test data for AES based F8 encryption, F9 authentication

I am working on implementation of F8 confidentiality scheme for encryption/decryption and F9 based authentication scheme. These are specified by 3GPP standard, but the implementation in standard is ...
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crack AES CBC with chosen Ciphertext, IV and known plaintext [closed]

I am currently tackling a challenge involving AES CBC encryption where i have the ability to choose both the IV and the ciphertext, and then provide it to a service. The service decrypts with an ...
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Help required for analysis of my cryptograpgic algorithm [closed]

Can someone please help me to understand what steps must be taken to check how much a custom algorithm is vulnerable to know attacks
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Configure .Net AES to produce results of FIPS 197 [migrated]

For testing I want to configure any .Net AES algorithm to produce the results given in the FIPS 197 publication (Appendix B). I tried different parameters (block size = key size = feedback size = 128, ...
Torsten's user avatar
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Queries about RNCryptor libraries [closed]

https://github.com/RNCryptor/RNCryptor I notice this one of the applications in IOS is developed with this library. The password for AES decryption is stored in plain text. A hooking library like ...
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New Impossible Differential Attacks on AES reduce time complexity

I am interested in the following snippet from the paper New Impossible Differential Attacks on AES. Analysis of Steps 3–4 of the 7-Round Attack in the 8-Round Attack The most time consuming steps of ...
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Is AES-CTR mode with predictable IV vulnerable to CPA attacks?

I'm just confused about this topic problem. I know that the CBC mode will be vulnerable to CPA attacks if the IV is predictable, but what about the CTR mode?
zephyr Victor's user avatar
3 votes
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Is using KDF more insecure that generating key directly? (AES 256 CBC)

I am writing a PHP application that requires files to encrypted using AES-256-CBC. I have two options: Option #1 Generate a totally random AES key => User Key Generate another totally random AES ...
Mathew Paret's user avatar
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Difference between AES-128 FIPS-197 & AES-128 CBC workflow

For a single block of 16 bytes... The following is the workflow of AES-128 FIPS-197 which produces the correct output using NIST test vector from page 35: ...
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Design criteria of block ciphers in quantum setting

Some design criteria of block ciphers are already known for the resistance against known attacks like differential, linear , boomerang, etc. Does there already exist any study of design criteria of ...
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When using AES, is doing encryption followed by decryption with the same key efficient?

It seems that rekeying between block cipher calls of AES is expensive. Meaning that calling $AESenc(K_1,M_1)$ and then calling $AESenc(K_2,M_2)$ with $K_1 \ne K_2$ is slower than calling $AESenc(K_1,...
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Authenticate with roles without a server

Introduction part I'm writing an application that requires authentication to be used, specifically the database and config file can only be read an authenticated user. However this authentication is ...
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1 answer
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Statistical differences between ciphertexts generated by AES in ECB vs CBC mode?

Given two ciphertexts encrypting the same (natural language) plaintext, where we know that one of the ciphertexts was encrypted with AES-CBC (and unknown IV) and one was encrypted with AES in EBC mode,...
mudskipper's user avatar
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Understand Putty ppkv3 flow

I asked a question yesterday about how the ppk file is generated. I got the answer but how can I derive the aes key and the IV? For example by using CyberChef? I have the passphrase and the salt, how ...
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Putty PPK Encryption Questions (or AES-CBC)

I am learning about aes-cbc and to simplify things we need two parameters for encryption and randomness (key and IV). IV is random at runtime and will be used to randomize the first cipherblock which ...
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How Helpful is NXP's LRP Encryption Protocol vs AES for short keys?

NXP has a custom (I think) encryption protocol known as "Leakage-Resistant Primitive", or LRP, built on top of AES. I think the goal of this is to basically "expand" the length of ...
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Row level database encryption scheme

I am developing a row level database encryption scheme. Ideally I would not do this and instead rely on something vetted, but I haven't been able to find such a scheme online. My primary concerns are: ...
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Key Exhaustion Risks in Symmetric and Asymmetric Cryptography

For the symetric keys it is recommend that the same key should not be used to encrypt large number(2^32) of cipher blocks to avoid the key-exhaustion risk. Curious to know whether the asymmetric key ...
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Security of $E(c,k) = AES(c,(k \oplus c)\cdot (2^{n} - 1 - c)) $ used multiple times with low bit keys $k$. Avoids MitmA?

More precisely the Encryption function will be $E(c_i,k_i,i)$ with a 128-bit cipher/number $c_i$, a 16-bit encryption key $k_i$ and a 8-bit index $i$ as input using a Xor key obfuscation $k'$ with ...
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Can two different AES keys have the KCV by chance?

I am trying to check KCVs of a few keys. I am generating the KCV for the keys using the method mentioned here https://crypto.stackexchange.com/a/11873/115990 Question: Can KCVs of two different AES ...
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How does MixColumn collapse 4 active S-boxes into 1?

In AES Proposal: Rijndael, page 34, there is the following figure with MixColumn transformation pattern for two columns: I'm trying to reproduce these paterns. The pattern in the column marked in ...
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Understanding the Simplified Perspective in OCB Security Proof: Exploring the Role of Collisions and Oracle Models

In the security proof of OCB (Offset Codebook Mode), it appears that only collisions at the input and output of the block cipher are considered. Typically, security proofs for cryptographic modes ...
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When using AES-NI as a high-speed permutation, does AESDEC offer better diffusion?

If I was to use AES-NI as a high performance 128-bit permutation/PRF would AESDEC offer faster/better diffusion than AESENC? The reason I ask is because both instructions have the same cost, but the ...
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Using AES-CBC with a random number plus a counter for the IV

I understand that AES-CBC uses the following scheme for encrypting data (diagram from Wikipedia): And, I understand that we don't want initialization vectors to be predictable or constant, and also ...
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Can I prove AES-GCM nonce reuse just from the bytes?

I have AES-GCM output with GMAC tag. The plaintext consists of some bitfields I know the structure of. When I generate input which should only affect timestamps and counters in very specific bytes, I ...
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New NIST Journey: Accordion Cipher Mode

NIST recently unveiled the criteria for crafting a new block cipher mode of operation for AES called Accordion Cipher Mode. Simultaneously, they've announced Ascon as the Winner in the Lightweight ...
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AES-128 ECB Standard Confusion

Forgive my ignorance, but I've run into some confusion in an AES implementation I'm testing. To the best of my understanding, ECB provides no diffusion, the same plaintext with the same key will yield ...
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4 votes
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Utilizing block cipher (AES) while saving bandwith

I'm helping a company to redesign their cryptographic protocol for communication within a network of embedded devices. So far I have discovered several insecure practices, such as using very short (6 ...
JustSomeAccount's user avatar
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App for Secure delivery of the gray images using AES, DH, DSA - Help in implemeting the system structure

I have this uni project that I have to implement in code: "App for Secure delivery of the gray images, encryption-decryption with AES in OFB mode + secret key delivery using Merkle–Hellman ...
Mustafa Shama's user avatar
3 votes
1 answer
721 views

Is AES a group?

The question I'm wondering is whether the AES cipher is a closed cipher (which is equivalent to AES being a group). And this question interests me due to the lack of understanding of whether it is ...
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Using longer key with PKCS#5 derive_key() function for AES256? [closed]

I have code where someone made the key 64 bytes (32*2) and passes to the derive_key() function. It then uses the key created for ...
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Is it possible for a given plaintext and ciphertext to have two different keys? [duplicate]

This has probably been asked before but for a given ciphertext and plaintext pair, is it possible to have two different keys producing said pair? Or there are no collisions in AES, unlike hashing ...
user2338802's user avatar
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1 answer
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Do I need to use unique IVs if all encrypted data is unique?

I am designing a service where each user has both a unique 256-bit private and public ID. These IDs should be derivable from one another, but only within the backend of my service (as to not expose ...
Ryan Hilbert's user avatar
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1 answer
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Encrypting the nonce in AES-CCM

I'm working on a network where nodes communicate using AES-CCM encryption, within a context of tight bandwidth limitations, making every bit count. The setup uses a nonce that combines a 16-bit node ...
byte-carlton's user avatar
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1 answer
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What exactly is RSA_WITH_AES256_CBC_SHA256?

Quick disclaimer, I am pretty new to cryptography. I only understand the basics of asymmetric and symmetric encryption. In particular, RSA and AES. I have a project where my service is receiving an ...
Aurelian Milleram's user avatar
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Whitebox Cryptography Advances

I have an issue about AES whitebox protection as it is possible to decrypt data and get the whitebox encryption and decryption logic even without the ability to extract the original key. In my ...
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Known message attack on ENC-MAC with AES encryption

The assignment I have is as follows: Let $l=2^{128}$ and let $x$ be a random integer satisfying $0\le x \le l$ Let $\oplus $ be the XOR operator and $E_k$ an AES encryption with $key=k$ Let the ...
Danny Blozrov's user avatar
5 votes
1 answer
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What best to put in unused nonce bytes when using AES-GCM-SIV

I want to use AES-GCM-SIV for authenticated encryption of messages in my protocol. Since it is a wireless protocol I want to transmit as few bytes as possible. For successful decryption I need to ...
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Would this 3AES-192 scheme achieve 384-bit key security with just a 384-bit key?

For starters, I don't need any don't-roll-your-crypto stuff. We're discussing a hypothetical. So the idea is 3DES needs 3x the key size and achieves only 2x key size bit security. So using the 3x ...
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Exposing the vulnerability of CTR mode of operation

In the CTR mode of operation, the plaintext block is treated as a stream cipher, where each byte of the plaintext gets XOR-ed with each byte of the key (which is generated using a nonce and a counter) ...
Abhinav Tahlani's user avatar
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What should be passed as the authentication tag when creating a SealedBox? And can it be made public?

When creating a SealedBox, one of the parameters which needs to be passed is an authentication tag: https://developer.apple.com/documentation/cryptokit/aes/gcm/...
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Find two hard to reverse functions f and h such that f ∘ h ∘ g = h (f and h injective, no constraints on g)

I am looking from 3 functions $f,g,h$ from $\mathbb N \to \mathbb N$ (they can be bijections, they need to be injective at least), such that: $$f \circ h \circ g = h $$ and $f$ is hard to reverse ...
Mathematical_Noob's user avatar
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1 answer
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Given and encrypted message, is it theoretically possible to decrypt a message without the key or guessing it? If so, what methods could be used?

Decrypting an AES-Encrypted Message Without the Key: A Cryptographic Challenge Summary: I am investigating the possibility of decrypting an AES-encrypted message when the encryption key is unknown ...
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High throughput authentication on ARMv8

I am working on a project where I need to authenticate data in parallel with computations on that data. The idea is to stream data from memory onto the chip only once; while the data is on-chip, we do ...
Nate's user avatar
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2 answers
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AES CTR mode is insecure if key is chosen from a tiny keyspace

Given AES-128 with a 128 bit key, but the key is chosen such that its only last 16/32/48 bit are random rest are 0, how can i exploit this to know the key being used, given i have access to oracle ...
goose57's user avatar
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4 votes
1 answer
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Why is s=6n in AES Key Wrap?

In AES Key Wrap, we apply 6n AES encryptions for an input of n 64-bit blocks. Informally speaking, we wrap the key 6 times. What is the motivation behind 6? Why not 4 or 10? Is there something like a ...
guestQWERTY's user avatar
1 vote
1 answer
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Pitfalls of manual AES encryption for data transfer

Context I've used OpenSSL to encrypt some socket communications. I am however using some functionality from the windows API that prevents me from using OpenSSL's opaque builtin sockets, so I am ...
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AES encryption step: calculate the byte substitution process

I am a self learner and tried to learn AES, so I have a book written in my native language. It has some practical examples about finite fields and AES. It has a question that asks me to calculate the ...
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In AES, while Converting Plain text to HEX in this image, how is X 23 and not 17 while all others are in Hex state

In AES, while Converting Plain text to HEX in this image, how is X 23 and not 17 while all others are in Hex state.
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