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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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aes-ctr(key, ++iv, sha-1(plainText + aes-ctr(key,iv,0^128))+(plainText + aes-ctr(key,iv,0^128))); is it secure?

Proposed Cipher suite: aes-ctr(key, ++iv, sha-1(plainText + aes-ctr(key,iv,0^128))+(plainText + aes-ctr(key,iv,0^128))); Security targets achieved: Encryption of the plain text. Integrity of the ...
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How an underlying cipher suite effects security of MAC functions? Example: MACX = aes-ctr(sha1);

The MACX = aes-ctr(sha1) is defined as follows: Inputs: ...
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Inversion in $GF(2^8)$ AES [duplicate]

I was wondering how you would calculate the S-box in AES. I found that you have to calculate the inverse of the polynomials in $GF(2^8)$. I found out that to calculate the inverse, you have to use the ...
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Can AES be broken by factorization (using Quantum Period Finding)?

I am trying to understand the paper "Breaking Symmetric Cryptosystems using Quantum Period Finding", and I reckoned the paper is roughly implying to break secret-key cryptographic system by finding ...
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AES_256_ENCRYPT_CTR(key, sha-1(plainText)+plainText) VS AES-GCM, which is more secure? [duplicate]

What if we encrypt sha-1 hash of the plain text, along with the plain text using AES-256 in CTR mode? How much future proof the above method would be in comparison to AES-GCM or any other method ...
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Disadvantage of the using a counter within plain text for encrypting with AES256 and authentication?

What if we use a counter within the plain text and then encrypt the plain text with aes 256 to encrypt & authenticate? For example: encryptAES(32bit_counter+plain_text_of_96bit); or encryptAES(...
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AES decryption of MixColumn

In the encryption of MixColumn you use the constants 01, 02 and 03. I don't understand why the inverse of 01 becomes both 0D and 09. I also don't understand how you get 01, 02 and 03 in the first ...
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How to apply IV and tag to protect messages encrypted using AES-GCM?

I'm applying the Arduino Crypto Library for the code fragments. In the above library, example of encryption and decryption using GCM given as follows: For encryption: ...
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can't decrypt AES-256-GCM log file! [HELP] [on hold]

i'm trying to decrypt a log file that containt some chat messages ( in french ) it is encrypted with AES-256-GCM then encapsulated into a TLS session: Take a look at the file here https://ufile.io/...
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Is this device authentication method (using AES-256) secure?

Let's say we have: client_id_ran: 256 bit random text (chosen only once for whole system) used to generate client_id by ...
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Decrypting ciphertext that is missing a block

In the AES encryption, suppose that the key is known. The ciphertext is also known except for a block of the same size as the key. In the worst case scenario for the attacker, how hard is it for ...
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Is Finite Field Multiplication Distributive? Moving Affine Transform in AES

In AES the output of the SubBytes step is equal to: $a_{0-15} = d*c_{0-15}^{-1}+b$ where $d$ is a constant 8x8 matrix and b is a constant 8x1 matrix both in $GF(2)$. The inversion is done in $GF(2^...
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AES-XTS vs AES-CTR for Write Once Storage

I have a disk on which each sector can only be written once (like a journal, only appending is possible). Unused sectors are reported as being filled with zeroes, while used sectors should not be ...
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S-AES RC[i] Generation. Can someone explain how to generate the RC[i]s for these two problems I have?

I don't know exactly how to find the RC[ 1 ] of 80, or the RC[2] of 30. Can someone explain how to find them? Here is a picture of the problem I am having with two questions.
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What problems might you encounter if you use a block size much greater than AES?

What problems might you encounter if you use a block size much greater than AES (1000 bits, say)?
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Is it a cryptographic risk to share the same encrypted data over and over again?

Regular scenario Let's say I have secret files which I will encrypt. The resulting container will be shared and might be intercepted. Not good, but that's okay - that's why I encrypted the data in ...
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Is it common we extended Key size to 512 bit in AES Algorithm? [duplicate]

is it common , we increase key size to 512 Bit in AES Algorithm?
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Does AES encrypt /dev/null and feed output to AES again increase entropy of the ciphertext?

I just thought about what would change if would pipe the output of openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" -nosalt < /dev/zero | pv -pterb ...
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How can the Rijndael SBox be written as a linearized polynomial?

In Cryptanalysis of Block Ciphers with Overdefined Systems of Equations Nicolas Courtois and Josef Pieprzyk state (in Appendix A) that the Rijndael SBox can be written as a "linearized polynomial" $S(...
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Security of AES after key expansion 4-MB with ECB and CBC

My question is, how does the security depend or change if I encrypt with AES-128 in total 4-MB of Data? With Electronic Code Book Mode and Cipher Block Chaining Mode ? Does an adversary still ...
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is there a way to specify the encrypted message length when using private and public keys?

is there a way to specify the encrypted message length when using private and public keys? mainly I want the encrypted message to be 32 bytes? as I'm currently using RSA but that results in a length ...
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Is the hash function $h(x\|y) = AES_x( y)$ collision resistant?

If $x$ and $y$ are both 128-bit strings would the function $h(x||y) = AES_x(y)$, where $x\|y$ means concatenation, be considered collision resistant ? Is there an easy way to find $(x_1, y_1)$ and $(...
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Key derivation: bit lengths

This is a follow-up question to HKDF: ikm, salt and info values Based on the feedback, I have now decided to implement my key derivation for AES-GCM-256 file encryption roughly as follows: ...
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Pre-computing a log and exp table for a primitive polynomial in $GF(2^8)$ [duplicate]

I'm new on the topic of finite fields, specifically $GF(2^8)$. I've come across the information that it's possible to implement multiplication using logarithm and exponential tables. But how are ...
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Countermeasures to prevent integral cryptanalysis against 4-rounds AES

Integral cryptanalysis against 4-rounds AES is practical (Security of the AES with a Secret S-box). I did two experiments in order to find the impact and remove the integral distinguisher of 4 rounds:...
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Is it possible to do a known-plaintext attack with this set up of AES CTR mode?

Is it possible to perform a known-plaintext attack to extract the key from AES byte encryption? The encryption is setup with the following two lines: ...
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Hash using AES and key 0

Consider the following hash function for a message x = x1||x2|| · · · ||xn: h(x) = Mn i=1 AES0(xi) = AES0(x1) ⊕ AES0(x2) ⊕ · · · ⊕ AES0(xn) where the key used in AES is k = 0. Can someone explain what ...
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Writing AES-CTR decryption routine in python [migrated]

I have the following code ...
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Who said “32 round Rijndael” in the third AES Conference

This is a historical question. In the third AES Conference of NIST (AES3), April 13-14, 2000, New York, near the end of the conference, one representative for each of the last 5 candidates sit on a ...
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AES-CTR-MAC alternative

I have to send small (~10 bytes) authenticated messages over an insecure channel. I was thinking of an alternative to the "conventional" AES128-CTR-MAC, which will take 16 bytes for the CT and ...
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How to find a collision with a given prefix and a known key in an AES ECB symmetric block cipher?

I should be able to find a collision for a vulnerable hash function which uses AES ECB given a prefix, but I am unable to find a reasonable solution (besides brute-force attack). The hash function is ...
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Is it possible to find the key for AES ECB if I have a list of plaintext and corresponding ciphertext?

Assume I have a list of plaintext text and its corresponding ciphertext which was created using a specific key with AES in ECB mode. Can I recover that key? If, how big does the list of plaintext ...
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How secure would AES be with all round keys equal? [duplicate]

In effect the same 128 bit key is XORed at every round and before and after as whitening. Would it be 2^128? What are the dangers of such a naive key schedule and does AES suffer from them? Edit: ...
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Recovering plaintext from AES-128 given round key 10 and ciphertext

I'm working on an old CTF challenge where AES-128 was used on a 16 byte block. I have the round 10 key and the ciphertext. What techniques exist for obtaining the plaintext?
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Finding colliding messages for AES decryption

I'm doing a school problem where I'm supposed to find a colliding message in a hashing algorithm that is weak-collision resistant. The hashing algorithm is AES with a key & message size of 128. ...
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Gate count for Ring-LWE

In one of my recent research, I need to compare the number of gates needed in Ring-LWE encryption to AES in the circuit model. For AES we can find some estimation like this site, but for Ring-LWE we ...
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How to get the datapacket from wireshark? [closed]

I have a pcap of my twitter traffic using wireshark. The cipher suite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 method is used for for encryption data.. I have a tweet of 42 characters are traced in the ...
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Daredevil attack not working on AES

I have the following files: Powertrace for AES encryption in numpy format Plaintext bytes used for encryption in numpy format Using the code provided here: NewAE I converted the numpy files into ...
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Why does TLS 1.3 support two CCM variants?

One of the important improvements introduced in TLS 1.3 is the pruning of the many previously available cipher suites to only five secure options (for symmetric ciphers), that are each supposed to ...
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Does re-transmission really reduce security?

I am using AES with GCM and a colleague told me "Repeating a VCC with the same key and a different message reduces the security of the key." He did not have any additional detail to offer. What he ...
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Simulation of Chosen Plaintext Attack on CBC, Predictable IV with OpenSSL

I would like to simulate the CBC IV attack where the IV is predictable. It's described in the answer to this question: chosen plaintext attack on CBC, predictable iv (Only "Yes" and "No" are valid ...
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How to encrypt file with RSA and AES that anyone with RSA key can decrypt them?

How to encrypt a file with RSA and AES-256 that anyone with RSA key can decrypt them?.
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AES and DES - reusing the same round keys

Both DES and AES use key expansion to generate the round keys (for Feistel network or for the AddRoundKey operation). Each round uses a different key. Why do we need that? Why we cannot use the same ...
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Encrypting AES in ECB mode

I'm fairly new to cryptography and am starting to understand this weird art of Mathematics and theory. One thing I am trying to understand and do is encrypting a plaintext into ciphertext using AES in ...
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Is AES ECB good enough for key spreading?

My apologies if I get my terminology wrong - I am new to this stuff. I am writing a routine (in c) to encrypt plaintext. I am using TinyAES to perform a CBC on the plaintext and sending a (pseudo)...
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Perfect Nonlinearity of AES S Boxes

Can someone give a clear definition of what a perfectly nonlinear function is? Can we say that AES s-boxes are perfectly nonlinear and why?
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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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AES Mix columns bit example

I have been given a 4x4 matrix and each entry is an 8-bit long byte. I have been given the 4x4 matrix that I need to multiply each column by of the first matrix by. $$\begin{pmatrix}2 & 3 & 1 ...
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Does password length affect AES encrypt/decrypt velocity?

I'm implementing crypto in Node, following this article: https://lollyrock.com/articles/nodejs-encryption/ It defines: ...