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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Plz help to understand this paragraph . According to concept AES is not used Feistel structure but here both are used

In Dual Watermarking in Tele-radiology using DWT for Data Authentication and Security, the authors wrote: The encryption process uses the Feistel structure consisting multiple rounds for processing ...
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Decoding a challenging string [closed]

Cyphered text -> 8Xq5Sc7kB/W5XUdtNtl7C8cdVNR7kQxnFaF+H8Mzxb/SufcU key used -> 22f1ef0d0a9dd7d16a346e3f99848f0c Decyphered text -> here How do I get the decyphered text from the cyphered text ...
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How to change any symmetric algorithm to obtain hash of key and hash of data from encrypted output? [closed]

I want to know how I can change any symmetric algorithm like AES to obtain the hash of the key and the hash of the input from the encrypted output? How can I change any asymmetric algorithm to get the ...
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Using shared secret as Out-Of-Band authentication data in Bluetooth pairing

According to the Bluetooth Specification, the pairing process starts with Slave sending a connectable advertising packet and then the Master initiates the connection. In LE Legacy OOB authentication a ...
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Are there any block ciphers (like AES) which are (or can be) commutative under composition for different keys?

Let $BC$ be a block cipher with similar security as AES (in ECB mode). This $BC$ is applied to a message $m$ of same bit size. The result is a cipher $c$. e.g.; $$BC(key_A,m) = c_A$$ $$BC(key_B,m) = ...
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ε-close to t-wise inependence of SPN (AES)

According to theorem 3.13, the 6 rounds of AES is 0.472-close to pairwise independence. It is also mentioned t-wise independence used to analyze higher order derivates attacks. it is also mentioned 3-...
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Encryption of small data with fixed key and incremental IV

I have a Bluetooth device that sends a small package periodically (without receiving). I want to encrypt and authenticate the data using AES-128. It has an embedded random and unique key which is ...
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MS CryptoAPI RC4-1024 vs AES-128?

I'm trying to figure out MS CryptoAPI to generate a symmetric key on one computer then an RSA key on another, send over that public key to use to export the symmetric key to that other computer. I'm ...
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Why using same nonce (IV) twice voids confidentiality of plain text or even key?

I understand roughly (without details of GF algebra) the scheme of GCS/GMAC: IV is to be put into Counter-0, so initializing counters. It is known, that using a IV twice can not only reveal the plain ...
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Does reusing IV in AES-CBC weaken it?

Rsynccrypto allegedly uses AES-CBC with a twist: If the last few bytes of plaintext meet a condition*, then stop, pad the current block and start encrypting new block from the current position in file ...
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CTR mode calculate messages before new key is required

I am studying a cryptography video on Coursera here titled: Modes of Operation: Many Time Key (CTR). I have just two simple questions: At around 4:30 in the video they show 2^48 without saying where ...
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AESGCM with arbitrary tag length in Java [migrated]

For algorithm test vector evaluation, I am trying to perform an AESGCM encryption and decryption with arbitrary tag length values such as 32 bits. When I try to initialize my cipher with such an ...
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Splitting an AES-256 key into two?

I understand there are already few question here which are similar but mine is a bit different in that I want to split AES 256 bit into two 128 bit key and then use a different AES key of 128bit to ...
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Cyclicity of AES [duplicate]

It is known that AES is extremely secure, with its highest standard(AES-256) being able to protect the national secrets of most governments. Due to the nature of its steps, there's the question about ...
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So is AES-256 more secure or less secure than AES-128 after all?

It seems there are attacks that work more effectively on AES-256 than AES-128, which makes it less secure in some cases. But the bigger key size should add some safety margin on the other hand, for ...
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Decryption of Kerberos ticket contents using AES256 keys [migrated]

I am using Microsoft CNG functions to decrypt different parts of the Kerberos tickets and encrypted items in Kerberos messages. The decrypted content that I am getting is not the correct one. I was ...
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How does encrypting a file with AES affect file size? [duplicate]

I am wondering if encrypting a file with AES will reduce or increase its file size and generally by how much. Thanks for any tips or advice.
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End to end encrypted chat design

I am in the process of creating a flutter application that will include direct messaging. You can message 1 person or a group of people. I want this to all be encrypted for privacy. The method I was ...
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Proper implementation AES-256 for single block E_k then being used on AES-GCM

My first objective is to implement AES-GCM in PowerShell 5.1 since there is not an implementation that not use external dll libraries. According to the GCM schema of encryption: the E_k block should ...
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PRNG For RSA (ANSI_X9.31)

I have a query please , I want to know how to generate random numbers using ANSI_X9.31 algorithm for RSA Algorithm please . Thank u
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¿Can it be proved that both AES's ShiftRows and MixColumns are linear transformation? (if we leave out subBytes and key addition)

I've been researching a bit and found that the mixColumns step could be expressed as matrix multiplication like this: But I'm not sure what's the mathematical proof for it and I can't find an example ...
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Securing counter value for OTP [closed]

I'm working on a project that needs an OTP based on counter value and needs some advice. Suppose we encrypt the counter value C in this way and let's say our sending packet is P = AES(key,C). If ...
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How secure is AES 256bitkey generated from PBKDF2

I am using CryptoJS AES 256 encryption: CryptoJS.AES.encrypt(realData, generateKey(passphrase), {iv: iv}); The secret is generated through: ...
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Crack AES encryption via passphrase dictionary attack?

How easy would it be to crack a AES-256 encrypted file, that is protected by a passphrase? I understand that the trying to brute force a AES-256 encryption key would be on the unfeasible side, even ...
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Why is it not possible to attack an AES by creating a function to model the substitution that occurs in a s-box?

I realise that s boxes are able to make the transformations done in AES non-linear. However I am unsure how this makes AES secure. For instance if we had no s box then it is possible to calculate the ...
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Deterministic data masking

We are building out data masking framework mainly to mask PIIs. Our scale is pretty large, and masking will be done at ingest time, so we want the masking to be done in a very performant manner. Some ...
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Does my asymmetric/symmetric mixed file encryption pseudo code pass sanity check?

I realize this depends on my implementation and the implementation of the libraries I use. I am asking about my process assuming that the encryption libraries and my code are not flawed/compromised, ...
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A few questions regarding the 4-Round AES-Distinguisher (by Gilbert and Minier) and DS-MITM

I am struggling to understand the DS-MITM attack on AES (Original Paper). Especially the 4-rounds distinguisher by Gilbert and Minier (section 3). I get the basic idea that we check exactly on which ...
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Online AES Calculator

I am currently looking into how AES works and found a calculator online: http://testprotect.com/appendix/AEScalc I understand that the AES process has 10 rounds of calculations. Does this mean that ...
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How to minimize AES output size?

I work on a project about CAN bus and I want to encrypt the data among nodes but I have have a problem because CAN bus nodes receive and send 8 bytes among each others and I know the size of AES ...
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Is OpenSSL enc using AES-256-CBC to encrypt large files safe?

I first generate a keyfile with openssl rand -hex 64 -out keyfile. I then encrypt the file with ...
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Decrypt encryptedKey session key using - AES-128 - PKCS-1#rsaes-kem-kdf2-kw-aes128

I have basic knowledge about how encryption algorithms work such as RSA, AES and so on. I have an XML response encrypted with both AES and RSA. I tried using OpenSSL to decrypt with several steps but ...
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AES-GCM can IV be stored alongside in DB?

I'm trying to encrypt and store strings in PHP as per example #1 on the PHP openssl_encrypt documentation. ...
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How to use nonce, counter, and IV in AES-256-CTR?

preface: i am not cryptographically savvy. there are similar questions on this board but they do not give the answer i need. how do i construct a valid IV, given a nonce? What does this have to do ...
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Is this a valid AES instruction reordering?

I'm trying to understand a verilog AES implementation. I know the order of the AES encryption steps to be as shown: However the code I see doesn't do this. They do the following flow graph: at the ...
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in what condition, 2 different AES 128-bit Keys generate at least 6 bytes identical ciphertext on same plaintext

as mentioned in the title, and read some past discusstion on AES collison here. it shows it's possible that, AES(k1, m1)=AES(k2, m1) just wondering what condition those 2 keys need to meet. Thanks.
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Is it possible to crack AES-256 ECB when provided with the ciphertext and a portion of the corresponding plaintext? [duplicate]

AES-ECB encrypts the message by breaking it into blocks and encrypting them one by one. Provided the knowledge of the ciphertext, a portion of the plaintext that corresponds to a block in the message, ...
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Do some Block Cipher Modes encrypt the nonce and then XOR it with the data?

Reading https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_(CTR) it looks like CTR (and some other modes) encrypt the nonce (plus count, for CTR) rather than the plaintext. The ...
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Multiplication in Tower Field $GF(2^4)^2$

I'm currently reading an article which deals with "Squeezing Polynomial Masking into Tower Fields " for performing an efficient multiplication of elements in $GF(2^8)$. Thereby it is ...
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Can an encryption key be inferred by knowing the plaintext and the corresponding ciphertext?

Thinking about validation methods for guaranteeing a proper key is used. Will keeping a dummy plaintext value and its corresponding ciphertext in plaintext code expose any risk?
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Is it possible to do partial message authentication?

I want to authenticate part of a message, not all of it, while creating the MAC over the entire message. Let's say I create a 16B MAC over one hundred message blocks that are 64B each. Then I send one ...
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Is a Test Vector feature a Security Hole?

I have a system where a block cipher key (likely AES) is entered via a 'command line' over a serial console, probably as hex. The system has no 'print key' feature, so the key is hopefully 'ingest ...
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Security of generating one long hash and using half as a secret key and half as a “public” hash vs generating two hash values?

My question is what would be more secure, generating 2 hashes (one key and one hash) with the same password and two different salt values, or generating one long hash with a single salt, taking the ...
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Random data CBC padding scheme?

When using AES in CBC mode, padding is required when the last plaintext block has not the length required by the cipher. Let's say $k$ mode bytes would be required to fill the block. My idea was to ...
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7-Zip Encryption: Practical Effect of Lacking Salt

A previous discussion on Cryptography StackExchange leads me to understand that 7-Zip does not use salt to derive an encryption key from password to use its AES-256 encryption; that this is a ...
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How do I preform the inverse key expansion of aes decryption? [duplicate]

I’m working on an aes encryption and decryption project in 8086 assembly! I managed to code an encryption algorithm and it worked perfectly. No I’m working on the decryption algorithm. I’ve managed to ...
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Where to get AES GCM NIST-like test cases

I'm implementing AES GCM 256 bit at the moment. Now I'm finished with copying the content of the standard as a program and now have to make it actually work. With the test cases in the official NIST ...
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Finding IV for forgery of AES CBC-MAC with non-fixed IV

As CBC mode might do several rounds, how it could be possible to find another IV for forgery attack? This is an example from my course: Assume you receive a pair with the plaintext $P_1$ and its MAC ...
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Decrypting the same message with the same IV using aes-256-cbc

Is it safe to use the same IV when decrypting the exact same encrypted message. From my understanding, there is a security flaw when using the same IV for numerous different messages, as attackers can ...
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Ciphertext length in TLS 1.3 additional data

RFC8846 says: ...

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