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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Finding block mode and key length from encrypted data

I have an AES encrypted data and the key, but I am not able to tell the block cipher mode [ECB|CBC|CTR] used in encryption or know the key length. Below is the encrypted data output in java. ...
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What are the RCons for mini-AES if you want to encrypt more than 2 rounds?

I'm implementing impossible differential cryptanalysis on mini-AES using Raphael phan's paper. I've coded mini-AES using Raphael phan's first paper on the structure of mini-AES, where he only mentions ...
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Is there a Block cipher (mode) with a not symmetric variable which if it is altered always produced a different cipher?

The BC should look like this $$BC(m,k,n) = (c,n')$$ $$BC^{-1}(c,k,n') = (m,n)$$ with the additional variable $n$ not symmetric, so in almost all cases: $$n \not= n'$$ $m$... plaintext $c$... ...
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Use name as the initialization vector to encrypt passwords for users

I'm using AES-256-CBC to encrypt password for a set of users, and for each user in the database we gotta generate and store the password in the database. The ...
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Is it possible to generate a read-only key for a symmetrical encryption (AES)?

I am working with hardware that can only encrypt with AES. The problem with this is that the message must be publicly verifiable, without the encoding key being exposed. This is the textbook use-case ...
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AES-GCM and tag length

Due to protocol limitations, I can put in 24 bytes of data only for tx (excluding headers), if I use AES_GCM for encrypting my data, I understand I don't need to worry about padding. So for instance, ...
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Clarification regarding AES-CTR

I was recently trying to perform a AES-128 CTR Encryption and Decryption. I had a observation that if a AES-CTR encrypted value is encrypted again (with same key and Iv) it results in the plain text ...
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Threshold of resistance against Linear Cryptanalysis

In the AES proposal, the last sentence on page 30 it is said: To be resistant against LC, it is a necessary condition that there are no linear trails with a correlation coefficient higher than 2^(n/2)...
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Where did the number of initial plaintexts required for impossible cryptanalysis on Mini-AES came from?

I'm implementing impossible differential cryptanalysis on AES and I've started with implementing it on mini-AES to fully understand the process using R.Phan's paper as a reference. But I don't ...
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Encrypting Small messages (BLE Beacon) - with little entropy - symmetric [closed]

I want to encrypt Bluetooth Beacon data. I was wondering if having very little entropy in the clear text would make the key easier to guess? The maximum data length is 31 bytes An example of the data (...
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Can AES be broken if i know the pattern of the strings encrypted? [closed]

Consider i am encrypting a column in a database table with AES. If i leak the information that the column is a hyphen separated Social Security Number thereby revealing each row of the column is of ...
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Can Quantum Computers crack RSA and AES?

Im trying to learn more about cryptography and ran into a post, Is AES-128 quantum safe?, which asks if AES-128 is safe. From the articles and replies it seems that AES-128 (symmetric key) is safe ...
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What mode in EVP for AES-128 should I use for cryptanalysis of AES?

I've been trying to use AES from OpenSSL and got to know that I need to use the EVP-based implementations rather than the AES_*. I need to use AES-128 ...
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When the input size in a PRF is larger than the output and many inputs will generate the same output, but why AES-256 in CTR mode is considered safe?

I know that if the input size in a pseurandom-function is larger than its output, many different inputs will generate the same output by the Pigeonhole principle (I also read an article related to ...
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In AES, why do we multiply the columns by a polynomial with a repeating coefficient?

In the MixColumns step of AES, one multiplies each of the columns of the $4\times 4$ box of bytes by the polynomial $a(x)=\{03\}x^3+\{01\}x^2+\{01\}x+\{02\}$ (modulo $x^4+1$). But in this polynomial, ...
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Is it possible to reverse GHASH from GCM?

How can I create a "reverse" GHASH algorithm for GCM that allows me to compute an input value that generates a specific chosen output, given that I know the authentication key H? If this is ...
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Application firmware sign-then-encrypt vs encrypt-then-sign

I know that there are previous questions on the subject e.g. here, however I would like to ask it for my particular (simple) case. I have an application firmware that is downloaded to a microprocessor ...
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GCM-SIV vs CBC with fixed IV?

I keep hearing CBC with fixed IV mode is bad because it has similar issues to the codebook breakdown of ECB mode. However, people seem quite willing to recommend AES-GCM-SIV for deterministic ...
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RSA Key Generation & encrypted output using OpenSSL

When is it generally acceptable, if ever, to generate RSA keys without encrypting the PEM output with another encryption algorithm? I am working on a CI/CD process and want to leverage asymmetric ...
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Problem in matching AES CTR encryption and decryption with two different engines

I have a problem in combining encryption with a host software tool based on LibTomCrypt sources, then decryption with the hardware BEE (Bus Encryption Engine) of an i.MX RT1062 NXP processor. I am ...
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Do multiple keys mitigate Grover algorithm?

Grover, a quantum algorithm, weakens AES and ChaCha20. Is it possible to use multiple symmetric keys to encrypt a message multiple times to achieve 256-bit security for quantum computers?
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How to improve the performance of encryption algorithm in circular operation?

I wrote a block symmetric encryption algorithm similar to AES in C language, but in the actual test, the operation speed is not very satisfactory. It takes nearly 1 second to encrypt a 16MB (16777216 ...
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How does AES-CBC encryption achieve non-repeating blocks of ciphertext?

I am very interested in encryption algorithms, especially AES encryption algorithm in symmetric encryption. To this end, I have studied a lot of theoretical knowledge about AES encryption algorithm ...
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Implementing AES GCM but not getting correct output from cipher block

I'm implementing 128-bit AES-GCM (but only the encryption/AES-CTR aspect). When I set the Secret Key, Plaintext and IV to Test Case 2, page 27 of the GCM spec (see below) I get the wrong value for the ...
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AES GCM Difference between the IV and the Secret Key?

Below is part of AES GCM diagram. However, it only shows the behavior of the IV/counter. The GCM specification examples state both an IV and a Secret Key as two inputs. Can someone please explain ...
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What is Inverse equivalent (decrypt) in the AES specification examples?

Referring to the AES specification: https://nvlpubs.nist.gov/nistpubs/fips/nist.fips.197.pdf Printed pages 35-37... The first detailed walkthrough is encryption, the second is decryption.... I don't ...
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AES key encryption on one time pad

I need to use the following scenario: There are 2 keys: AES-key and OTP-key (one-time pad). I encrypt the AES-key (as if it were plaintext) with an OTP key. Then I send the encrypted AES-key to ...
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Understanding symmetric encryption security in relation to password-based key derivation

Here are some assumptions on which the question is based. If anything is wrong with this, please point this out straight away: Let's say I have a file I want to encrypt with AES256 symmetric ...
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Protecting against CPA for AES128/ECB by using padding

I was going to encrypt with AES, But I noticed ECB mode is not safe for CPA. So I thought about preventing CPA by padding input text to a multiple of 16 bytes. First, perform custom padding system: ...
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How to encrypt with CBC, step by step?

I have this message "Hello from another world" Can you explain how to encrypt it with CBC step by step? Are the message characters ...
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Is AES distinguishable if the attacker has an decryption oracle?

Let the following game be given: G^IND-CCA': Prepare a key k <- KeyGen(1^Kappa) Choose a hidden bit h <- {0, 1} uniformly random Prepare a decryption oracle O_Dec. Given a cipher text c, it ...
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Can the IV be reused if the key is changed?

I am using AES-GCM-256 to encrypt data in a database, and am using a single key that I salt with a unique random value for each user to encrypt their information. I am using the same IV for all of ...
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Sharing encryption key via intermediary without the intermediary having access to the content

Please bear with me... I want to store some data in an untrusted location (a server). I will want to share this with other people. I encrypt the data with AES encryption and a 20 character password. ...
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Is it possible to use AES to produce a private ECC key?

I am working with hardware that can store an AES key securely--the hardware can perform AES encryption/decryption using a stored key without revealing the key to the caller. However, I would like to ...
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Implementation of XSL attacks on block ciphers using dynamic S-Boxes

For those who are not familiar with; XSL attacks basically focus on deriving a set of equations from the internal mechanics of a block cipher and then solving the same equations to recover the secret ...
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Can we find pairs $(c,m)$ with $f(c)=f(m)=true$ in $c = AES(m,K)$ with a fixed known Key $K$ significantly faster than brute force?

Different to the usual adversary use case we do not want to find the hidden key but instead pairs of $(m,c)$ which each fulfill a certain property $f(x)=true$ An example property could be e.g. 42 ...
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Maximum Security of RSA

Table 2 of NIST SP-800 56B provides Estimated Maximum Security Strength of different modulus sizes. It means that RSA-3072 provides security of 128-bits at Max. Is it the case for symmetric algorithms ...
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Chosen-plaintext attact on AES with MixColumns omitted

Jean-Philippe Aumasson' "Serious Cryptography" says: "Without MixColumns, changes in a byte would not affect any other bytes of the state. A chosen-plaintext attacker could then decrypt ...
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Should I implement a key store / key management system into my python library? [closed]

I've created a python library that uses both RSA and AES encryption to allow for hybrid encryption of text or images. I am wondering if I should implement a keystore and/or a better key management ...
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Any simple, cryptographically secure AES-based DRNG?

I am looking for a DRNG/DRBG (cryptographically secure) algorithm/function (which I can program into js). I am looking to use a DRNG as a seed generator for generating multiple, identical AES keys on ...
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Is this property generally true for AES-128?

Let $E_{k}(P)$ be the AES-128 function with key $k$ and plaintext $P$, both 128 bits. I want to know if the following property is generally true for AES or if have I stumbled upon a special set of ...
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In AES-128-ECB, if byte 15 is over 128, the padding block changes value. What's the reason for this behavior?

For example, if we run this openssl command: openssl aes-128-ecb -a -in <(echo -n "AAAAAAAAAAAAAAAA") -K "deadbeefdeadbeefdeadbeefdeadbeef" ...
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Designing a scheme to store encrypted data on a backend

My goal is to design an encryption scheme for the application so that the backend stores encrypted data and the whole process of encoding and decoding happens on the frontend. And you can be sure that ...
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Symmetry shares

I’m sorry if this is already answered, however, regarding symmetric key components to create a symmetric key using xor (So eg comp1 xor comp2 xor comp3 = key) If in the case of an AES KEY, which goes ...
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CCM in the RUP setting reduced to CTR?

I have a question regarding the paper: Andreeva, E. et al, Securely Release Unverified Plaintext in Authenticated Encryption , 2014 (DOI: 10.1007/978-3-662-45611-8_6) AE schemes such as GCM [28] and ...
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AES subkey calculation not working for subkeys beyond 0 and 1

How should I generate the remaining keys when performing subkey generation in AES encryption? I generated keys 0 and 1 first, but the other keys I generated later were wrongly generated, so what steps ...
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What are the best known cryptanalytic attacks against AES-128 with 9 rounds?

What are the best known cryptanalytic attacks against AES-128 with 9 rounds? I found many such attacks on AES-192 and AES-256 with 9 rounds, but not for AES-128 with 9 rounds. Are there any ...
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By using a block cipher multiple times in a row is a 128-bit BC as secure as a 256-bit BC which uses his 128-key only as part of the message?

For given 128-bit numbers $S$ and $E$ we want to find a series of keys $k_i$ with $$ E = BC(BC(BC(.....BC(S, k_1),k_2) ..k_n)$$ We can either use a 128-Bit blocksize block cipher similar to AES (ECB ...
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Is it safe to encrypt a message with AES-ECB two times?

Suppose we have a function that returns a chipertext of a known plaintext that has been encrypted twice with AES-ECB with two unknown keys, is it possible to get both keys ?
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Old openssl version does not support -iter or -pbkdf2, how does it derive the encryption key for AES?

When using openssl or libressl to encrypt or decrypt data with AES, I typically specify ...
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