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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Is this a provably secure scheme to encrypt a private key?

I got this idea to use the features of the one-time pad, an encryption technique that provably cannot be cracked, but this time applied to encrypt a private key. A possible application could be to ...
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Using AES to create a secured MAC

Considering public message M and private key K, would it be safe to create the MAC tag this way: $$MAC(M,K) = AES(m_1) \oplus AES(m_2) \oplus \cdots \oplus AES(m_n)$$ when $m_1,m_2,\ldots,m_n$ are n ...
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ECIES vs. RSA + AES

I am confused about the distinction between RSA and ECC (Elliptic curve) regarding encryption and would appreciate it if someone could confirm whether my understanding is correct. To encrypt a large ...
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Which AES mode when using Poly1305-AES

I am reading DJ Bernstein's paper on the Poly1305-AES mac (https://cr.yp.to/mac/poly1305-20050329.pdf). I understand that AES is needed to provide the array s. In its paper on page 5 we can read: ...
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Is a stream cipher and a (cryptographically secure) PRNG nearly the same thing?

If I let the authentification tag aside (which is important), encrypting with AES-GCM and a fixed key and nonce: ...
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Encrypt a big file in blocks with AES-GCM: how many nonce do we need?

I need to encrypt big files using AES-GCM, potentially 10 GB or more. For memory (RAM) reasons, I need to processs them by blocks (let's say 16 MB), rather than doing ...
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Why Abstract Algebra in Cryptography?

I come from an engineering background, but not from computer science or anything to do with pure math. I studied applied math in college--never abstract algebra, number theory, or discrete math, ...
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How to be able to change the password to access data encrypted with AES-GCM, without reencrypting?

Let's say you need to encrypt plaintext which is 1 TB big. You have a password pwd. This very classical AES-GCM process is ...
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Byte order in AES-CMAC test code

I'm looking at the AES-CMAC RFC and I found somehow counter-intuitive the way test vectors are used in the test code. Let's look at the key K ...
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What is the longest AES key that has been recovered in practice?

I can recover something trivial like a 16-bit AES key in practice. I'm confident that a 64-bit AES key can be recovered. However, I have been unable to find any documentation of the biggest AES key ...
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Binary neural network encryption quality

I am creating a Binary Neural Network that encrypts payloads and I would like to compare it to AES in quality, for example: With BNN you would need XX years to decrypt where with AES would take YY ...
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How to encrypt many files with AES-GCM, without running the key derivation function each time?

Linked question: AES encrypting multiple files With a password, I have 100k files to encrypt. (Maybe 100k files today; or maybe 50k today, 10k tomorrow, and 40k ...
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Generation of Rijndael S-box [duplicate]

I'm an electrical engineering student and was doing a brief research regarding the round transformations of the AES-128 and came across the Wikipedia article describing the generation of the ...
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What is most secure way for one party to encrypt 4 bytes in less than 40 bytes, which will be publicly available?

I have a project where a user needs to store a U32 encrypted on a blockchain such that they can recover it themselves: the user will always have their key available but may "forget" the U32 ...
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Is it OK to use a doubled key for XTS-AES?

https://en.wikipedia.org/wiki/Disk_encryption_theory#Xor%E2%80%93encrypt%E2%80%93xor_(XEX) reads: The standard supports using a different key for the IV encryption than for the block encryption; this ...
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Symmetric Crypto Primitives derived from Rijndael Block Cipher

Rijndael Block Cipher supports multiple block/ key lengths and a subset of these was selected as AES. What other cryptographic primitives are derived from Rijndael or make use of its round function/ ...
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AES CTR - Counter Management

Let ssuppose that we are using AES in CTR mode to encrypt a number of blocks ($x$ bytes each). How is the current used IV (nonce+ctr) synchronized among both communicating entities? I suppose that the ...
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How long brute force AES-128 at 24 bits of key

I have 1 block of encrypted data with AES-128, but I know 104 bits of 128 bits the key. How long it will take to brute force 24 bits of a key at Intel I 7 CPU? How can I calculate that?
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What is the importance of AES add round Key (K0)?

A high-level overview of AES is according to Wikipedia Key expansion; Initial round key addition; 9, 11, or 13 rounds; Final round (making 10, 12, or 14 rounds in total). I can understand all the ...
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Are there any Cryptography Algorithms that involve Lots of Number Theory?

I am looking for a good, meaty cryptography algorithm that involves a good amount of number theory in which I can explore. I'm researching, and AES (Advanced Encryption System) seems interesting, but ...
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Why is a weakened AES is easy to crack with KPA? [duplicate]

I started to study a cryptographic course and I got stuck on a question about AES: If we take the AES algorithem and only perform mixColumns and addRoundKey operations as well as only using one key ...
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Security analysis of Rijndael (AES)

I was studying the Rijndael Block Cipher for an assignment. I am looking for a (layman-ish) explanation as to why the cipher is secure. Googling did not seem to be give any good explanations. The ...
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Encrypting data with two separate keys

Goal We want to find the most secure way to encrypt message of arbitrary length M with AES such that the recipient can only decrypt if they have both AES keys ...
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Formally, what is AES?

AES is supposed to be a symmetric key block cipher. The theoretical counterpart to this is a pseudorandom permutation. I'd like to say that AES is a PRP (well, supposedly at least), but that doesn't ...
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Zerologon question - AES-CFB8

I was reading the zerologon whitepaper by secura named: Unauthenticated domain controller compromise by subverting Netlogon cryptography. I'm trying to understand the zerologon attack. The issue is ...
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Why are the ciphertexts of Ansible Vault's AES256-encrypted files disproportionately composed of '3' and '6'?

I was encrypting some Ansible secrets this morning and noticed that the ciphertexts seemed to have a lot of 3s and 6s in them. I did some frequency counts and found that yes, in fact, about 40% of the ...
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How to securely encrypt/decrypt data with a maximum chunk size?

I am aware of the different modes so that a "raw" block cipher such as AES (ECB) can be used to encrypt more than a single block of data (CBC, OFB, CTR, etc) and modes such as AES-GCM which ...
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End-to-end photo storage

I've been tasked with developing an app that will need to store photos a user takes securely, and I've been struggling to think up a method to do this. What I was thinking so far is as follows: When ...
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CMAC operation on HSM

I have generated an AES key on HSM and I need to calculate the CMAC between this key with an input value. Is it possible to do this on HSM? What is the mechanism to invoke?
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An attempt at using AES as a stream cipher

You have a 2048 bit private key, which is 2,048 randomly generated bits. It is not an RSA or ECC key. It is the master key that is used for every message. You receive a message to encrypt and ...
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Malleability for varying length message

Given ciphertext for a message encrypted using $AES-CTR$ along with actual, desired message and IV, I need to perform malleability attack on the ciphertext to change the original message from $M$ to $...
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PKCS11: CKA_VALUE_LEN attribute and Unwrap key

In PKCS11 specification v2.40, we see some confusion with CKA_VALUE_LEN attribute and UnwrapKey behavior. From PKCS11 spec 2.40 ...
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Is it safe to use the CBC-MAC as a Initial Vector and Key Check Value in deterministic encryption?

I want to deterministically encrypt a short message <50 bytes with AES-128 CBC. I also want to be able to detect if the correct key is being used. Ciphertext and IV integrity will be guaranteed by ...
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AES MDS D-XOR and S-XOR count

I am trying to implement the D-XOR and S-XOR count in python but despite reading multiple articles on how to perform the calculation I have failed to understand the process used. I would appreciate it ...
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Encryption for data tokenization

Somewhat of a crypto noob here. I've been doing a lot of reading and think I have something but would appreciate any feedback, including "you are full of it". I'm looking for a way to ...
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What security vulnerabilities exists when encrypting then hashing to be able to search values in database?

im trying to find a good way to allow searches against encrypted data in the database. Lets say i want to encrypt phone numbers, if its encrypted securely i cant search against phone numbers directly ...
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MDS Matrix Elements

Can zero be one of the elements used in an MDS matrix (in the context of AES)? Based on what I have read all entries of an MDS Matrix need to be non-zero. Also, I would appreciate any help in ...
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CBC-MAC variable-length weakness with MAC size greater than the encryption block size

The title mostly explains it; CBC-MAC variable-length weakness with MAC size greater than the encryption block size I've seen that by having the pairs $(M,T_m)$ and $(N,T_n)$, we can generate a ...
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AES Encryption vs Decryption

We recently learned about AES in class and it was heavily emphasized that encryption and decryption in AES are not the same because the functions are not reversible. Why then, when we got to block ...
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How are m2 and m3 boxes computed? [duplicate]

I stumbled upon an AES implementation that uses boxes with multiples of 2 and 3 for its MixColumns operation. When inspecting the m2 box, I saw that the first line is : ...
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Can you change an AES encrypted message if you control the IV?

Let's say that an attacker has the plaintext, the ciphertext and the IV of a specific message. If the attacker can control the ciphertext and the IV, could he forge valid plaintext? Let's say that the ...
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Converting a plaintext to hex for AES encryption

Looking through AES process I see it uses a substitution table which need the input in the form of hex. Im wondering if i have a plaintext of 16 bytes such as 'j±…<Ãà!Dȶ;5˜‰*', how can I convert ...
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How to alter text that was encrypted with AES CBC using PKCSPadding7

Assuming, I had a ciphertext along with its decrypted plain text result but not the IV or the Secret Key. (keep in mind that the text was encrypted with AES/CBC/PKCSPadding7). How would I go about ...
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Issue with only applying key addition layer before first round of AES

What would be the issue if AES only applied the key addition layer once, before the first round? As in, how would this make the algorithm vulnerable to attack?
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Questions about Symmetric Encryption part of TLS

In TLS, we use DHKE for establishing the session key & then encrypt the actual communication with session key using symmetric encryption. While reading about DHKE, I learnt that you could use the ...
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Identify AES Mode

Let's say I have an API that accepts Plaintext and IV as input parameter and returns the ciphertext. I know that API is using AES 128 encryption but now I need to identify which encryption mode (ECB, ...
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Re-encrypt modified file section with AES-CTR

I am trying to encrypt a file using AES/CTR/NoPadding. The goal is to re-encrypt the new/changed blocks and leave the old ones unchanged then generate a new MAC. My thinking is that when the file ...
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Random salt and PBKDF2 key

Suppose I wrote a function $$(salt,IV ) = \text{keyIVGenerator}(passwd)$$ which generates a random salt of size 32-bytes and a random Initialisation Vector (IV) of size 16-bytes. Then, use a Key ...
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Designing a secure UDP-based communication protocol

SUMMARY UPDATE: I have changed the title of this question from "Using an encrypted packet counter as a counter value in AES-CTR" to "Designing a secure UDP-based communication protocol&...
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Can I derive IV, if I know Encrypted Txt, Key and Encryption Method?

I want to know is there any way to derive the initialization vector, if I know all the other details. AES SHA 256bits CBC pkcs5padding Input: Hello Key: 123 Output: xORGCDL88sa8cUrK8JNSCQ== Now, how ...

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