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.

Filter by
Sorted by
Tagged with
0
votes
0answers
26 views

AES - running time in Python [closed]

How long will it take for AES to encrypt a 128-bit message in Python on average? I create a certain algorithm and test it here: https://repl.it/languages/python I want to compare the algorithm's ...
1
vote
0answers
23 views

AES implementation for non-password multi-document decryption usecase

I am trying to encrypt/decrypt multiple user documents (consider text) in an application. Unlike the use case of passwords where decryption happens once during an API call, in this application during ...
2
votes
1answer
41 views

RFC 4493 (AES-CMAC) algorithm with 256 bit key

I apologize for the newbie question. If I were to use a 256-bit key and AES256 (assuming I had the function instead of AES128, the length of the for loops in the functions xor_128, leftshift_bit, ...
0
votes
0answers
39 views

Problem on Encrypted data (possibly AES192) stored as a database entry on an Android device [closed]

I am (a newbie in cryptography) working on an Android app. During the initial setup the App asks user to setup a password (optional). A token named ...
0
votes
1answer
66 views

Would knowing the random seed help to break AES or similar?

Consider I knew the seed of the random number generator that Bob uses to send encrypted emails to Alice. Would I have an advantage in deciphering the message? Also, how does, for example, openssl ...
0
votes
0answers
24 views

How to prevent cache timing attack on table lookup AES implementation?

I've been trying to find a solid method to prevent cache timing or other possible side channel attacks on an AES implementation, that uses lookup tables for S-box substitution. I realize that there ...
0
votes
0answers
16 views

How does breaking AES with a side channel attack (CPA) differ from a side channel attack on something like a microcontroller?

I'm studying CPA side channel attacks. CPA stands for Correlation Power analysis and it can be used to break AES. I'm familiar with the process to crack AES on a microcontroller. I was just wondering ...
1
vote
1answer
126 views

How likely is it that AES-256 is crackable within 100 years (2120)?

When people ask for a block-cipher with a larger key space than AES-256 replies usually just state that there is no need. I see where that is coming from the future is hard to predict. The two main ...
0
votes
1answer
125 views

Using last 64 bit of aes as hash of the message vs first?

If I Generate some key K for the AES algorithm. Encrypt a message M with key K and take the last 64 bits of the result as the hash of M. Would there be any disadvantages? What if I took first 64 bits ...
0
votes
0answers
25 views

KDF options for a ECDH shared secret

the answer to this question suggests that the x-coordinate of an ECDH shared secret is itself usable as an encryption key without apply a KDF.... if so, then what additional security is provided by ...
7
votes
2answers
171 views

One round of AES-128

Maybe it’s a silly question, I’m interested in the best known/chosen plaintext attack on only one round of AES-128. More specifically, what is the smallest number of known/chosen plaintext/ciphertext ...
1
vote
1answer
94 views

Does clustering the AES Sbox look up table to 32 bit entry per index, help reduce vulnerability to cache timing attacks?

I've been searching for some, easy methods to help mitigate, a cache timing attack on software AES implementations. Currently, my implementation uses, a usual 256 byte S-box ...
3
votes
1answer
135 views

How to find the inverse of a 3x3 MDS matrix

I implemented a block cipher similar to AES. But the reason I can't decrypt is that I can't get the inverse MDS matrix. The MDS matrix I used is a 3x3 MDS matrix on $GF(2^8) \implies GF(2^8)$ like AES ...
0
votes
0answers
35 views

Requirements for AES-GCM Initialization Vector (IV)

AES-GCM requires a different Initialization Vector (IV) for every new stream of data that is encrypted using the same key. TLS generates the IV by XOR-ing a random static nonce (generated from the ...
0
votes
0answers
21 views

E2EE encrypted chat where messages are only readable by participants and admin users

As the title suggests, is there a way to have an E2EE chat between two users, and have them be visible later by an admin user. I know this defeats the point of E2EE, but i want to have the messages ...
4
votes
2answers
184 views

What makes AES look like an ideal cipher?

There are 2128! permutations on 128-bit inputs. AES supports a maximum key length of 256 bits, therefore offers at most 2256 permutations. The total number of 128-bit permutations is much larger than ...
2
votes
0answers
46 views

Why is double encryption used to generate EphIDs in DP3T?

The most famous proposed COVID-19 application is DP3T. In this app a user constantly broadcasts EphIDs generated from a secret key as follows: $$EphID 1 || ... || EphID n = PRG( PRF(SK_t , “broadcast ...
1
vote
1answer
53 views

Does AES-CBC always use PKCS#7?

I need to add AES decryption with a 256 bit key to our software, and of course I won't do it myself; rather, I chose a library that works fine for our needs. It supports various modes of operation, ...
1
vote
1answer
38 views

What should an identifer in the client-server model?

I am fairly new to cryptography and I am trying to understand this picture here. I have some questions regarding this picture. What should be an identifer for a side? For example, in the picture, it ...
0
votes
1answer
52 views

AES-128 - encrypted public domain text

I work with Historical Geographic Informations Systems on the academic level. I note this to give you an idea of my technical knowledge when it comes to computing, but that most of my knowledge of ...
0
votes
1answer
41 views

Using ECDSA to sign a ECDiffieHellman-derived key

Assuming that Alice and Bob know the hash of each other's public key, take this method: Use ECDiffieHellman with temporary private keys each time to generate a per-session shared symmetric key Create ...
2
votes
1answer
45 views

Is it possible to perform CPA(Correlation Power Analysis) when attacker has only specific round's waveform?

I read Quite a lot document about breaking AES using CPA. But most of them, assuming that attacker has the first or last round of the waveform(trace) and exploit SubBytes. My question is if the AES-...
0
votes
0answers
27 views

Is there a more efficient C# CryptoStream implementation for streaming decryption of large files

I am using LibVLC and Unity to playback locally stored encrypted 360 videos. VLC's Unity package has a feature to play content via a C# stream. I am using a FileStream wrapped in a CryptoStream to get ...
0
votes
0answers
47 views

AES. Algorithm of multipication in finite field [duplicate]

I multiply 2 numbers using their polynomial representation and addition via XOR. Do I need to find the remainder of the division by $x ^ 8 + x ^ 4 + x ^ 3 + x + 1$, using the operator "%" or by ...
0
votes
1answer
63 views

Zk-Snarks vs Homomorphic Encryption

I have been reading a bit about encryption algorithms. I have come across these two algorithms.My use case is the ability to work with encrypted data and my data will be string data. I see that ...
1
vote
1answer
71 views

Encryption & decryption in AES CBC mode - Which is faster?

I wrote a small code to compute the time consumption by the AES in CBC mode, I noticed that the encryption is faster than the decryption, my question: Is my result correct? If yes, why is the ...
0
votes
1answer
45 views

Block ciphers as secure as AES but immune against cache timing attacks?

This is a question out of curiosity! I really don't know of any other block cipher that is as secure as AES that has a substitution permutation structure and can be used as an alternative to AES to ...
0
votes
0answers
36 views

How does a cache timing attack work on AES with lookup tables?

I was trying to make a software only implementation of AES (Rijndael). At first I was able to implement it using table lookups for the Galois field multiplication and also for the SBox, but, I really ...
1
vote
1answer
264 views

32bit AES equals to 8bit AES?

I am looking into an article about 32bit CPU/MCU software implementation of AES and there are some weird changes over there. Like shift-rows. It seems that the shift-rows in the 32bit implementation ...
0
votes
1answer
56 views

Text encrypted with key1, key1 encrypted with key2, meaningful?

Simplified Question Does it make sense from a security / cryptographic standpoint to encrypt a text in the following way: create only one AES key K_Azure create ...
0
votes
0answers
31 views

When connecting via SSH, does the Diffie-Hellman key exchange take place over an unencrypted TCP session or does encryption occur before the exchange?

I'm a cybersecurity student and I'm eager to understand the basic processes of an SSH session. I wrote down the stages to the best of my ability but need help understanding what happens right after ...
2
votes
0answers
37 views

Why are polynomials chosen with coefficients in $GF(2^{8})$ in Section 4.3 of NIST FIPS 197 for implementing AES?

I was trying to understand AES (Rijndael) from a very mathematical perspective. I'm quite new to abstract algebra and Galois Fields. I understood that we are considering a byte (8 bits) as a ...
1
vote
1answer
74 views

Crypto system design : How to design Encryption for Zero width characters

Zero width character's can be used to hide text in plain sight.I am building a system where user's can provide their secret message , cover message and a password (key) which I would encrypt and give ...
0
votes
0answers
37 views

Clarification on polynomial used in Rijndael MixColumns implementation

I'm seeing the fundamental function in open source code for Rijndael MixColumns implementation. (Picture below) If i translate the 8'h1b correctly, it is represent the polynomial of $x^4+x^3+x+1$. ...
-1
votes
1answer
63 views

Which is more secure, AES CTR or OTP with generate key?

My idea of the OTP is to generate from 50 letters (5 words, each 10 letters) a new pad of 2000 random letters, then attach user email to the pad end (to make it unique). The keywords and the pad will ...
0
votes
0answers
16 views

stitched aes_128_cbc_hmac_sha1 encrypt-then-mac

Is there implementation of stitched aes_128_cbc_hmac_sha1 encrypt-then-mac? I can only find mac-then-encrypt implementation in OpenSSL 1 How hard is it to change to encrypt-then-mac and compile it?
0
votes
1answer
49 views

AES 5-round Square attack, how to choose plaintexts?

I know that we need to generate a delta-set (with 256 plaintexts). During the attack, we guess 4 bytes of round 5 key and 1 bytes of round 4 key, which allows us the byte at one position of the state ...
0
votes
1answer
32 views

AES difference propagation

when does active S box count reduce in AES difference propagation? what is the relationship between active S-boxes and MixColumns? can you please explain it with an example?
0
votes
2answers
81 views

How do AES and DES ensure data integrity?

I have been trying to study for cryptographic symmetric algorithms (AES,DES) and came up with a question whether these two on their own ensure integrity (i.e data has not been altered). Do these two ...
1
vote
1answer
43 views

Nonce of AES-GCM generated by Counters

i am trying to generate the nonce for AES-GCM. I know people usually generate it by Counters and LFSRs. I am confused about the meaning of Counters. Is that means Counter (CTR)? Why it can generate ...
0
votes
0answers
40 views

Apply HKDF After DIffie-hellman Key Exchange

Im trying to use HKDF after DIffie-hellman key exchange. However, i got stuck on HKDF part. ...
0
votes
1answer
60 views

Is the order of the steps in AES commutative?

Say I wanted to change the order of the 4 steps within a round in AES, would it change the final result?
1
vote
1answer
62 views

Safe way to derive IV from the DH shared keys for AES-GCM?

I am preparing to use AES-GCM to make a secure communication program. Here is the procedure DH key exchange to get shared keys SHA256(shared keys) Use AES-GCM to encrypt a message while the key only ...
0
votes
2answers
75 views

What is the need of having a key schedule before executing AES [duplicate]

Can someone explain to me why does using a key schedule make's AES more secure if instead of calculating and adding your round key's, you just keep on adding the cipher key. ?
0
votes
1answer
59 views

Security of using constant salt when saving encrypted data to database

Let's say that I want to save some encrypted data to a database through a Spring Boot microservice. For that I will be using Spring Security Crypto that, as the documentation says it uses AES256 with ...
2
votes
1answer
48 views

Which is the irreducible polynomial in GF(2^256) used in AES256-GCM?

I was able to find the irreducible polynomial used in AES128-GCM: $x^8+x^4+x^3+x+1$. But I cant' find the one for AES256, I'm searching in OpenSSL implementation of AES256 but with no luck so far.
1
vote
2answers
110 views

Can an AES-GCM be cracked if the key is known but the nonce isn't?

I'm kind of new in this field and I've been trying to learn it. I'm now facing an issue where I have a couple of packages encrypted with AES-128 GCM and I have the key that was used to encrypt these ...
0
votes
1answer
41 views

Finding IV in AES-128 having partial Key and plaintext

Let's suppose we have the plaintext, 14/16 char of the key and the first 2 and the last 36 chars of encrypted data (that is 64 char long). What I want is to find the IV. The cipher algorithm is AES (I ...
1
vote
1answer
44 views

Can any part of AES encrypted blocks be used as PRFed value?

Suppose we need a PRF whose output space is 255bit. Then, what I can do with AES with 128-bit security is producing 2 AES blocks that are of 256-bit. Then, I will remove the most significant bit of ...
0
votes
1answer
43 views

Behavior of AES-CTR with 128-bit nonce and possible overflow

If I feed 128 bits of randomness into AES-CTR as its IV / nonce / initial counter, what will happen if I feed in a random 128-bit integer that overflows and wraps around? I've written a test for this ...

1
2 3 4 5
40