Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

2
votes
1answer
86 views

Can I work around these padding issue in AES 256 ECB due to Reed solomon encoding?

Disclaimer: I do NOT believe AES-ECB to be at all useful for encryption. That said, due to time and bureaucratic issues that I'm not in control of, I need to use AES-ECB. I get packets of data that ...
7
votes
1answer
2k views

Is the cipher “Kalyna” with a 512-bit key length more secure AES with a 256-bit key?

Recently I have found out that Ukraine has its own symmetric encryption algorithm "Kalyna". Developers of this algorithm said that their algorithm is more secure than AES because of longer key length ...
1
vote
1answer
100 views

what method of transposition does AES 256 encryption use

I'm interested in learning how to use AES-256 encryption in C/C++. I'm still a beginner in Cryptography but I'm confident in my abilities to program. There is still a lot for me to learn about this ...
2
votes
0answers
133 views

How to implement security - authenticity/confidentiality/integrity for 6/14 bits radio messages?

I just took over two radio systems (using 433Mhz) - one communicates with 6 bit messages, one with 14 bit messages. Both have a lots of transmitters and one receiver (and, yes bits not bytes). For ...
0
votes
4answers
2k views

Can I find the encryption key if I know the plain text and the encrypted text (DES and AES)?

If I have the plain text and its output after encryption with a key K1, is it algorithmically feasible to find K1? I am specifically interested in the cases of DES and AES encryption algorithms.
0
votes
2answers
62 views

Does selecting a set of random numbers for the key and IV insure security?

For AES 256 - if I use a random 32 byte sequence for the 256 bit key and another 16 byte for the 128 bit initialization vector, does this insure that my cipher text cannot be broken in any short ...
3
votes
2answers
641 views

Should text be hashed before being used as an encryption key?

Let's say I have an API that provides an encryption wrapper around another API. I give the consuming programmer the option of either passing a string or byte array as an encryption key. The byte ...
0
votes
1answer
205 views

Using the encryption matrix from AES, how do you compute the decryption matrix?

So I don't want the answer but somewhere to start with this problem, first I want to know if my logic and thinking is on the right path before I dive right into computing the decryption matrix so here ...
0
votes
0answers
74 views

What is the difference DET-ABE Vs CP-ABE and KP-ABE?

I can't understand what's does it mean DET-ABE (digital envelope technique ) exactly , and is there a difference between it and the the cipher or key policy attribute based encryption, could someone ...
5
votes
2answers
430 views

Can AES-CBC be safely used in combination with RSA, or must it be CBC-MAC?

The plan is to encrypt files using an AES-256 in CBC mode secret key. The secret key itself will be encrypted with a RSA 2048-bit public key. Is using AES-CBC sufficiently secure if used in ...
1
vote
1answer
365 views

What is the advantage of CFB over OFB?

I was wondering if CFB can be better than OFB in any ways. I would like to know in what cases one would use CFB over OFB.
3
votes
1answer
265 views

AES CCM Mode (CTR with CBC-MAC)

For CCM mode of AES can anyone explain what the difference is between $B_i$'s and $m$? Is the nonce value for $B_i$'s and $A_i$'s the same? What is $l(a)$ and $L$? What is the minimum value of size ...
-1
votes
4answers
176 views

IV vector is not random. Is it critical?

Reading the spec of one of the IoT protocols, I found that IV for it one isn't actually random, it consist of $n$ bytes that represents manufacter-specific string; the same for all devices plus 6 ...
1
vote
1answer
102 views

How is the plaintext to ciphertext expansion ratio on AES cipher?

My understanding for AES cipher is just mapping a plaintext of a some length to a ciphertext of the same length. Is the ratio always |Ciphertext|/|Plaintext| = 1? Please correct me if you have ...
1
vote
2answers
766 views

How can I share a number with an opponent?

Let's say I have a message (eg: Hello, world!) and I want to encrypt this message using symmetric encryption (AES-256). I am using a list of keys, where I randomly ...
1
vote
1answer
171 views

Is zero IV with AES-CBC safe if CPA is not possible and indistinguishability is not an issue?

Is using zero IVs with AES-CBC safe, if chosen-plaintext attack (CPA) is not possible and ciphertext indistinguishability is not an issue? Practical example: ...
-1
votes
1answer
2k views

Generating AES-256 Private Key from user string

So I wish to encrypt a string using AES-256 and want to provide the user to specify the password for unlocking the string. I plan to use sha-256 to hash to users entered password and use this as the ...
2
votes
2answers
449 views

AES CBC: how shall i get to know with AES CBC method, the received Cipher Text is padded or not [closed]

Algorithm: AES - CBC mode with PKCS7 padding KeyValue: 10a58869d74be5a374cf867cfb473859 IV: ...
0
votes
2answers
114 views

Does AES-GCM without security tag turn into regular CTR Mode?

We are looking to implement a simple password based key agreement scheme. Part of this is deriving a symmetric key from a common passphrase known to both parties involved. This symmetric key is then ...
1
vote
1answer
273 views

Would it be safe to store GCM nonce in the encrypted output?

I'm looking to use AES-256 GCM to encrypt and authenticate a file containing sensitive information. I am a bit loss on where to store the nonce that is required for GCM. Would it be adequate/safe to ...
2
votes
1answer
139 views

Security strength for encryption and authentication (wrapping) of cryptographic keys

Let $K$ and $M$ be AES secret keys. The purpose is to wrap $K$ using $M$ to allow $K$ to be used at a later time (see, e.g. NIST SP 800-38F, section 3.1). One method to achieve this goal is to use $M$ ...
4
votes
4answers
522 views

Text partially decrypted regardless of IV

I'm trying to work out which AES cipher is best to use. I'm working with the OpenSSL ruby gem. While testing the various options I noticed that most of the ciphers result in partial or even full ...
1
vote
2answers
745 views

AES encryption using a Diffie-Hellman question

this is something that has always nagged at me and I've wanted to know the answer to. Does AES create it's own shared secret symmetrical key after the DH process has completed? I'm not as familiar ...
2
votes
1answer
892 views

AES encryption algorithm (MIX COLUMNS)

During the mix columns step, getting the first element value is done using the equation (1st*02)+(2nd*03)+(3rd*01)+(4th*01), where *02 means shifting 1 bit to the right then XORing with 1b if the ...
1
vote
1answer
208 views

Crypt-analysing modified AES algorithm with no shift-rows, and no key-expansion

I came across an answer about consequences of AES without any of its operation In the question in the given link, it is mentioned that "if Shift Row is removed, then attacker can treat input block ($...
3
votes
1answer
394 views

Is there a real purpose to use Twofish, Serpent or Threefish instead of AES?

I am wondering if other ciphers like Serpent or Twofish or even Threefish have really an use in real life, because AES seems to be very efficient in most situations. But for example TrueCrypt or ...
6
votes
4answers
4k views

Is using the same IV in AES similar to not using an IV in the first place?

So if I understand how an IV works with AES, I'm supposed to generate a different IV for every message because using only a key, I will get the same encryption if the message was encrypted twice (...
0
votes
0answers
183 views

Understanding how to use RSA and AES in S/MIME

I'm sorry if the question is dense, my understanding of this topic is not thorough. I have to send an email adhering to: Encrypting the email message via AES-256 Encrypting the email with their ...
4
votes
1answer
622 views

Understanding WannaCrypt's hybrid encryption scheme

I'm confused about how WannaCrypt's hybrid encryption scheme works after watching Computerphile's "How WannaCrypt Encrypt's Your Files" video a number times. Below is my thought process to make it ...
5
votes
2answers
171 views

Security of the AES with a Secret S-box

In this paper they change the $AES$ S-box to a uniformly random one and answer the questions: How does the security of AES change when the S-box is changed by a secret S-box? Would it be safe to ...
3
votes
1answer
106 views

Using multiple cryptographic keys for encryption?

I am setting up an encryption methodology for items in a database. To decrease the likelihood of data being compromised due to the keys being compromised I would like to use an application level key (...
0
votes
1answer
307 views

AES in OFB mode and IVs

I'm trying to understand cryptosystems and their implementations to understand how to properly implement them. I have a function implementing AES-128 in OFB mode. Let's call it ...
1
vote
1answer
793 views

AES S-box calculation

I am trying to design the s-box for AES. Quoting from Wikipedia, the algorithm for applying affine transformation in AES s-box calculation is ...
0
votes
1answer
61 views

Number of Substitution boxes

How many possible 16 bit S-boxes exist? (AES uses 8 bit substitution boxes) I first taught of calculating 128(keysize in bits)/8(bits) =16, but I believe it's wrong.
3
votes
2answers
430 views

Is it secure to hash an AES key?

Let's say I want a way of generating a deterministic public ID for a specific symmetric cryptographic key (AES, for example). Would it be secure to use SHA-3 (or SHAKE) to hash the key, and then ...
4
votes
1answer
589 views

AES s-box – How do I calculate the inverse of this field equation?

I want to implement AES algorithm,instead of LUT based S-box, but I’m stuck at point creating "Inverse of equation" during implementation. In creation of S-box I am using the following steps: ($...
0
votes
1answer
91 views

Affine of Inverse Sboxes

"All 8x8 s-boxes created using Galois Field inversion plus an Affine Transform have the same non-linearity, as the Affine Transform does not change the linear or differential properties" is what this ...
2
votes
1answer
44 views

AES S-Box: Possible options for constant to calculate S-Box values

To calculate the values of S-Box in AES, I came across a lot of resources where constant {63} was chosen. It is said that {63} satisfies the condition of S-Box that it should not have any fixed points ...
1
vote
1answer
70 views

AES S-Box: How is value for 01 mapped to 7c?

If irreducible polynomial $m(x) = x^8+x^4+x^3+x+1$ is chosen, or even for any other value, the multiplicative inverse will not exist for $01$, as $0000 0001$ will perfectly divide $m(x) = 100011011$ ...
-5
votes
1answer
194 views

the counter mode of encryption CTR - AES [closed]

To attack an encryption algorithm, you ask the encryption oracle to encrypt a polynomial number of messages of your choice and observe the outputs. Then, you give the oracle two messages m0 and m1....
1
vote
1answer
802 views

symmetric AES encryption with php produces different result than openssl MacOX

I need to make a simple very basic encryption with AES 128 ECB mode. The idea is to generate a cryptogram, code it in base64 and then decipher that text from a web service in php to process its ...
1
vote
0answers
129 views

Problems key AES 128 key from last round key

I have written an algorithm in Python to find the main AES 128 key from the last round key. However, it doesn't work; I can not find back my main key. I know that the general principle is to do $w[i] ...
0
votes
2answers
143 views

Why we use a fixed inverse Multiplication Matrix in AES

I just want to know that in AES we use following multiplication matrix for encryption. 2 3 1 1 1 2 3 1 1 1 2 3 3 1 1 2 and for decryption it use's following ...
1
vote
1answer
257 views

Matyas–Meyer–Oseas for super-fast single-block hash function

Is it basically safe and correct to use the Matyas–Meyer–Oseas construction to turn a fast block cipher like AES into a really fast single block hash function? By single block hash function I mean ...
1
vote
2answers
816 views

Use AES in Web Crypto with public/private key pair

this is a very top-level question - as I'm just starting to delve into crypto. The main objective is to be able to communicate between 2 mobile devices through a BAAS server such as Firebase so that ...
0
votes
0answers
118 views

GPG AES-256 Malleability

If Alice encrypts a file with GnuPG software using the AES-256 mode, and sends the encrypted file over an insecure channel (like E-mail or HTTP) to Bob. Both Alice and Bob know the password, but only ...
1
vote
2answers
869 views

AES S-Box Lookup Table Hardcoded?

From what I've looked up on various AES projects, the impression I get is the lookup table is hardcoded with the values from this Wikipedia entry page: https://en.wikipedia.org/wiki/Rijndael_S-box ...
0
votes
1answer
95 views

Are sufficiently large key sizes enough to deter quantum attacks for symmetric key ciphers? [duplicate]

Are sufficiently large key sizes enough to deter quantum attacks for symmetric key ciphers such as AES?
1
vote
1answer
105 views

What kind of ciphers does not depend on order of operation?

What kind of cipher does not depend on order of operation ? For Instance if we have two operations encryption Enc(m,k), decryption Dec(m,k) and some message m. For which ciphers the following is ...
-1
votes
2answers
316 views

AES S-box input and output question

I am new to cryptography. I am looking to understand how to answer this question from my class: Find below the S-box of AES. Given the input 01010011 in binary, calculate the output.