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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How AES treat string input to encrypt data and what will happen if the cipher key is less than that expected?

The official docs of AES have several example of how hexadecimal or byte input can be encrypted. I have some problem about the input text and cipher key. My question is: How can encrypt string input ...
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In which step does AES use the key to encrypt data?

AES has the following steps in encryption: SubBytes, ShiftRows, MixColumns, and AddRoundKey and the following steps in decryption: InvSubBytes, InvShiftRows, InvMixColumns, and Inverse of AddRoundKey. ...
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Can a 1 byte difference in AES 128 bit keys make huge difference in output?

If we take some randomly generated key of AES-128 and we change any random 1 byte of that 16 byte key, will this make huge difference in the AES cipher text generated over same input string? Does ...
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42 views

Using AES for smaller blocks in a Feistel network

I was wondering how decryption would work for FPE in the case of cycled Feistel ciphers. I understand that simply reiterating through the networks with reversed key order will generate the ciphertext ...
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35 views

Execution speed of AES_128 GMAC operation

I have read about the speed performance of AES_128_GCM on specific processors Intel and AMD that support AES New Instruction set. As compared with CMAC and HMAC is it relatively slow for other ...
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AES GCM 128, c#: very 12 byte tag instead of 16 [closed]

I'm using Security.Cryptography.dll and I'm wondering if there is a way to decrypt and check tag which is shorter(12 bytes)? I have situation where only 12 of 16 bytes of tag are sent in network ...
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8 views

Does we need IV if we're generating a new Symmetric key for every message? [duplicate]

We need to encrypt individual messages, for every message we: Generate a new AES key Encrypt the message with the key (AES/CBC/PKCS5Padding) Encrypt the symmetric key with with a public key ...
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5 views

Length of output of AES 128 encryption in python [migrated]

When I am trying to convert to hex the output of my AES 128 encryption code using pycrypto. I am using hexlify .the output is 64 bits for a 32 bits input. The output is always double the size for any ...
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77 views

64bit nonce in AES-CTR, why not 128?

I'm just a bit confused about the nonce/IV in AES-CTR ... it seems the suggested way to go is have a 64bit random nonce, and use the last 64bits as the counter, "starting at 0". I'm just wondering ...
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Determine AES key given encrypted and unencrypted files

Given an encrypted file, the original unencrypted (cleartext) file, and knowledge of which AES encryption algorithm was used, is it possible to determine the key that was used to encrypt the data in a ...
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485 views

Why does “2xAES-256” provide “99.99%” security strength whereas “1xAES-128” provides “40%”? [closed]

I recently was "directed" to FlipsCloud, a company selling security solutions (as far as I can tell). In particular I've investigated their page and found a page on their "encryption features". This ...
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37 views

Problems implementing AES in CBC+CTS mode

I'm trying to implement an AES cipher in CBC+CTS mode, but I'm unable to get the second last plaintext block to decrypt properly. I've attached my code, it's based on the steps listed under CBC ...
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45 views

AES-CBC pre-determined IV vs. null IV

Is there any security advantage to using a pre-determined IV in CBC mode over a null IV? I'm implementing a license key system similar to this article on CodeProject, but I'm confused by the authors ...
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56 views

Does AES(x || x) provide secure message authentication when message fits in a single block?

Suppose I have x = <64 bits of data>. I build a 128 bit block $P = x || x$, and transmit a message $M = AES(K, P)$. The receiver has the same $K$. The ...
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1answer
65 views

How bad it is using the same IV twice with AES/GCM?

I understand that initialization vectors should not be used twice when using AES/GCM. I am using a counter as initialization vector. Every time I send out a new packet (I am developing an UDP based ...
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1answer
32 views

Ciphertext and tag size and IV transmission with AES in GCM mode

I am completely new to using AES in GCM mode of operation, and I have not a very large background in cryptography as well. I have been playing with OpenSSL trying to encrypt and decrypt some messages. ...
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1answer
43 views

How does DPA work on AES?

I am really not much of a crypto guy so I don't really get how a differential power analysis on AES works. Can somebody explain it to me how it basically works?
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203 views

AES + CBC encryption for a stream of UDP packets

I am developing an application that is based on UDP, and I need to send a stream of packets. As you can imagine, packets can get lost or corrupted. I need to make sure that the content of those ...
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1answer
101 views

Quantum computing vs AES s-box equation

Do quantum computers have any affect on the ability to solve the non-linear AES s-box algebraic expression, or does solving it still fall under search algorithms (Grover's)? If quantum computer do ...
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79 views

Is this a secure method of encrypting with authentication?

My goal is to allow two clients to send files securely over an untrusted network without the need for more than one block of information to be sent. Both clients have ECDSA keys of size 256 bits. I'd ...
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1answer
74 views

Calculating Multiplicative Inverse for Rijndael S-box using EEA

I am currently learning, and I'm stuck on something that I thought is very simple. On many academic sources they suggest using Extended Euclidean Algorithm to calculate the multiplicative inverse for ...
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52 views

How much pre-hashing a password increase security against brute force attack?

I am wondering how much hashing a password used as key for a symmetric key algorithm helps preventing brute force attack on crypted text. Let's assume I want to crypt text A using key B using ...
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Reasons for components of AES

I started reading "Cryptography: theory and practice" by Stinson, and I am trying to understand the reason behind the choices for the different components of AES since they seem quite arbitrary. In ...
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Is standardizing a modified AES a good idea?

"Recently" the Ukraine standardized a new block cipher Kalyna, which according to the abstract of"A New Encryption Standard of Ukraine: The Kalyna Block Cipher" by Oliynykov et al. (warning: the paper ...
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Why should the input value on a DPA attack be non-constant?

I actually was wondering if anyone could help me out with the following problem: Let's assume we are attacking the first SubBytes() operation on AES with the help ...
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51 views

Block Ciphers - Standardize plain text

I need to use AES-128 to encrypt a plain text about 720 bits. Is it correct to say that – in this case – the plain text will be divided in 5 blocks of 128, the result will be equal 640 bits, and the ...
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Implementing AES MixColumns with fewest XOR gates

I'm playing with Contiki (O.S. for constrained devices such as sensors and micro-controllers) and particularly with the AES encryption in software (the one available in Contiki source code). I'm ...
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Side channel attack on FPGA AES engine

I actually don't know if this is the right place where ask, but I try. The side channel attacks aren't a negligible problem. There are several ways to protect from these attacks its own IP inside the ...
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Which symmetric cipher is best for studying? [closed]

I would like to study a modern symmetric cipher (I have never studied a cipher before) and I was wondering which would be the best cipher for studying purposes of the following: AES (Rijndael), ...
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37 views

Encryption(AES) and verification per message

I want to send/receive messages with A (an peer) using TCP socket. I want to encrypt messages using AES CBC. Only I and A know a symmetric key K1 used in AES CBC, and K2 used in HMAC. The size of each ...
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How can complexity be increased or decreased in AES?

I have been studying data compression for a while. For educational purposes, after a lot of reading, I managed to create a software that performs encryption and authentication using AES256-GCM. ...
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51 views

Get AES key from client request

I get a request from a client who encrypts the message with the wrong AES key. Is there a way for me to know what AES key the client actually used? I understand I may get the decrypted msg which is ...
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50 views

Safe way to generate different encrypted output from the “same” plaintext

Imagine I want to send imaginary defcon levels to another party over the internet. I know there are good protocols for this like SSL, but lets say I only have a blackbox tool where I can input an AES ...
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Is DES slow in hardware or only in software?

I have been reading that DES is slow. Is it only slow in software or slow overall? Also, as far as Triple DES being slow is concerned, is double AES with two 128 bit keys slower than single AES with ...
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131 views

Is it OK to encode data using key equal to data

For some project, I need to store some short string in encrypted form. It would be ideal for the current purposes to encrypt it using itself. ...
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Unicity Distance - AES

I am quite confused calculating the unicity distance and I was hoping that someone can clarify some things for me. My main issue comes from somewhat a difference of the calculation given by our ...
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74 views

computational complexity class of decryption of AES [closed]

I haven't really seen what computational complexity class of decryption of AES is. Can anyone provide reference papers or answers here?
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What is meant by - computational complexity $2^x$?

Recently Bi-clique Cryptanalysis allowed to obtain following results on full AES ES that claim to have The first key recovery attack on the full AES-128 with computational complexity $2^{126.1}$ The ...
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Is it OK to use a hash of the key as nonce for AES GCM?

I don't see an immediate risk of using the hash of the key as the nonce for AES GCM. Is there something I could be overlooking?
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169 views

AES-CTR in BouncyCastle with string key, without IV or salt [closed]

Our team is encrypting data using a javascript snippet. My problem is I'm supposed to parse them back in my Java code. I am having troubles identifying parts of the algorithm. The code says it's CTR ...
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79 views

How was the MDS matrix used in AES chosen?

$$\begin{pmatrix}2&3&1&1\\ 1&2&3&1\\ 1&1&2&3\\ 3&1&1&2\end{pmatrix}$$ In the above MDS matrix used in AES encryption, why are the numbers $2$,$3$ and ...
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61 views

Why using AES in ECB (Electronic Code Book) mode a bad idea? [duplicate]

Why using AES in ECB (Electronic Code Book) mode a bad idea? is CTR mode better? Given only these two can be used for parallelization.
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Can AES in CBC mode be parallelized?

Is there any way to parallelize AES running in CBC mode? (The plan is to parallelize it using OpenMP)
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Authenticating small packets

I intend to authenticate small packets of data, between 16 and 256 bytes each. For some of them encryption will also be required. This will be used on small micro controllers, with RAM sizes ranging ...
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101 views

Can AES be considered as Perfectly Secure?

I am studying about the AES encryption standard, and as I know from the theory there is no known weaknesses today about this block-cipher. I would like to find out or at least to understand what ...
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215 views

Why don’t all AES encryption tools produce the same key from the same password?

Alice and Bob meet regularly. They have agreed face-to-face a 128 bit password which they want use to encrypt/decrypt emails written between them. They decide to use 256-bit AES. Alice wrote her ...
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296 views

What does a stream cipher provide that cannot be obtained with AES CTR mode operation?

I can precompute the key stream for the CTR mode operation and the encryption at that point is similar to a stream cipher. So why are there stream ciphers still used and proposed after RC4? Recently ...
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How many bits of entropy can I expect from /dev/urandom in iOS?

Apple's latest security documentation indicates that it now uses CTR_DRBG for generating pseudo-random numbers (previously Yarrow instead of CTR_DRBG), using "timing variations during boot" and ...
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Are pseudorandom permutation really permutation in mathematical sense?

In security, and specifically Block Cipher (AES, DES, etc), when we talk about pseudo random permutations, is the term "permutation" refer to the same meaning as in discrete mathematics. That is, the ...
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Post-quantum authenticated encryption

It is well-known that the Grover's algorithm reduces cryptographic strength of symmetric ciphers to a square-root - e.g. AES-256 becomes only 2128 strong. However, these statements are always made ...