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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Security aspects of using a global values as nonce and additional data for AES?

is it a good idea to use global values as nonce / additional data? What problems can occur? What should be take in account when we deal with such parameters for encryption. Thanks
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Can AES in CCM or GCM counter mode interoperate with AES in “plain” counter mode (CTR)?

I am exploring the use of Windows CNG to replace some OpenSSL-based code that takes advantage of AES in counter mode. From the outside, everything should look the same after the switch. The section ...
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Confused with the role of AES round keys

AES works when each plaintext block is arranged in a 4x4 array of bytes called states. State goes through 10 rounds of encryption consisting of 4 operations: bytesub, shiftrow, mix columns and add ...
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The perfect way of using IV in CTR mode

I understand that it is necessary to use the same IV for both encryption and decryption in the CTR mode. I'm thinking about the case when I concatenate the secret ...
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91 views

What is the importance of adding round key in AES

I know this may not be the place to ask this but I have found it difficult to find an answer to this question. I know the steps of the AES encryption algorithm but I am finding it difficult to ...
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private keys for multiple devices [closed]

I have an architecture where: a user can have multiple devices (phones) the server needs to broadcast the payload to all devices through the same channel (basically, all devices listen and receive ...
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88 views

How secure is file header encryption for large files?

I'm having trouble location information about whether or not encrypting a file's header is good enough. The files in question are media files that range in size from 500mb to 4GB. If I had no ...
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114 views

Deduplication: Encrypting the SHA-256 hash of a file chunk

I'm designing a data storage system that should be both able to deduplicate data that share the same encryption key, and be reasonably secure. I know that this kind of encryption quality can be ...
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Encryption for a short packet size

I have an 8051 microcontroller with a radio that can send packets with up to 32 bytes and I want to have the messages encrypted. It is a sensor network so I really only want to send one packet per ...
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138 views

How to calculate AES logarithm table?

I would like to know how to find multiplicative inverses in $\mathrm{GF}(2^8)$. I know how to multiply two elements of $\mathrm{GF}(2^8)$ (for example, I know that ...
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72 views

Post processing of AAD and len A||C in a hardware AES GCM implementation

I'm new to GCM and I need to implement it in hardware, using FPGA. The data bus is 640 bits, so I will use 5 adder/multiplier blocks in parallel. The message size and AAD size are constant. My design ...
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(Re-)Using deterministic IV in CTR mode / How to: deterministic AES

I am aware of the requirement of an IV to be unique in CTR mode (Why must IV/key-pairs not be reused in CTR mode?). However I wonder if I can use an IV depending on the plaintext deterministically. ...
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Can I simulate iterated AES-ECB with other block cipher modes?

I am trying to write some code using the Web Crypto API (http://www.w3.org/TR/WebCryptoAPI/#algorithm-overview) which provides only some of the block cipher modes for AES, intentionally excluding ...
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107 views

Encryption and HMAC in a PSKC file

This is the PSKC standard https://tools.ietf.org/rfc/rfc6030.txt In Section 6.1 6.1. Encryption Based on Pre-Shared Keys They have the following ...
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96 views

Is AES-GCM length extension attack possible using authenticated decryption?

I am looking to encrypt a piece of data using AES-GCM with a full 16-byte GCM Tag and send it over the network using UDP. Is it safe to assume using the AEAD nature of AES-GCM that performing ...
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177 views

How to customize a standard encryption algorithm?

I want to modify and customize AES encryption algorithm and develop a variant of it. What factors should I consider so that it does not become weaker? What skill sets would be required to undertake ...
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Generate CA with aes256 passphrase protected DSA key

I want to create my own Certificate Authority with an DSA key. I figured out to create it with: ...
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142 views

Is it safe to AES-CBC and AES-CMAC both using the same key?

There is a very similar question (Using a derived key for CMAC) but it doesn't quite answer this one (at least for me it does not). I have a situation where I need to transfer some data. My data has ...
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At what point does passphrase strength match the strength of the cipher?

Let's say that I have an ordinary hard drive encrypted with VeraCrypt 1.0e full disk encryption and implementing: -AES -RIPEMD-160 Hash Algorithm Now let's say that for an arbitrary machine, the ...
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Find LFSR with Berlekamp-Massey algorithm?

in the paper "A Compact Rijndael Hardware Architecture with S-Box Optimization" (http://link.springer.com/chapter/10.1007%2F3-540-45682-1_15) at page 6 figure 3, i think they constructed a LFSR for ...
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Is there an alternative AES schedule?

I'm currently reversing an AES implementation for disk encryption. The odd thing I'm stumbled about is a key schedule where the encryption round keys are not the same as the decryption round keys (in ...
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secure embedded/microcontroller crypto using AES-ctr with hmac-sha2

The embedded device is a low-power 8-bit microcontroller (memory usage is constrained to about 10kb code, 1kb ram). As the device is battery-powered and manual service should be minimal, more powerful ...
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Where to store the file extension to retrieve it correctly after decryption

I am using Java to write AES-256 to encrypt various files with different extension, the problem is, where am I suppose to store the file extension so the if the data is decrypted, the file extension ...
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AES - Encrypting multiple blocks of files

On my site, users can download files which are stored on public hosting, so I need to encrypt them. A downloaded file is divided into blocks of 1 kB and I want encrypt them individually, using the ...
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299 views

Java: How to handle authenticated encryption for big files

First I need to mention that I can't use BouncyCastle to implement this solution. I have to encrypt files into the file system. Those files are not going to be tranfered over the wire to any other ...
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Encryption of big files in Java with AES/GCM

I have to encrypt big files. Say their size ranges from 500mb to several of gigabytes. I would like to use AES/GCM/NoPadding as provided by Java 1.8 since that gives me automatic authentication and ...
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if using cbc+hmac dealing with small size of data(less than 128bit) , will it cause any problem?

if use AES-cbc,HMAC-SHA256, and there is some txt needed to be enc, and I divide this txt into small packages with variable length, then enc them. some of these package can be less than 128bit. Is ...
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Is the output of AES-CBC + MAC the same size as the input?

I use AES-CBC and HMAC-SHA256 to encrypt a text file. Will the output be larger in size than the input or will it be the same size? Is it more secure secure if the size of the output is larger?
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Importance of ShiftRows in AES

If ShiftRows is excluded from AES, then an attacker can attack the modified AES by simply treating $128$-bit input as $4$ $32$-bits blocks. The attacker can attack these $4$ blocks separately. ...
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Why we can't implement AES 512 key size?

Out of curiosity why we can't implement AES 512 key size? Please explain somehow i can understand! I'm not an expert.
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Key derivation for AES-Encryption key and HMAC

Okay so I have two options for how I would derive two keys for AES encryption and HMAC they are as follows: Run BCrypt on a users passphrase and then use the bouncy castle implementation of HKDF in ...
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Best practices (if any) to add metadata to encrypted files

I am encrypting files using AES/CBC/PKCSPadding, with 256 bits long keys. So far the first 16 bytes of each encrypted file are the IV. I would like to store some more information regarding the ...
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CCA security of a system that splits messages and encrypts each packet

Propose a symmetric key based crypto-system for implementing a secure email system. This system is based on AES and CCA secure. Suppose that you have to encrypt a large message and that this message ...
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Consequences of AES without any one of its operations

Suppose AES-$128$. There are $4$ operations in AES's encryption, they are SubByte, Shift Row, MixColumns and AddRoundKey. Question: If I remove one of the following opearations, what will happen to ...
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AES with weak keys

Suppose that the key generation is insecure; each key bit is independently generated, but the value of each key bit is '$1$' with probability $0.90$. These keys are used in AES. What is an efficient ...
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Storing AES encrypted RSA private keys on a server

I'm thinking about creating an encrypted messaging web application where users create RSA key pairs, they store the public key on the server for others to see and also store an AES encrypted private ...
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Storing salts and iteration number?

I have a function that derives two sub-keys from one passphrase using PBKDF2 one which is used as a encryption key the other for HMAC generation, because these two sub-keys will need to be regenerated ...
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Is it possible to decrypt the entire message with one half of the key in this example?

In this scheme, a 256 bit key is split into two 128 bit sub-keys. Message blocks are 256 bits and are also split into two sub-blocks. Before encryption, each sub-block is xor'd with it's partner and ...
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What is more secure, a ciphertext encrypted with AES-256 or encrypted with 3 different AES-128 keys?

Or better yet, is encrypting a block with 2 AES-128 keys just as secure as encrypting a block with 1 AES-256 key? By the way, I've only recently been learning cryptography stuff; I've made working ...
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Brute Force AES Calculations

I have an encryption service in which the user decides the length and the type of key, so I would like to build a tool that educates the user on the brute force times for the key they created if using ...
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Is splitting AES ecrypted data safe?

Say I have a key, an iv and an AES/GCM/NoPadding encoded string and I want to split this information between three people such that only jointly can they reveal the ...
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AES mix column stage

In a PDF related to AES algorithm for mix column stage is written: The multiplication mentioned above is performed over a Galois Field. The mathematics behind this is beyond the scope of this ...
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AES: Changing plaintext to state

Can someone explain this to me? For example how M chanes to 0c? Changing plaintext to state:
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AES— Brute force attack versus Known plain text attack

I am taking a codes and cryptology course and the following is a questions on a past exam that I could not and still can't solve: ...
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Direct sum of Binary numbers In Mixcolumns

I have just started learning cryptography and I am trying to make sense of the direct sum on some binary numbers. I am trying to find a column of a state space after a Mixcolumns operation has been ...
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Is AES's parity key-dependent?

Is the parity of the permutation of the set $\{0,1\}^{128}$, defined by AES encryption for a certain fixed key, dependent on this key? DES, and any pure Feistel cipher, has even parity for any key. ...
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Encrypting twice with different modes?

I was using a SOCKS5 proxy today (tunneled through SSH) and I began to wonder what the effect of encrypting twice (TLS over encrypted SOCKS5 in this case) would have on the security of the transmitted ...
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AES: Guess Password using the unencrypted text?

I am using the same password for some encrypted files currently (I know this is bad practice, though), and I wonder whether an attacker could decrypt if one decrypted file fell into his hands.
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How exactly does AES-NI work?

I am looking in to AES-NI which is now supported by many new CPU's and I have read a few papers which states that AES-CBC works faster with AES-NI, but I am unable to understand how exactly AES-NI ...
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I'm using AES-CTR as a CSPRNG - Do I need an IV?

I'm using AES128-CTR for generating pseudo-random values, which is considered secure for up to 1MB (at least from what I've read). I simply encrypt a 128-bit little-endian counter, starting from 0. ...