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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AES - Size of T-Boxes and obtaining T-Box values

In article "A high performance ST-Box based unified AES encryption/decryption architecture on FPGA" (http://www.sciencedirect.com/science/article/pii/S0141933115001945) two 32Kb dual-port BRAMs are ...
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How secure is AES-256?

The cipher AES-256 is used among other places in SSL/TLS across the Internet. It's considered among the top ciphers. In theory it's not crackable since the combinations of keys are massive. Although ...
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About the Security of PCBC Encryption Mode

We are designing an encrypted file system. We plan to use the PCBC (Plaintext Cipher Block Chaining) encryption mode for encryption. This is because we desire the feature ("small changes in the ...
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Is webkey a reasonably secure authentication system?

I just created Webkey in the last couple days. This should allow any website to do single-password auth with a much higher level of auth security and convenience for users (single password with ...
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128 bit 3DES Key and AES Key: what's the difference?

Apologies if this is really basic but I couldn't find the answer to this. I have heard some Info Sec colleagues talking about creating an AES key in preference to a DES or 3DES key but I don't know ...
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707 views

how much is secure to encrypt a password using itself (as encryption key) for storing it on a unsecure media?

I want to store a password securely on a storage (suppose in a usual unencrypted file). I use this password as AES key to encrypt itself (using AES-ECB) & then store it on the media (the password ...
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Why need mapping to slots to embed bytes in AES-homomorphic encryption?

The encoding of each AES bytes $๐›ผ_๐‘–$ is using CRT(Chinese remainder theorem). It means that there is an aggregate plaintext $H$ such that: $H \mod F_0 =๐›ผ_0(MappingData[0])$ $H \mod F_1 =๐›ผ_1(...
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Cloneability of AES-128

I would like to implement an anti-counterfeiting scheme for tools my company manufactures. This would ideally be done via RFID/NFC tags. However, the environment in which these tags operate would ...
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40 views

Can I open a file in plaintext (already decrypt) but the cipher doesn't change?

I want to create an app that encrypts a file and saves it to the Dropbox. Thus, I open and edit this file, I want the file is already decrypted, but the encrypted file that stored in Dropbox still in ...
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363 views

What is considered a “weak key” in AES?

I need to construct an AES key from an array of bytes (in Java), but I first I have to check if the key created from these bytes would be weak. Java can check for weakness for DES, but not for AES. ...
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44 views

Proper authenticated encryption

I am using AES-CBC, authenticating using HMAC-SHA512 and I was wondering whether my thought process and implementation are correct. The message send over the network is: HMAC(64Bytes),IV(16Bytes),...
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How to protect key in software

I need to encrypt/decrypt data from my software by AES, the problem is how to make the AES key secure, there is no HSM, should I hard code the key in my code? It seems that a hacker can read the key ...
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44 views

Sodium crypto_aead_aes256gcm_encrypt ciphertext length > plaintext length

Using the crypto_aead_aes256gcm functions from Sodium produces a ciphertext of "at most mlen (plaintext length) + crypto_aead_aes256gcm_ABYTES bytes (16 bytes) are put into c (ciphertext), and the ...
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Decrypting a file encrypted with AESCRYPT using key instead of password

i have encrypted a file using aescrypt and took memory image while the file was being encrypted and hence have the key that was used for encryption in the image but not the password, can i decrypt the ...
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I am trying to understand how AES works

I am trying to understand how AES encryption operates. I am trying to run through the steps on paper to understand. So far, I am creating a simple example. I have the plain text "MESSAGE TESTTEXT" ...
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84 views

Is it acceptable to write the nonce to the encrypted file during AES-256 GCM? [duplicate]

I've used AES-128 in CTR mode in the past and using the same key but different IVs for each file, I wrote the IV to the first 16 bytes. Is it safe to do so with the nonces used in AES-256 GCM? I'm ...
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62 views

PyCrypto and AES: can i use a longer key than the block size (16byte)?

I see that in many scripts are used keys of 16 characters for a block of 16 byte, but can I use key of 40 (for example)? And then why in some scripts with aes module the block size is set to 32 byte ...
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AES key reuse and guessing the key

Bit of a noob question and a fair bit of Googling didn't help. I understand that the current encryption standard is AES256. A few questions Is the point of this (and other encryption techniques) to ...
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103 views

Why does AES ciphertext entropy always close to 8?

I have three binary files: 31744 byte length (1), 5712980 byte length (2) and 10806008 byte length (3). The alphabet is all 256 symbols from 00 to ff. I compute the shannon entropy, replacing ...
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Which of these 3 AES 128 symmetric encrypt/decrypt routines is most secure?

I am developing a symmetric en-/decryption routine written in c# for a database containing user-specific, sensitive information. I have narrowed down the implementation to 3 different approaches, ...
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Stopping timing attacks on AES: Why is it important to prevent the OS from interrupting the AES computation?

I read the paper Cache-timing attacks on AES (by Daniel J. Bernstein), but I don't seem to understand everything. The author dedicates a long section on how to prevent the OS to interrupt an AES ...
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132 views

HMAC-SHA1 vs. AES

This might be a very silly question, but I am a total novice in encryption. I don't know where to start searching for an answer to this problem. I am building applications using a proprietary ...
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is it possible to reverse engineer the key on a AES-256 encryption? [duplicate]

If I have the original text and the encrypted one, is it possible to reverse engineer the key? And more importantly is it doable ? I tryed to look up the algorithm but i'm way too rusted and with no ...
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Difference between AES-CCM and AES-CCM*

I'm trying to understand the different between AES-CCM and AES-CCM* (as defined in IEEE Std 802.15.4โ„ขโ€2011, Annex B). I see that there are more restrictions on L and M and also M=0 is allowed: L = 2 ...
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Is there any benefit to verifying PKCS#7 padding when using AES CBC and HMAC?

As I'm using HMAC to ensure integrity and authenticity of the ciphertext, is there any additional security benefit to verifying PKCS#7 padding when decrypting using AES CBC? A previous question asked ...
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Rijndael variant using AES for key schedule? [on hold]

The weakest part of Rijndael is considered to be the key schedule (I believe that this is true for all variants, including ones not standardized as AES). One solution to this problem is to use (...
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Help with breaking AES reduced to 2 rounds

I was studying Rijndael AES proposal, and its cryptanalysis. I started with writing code to break AES reduced to 2 rounds. I am using 128 bit key size and 128 bit block size. 2 round AES means the ...
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Trying to understand MixColumns with Hexadecimal matrix

I am trying to read and understand the textbook's exercise questions. The sample solution at the end the textbook has a final answer and it does not clarify how it got the result. I am trying to ...
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142 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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Assuming a 1024qb quantum computer, how long to brute force 1024bit RSA, 256bit AES and 512bit SHA512

Assuming in the future there was a functioning 1024 qubit quantum supercomputer and it could run Shor's algorithm or Grover's algorithm to crack encryption very quickly. I'm interested in how the ...
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Is AES solvable by reducing to SAT?

Consider a known plaintext attack on AES โ€” just so we have an actual system of equalities that we can feed to a SAT solver. Is AES solvable in this way? In other words, will the algorithm eventually ...
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Fixed-prefix IV in CBC mode

I know the Initialization Vector needs to be unpredictable. Does it apply to the IV as a whole, or to every bit in the IV? I have multiple devices with poor entropy sharing the same key and I want to ...
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What about using AES-ECB with random IV?

Let P1P2...Pn be n blocks plaintext, and M0 be a random IV. Then a n+1 blocks message M0M1...Mn can be constructed by setting Mi+1 = Mi xor Pi+1. Finally, we use AES-ECB to encrypt this message. Is it ...
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Apple encrypted DMG volumes strength?

Apple OS X can create encrypted AES 128/256 DMG volumes. Here is written about a men who was able to hack it. And also that DMGs use PBKDF2-HMAC-SHA-1. I couldn't find more information about encrypted ...
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Active s-box of 8x8 MDS for AES

one way to enhance the security of AES by increasing the number of active s-boxes .larger MDS matrices are used to increase the number of active s-boxes. using 4x4 MDS matrix generate 25 active s-box ...
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How to perform AES MixColumns as matrix multiplication in GF(2) (boolean values)?

AES MixColumns is done by multiplying a $4 \times 4$ matrix and a column of the AES state (a vector). Addition and multiplication are done in $\operatorname{GF}(2^8)$. In the paper White-box AES, the ...
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AES CTR with similar IVs and same key

Let's say there is a piece of software that uses AES CTR to encrypt different messages using the same key but with slightly different IVs. So for example, a 16 byte IV, the 2nd 8 bytes are always ...
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Applicability of birthday attack to AES brute force

Is the following snippet from a recently published cryptography book correct? EDIT: Expand the snippet from the book to make the context (symmetric key search) more clear. You can apply this to ...
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ChaCha20 immune to timing attacks

What are the reasons because of which ChaCha20 is immune to timing attacks ? Also why is not AES immune to timing attacks?
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Does encrypting twice using the same block cipher produce a security weakness?

If I use the output of a cipher, for example a block cipher such as AES and encrypt it again with the same algorithm, I read that this introduces weaknesses into the overall security of the system. ...
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Is it possible to decrypt cryptowall-encrypted files? [duplicate]

I am writing regarding a certain ransomware program called cryptowall (prop 4.0). I have lost many documents to this, and as it so happens, I have a few file duplicates before and after they were ...
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PHP AES 256 CBC faster than AES 128 CBC? Or am I doing something wrong?

for last couple of days I'm learning a bit about encrypting data in PHP, as I need a good encryption/decryption function for storing user's passwords in DB. I use ...
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How to correctly encrypt data with proper authentication using AES-256-CBC in php?

I have been using the openssl function for encrypting data with AES-256-CBC in php. I have been able to encrypt it using an unique IV (by generating with openssl_random_pseudo_bytes)for each new ...
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Effect of the birthday bound on AES-GCM

What is the effect of the birthday bound on the security of AES-GCM, when a very large number of messages are encrypted? I am looking for attacks that are useful in obtaining information about the ...
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Why was AES limited by NIST to a 128-bit block size, although Rijndael could support more? [duplicate]

Rijndael could support block sizes up to 256 bits; this seems to be useful in AEAD. Wht did NIST restrict AES to a 128-bit block size?
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Importance of timing attack resistance with AES

I've implemented AES in my library with several variations: a straight C version, a version using x86 SSSE3, and a version using x86 AES-NI. The SSSE3 and AES-NI implementations are constant-time, ...
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Are there any test vectors for the CMS content type AuthEnvelopedData (for AES-GCM)?

I am looking for CMS AuthEnvelopedData test vectors for AES-GCM mode. I havenโ€™t seen any ready-to-use test vectors for it. There are test vectors for AES-GCM mode but not for its CMS support. I even ...
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What is the difference between PKCS#5 padding and PKCS#7 padding

One runtime platform provides an API that supplies PKCS#5 padding for block cipher modes such as ECB and CBC. These modes have been defined for the triple DES, AES and Blowfish block ciphers. The ...
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128 Bit AES Issue

I'm trying to use the 128bit TI_aes implementation on my 16bit microcontroller and I'm having the weirdest issue. Every input where two bytes within a word are identical two nibbles within a byte ...
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AES128 Decryption in Objective-C just slightly off

I have been asked to integrate a home-grown CRM system with a 3rd-party data service provider (DSP). The DSP has encrypted the information they are providing. I only have their decryption ...