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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Is it safe to use GZIP to avoid padding related attacks

I am designing a library that supports encrypting some in-memory data using AES in CBC mode. Now I need a padding but it seemed to me that Apple's CommonCrypto library and OpenSSL have different ...
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291 views

Is this method for exchanging private key using RSA sound?

Bob know's Alice's public key, and he wants to make sure he's connecting to the one which has that key. Furthermore, Alice wants to verify when she gets a connection from Bob who'll give his public ...
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506 views

Decryption a chunk of file with AES

We are having a requirement to store large files (~1GB) encrypted and decrypt them when reading. We are looking to use AES-CTR or AES-GCM mode to encrypt the data. There are scenarios where we want to ...
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9k views

AES vs Blowfish taking key-length into account

I understand that Blowfish is getting old, but is still a secure algorithm, and that AES is very popular, and is recommended by most people. My question is, how do the two compare when a 256-bit key ...
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573 views

Is there a standard for OpenSSL-interoperable AES encryption?

Many AES-encrypted things (files, strings, database entries, etc.) start with "Salted__" ("U2FsdGVkX1" in base64). I hear it's some sort of OpenSSL interoperability thing a b c. Is there some ...
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231 views

Signing 14 bytes of data

for an embedded device I need to sign a 14-byte string and want to verify that string on the device. Since there is already an AES-Library on the device, I thought about using the following scheme: ...
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3k views

In which order are the round keys used during AES decryption?

In the Add Round Key step in AES decryption, which part of the expanded key will I XOR first to the result of the SubBytes step? Is it the 10th round key? For example, is this the right order? ...
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AES-NI implementation examples

Newer Intel and AMD processors have hardware support for implementing AES using the instruction set AES-NI (instructions AESENC, AESKEYGENASSIST etc). Do you know of any clean example implementation ...
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Is AES restricted to only 64 characters for the key/password?

I am wondering if AES only supports 64 character passwords? When using truecrypt, the maximum character limit on passwords is 64 characters; however, when using WinRAR, the limit is 128 characters. ...
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155 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 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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Probability that two different files can have same MD5 hash for both an unencrypted and encrypted version (AES256, same key between files)

This math is way over my head, and don't even know if it can be done, but here are the assumptions: Take unencrypted File [Fu] of variable length, but assume 100KB as an example. Let File [Fe] be ...
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142 views

Getting 88bytes cipher output from 48bytes input in AES

The other day I saw this Hybrid Cryptographic Algorithm in the Google and felt curious about it. I am trying to understand this Hybrid Algorithm. And hopefully its not so hard to understand whats ...
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435 views

Some questions about encrypting (AES) a file with password

I'm relatively new to encrypting, and I have some questions. I intend to write a standalone C# program that will write and read an encrypted file with sensitive data using a password entered by the ...
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246 views

Message lengths with AES CTR mode?

Im working on my own AES implementation as a personal educational exercise (not for production use), and a book im using as a resource states: In the case of CTR, we are merely XORing the output ...
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248 views

Is it overkill to run a key generated by OpenSSL through pbkdf2?

I'm generating a key & iv with OpenSSL via: ...
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3k views

How to obtain KCV from the key

Simple question: we have AES 128 encryption and a key. How can we calculate the key check value (KCV)? One example: key is 48C3B4286FF421A4A328E68AD9E542A4 and KCV should be 77DC84. I am trying it ...
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822 views

Achieving 256-bit encryption strength with PBKDF2 - HMAC-SHA1

I am interested in the theoretical consideration of the bit strength of an encryption key and its precursor. Assume a given environment as follows: a. My encryption algorithm is AES-256 b. My key ...
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530 views

Review of AES encryption concept for an open source project

i'm working on an opensource project, A generator for static (html/js), password protected photo galleries. The generator AES 256 encrypts many images with the same key in PyCrypto, and decrypt them ...
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753 views

How to break AES CBC with PKCS#5 padding?

If I have a string encoded with AES CBC with PKCS#5 padding, how can one possibly decrypt/crack it? What are the approaches that one can take to break its security?
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Shortcuts / practicality of brute forcing block cipher (AES) + ECB with known plaintext

I know the plaintext (26 bytes long) and cryptotext of block cipher (suspected to be AES) in ECB mode. I can generate hundreds or thousands of such samples, but the samples are not arbitrary. What are ...
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32 views

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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222 views

Evaluating Algebraic Complexity of a S-box

While studying the design and the desirable properties of an AES S-box , I came to know that Algebraic Complexity is also an important property of an S-box which is usually considered while evaluating ...
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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 Affine Transformation in $GF(2^4)$

in $GF(2^8)$ the AES affine transformation is defined as \begin{equation*} b( x ) = ( x^7 + x^6 + x^2 + x ) + a ( x )( x^7 + x^6 + x^5 + x^4 + 1) mod (x^8 + 1) \end{equation*} where the polynom $( x^7 ...
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Cracking an appliance's network protocol

I'm trying to crack my thermostat's network protocol. I've captured several rounds of network traffic and here is what I've got to work with. Communicating via HTTP POST The POST data is JSON ...
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Where is the OID and ASN.1 specified for AES_CMAC?

I have a requirement to implement AES_CMAC as the authentication algorithm in a CMS library. I just can't seem to find the OID and the ASN.1 definition for it. I expected to see the OID under ...
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AES multiple devices to server communication

I have multiple devices connecting to a server, whose communication needs to be encrypted. At the moment I have an AES library doing the job (possibly inadequately): I am using a database of keys on ...
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63 views

Separate TLS Client Write and Server Write Keys in AES-CCM Mode

I am designing a system that uses TLS-like handshaking on a resource-constrained embedded system. I have settled on AES-CCM mode for symmetric session encryption and authentication, allowing ...
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Timing attacks against RSA, DH and AES

I have been reading about “Timing Attacks on RSA: Revealing Your Secrets through the Fourth Dimension” by Wing H. Wong. I was wondering if this attack is feasible while signing with RSA and, if yes, ...
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File Encryption (EFS method)

I'm implementing (for learning purposes) a file encryptor, which uses the following method (from http://en.wikipedia.org/wiki/Encrypting_File_System). I have 3 kind of keys: RSA public/private, AES ...
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How do I enable AES-NI (hardware acceleration) for Node.js crypto on Linux? [closed]

I wrote a basic function to test the speed of the AES-256-CBC mode of the Node.js built-in crypto functions. These functions use OpenSSL, so they should support AES-NI, but when I correctly enable ...
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How to use HMAC-SHA1, HMAC-SHA2 in conjunction with AES

I understand how to compute HMAC-SHA1, HMAC-SHA2 etcetera. Please explain why/how is the resulting HMAC value is used in conjunction with AES for encryption/decryption and signing/verifying. In ...
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AES key padding

Is the initial AES key (expanded to the key schedule) byte padded if less than e.g. 16 bytes? Is there a safe way of determining if decryption was successful (i.e. used the correct key)?
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Secure Hash Function based on AES

How secure would a hash function be which appends an extra block of 16 zeroed out bytes to the end of the message and then AES-encrypts it with a well-known password (say the first 128 bits of pi) ...
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522 views

How to encrypt a file for random access

I am a programmer familiar with C/C++ and Python. Lately, we got an assignment from a team asking us to work on one of their projects: we need to make a small program to encrypt a large file using ...
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202 views

Decryption issue with self-coded AES-128

I have written my own AES-128bit implementation in Java, till yesterday I thought it would be alright. (I was working on the encryption) Now I’m trying to decrypt my encrypted cleartext, but this ...
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220 views

How resilient to attackers with extreme resources available is this encryption method?

How could the following scheme be made more resilient to attacks capable of utilizing massive amounts of resources? Assume all random values are cryptographically secure. Key derivation: scrypt ...
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What parts of AES encryption result are safe to pass on the network

I'm using AES to encrypt the message. both sender and receiver know the passphrase, but only sender knows IV and salt I assume that receiver also needs to know IV and salt to decypher text; is it ...
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What's the difference between AES and earlier block ciphers?

Is there any difference except speed and key and block size from user's point of view? Or does AES have something that ideal block cipher doesn't have?
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What is the probability of breaking the AES algorithm?

I am doing a project which requires the encryption to be done using AES. Is it really possible (technically) to crack AES? If yes, please tell me: What is the probability of breaking AES? How ...
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668 views

Is storing original file size in an encrypted file header a bad idea?

I'm encrypting a file using AES-256 in CBC mode. I'm padding to the 16-byte input multiple by using the PKCS#7 limit. The problem I'm currently having is that if I'm transferring or reading the ...
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2k views

Double Encrypting with two different keys

In terms of security, would it be MORE or LESS secure to take, say, an RC4 output (or Serpent) or other, that is encrypted with one key, and to encrypt that output with AES (using a different key)? ...
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decrypt AES without whole key

Is there a way to decrypt a AES cipher Text which was encrypted twice with some key, when having a part of this key? (the last 3 bytes of the key are missing)
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AES GCM symmetric encryption of data at rest in c#, ciphertext much longer than plaintext

I've written encryption/decryption routines using AES GCM. Code can be found here. I recently realized that the cipher text is longer than I believe it should be. It should add the tag and IV onto ...
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335 views

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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AES256-CBC vs AES256-CTR in SSH [duplicate]

I used AES256-CBC to SSH to a remote server. Recently, it stopped working with the following message: ...
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Combining multiple symmetric encryption algorithms - implications?

I was just wondering if I add more security by combining two or more symmetric encryptions on a plain text. For example: Plaintext → AES → Twofish → Serpent Of ...
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Generate fixed length cipher text from arbitrary length plaintext

Using an encryption algorithm like AES, is it possible to generate a fixed length cipher text no matter how long the plain text becomes?
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AES Message Authentication Vulnerability

My securities instructor recently posed this question to the class and I am bending my brain in half trying to figure it out. Suppose $y_1 = AES(K, x_1)$ and $y_2 = AES(K,x_2)$, and suppose you ...