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 to generate the APA SBox?

I am trying to generate the S-Box provided in the Affine Power Affine paper (PDF) but I'm not sure I understand it fully. The essence of the paper is this: ...
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Determining nonce between unsynced systems

It's my first venture into cryptography, and I'm struggling with how to use a nonce in an encryption standard between two digital radios. The two radios support AES encryption, only requiring a ...
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174 views

How does ccrypt work?

On many Linux/GNU distributions CCrypt (ccrypt) by Peter Selinger is available as a command line utility to encrypt files. How does the protocol work and is it ...
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176 views

IV's for different AES encryption modes

I wanted to know if my understanding is correct! I have been reading up on aes encryption and modes(specifically CTR and CBC) and it took me sometime to understand the concept of IV. If the IV is ...
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214 views

Symmetric mutual authentication with client using a derived secret

I'm attempting to find a client/server authentication protocol that allows the client and server to authenticate each other when the client doesn't know the server secret but does have a sensitive key ...
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545 views

CBC-MAC: is it secure to authenticate a fixed length ciphertext?

Suppose I have a fixed-length arbitrary ciphertext. To authenticate such ciphertext: I generate a random AES Key $K_{auth}$. Then I compute the CBC-MAC Tag of the ciphertext with $K_{auth}$. ...
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66 views

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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242 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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693 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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233 views

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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572 views

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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111 views

AES Affine Transformation Polynom Representation

I have been reading on the polynomial representation of the AES Sbox in the PDF “Essential Algebraic Structure Within the AES” by Murphy and Robshaw (www.isg.rhul.ac.uk/~sean/crypto.pdf) on page 7, ...
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184 views

How often do I need to rotate AES 256 keys

I'm trying to design a protocol for a resource constrained environment. The device has to communicate with a server through an insecure node. My plan is to use AES 256 end to end for all ...
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263 views

EAX: OMAC and CMAC

OMAC is specified as the underlying algorithm to provide authentication within the EAX authenticated encryption (with associated data). Would that be OMAC1 or OMAC2? If it is OMAC1, does that mean it ...
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266 views

Recover plaintext from truncated ciphertext using AES for FPE

I am trying to implement an FPE for a 19-digit long number. I am trying to follow the lecture of Prof. Dan Boneh and here is how I understand it: Get the nearest power of two greater than $10^{19} ...
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79 views

Modes of Operations Exercise

I am currently stuck at an exercise for my Cryptography Class in University which is: Alice wants to send a message $M = (M_1,M_2) =$ "Pay Bob \$100 from bank accout $12345$" to her bank (encrypted). ...
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162 views

Does AES 256 really make sense in hybrid crypto systems when the PKI is the bottleneck?

AES 256 is used widely in hybrid crypto systems (e.g. SSL/TLS). According to keylength.com a 2048 bit public key corresponds to 112 bits of security. Does it make sense to use AES 256 in this ...
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237 views

AES and One Time Passwords

I have used AES to secure my short term wireless network(1 day lifetime). The same symmetric key is used for securing entire network traffic. is it possible to improve security with onetime password ...
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392 views

What is the forward cipher function of AES-XTS?

We're using OpenSSLs EVP_aes_265_xts encryption on data (with unique, random, IVs for every new message encrypted) - which is working well. But, I've been asked; what is the forward cipher function ...
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2k views

AES CBC Security

I am building an Apache webserver with TLS 1.2 and OpenSSL 1.0.1. So far, I have enabled 2 encryption algorithms - ECDHE AES256 GCM and ECHDE AES128 GCM. Firefox and Chrome(ium) use NSS which ...
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110 views

How unsafe is to share parts of a password

The best way to ask this question and have a concrete answer is to set a very specific example. This is the example I would be interested in reading an answer to: Consider that my friend Alice has ...
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392 views

crypto design with AES256 MODE OFB

I have the following APP Design key store (contains 1:n user payload as 1:n key store entries) key store salt (is used to extend to key store password to 256 bits, stored in clear text) key store ...
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251 views

What is “serial concatenation”? [closed]

I have a third-party point-of-sale API (Speedflow Pay-N-Get) that I am trying to communicate with over HTTP, but I have a problem with it. In a nutshell, a request is encrypted using RSA, and the ...
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917 views

Proper way of doing encryption and authentication (PBKDF2 + AES)

I'm currently in the planning phase of an authentication and storage-ish service. The client needs a file ("ENCFILE") which he will work with. This file will be encrypted with AES256, and stored on ...
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332 views

What's wrong with my security model - or how can it be attacked?

I'm working on a little personal project where security is very important, and I've thought for a while about the best way to do this. Now I am looking for a little outside help on good practices. The ...
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2answers
492 views

How practical is proxy re-encryption for AES?

In proxy re-encryption schemes, a proxy is given special information that allows it to translate a ciphertext under one key into a ciphertext of the same message under a different key. How ...
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3k views

AES AddRoundKey

Looking at the first step of AES encryption I see that we XOR the key with the plaintext block. Why is the actual key involved at all, why not just use the round keys derived from the key schedule?
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Deriving HMAC key and cipher key from passphrase? [duplicate]

I'm encrypting a file with AES-256 in CBC mode. I needed to add an HMAC for authentication and validation of the file contents and passphrase, so I used a SHA-256 HMAC over chunks of my file ...
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331 views

Understanding padding oracles - is an attack plausible in my scenario?

I have a scheme that, long story short, uses AES in CBC mode to encrypt third-party credentials for user accounts with a password-derived key. It's been mentioned that the use of CBC mode is a ...
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2k views

Blowfish: hex digits of pi used for s-boxes?

Preface: here is the official site for the Blowfish algorithm: http://www.schneier.com/blowfish.html The Blowfish algorithm uses an s-box, which consists of hex digits of pi (found here: ...
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564 views

What would be the most effective way to brute force a 16 char AES key?

I have a file that is encrypted in AES using a 16 char string. The string is (a-zA-Z0-9) and .,?!. Also, it only contains words ...
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693 views

Does the MixColumns step come before or after AddRoundKey in AES decryption?

I found these images depicting the AES decryption process: In the first image, the MixColumns step comes before the AddRoundKey step, while in the second image, the AddRoundKey will come before ...
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43 views

total effective key length of the AESX-192

If I have a AESX-192 be a block cipher which is similar to DESX but has the DES being replaced by AES and the AES key size is 192 bits. How should I compute the total effective key length of the ...
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Compressing AES [duplicate]

I have this program which encrypts multiple files using AES then compress it using LZO into one single file. The problem is that the final file is almost equal in size than all the files which means ...
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If you use an AES key just once, do you need to use IV, and/or pad the message? [duplicate]

I am developing an application that is going to use AES encryption. Since it is going to use a different key for every message encrypted... Would it be secure to use a constant IV? (i.e null bytes) ...
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23 views

change in bits leads to change in rounds the reason? [duplicate]

In AES algorithm why there are 10 rounds for 128 bits whats the reason behind it like we have in raid storage technology or something else
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37 views

AES-GCM Hash sub key parameter in Intel's IPsec library

I am trying to use Intel's optimized AES-128-GCM implementation (from the Intel white paper “Fast Multi-buffer IPsec Implementations on Intel Architecture Processors”, you can find the code here). ...
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103 views

bank websites using AES_256_CBC vs AES_128_GCM/CBC [duplicate]

Hello i have just recently started learning about cryptography, so i was doing some little research on what kind of encryption techniques and modes that were used in bank web pages. I have noticed ...
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Are there key collisions in AES-192, AES-256?

Suppose we have a single, fixed plaintext block $p$ of 128 bits. Call the set of all possible 128 bit blocks $B$. We could define fixed plaintext AES-128 as a function $f(k) \to B$ that takes a 128 ...
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21 views

EC algorithm to derive bits/keys and sign/verify [duplicate]

Looking at the question “ECDSA vs ECIES vs ECDH” it appears that you can either have a tool that can derive keys or bits, or can be used to sign and verify something. Is there an EC way to do both ...
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Simplest way for strong cryptography in chat

I am a beginner in cryptography and I am interested for several weeks on this for my chat application. Basically, it is a centralized model. All messages are stored and potentially visible by ...
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equation of mixcolumn in the aes field

$c(y) = (03)y^3 + (01) y^2 + (01) y + (02)$ Let $d = (01)b$ in the AES field $GF(2^8)$. Provide exact equations for the bits $d_i, 0 \leq i \leq 7$, in terms of the bits $b_i$ of b. Can ...
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60 views

Perfect Secrecy of AES file Encryption

Why does AES file encryption not ensure perfect secrecy? I understand that $\Pr[E(K,M_1)=C_1] = \Pr[E(K,M_2)=C_2]$ given $M1\neq M2$ holds for perfect secrecy of a scheme. However, this seems to hold ...
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Encrypting a 160-bit plaintext into a 160 bit ciphertext with a 128-bit Block Cipher [closed]

So I have a kind of interesting issue. I have a field in my data store which must take exactly 160 bits of information. Some users will choose to make this data encrypted, some won't, so some of those ...
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237 views

How to calculate the avalanche effect in aes-256?

I am a beginner in cryptography. I'm testing AES-128 bit key, AES-256 bit key, and Camellia-256 bit key. I'm using AES-256, 9 character salt, CBC mode, PKCS #5 padding, and the ciphertext using ...
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97 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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79 views

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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659 views

nonce of AES-GCM in SSL

It seems that the nonce of AES-GCM in SSL has 3 parts: salt, 4 bytes, generated in handshake, not changed in whole session nonce_explicit, 8 bytes, chosen by the sender and carried in each SSL ...
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222 views

FileVault AES-XTS decryption with cipher text that's missing a part

My mac was recently upgraded to OS X Yosemite and FileVault2 full disk encryption was turned on. Encryption finished, but things went horribly wrong and key parts of the disk are filled with all 0s ...
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AES-128/192 safer than AES-256 in practice? [duplicate]

Related-key attacks can break AES-192 and AES-256 with complexities 2^176 and 2^99.5, respectively. Quote from: http://en.wikipedia.org/wiki/Advanced_Encryption_Standard It seems that more ...