(or Advanced Encryption Standard), a symmetrical block-cipher algorithm with a 128-bit block size, and key sizes of 128, 192 or 256 bits.
2
votes
1answer
92 views
Winzip AES256 vs PGP
If I use the AES256 option in Winzip to encrypt a file, is it any less safe or less secure than using pgp encryption?
2
votes
1answer
208 views
Is AES-256 a post-quantum secure cipher or not?
We know Grover's algorithm speedup brute-force attacks two time faster in block ciphers (e.g brute-forcing 128 bit keys take $2^{64}$ operations not $2^{128}$).
That explains why we are using 256 bit ...
2
votes
1answer
462 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 ...
2
votes
1answer
73 views
Security implications of using constant string to verify AES key?
I know that you can use for example CBC-MAC to verify data integrity and thus the password upon decryption.
But would there be security implications of just adding a constant string to the plaintext ...
2
votes
1answer
136 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:
...
2
votes
1answer
717 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?
...
2
votes
1answer
586 views
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 ...
2
votes
1answer
252 views
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 ...
2
votes
1answer
306 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 ...
2
votes
2answers
504 views
Using an RSA private key simultanously as an AES encryption key to generate random numbers?
Currently I'm implementing a PRNG for an embedded system. Using the RFC 4086 I've decided to use the X9.17 - to be more specific the succesor X9.31- standard to implement my PRNG. X9.17 uses DES, but ...
2
votes
0answers
97 views
Single-purpose symmetric encryption scheme for single files
I'm writing a simple password manager program that will encrypt/decrypt a single file (it's size will most likely stay under a few K). This is my initial file format design:
...
2
votes
0answers
54 views
Implementing PKCS#7 Padding on a Stream of Unknown Length?
I have a fairly simple Python program using PyCrypto to use AES+CBC to encrypt a stream of input. In order to adhere to the 16-byte input size multiple, I've implemented PKCS#7 by hand. (While I know ...
1
vote
2answers
178 views
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) ...
1
vote
2answers
212 views
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)?
1
vote
1answer
116 views
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 ...
1
vote
1answer
96 views
How can encryption software accept password lengths which are not one of the AES key lengths?
AES comes with key sizes of 128, 192, and 256 bit.
But in Truecrypt or other crypto software we can use passwords of different length, even less than 128 bit or more than 256 bit.
How is this ...
1
vote
4answers
341 views
How easily could this be cracked?
I'm looking into encrypting files like this: First, I SHA-1 hash the password. Let's say the password is something normal like "hello123", and then hashed. Then I encrypt a file using this:
...
1
vote
3answers
661 views
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.
...
1
vote
2answers
137 views
Is it worth applying a MAC on data in a HSM?
I'm building a basic HSM out of an Arduino, and am using the following scheme to store data:
Master symmetric key $k_m$ stored in firmware (secure bit set to prevent trivial extraction).
Secondary ...
1
vote
2answers
155 views
AES+CTR+HMAC Encryption and Authentication on an Arduino
In my project we would like to encrypt and authenticate the the communication channel between our server and our Arduino nodes, which relies on an underlying TCP channel.
We have chosen AES in CTR ...
1
vote
1answer
214 views
AES CBC mode or AES CTR mode recommended?
what's benefits and disadvantages of CBC vs CTR ? which one is more secure ?
1
vote
1answer
366 views
1
vote
2answers
1k views
Initialization vector length insufficient in AES
I use AES with AES/CBC/PKCS5Padding with the following encryption and decryption code sections in Java:
...
1
vote
1answer
900 views
Cipher Feedback Mode
I can't understand what CFB really is. It said in Wikipedia that CFB is same as CBC, but I find that CFB is more difficult than CBC.
Can someone explain to me how CFB works. Such as how ...
1
vote
2answers
207 views
Would a “Triple AES” (in the sense of how Triple Des works) serve for a dramatic increase in safety?
The system requires to be as paranoid as possible regarding security. One of the few contemplated changes to the current design is to use multiple encryption. First proposal was to use Serpent on top ...
1
vote
2answers
183 views
is AES secure for java application licensing
I have to license a java application and want to code a quick implementation, the scheme I came up with is:
1) The Application calculates a string X which we assume to be the md5 sum of the ...
1
vote
1answer
160 views
Use of CBC-AES-256 to encrypt usernames
I came across some code in our project that encrypts usernames (limited to 50 chars, most are less than 10) using the following parameters:
IV size is 16 bytes
Key size is 32 bytes
Algorithm is ...
1
vote
1answer
54 views
Two files encrypted with related data versus one file
I have some code that takes a list of credit-card numbers, splits the number into two chunks, one chunk is 8 characters long, the other chunk is the remainder.
Each series of chunks is saved into ...
1
vote
2answers
233 views
Where i can find an AES implementation in python?
Where i can find a "reviewed" version of AES implementation in python. Not an API like PyCrypto whereby you can call AES algorithms in a single line.
1
vote
2answers
197 views
Can one build a one-way function from AES?
We change the AES block cipher encryption:
we delete the key schedule algorithm
the user now provides a string of 1408 bits
we divide the string to 11 sub keys, and use them directly in the ...
1
vote
2answers
406 views
Is AES in CBC mode secure if a known and/or fixed IV is used?
I have a need to encrypt credentials for a third-party app used by a secured internal app. Over on ITSec.SE, I was helpfully shown a scheme to encrypt the third-party credentials based on a hash of ...
1
vote
1answer
315 views
AES GCM implementation in c#
I am implementing an AES cipher in GCM mode in c# and have a few questions. My code is based on the code found here for reference. I'll copy in the relevant portions.
...
1
vote
1answer
99 views
Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)
Encrypt a single file, chunk-by-chunk, each chunk using different key.
I am a security newbie (only took 2 security courses before)
But currently I am using this encryption method for my Android ...
1
vote
1answer
98 views
Proper uses for CTR and CBC AES block cipher modes
Assuming the following:
Key is randomly generated is being used (32 bytes+)
IV is also randomly generated
Crypto random key generator is used
Data being encrypted contains common bytes like ...
1
vote
1answer
83 views
Partial decryption of large file in AES-GCM (or other modes)?
Lets assume
a 4gig file that is internally made of 1 million pages of 4k bytes each (page).
the file was originally AES-GCM encrypted
these pages (or entire file) lives across the internet i.e. ...
1
vote
1answer
84 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 ...
1
vote
1answer
120 views
AES key/ciphertext space sizes
This is giving me a brain ache now... If I have AES-128, block is 128 bit, then every plaintext (128-bit) can be encrypted to some ciphertext that is also 128-bit. This is the block size. But: 128-bit ...
1
vote
1answer
1k views
How to decrypt AES in CBC
i am having problems understanding how CBC works! I know that it is a chain and the IV is XORed with the PT but then what? I mean we encrypt it with key k and the result is the CT which we use for the ...
1
vote
1answer
50 views
Counter Mode: static IV but different keys [duplicate]
Given we are using AES counter mode, suppose we randomly generate several keys, all of them are using same IV (say, zeros). Does this lead to any security issue?
I know that in CTR mode, same key-iv ...
1
vote
1answer
118 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 ...
1
vote
1answer
82 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 ...
1
vote
1answer
348 views
Most effect way to brute force 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 .,?!. It also only contains words from a dictionary (but they can be lower/upper case). What would be the ...
1
vote
3answers
200 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 ...
1
vote
1answer
727 views
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.
...
1
vote
0answers
37 views
Parallelizing AES GCM in BouncyCastle [migrated]
I'm using AES-GCM with the BouncyCastle provider in Java and it works fine. The NIST documentation seems to suggest that GCM is an algorithm that allows parallelization -- however, on looking at the ...
1
vote
1answer
108 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?
1
vote
2answers
149 views
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 ...
0
votes
3answers
269 views
Is AES really used for Top Secret stuff?
I've read almost everywhere that AES-256 can be used for Top Secret material (in the US). Is it really used or is it some kind of decoy to hide the more advanced algorithm they might use ?
0
votes
2answers
151 views
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?
0
votes
1answer
156 views
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 ...
