(or Advanced Encryption Standard), a symmetrical block-cipher algorithm with a 128-bit block size, and key sizes of 128, 192 or 256 bits.
4
votes
1answer
65 views
Security for IV in AES-GCM mode
I'd like to use AES-GCM instead of HMAC for authentication and privacy in a token used in a web application, but I'm unsure how to securely tag each token with an IV. Is it safe for me to prepend the ...
3
votes
0answers
96 views
CBC with fixed IV but changing data [duplicate]
Possible Duplicate:
Using CBC with fixed IV
I am using AES in CBC mode.
For some reasons I have some issues for transmiting the IV. So I am using a fixed IV.
If the first 128bits of the ...
1
vote
1answer
213 views
AES CBC mode or AES CTR mode recommended?
what's benefits and disadvantages of CBC vs CTR ? which one is more secure ?
6
votes
1answer
358 views
Difference between Rijndael 128 / 256 blocksize implementations? (and impact of block size in general)
Can anyone shed some light onto the advantages/disadvantages of using Rijndael with 256-bit block size, as opposed to the 128-bit (AES) implementation? (please note: I'm not referring to key-size ...
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.
5
votes
2answers
218 views
Should I salt an AES password at each encryption?
I saw a sample code where the same password is salted with a different value (using PBKDF2) for each encryption. That means that the salt must be stored for each encrypted message.
I don't understand ...
0
votes
3answers
206 views
AES-GCM and its IV/nonce value
I was reading about the differences between the GCM and the CBC more here and I have a follow up doubt on the same.
In the CBC mode the person who performs the encryption is the one who provides the ...
0
votes
1answer
69 views
AES 128bit round level recommendation
we don't want change standard just after every attack, now for AES 128bit blocks i think 16 round is secure, but what is best round amount ? we had attack for 7 round then 10 round and it going so on ...
2
votes
1answer
460 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 ...
0
votes
1answer
347 views
AES key length greater than 256 bits - is it dangerous to do an implementation outside of the standard?
I'm making a digital-asset manager written in ActionScript 3, it will be used to manage highly sensitive information. I'm using the AS3Crypto library (which has quite a good reputation) to implement ...
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 ...
0
votes
1answer
227 views
5
votes
3answers
352 views
Why is OCB-AES mode not becoming a standard for authenticated encryption?
The OCB mode of authenticated encryption (used for example with AES) is the fastest way to provide authenticity and confidentiality without having to strive into questions like: Encrypt then MAC, MAC ...
3
votes
1answer
236 views
On-the-fly computation of AES Round Keys for decryption?
The usual implementation of AES first computes all the Round Keys sequentially starting from the key, and stores them in RAM for later uses. However, when enciphering a single block with a key that ...
0
votes
2answers
151 views
AES key expansion vs. a hash
Is there something special about the AES key expansion algorithm that makes it secure, or it is a compromise between security and speed? For example, say with a key I expand it by taking pbkdf2(key) ...
0
votes
2answers
158 views
How can I add more rounds to AES?
I'd like to understand a bit more about the AES key schedule if anyone would mind explaining that. For instance, why is the way the schedule generated (with recursive xors and occasional ...
5
votes
2answers
141 views
AES encrypting multiple files
So if I want to encrypt all the files in a folder with AES (same password) I take each file and generate the key schedule using PBKDF2. As the PBKDF2 algorithm takes in a salt then this salt should ...
0
votes
1answer
135 views
AES Secure key generation and storage
I have a client-server application, which is transferring data between its components in a secure way. I currently use AES algorithm with CBC mode to transfer data and file. This is the scenario: ...
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
2answers
153 views
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 ...
4
votes
1answer
198 views
AES timing attacks
I'm just interested in cryptography, so please don't expect me to be an expert. ;) I recently read about AES cache timing attacks and found it very interesting. I read the article Cache-timing attacks ...
3
votes
2answers
155 views
Is storing the hash of a key together with ciphertext encrypted with that key secure?
Is it secure to store the hash of a symmetric cipher key along with data encrypted with that key? Are there any circumstances or algorithms in which this combination could lead to potential weaknesses ...
2
votes
1answer
113 views
Can I use my random IV (for AES) as a salt for PBKDF2?
Also, where do I store my salt (can I just store it at the beginning of the encrypted file)?
0
votes
0answers
39 views
NIST Standard for Advanced Encryption Standard Algorithm [duplicate]
Possible Duplicate:
Advantage of AES(Rijndael) over Twofish and Serpent
What is the reason of NIST why Rijndael choose as the Advanced Encryption Standard
0
votes
2answers
100 views
Is this how padding can work?
So for block ciphers you need a fixed size block.
If the plaintext length is not a multiple of the block length then you need to pad it.
One way you could do this is that for the last block you just ...
3
votes
3answers
323 views
Relative merits of AES ECB and CBC modes for securing data at rest
I need to store several million Payment Card Numbers (PCNs) securely in a mainframe database (that is, 'at rest'). I assume that any attacker will have access to all of the stored data.
I assume the ...
3
votes
2answers
351 views
Implementing AES in C++: 4x4 Array of unint8_t, or 4x1 array of uint32_t?
I'm implementing AES in C++, and, inspired by the way words are handled in SHA, I decided this time to handle the state as a one dimensional array of 4byte unsigned integers as opposed to a two ...
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)?
0
votes
1answer
184 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: ...
2
votes
1answer
380 views
Advantage of AES(Rijndael) over Twofish and Serpent
I'm trying to figure out a suitable encryption technique and after reading a bit, I figured the current AES 128-bit encryption is suitable for what I'm trying to do. However, this is more due to the ...
0
votes
2answers
289 views
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)
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:
...
19
votes
4answers
2k views
Is AES-256 weaker than 192 and 128 bit versions?
From a paper (via Schenier on Security's Another AES Attack) (emphasis mine):
In the case of AES-128, there is no known attack which is faster than the 2128 complexity of exhaustive search. ...
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 ...
2
votes
2answers
429 views
Is it possible to obtain AES-128 key from a known ciphertext-plaintext pair?
I have a file, which was encrypted with AES-128 in ECB mode. I know the format of the original file and know that all files in this format have the same headers. So, I have an encrypted block and the ...
2
votes
2answers
817 views
SHA-256 and AES-128
Does it make an encrypted string more secure if I use SHA256(x) instead of x as the secret key for AES-128 encryption? I do know that SHA-256 produces 64 characters of hashed string regardless of what ...
0
votes
1answer
132 views
Design criteria for AES
I hope somebody can help me understand the design criterias for AES. Therefore, I would be really thankful if somebody could explain "non-linearity" in this context.
A criteria for the s-box in AES ...
2
votes
4answers
338 views
Which is more secure using a CSPRNG for a One-time pad, or AES?
In reading about the One-time pad it appears to need truly random key for the pad. Since true random values are not practical to generate this presents a problem (thus making One-time pad less ...
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 ...
7
votes
1answer
5k views
What is safer: ZipCrypto or AES-256?
Like in title: which one of these encryption methods (ZipCrypto, AES-256) is more secure and why? I am asking about it because I'd like to know which should be preferred when compressing files with ...
3
votes
1answer
403 views
Implementing AES encryption for firmware distribution system
I need to implement an AES encryption for firmware distribution system.
I have a bootloader that can decrypt various AES variants (ECB,CBC,CTR).
When I approached this I found few issues that aren't ...
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 ...
3
votes
1answer
256 views
Is this a good way to encrypt a file?
I need to encrypt a file, distribute it over an insecure channel, and decrypt it later. Using a symmetric-key algorithm. Here's what I intend to do:
Get a password P from the user. Generate a 16-byte ...
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) ...
7
votes
4answers
1k views
What is the effect of the different AES key lengths?
How does a changing key length affects the ciphertext, not only in case of AES, but in general? I know that the key spaces become much larger and the number of rounds in case of AES changes, but is ...
2
votes
1answer
1k views
How do I store encrypted files on a web server and decrypt them locally?
I want to store files (images) on a public webserver and let users see them if they know a password. The server shouldn't have the unecrypted files and the server can only serve files, not perform ...
3
votes
1answer
321 views
AES CCM vs CCMP
Are the terms AES CCM and AES CCMP are equivalent, or is there any technical differences between the two?
9
votes
2answers
534 views
Blum Blum Shub vs. AES-CTR or other CSPRNGs
Following on from D.W.'s comments on a previous question, what properties does Blum Blum Shub have that make it better / worse than other PRNGs? Are there significant implementation difficulties or ...
2
votes
1answer
106 views
Aes encryption -The relevance of static matrix in mixcolumns operation
Can someone explain to me the relevance of the static matrix used for the mixcolumns operation in aes encryption.i.e the relevance of why the byte is multiplied by 2 + next byte multiplied by 3 + next ...
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 ...
