(or Advanced Encryption Standard), a symmetrical block-cipher algorithm with a 128-bit block size, and key sizes of 128, 192 or 256 bits.
9
votes
2answers
543 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 ...
20
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. ...
2
votes
2answers
449 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 ...
1
vote
2answers
414 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 ...
4
votes
1answer
297 views
How was the complexity of the Biclique Attack calculated?
The abstract of the Biclique Attack paper claims:
The first key recovery attack on the full AES-128 with computational complexity $2^{126.1}$.
What does $2^{126.1}$ mean in this context? And ...
3
votes
1answer
410 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 ...
0
votes
1answer
134 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
340 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
262 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 ...
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 ...
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 ...
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 ...
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) ...
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 ...
1
vote
3answers
201 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 ...
2
votes
1answer
547 views
What is the difference between these AES encryption methods
I am using AES encryption (Rijindael) with Base-64 encoding in Obj-C and VB. I am currently using the following two projects to achieve this:
Obj-C: ...
3
votes
1answer
325 views
AES CCM vs CCMP
Are the terms AES CCM and AES CCMP are equivalent, or is there any technical differences between the two?
3
votes
3answers
470 views
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, ...
2
votes
1answer
110 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 ...
0
votes
1answer
751 views
Counter Mode in Advanced Encryption Standard(AES) Algorithm
In Advanced Encryption Standard, If I used "Counter Mode", in it's nonce value, what should I do?
ex. should I divide the nonce value into two? ex. I have 128-bit of nonce, should I divide it from ...
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 ...
-3
votes
1answer
424 views
Advantages of each encryption mode [closed]
What is the advantages of each encryption mode to other encryption mode..
for example what are advantages of CBC to PCBC, CBC to CFB
just like that.
so that I can filter what would be the best ...
1
vote
1answer
917 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 ...
0
votes
1answer
364 views
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 ...
2
votes
1answer
287 views
Poor man's SSL - is this method as safe as SSL/TLS?
I need to send data between two applications. I've got requirement that says that data should be transmitted using secure protocol such as SSL/TLS. Data is sent using TCP sockets and I don't have ...
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
1answer
188 views
Is truncating a hashed private key with SHA-1 safe to use as the symmetric key for AES for data at rest?
I realize this is mixing the purposes between asymmetric and symmetric crypto, but I was wondering if it is safe to use a hashed, truncated private key (asymmetric) as the symmetric key for encrypting ...
0
votes
1answer
79 views
Using “Additional Authenticated Data” as a secondary key
In implementing a cipher in GCM or CCM mode, you are provided the option to add "Additional Authenticated Data" (AAD). This AAD is required for decrypting the cipher text, and seems to be used when ...
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:
...
1
vote
1answer
379 views
3
votes
1answer
112 views
How to communicate authentication tag for GCM?
I have written some code to do AES in GCM. I currently manually append the tag property to the ciphertext, is this the proper way to communicate the authentication tag?
1
vote
1answer
317 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.
...
4
votes
3answers
767 views
Are there any simple and yet secure encryption algorithms?
Being very new to C++ and cryptography, I finally managed to implement a version of the Vinegere algorithm. I would like to try something a bit more complicated. I have looked at AES and DES and ...
2
votes
2answers
300 views
Capacity of Advanced Encryption Standard in terms of File Encryption
what is the capacity of AES in terms of File Encryption?
is it really good to encrypt a large files in AES? ex. I am encrypting a 8GB of File... is it still good to used AES?
is it still good to used ...
0
votes
2answers
92 views
Distinguishing Encryption Methods from the Output
Suppose that you see all IP communication packets between two computers for a day, as they pass through a connecting router, and this amounts to 10MB. You additionally know that all data transmission ...
2
votes
1answer
183 views
Is symmetric encryption vulnerable to plain-text-attacks?
Imagine that Bob sends a message to Alice for symmetric encryption to send to Charlie. (Only Alice and Charlie know the key.) Alice sends the encrypted message back to Bob to send to Charlie. Can Bob ...
0
votes
1answer
196 views
File Encryption/Decryption in ECB mode [duplicate]
Possible Duplicate:
Removing Padded Value in Decrypted Message
I tried to encrypt and decrypt a file in ECB mode using AES Algorithm but I encountered one problem during decryption, I don't ...
0
votes
1answer
396 views
Removing Padded Value in Decrypted Message
How to remove padded value in Decrypted Message?
I am using AES Algorithm..
ex:
this is the decrypted message..
"abcdefghijklmn "
there is a 2 space in that decrypted message which is equivalent ...
-1
votes
1answer
386 views
How to encrypt a File using AES Algorithm? [closed]
How to encrypt a file using private key in Java.
Adding this question, how to generate the private key for the same.
Before posting I went through some question like How to perform file encryption ...
3
votes
2answers
138 views
Is this streamable combination of encryption and MAC secure?
I want to combine encryption and MAC.
For encryption I use AES-256 with CBC and PKCS5Padding.
For MAC I use HmacSHA512.
I use the Encrypt-then-Mac approach (calculate MAC over the ciphertext and ...
2
votes
1answer
731 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?
...
4
votes
1answer
186 views
Is it secure to use the hash of key as the IV in AES encryption?
I need to store some sensitive data for a program. For each copy of the program, there will be a unique key for encrypting one (and only one) file using AES encryption (OFB). The key will not be ...
3
votes
1answer
323 views
Does the Biclique attack on AES pose a credible risk to its security?
I have heard a lot about the biclique cryptanalysis research on AES, which as far as I know is the closest anyone has got to breaking AES.
Exactly how close did they get? Does this attack propose a ...
3
votes
1answer
329 views
Advanced Encryption Standard Algorithm Secret Key
just a follow up question with this question..
How does the key schedule of Rijndael looks for keysizes other than 128 bit?
A 256-bit key can still encrypt a block of plaintext in 128 bit?
but in ...
2
votes
1answer
303 views
How were the AES key and block length subsets of Rijndael selected?
My intuition tells me it's a trade off between speed and security, but how did the standardisation process select these three seemingly arbitrary key lengths (namely, AES-128, AES-192, AES-256).
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:
...
5
votes
1answer
228 views
How to enhance randomness of AES?
I'm using PHP to encrypt a string and Java to decrypt it on a remote server. To perform the encryption, I'm using the strategy that can be found here.
My problem is that the strings I encrypt are ...
0
votes
1answer
1k views
How does one implement the Inverse of AES' MixColumns
I got an answer in the related question about Mixcolumn for encryption, but how about decryption?
what will I do?
Because it said that I will used this:
During decryption the Mix Column the ...
3
votes
3answers
819 views
How does the key schedule of Rijndael looks for keysizes other than 128 bit?
It said in Wikipedia that:
[....] Rijndael can be specified with block and key sizes in any multiple of 32 bits, with a minimum of 128 bits. The blocksize has a maximum of 256 bits, but the ...
