All Questions
16
questions
0
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1
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474
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AES-128 CBC encryption : ciphertext size seems too large
I am trying to encrypt messages with the AES symmetric algorithm using C language.
I am using a key, an Initialization Vector (IV) and a plaintext, all with a length of 16 bytes.
I expected as output ...
- 1
0
votes
2
answers
125
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Multiple IV CBC
CBC's encryption is not paralelizable but I could divide a 64 block message in 4 16 block parts and encrypt those 4 parts separatly in parallel using a diferent IV for each one. Is this unsecure ? Is ...
- 363
2
votes
0
answers
42
views
Looking for a way to enlarge a message so that any modification to the "enlarged" message makes recovering the original message impossible
Let's say we have a message m of small size.
I am looking for a system $S$ so that $S(m)$ is arbitrarily large, we can easily compute the inverse $I(S(m)) = m$, and any modification to $S(m)$ makes it ...
2
votes
2
answers
283
views
Weakness in a CBC-like XOR cipher
A simple symmetric encryption algorithm can be written as follows:
Input message M and 64 bit key $K$
Divide M into 64 bit size blocks $B_1...B_n$
Get first block $B_1$ and perform bit-wise $\oplus$ ...
- 23
0
votes
0
answers
234
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Another cut-and-paste attack on CBC mode
I am trying to see specific cases of attacks in the CBC mode, in particular, I am investigating some attacks such as Example of a cut-and-paste attack on CBC. Here I have posted something similar and ...
- 131
1
vote
2
answers
146
views
Why is it difficult to encrypt large amounts of information using quantum key distribution?
An article last month claimed that Toshiba Corp. and Tohoku University recently broke the record for the amount of data encrypted using quantum key distribution by transmitting "a few hundred ...
- 165
3
votes
3
answers
3k
views
Example of a cut-and-paste attack on CBC
I am reading the cryptography book by Stamp and there is a cut-and-paste attack on $ECB$ and this is easy to follow because $ECB$ is relatively simple, the problem is that I would like to see an ...
- 131
2
votes
1
answer
263
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Is it possible to narrow down the possible keys used for AES CBC encryption, knowing a given plaintext and its ciphertext, where IV=0? [duplicate]
I'm brute forcing a ciphertext with a given dictionary to figure out which key was used. However, it's been hinted at that there is a way to narrow down the dictionary to a smaller subset of ...
- 21
0
votes
2
answers
124
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Randomly initialised global counter used to encrypt the kth message with $\operatorname{IV} = \operatorname{IV} + k \hspace{5mm} mod \hspace{5mm} 2^n$ [duplicate]
The use of an increasing IV is not secure for a block cipher. That is, using a random IV for the first message then $\operatorname{IV} + 1$ for the second , $\operatorname{IV}+ 2$ for the 3rd etc. How ...
- 1
3
votes
1
answer
441
views
Security of AES after key expansion 4-MB with ECB and CBC
My question is,
how does the security depend or change if I encrypt with AES-128 in total 4-MB of Data?
With Electronic Code Book Mode and
Cipher Block Chaining Mode ?
Does an adversary still ...
- 31
15
votes
2
answers
8k
views
What is the correct way to implement PBKDF2 + AES CBC + HMAC?
I've been doing a lot of reading on the proper way to implement AES CBC mode with HMAC authentication. I've seen many explanations, however, I've had a hard time finding an actual real example (with ...
- 591
1
vote
1
answer
280
views
Is it safe to use the same IV for multiple encryptions in AES CBC mode when you are always encrypting random bytes?
I am generating random bytes (16 or 32 bytes at a time), and I want to encrypt them using a 128 bit AES key in CBC mode. Am I really weakening this horribly if I am reusing the same IV and key each ...
- 13
3
votes
1
answer
2k
views
Generating an IV for ESP 3DES-CBC
I have an application written in C, running in Linux. It uses IPsec (ESP) (manually putting the IPSec packet together) to send certain packets. The algorithm used ...
2
votes
2
answers
901
views
IV Security Clarification
After doing lots of reading on SO and other websites relating to AES cryptography, I am trying to understand the security issues surrounding IV's.
There seems to be a lot of confusion and ...
- 89
4
votes
3
answers
1k
views
Ciphers in CBC mode reveal place of change in plaintext
Theoretically, when using a symmetric block cipher in CBC mode, the current block is dependent on the previous block. Suppose one plaintext is encrypted using CBC, and then one bit of it is changed, ...
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