Latest Crypto related questions

Score: 0
Kim Mỹ avatar
Can I use half of 256 bit key as AES 256 IV?
cn flag

After some google research, I have found out the IV used in AES 256 bit encryption must be a 128 bit key.

My AES256 encryption is processed with key of random 256 bit key and IV generated of text string.

I am thinking about MD5 to generate such key, but MD5 seems outdated.

So Should it be okay if I use SHA256 generate a 256 bit key than split the hex string of the key equally into 2 parts and use the f ...

Score: 1
How lattices and LWE are connected?
eg flag

I am a last-year master student in pure mathematics and I am working on my thesis. I am working on a connection between lattice-based encryption and Ring LWE and between Ring LWE and Homomorphic encryption. For the second part, I manage to find an appropriate paper to provide me with some information. However, with the connection of the lattice-based encryption and LWE things seems to be messier. Apart ...

Score: 0
RSA / AES issue : Decryption
cz flag

I perform the following commands because I need to decrypt a file -encryption key file- (which is longer than module):

cat key.enc | base64 -d > encryptedrawfile.txt

openssl rsautl -decrypt -inkey privkey.pem -in encryptedrawfile.txt -out key.txt

I obtain the following key.txt: ’àÝ g ™`çïrM¡.€:

Now I need to use encryption key decrypted to decrypt a file using this key considering aes-csc-12 ...

Score: 0
Thắng Vũ avatar
Fast implementations in c++ to find linearity of 16! sboxes?
cn flag

I have to analize 16! of 16 bytes sboxes but my code is to slow to handle it. Anyone have any fast implementation on that? Thank you.

Score: 1
Hern avatar
What are the uses of shared cipher texts and signatures?
is flag

In Distributed Key Generation(DKG), why is there a need to actually create a master secret which can then derive into a single public and private keypair(for signatures) and a secret key(encryption)?

I would like experts here to explain to me (explain in a layman's way) because it seems to me that having a master secret to both encrypt/decrypt and signs messages are not that recommended in terms of secur ...

Score: 0
Enumerating values from a linear congruential generator java Random()
mx flag

During my research on a java application, I discovered that the nextInt(64) function of the java.Random() class is used to generate the encryption key.

The key size is 16 bytes. I know that this generator is not recommended because it is vulnerable. Especially in this case, the value of each byte of the key is selected from a short range from 0x0 to 0x40.

I already got acquainted with the fact that  ...

Score: 0
Andy avatar
Only DRBG is used for PGP or could use other PRNG?
pe flag

-RFC4880 refer to DRBG at https://www.rfc-editor.org/rfc/rfc4880#section-16.2 -Could we apply other PRNG such as enocoro/photon for pgp?

Score: 1
cryptobeginner avatar
Even-Mansour Cipher: Efficient algorithms for sampling a random permutation
cn flag

My understanding of the Even-Mansour cipher is the following:

  • We draw a random permutation $P$ from the set of all permutation $P: \{0,1\}^n \rightarrow \{0,1\}^n$. This permutation is public.
  • We generate two random keys $k_1, k_2 \in \{0,1\}^n$.
  • To encrypt a message $m \in \{0,1\}^n$, we compute $E_{k_1, k_2} = P(m \oplus k_1) \oplus k_2$.

What kind of algorithms exists that allow us to efficientl ...

Score: 0
phantomcraft avatar
Entering a word in a S-Box (like Feistel ciphers do) and keeping the S-Box secret: Could this be called encryption?
pf flag

Let's suppose I take a data block of 64-bits and use it as an entry in a (big) S-box, and keep the S-box secret. S-box would be the "key". For "decryption" I just enter the result of this operation in the S-box again to get the "plaintext"

For making all the blocks different each other in a sequence of them I would use a scheme like CBC, enter the first block in the S-box and XOR the result with  ...

Score: 0
JAAAY avatar
Difference between Non-Interactive Secure Multiparty Computation (NISMPC) and Fully Homomorphic Encryption (FHE)
us flag

Until recently, I only knew about SMPC* and FHE, but now I just encountered the term NISMPC. I was wondering what is their difference and what is their difference in their use cases?

  • Sometimes in bibliography, SMPC is referred to just as MPC referring to the same thing.
Score: 5
RSA Signing - Existential forgery and message prefix question. It's a weird one
ua flag

I'm new to this. Please be kind. I have a theoretical question that I would like sanity checked:

Bob and Alice are doing RSA signing without a hash function -- just putting a message in, and getting a signature out.

The messages Bob and Alice are sending each other are random numbers.

Without a hash function involved an attacker can create a message with the signature they want. But they can't control  ...

Score: 0
WhyMeasureTheory avatar
Implementation of the chaotic map to produce (pseudo)-random number
in flag

For my project I used Henon map to generate (pseudo)-random number. I used the following code to generate the matrix of (pseudo)-random number.

def generate_by_henonmap(dimension, key):
    x = key[0]
    y = key[1]
    # Total Number of bitSequence produced
    sequenceSize = dimension * dimension * 8
    bitSequence = []  # Each bitSequence contains 8 bits
    byteArray = []  # Each byteArray con ...

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