Latest Crypto related questions

Score: 0
rsa attack with plain text, cypher text , public key
us flag

starting from the fact that there are different attacks on RSA, based on the starting situation, for example there are different studies, on attacks that find the private key having the freedom of an original arbitration text. But I was wondering this, in this situation: you have several plaintext texts and their encryption, you also have the public key (because you use RSA to authenticate) is it possib ...

Score: 0
Yotam Sofer avatar
does OFB mode has diffusion on the plaintext?
cl flag

In some block modes, if we change one bit (or more) in the plaintext, the whole block\ciphertext will be changed (i.e ecb: block will be different. cbc: whole ciphertext will be different) Does encryption in OFB mode will defuse the text? if we will change one bit in the plaintext, more than one bit will be changed in the ciphertext ?

Score: 0
When inputting a stream of raw binary values to a SHA256 hash and a value of 10000000 is encountered in the input stream, does the hash end?
ng flag

I am acquiring binary data from a sensor and storing it in a file. As each byte of data is read from the sensor, it goes into a SHA256 hash. The length of the acquired data stream varies from one session to another. It is possible that an individual sample having a binary value of 10000000 could be encountered in the input stream prior to the end of the session's stream. How does the SHA256 hash algorit ...

Score: 1
How to reverse engineer Salt from password, iterations, and key?
de flag

Let's say that a random key is derived using the following function (PBKDF2).

key = fn(password, salt, iterations)

Q1: How can I reverse engineer the salt from the password, iterations, and the key?

Q2: If the same salt is used for generating the key, how can I reverse engineer the salt from the password, iterations, and the key?

Score: 0
JDop avatar
Chinese remainder theorem in ECDSA for parameters in secp256k1?
jp flag

It is known that it is possible to apply the Chinese remainder theorem and attack RSA under precise conditions.

https://tls.mbed.org/public/WSchindler-RSA_Timing_Attack.pdf

But the question is, can the Chinese remainder theorem in ECDSA be applied to the parameters in secp256k1?

Score: 3
fgrieu avatar
What short signature standard?
ng flag

In some applications like QR-codes, saving 25 bytes out of 100 makes a difference in usability.

What choice is there for a signature scheme with (most important criteria first)

  1. As small as possible signature size (for a signature with appendix) or as small as possible added size (measured at 40-byte arbitrary message for a signature scheme with message recovery, but I'd prefer avoiding these), at co ...
Score: 0
Does Enveloped Merkle-Damgård require last compression to be done in one compression?
cn flag

Does "Enveloped Merkle-Damgård" require last compression to be done in one compression function call?

Since I have compression function with same size of input/output, I would have to make two compressions in last "enveloping" step. Does this invalidate their proofs?

Score: 1
Multiplication of pairings vs. exponentiation of the group elements
cn flag

Assume that we have a pairing as $e:G_1\times G_2\rightarrow G_T$. such that $g_1$ and $g_2$ are the generator of $G_1$ and $G_2$ respectively. In a protocol I have $A=\prod_{i=1}^n e(H(i),pk_i)$ where $H(i)\in G_1$ and its discrete-logarithm is unknown (since it is a random oracle) and $pk_i\in G_2$. I can design another protocol such that I can compute my target value $A$ in another way i.e., $A=e( ...

Score: 0
adi avatar
What authenticated encryption do kerberos use in windows?
cn flag
adi

I have learned about the kerberos protocol and seen that the windows version uses a couple of authenticated encryption schemas (like rc4-hmac-md5).

What type of authenticated encryption is it? Is it a:

  1. Encrypt-then-MAC

  2. Encrypt-and-MAC

  3. MAC-then-Encrypt

Thank you

Score: 0
Zi-Yuan Liu avatar
Does CPA model the challenge plaintext are the same
co flag

For a CPA-secure encryption scheme, suppose that there is an adversary who can find that the two ciphertexts are encrypted from the same plaintext.

Is this encryption scheme still CPA secure?

Or, CPA security only models whether the adversary can find out what plaintext is encrypted, regardless of the above situation

Score: 1
vince.h avatar
Short randomness in ElGamal and Paillier
vn flag

In the Paillier cryptosystem the encryption of $m \in \mathbb{Z}_N$ with randomness $r \in \mathbb{Z}_n^*$ is $c = g^m r^n \bmod{n^2}$.

My question is, what if short (E.g. 512bits) $r$ is used? Similar question exists for Elgamal encryption.

There are lots of topics related to ElGamal and Paillier, but I searched and did not find any topics regarding this.

Score: 1
RC6 Integer operations in modulo 32 between two 32-bit blocks
us flag

I am new to cryptography and I am trying to code the RC6 (Rivest cipher 6) algorithm. The algorithm requires addition, subtraction and multiplication in modulo 232. If I am performing these operations between two 32-bit blocks how would this work?

Any help would be appreciated because I can't seem to find any detailed explanation on this which would help me write code on how to execute these operations. ...

Score: 1
Bonjour Dolo avatar
Homomorphic sorting of a vector of FHE ciphertexts
ru flag

Bonjour à tous, Je dispose d'un vecteur contenant 15 nombre réel chiffrés avec les schéma de chiffrement homomorphe CKKS. Mon problème est que je souhaite trier ce vecteur par ordre croissant. Je ne sais pas comment m'y prendre. Votre aide me sera la bienvenue. Merci

Hello everyone, I have a vector containing 15 real numbers encrypted with the CKKS homomorphic encryption scheme. My problem is that ...

Score: 0
7337dtd avatar
Decrypting two time pad using the Vigenère scheme
de flag

If I define that $$m\oplus k :=(m+k) \mod 26$$ where A is 0 and Z is 25. How do I efficiently/properly decrypt if I was given two-time pad ciphered texts? I know that $m_1\oplus m_2 = c_1\oplus c_2$. Need to go efficiently to attack to get the two original texts from here.

Score: 1
I need a simple cryptographic code to put on a t-shirt
cn flag

I never worked with cryptography but I wanted to add an easter egg on the design I'm making for a t-shirt. I need it to have a key that will be embroided on the front design wich is:

15122017

that can be used to decrypt the text that is in the back (still have to think what to put). I tried testing the encryption on Cryptii.com with the rc4 encryption and it worked well both ways but when I tried decod ...

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