# All Questions

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17 views

### Why do we use prime numbers apart from hard factorization?

Why are prime numbers important in cryptographic constructs? I am not interested in RSA examples where factorization is the hard problem itself, that makes sense. However wherever I go I encounter ...
45 views

### Difference between Key Scheduling and Key Generation?

I am a little bit confused in the terms i.e Key Scheduling and Key Generation. What is the actual difference between these two terms? According to Wikipedia, the terms are described as: Key ...
40 views

### Any speed up methods for finding the index of a random value produced by the Inversive congruential generator?

The Inversive congruential generator produces random values with: $$x_{n+1} = a\cdot x_{n}^{-1} + b \mod P$$ (special case if $x_n=0$ -> $x_{n+1}=b$) starting with an initial value $x_0$ With well ...
7 views

### What does the server do on receipt of a one-time-password?

I'm trying to understand this question and I do not understand part of it. I have part of figured out, part of it not. Considering the hash function h(i) = (i + 5) mod 7, used in an implementation ...
16 views

### NTRU Key Exchange

With the NTRU scheme, is the key exchange only done by encrypting a symmetric key with the recipients public key (+ authentication) or can something similar to DH/ECDH be done, where public ...
26 views

### If there is an algorithm A can calculate the modular square root of input n, How to use it to get prime factors?

Suppose you are given an algorithm $A$ which takes $y \in \{0, 1, \ldots , N − 1\}$ as input, and outputs $x \in \{0,1,\ldots,N − 1\}$ such that $x^2 \equiv y \pmod{N}$. Design an efficient, ...
36 views

### Is there a point in storing hash or plaintext in the last column of Rainbow Tables

As I read up on rainbow tables, I found that most sources suggest storing a plaintext - the result of Rk(hk) - in the last column, while others just store the hash hk, basically stopping one step ...
34 views

### Difference between Tag and Signature

Is there a technical difference between tag such as tag generated by authenticated encryption, and signature such as the signature generated by a functional signature scheme or homomorphic signature ...
63 views

41 views

### Problem on RSA modification [on hold]

I'm working on the security of the cloud using RSA encryption algorithm. I need help with the simulation of the RSA algorithm against the modified RSA algorithm. Instead of the two prime number , I ...
17 views

### AEGIS/MORUS as a general purpose hash function

Can AEGIS/MORUS, ignoring its output except the tag and with a fixed key and IV, be used as a general purpose cryptographic hash function?
338 views

### Cracking a key using a combination of partial keys

As part of a cryptanalytic attack I've carried out, I used a divide-and-conquer strategy to divide the secret key $k$ into several equal-sized partial keys $k = {k_1, k_2, ...}$. The attack works ...
26 views

### Diffie-Hellman key exchange in four parties [on hold]

I understand the concept of 2 and 3 parties Here is the code of 3 parties ...
29 views

### What is the main difference between Unique signature and Verifiable Random Function?

The output of VRF contains two parts, the first is the output of the VRF hashing and the second is the proof of correctness. In a unique signature scheme, the signature also contains two parts which ...
41 views

### RSA attack using chinese remainder theorem [on hold]

After encryption same message for 3 different people using their public key (187, 3), (35, 3), (247, 3) there are cryptograms (109, 15, 208). What is that message? Use chinese remainder theorem. ...
32 views

### How to calculate base value in modular exponentiation

If you have $a^b \bmod n = c$, and $b,n,$ and $c$ values are given, is it possible to find a value for $a$ within a given range? So is it possible to find $a$ in $a^{2051} \bmod 3149=636$ knowing a ...
140 views

### If a new hash function were made that simply truncated sha-256 to the first N bits, how much insight would it provide into sha-256?

Clearly it would provide perfect insight if all 256 bits were used. What about if 255 were used? Would the general behavior and properties of "sha-255" be expected to be close to sha-256? What about "...
35 views

### Two possible plaintext's using OTP decryption

I am using this cipher-text c = 04 10 12 00 01 08 67 0A 19 65 0F 03 0A 00 with two possible keys ...
1k views

### Why is the core ChaCha primitive not good for use in a CRCF? Why create BLAKE?

Why is the core ChaCha primitive not good for use in a collision-resistant compression function (crypto hash)? Why go through the trouble to create BLAKE? What's wrong with using the core ChaCha ...
27 views

### Simply using password as a third “private key” for PAKE

I'm reading through the development of PAKE protocols, starting with EKE and SPEKE, their potential pitfalls, and what motivates their protocol choices. And I've been wondering, what is wrong with the ...
21 views

### How would you decrypt an affine cipher with only the ciphertext? [duplicate]

If I have only the ciphertext but the alphabet and the value of a and b are all unknown ... how would I go about this? I understand decryption with the key and alphabet, that is fairly easy but if we ...
65 views

### Elliptic curve commitments mod p

As far as I understand secp256k1 is defined over the group p with p = FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F I don't really ...
24 views

### How many ring-LWE samples are required for the (Search) Ring Learning With Errors problem to have a unique solution?

Consider the LWE distribution $\{(\pmb{a}_{i},\left<\pmb{a}_{i} , \pmb{s}\right> + e_{i})\}$ where secret $\pmb{s} \in \mathbb{Z}_{q}^{n}$, randomness is $\pmb{a}_{i} \xleftarrow{\$} \mathbb{Z}_{...
25 views

### What encryption / cryptography method is used here? [on hold]

I have no clue what sort of encryption is used in this piece. Does anyone has any clue? The only information I got is that the dots represents a space.
21 views

### How do I go about managing keys? [on hold]

I need a way to send a message and need a way to guarantee integrity and authenticity. I want to use HMAC but how do I go about using the public/private keys? And how do I get them?
214 views

### How can frequency analysis be applied to modern ciphers?

I am building a computer program that deciphers Caesar, Vigenere and monoalphabetic substitution ciphers. All of those are susceptible to frequency analysis. However, it does not seem to be real-world ...