# All Questions

26 views

### Generate valid signature and message pair without factoring the RSA modulus

How can I generate a valid signature and message pair without factoring the RSA modulus? I have the following information RSA public key = (1612093,97059503) and one plain message signature pair = ...
58 views

### Given p and q of DSA how do you show they are prime?

I am given p = 4916335901 q = 88903 and am asked to show these are prime as well as q|(p-1) in DSA. I am unsure on how to do this, what does q|(p-1) mean exactly?
120 views

### How to calculate the maximum output size for data encrypted with a RSA Private Key?

I have an an encryption algorithm I am working with that looks like this: prv_key_enc(sha1_hash(data)) Where, the RSA parameters are: RSA/ECB/PKCS1Padding 1024 ...
15 views

### Reseeding a PRNG with the generated PRN

Would reseeding a PRNG with the PRN from the previous generation have any effects whatsoever on the quality of the generated numbers; if so, does this depend on the PRNG used, or are the effects ...
28 views

### Attack of an RSA signature scheme using PKCS#1 v1.5 encryption padding

My best interpretation of this question is that Java's crypto API has been subverted to perform RSA signature using PKCS#1 v1.5 encryption padding. Assume the signature $S$ of a message $M$ is ...
44 views

### Right usage of PBKDF2 and login system questions

I'm developing the login part of my application and I was asking myself how to do it right. My application stores some users' data server-side that must be inaccessible from us, so all the content ...
19 views

### Number of possible keys in a Play fair cipher

So for the play fair case, the number of possible keys is : 26x26 = 676 possible keys But if we consider the repeated letters, how many unique keys will the play fair have? I mean how will ...
31 views

### Adding “salt” to “doHash” function in Java

For one of my university projects I am being asked to "Improve the code to satisfy the pre-image resistance requirement." Basically the program is a basic encryption server system, and when I type a ...
1k views

### Who uses the RSA BSAFE library?

Who uses RSA's BSAFE library? Does anyone know what products use it, or have any statistics on how many end users use something that is built on BSAFE? Background: BSAFE is one of the oldest ...
64 views

### Is this Pseudo Random Function (PRF): F(k,x) = f(k,x) - f(k,x-1)

I have a question about Pseudo Random Function. Let $f:\{0,1\}^n×\{0,1\}^n → \{0,1\}^n$ be a secure PRF. $F(k,x) = f(k,x) - f(k,x-1)$ is a secure PRF?
23 views

### SHA-256 Partial Collision of initial 36 bits and more

I was lucky enough to, by brute force, have found two different messages, whose SHA-256 hashes collide in the first 9 hexadecimal characters, which are 36 bits, ...
24 views

### Applications for stream and block ciphers

I'm taking a computer security/crypto intro class and I have two questions which I just don't know the answers to. I've been researching but haven't found what I'm looking for. Our class book doesn't ...
146 views

### Can any one explain Circuit Privacy using fully homomorphic encryption from Gentry's thesis?

Craig Gentry's thesis talks about circuit privacy being straight forward from fully homomorphic encryption in the last chapter. Can somebody explain in simpler terms what that means ? I have read it ...
101 views

### Functional Encryption (for Non Experts)

I recently stumbled across "How to Run Turing Machines on Encrypted Data". Given that it's now possible to run turing machines on encrypted data, what open problems remain in the realm of Functional ...
37 views

Trying to find related answer for a long time, but not convinced yet. What I am trying is to encrypt using RijndaelManaged. To create Key, I am passing password, ...
78 views

### 64 bit Elliptic Curve key?

For a simple proof of concept project i'm (attempting!) to do, i've started looking into openSSL elliptic curve cryptography. However instead of the standard key lengths, 160-512. I'm interested in ...
23 views

### Hill cipher cryptanalysis - known plaintext known key size

Hello I want to know how to go about this problem I know the plaintext "abcdef" and the ciphertext. The key size is 2. I really can't figure out how to find the key for decrypting and encrypting.
39 views

...
625 views

### Calculating the inverse modularity of the determinant for Hill cipher

I'm trying to decrypt a message encrypted with Hill Cipher, but I don't understand how to find the determinant so it solves the equation $det * 1/det = 1 mod 26$. The determinant for my key matrix is ...
### How to generate a random integer in interval $[1, 2^n-1]$ from random integer in interval $[0, 2^n-1]$?
For a project I am working on, I have access to a CSPRNG that outputs a random integer in the interval $[0, 2^n-1]$ for any integer $n$ greater than 0. I cannot use the zero values, so I have my RNG ...