All Questions

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Is H(x) = x^2 (mod p) pre-image resistant, second pre-image resistant and/or collision resistant

I have the function $H(x) = x^2 (mod p)$ where $p$ is a prime of length n bits and this function maps to the message $x$ to a n-bit hash value $H(x)$. I need to find out if it is pre-image resistant, ...
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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 ...
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Is ecryptfs safe after unmounting but before turning off the computer

I've read that one of the vulnerabilites of ecryptfs is leaks to swap memory, and that the solution is to encrypt swap. But even if swap is encrypted, it's still open until I reboot. I've also read in ...
121 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 ...
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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 ...
36 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 ...
47 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 ...
22 views

Number of possible keys in a Play fair cipher [duplicate]

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 ...
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Adding “salt” to “doHash” function in Java [on hold]

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 ...
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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?
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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, ...
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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 ...
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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 ...
38 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, ...
83 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 ...
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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.
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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 ...