9
votes
3answers
3k views

Is a die implemented in a physics engine truly random?

So, a fair die throw is really random, not pseudo. So, would a RNG implemented as the result of a die throw in a physics engine (say, Newton, Havok, Nvidia's PhysX) be regarded as both ...
3
votes
1answer
101 views

NIST implementation of the Lucas primality test

The NIST standard FIPS 186-4 describes an implementation of the Lucas primality test in section C.3.3. I can follow the algorithm but I am puzzled by step 6.2: ...
2
votes
1answer
332 views

Square roots, prime factorization

I´m stuck in my homework and since its homework, I would rather get some hints than full solution. The problem goes: factorize n = 88416763 in case that you know that the square roots of 51733469 ...
2
votes
0answers
117 views

Timing Attack on OpenSSL by Brumley

I am referring to this paper by David Brumley and Dan Boneh: Remote Timing Attacks are Practical (In proceedings of the 12th Usenix Security Symposium, 2003). In this paper on page 4, Brumley ...
1
vote
1answer
80 views

The use of the term “sound” in cryptography [closed]

We often see the term "sound" in cryptography. What is the sense of this word ? Thank you.
1
vote
1answer
121 views

Is SEAL 3.0 broken?

I'll like to know if SEAL 3.0 (cf http://web.cs.ucdavis.edu/~rogaway/papers/seal.pdf) is broken. I stumbled on Bernstein's website that claimed that SEAL 3.0 has been broken. (cf ...
0
votes
2answers
198 views

Cryptosystems used to generate public key certificate

Where can we find the cryptosystems used to generate public key certificate? Are the cryptosystems under the signature algorithm and signature hash algorithm? Do I need to analyze the packets ...
0
votes
1answer
313 views

RC4 encryption/ decryption with hashing

I am working on RC4 encryption/ decryption algorithm based on the following: A wants to send M to B, for that A did: H = Hash (K||M) C = Ek (M||H) A sent ...
2
votes
0answers
149 views

Multi-round Transposition/Playfair as a secure hand cipher in the computer age

Given that computers can be easily compromised, there is a need for a hand cipher that can withstand computer attack. Clearly the traditional hand ciphers fail. One time pads work. They also have ...
1
vote
1answer
98 views

Is $(f(X), G(X))$ pseudorandom?

If $f:\{0,1\}^n \to \{0, 1\}^n$ is a one-way function, $G:\{0, 1\}^n \to \{0, 1\}^m$ is a pseudorandom generator, and $U_m$ is the uniform distribution over $m$-bit strings. Is the joint distribution ...
2
votes
0answers
115 views

Using same key for encryption and ECBC-MAC k2

ECBC-MAC: $E_{k_2}(CBC-MAC_{k_1}(m))$ If we use same key for encryption (CTR or CFB) and k2 (end tag encryption) in ECBC-MAC in encrypt-than-MAC sheme, is it secure?
2
votes
0answers
66 views

How good is middle cube method with jumbled digits?

I had to make my own prng for a stream cipher for an inter school science project (I am mentioning that a lot). So I thought of cubing the seed instead of squaring it (like in the middle square ...
2
votes
1answer
107 views

Is XCBC where k2 and k3 might be the identical, secure?

XCBC paper says all three keys should be independent. It doesn't say they must always be different. However it seems this is necessary to differentiate padded message and message without padding. ...
1
vote
0answers
242 views

Brute Force AES Calculations

I have an encryption service in which the user decides the length and the type of key, so I would like to build a tool that educates the user on the brute force times for the key they created if using ...
1
vote
2answers
415 views

Is splitting AES ecrypted data safe?

Say I have a key, an iv and an AES/GCM/NoPadding encoded string and I want to split this information between three people such that only jointly can they reveal the ...
2
votes
1answer
194 views

AES mix column stage

In a PDF related to AES algorithm for mix column stage is written: The multiplication mentioned above is performed over a Galois Field. The mathematics behind this is beyond the scope of this ...
1
vote
2answers
271 views

Can DH_anon really be exploited by an attacker?

General consensus is that DH_anon (and ECDH_anon) ciphersuites should be disabled since they offer no way to verify if the server is the one you intend to communicate with. However, I have never run ...
0
votes
1answer
93 views

Showing that $2^{N-1}\equiv1\pmod N$ when $N=2^p-1$ for prime $p$

I got this question on a previous exam and I got it wrong. I've gone back through it several times since then, but I can't seem to get it. I would really like to know how to do it, so if someone could ...
1
vote
1answer
423 views

File format of an $2048$ bits RSA public key

From here, there are $14$ bytes specifying the file format of the key. I am still quite confused about the format bytes. For example, the following public key 30 82 01 0a 02 82 01 01 00 8e a3 d1 c7 ...
1
vote
1answer
76 views

Is Paillier cryptosystem commutative?

Is Paillier cryptosystem commutative? If not, how can we construct an oblivious decryption protocol based on Paillier?
0
votes
0answers
86 views

NRPAD and FPAD padding schemes (Korean Seed?)

I've got an API spec that specifies NRPAD and FPAD as possible padding schemes. I see these being used together with the Korean SEED algorithm. The SEED specification however is void of any padding ...
0
votes
1answer
81 views

Complexity of preimage resistance

Why is the complexity of pre-image resistance $2$ raised to the power of $n$? I have been looking in everything lecture about pre-image resistance, but I still didn't know the answer.
1
vote
1answer
256 views

How do I safely anonymize/hash a unique identifier to protect privacy?

I am building a system to collect a unique identifier (MAC addresses from 802.11 probe requests). The system will have several collection points over a large area, submitting to a central database. I ...
1
vote
0answers
198 views

How represent message in Menezes–Vanstone elliptic curve cryptography

I ask about represent message in Menezes–Vanstone elliptic curve cryptography I now encrypt function as follow $C_1 = (M_1 * K_1) mod\ P$ $C_2=(M2 * k_2) mod\ P$ My question is about how much the ...
1
vote
1answer
705 views

how to calculate non linearity of AES S-box?

S-box has to satisfy different design criteria. How to calculate non-linearity , propagation criteria for an AES S-box?
2
votes
1answer
92 views

How can a good encryptor be made?

I am making an encryptor software for a stream cipher with my own PRNG as a project for an inter school science competition. How can I make one so that after it generates the pseudo random nos. it can ...
0
votes
1answer
220 views

AES: Changing plaintext to state

Can someone explain this to me? For example how M chanes to 0c? Changing plaintext to state:
2
votes
3answers
4k views

Is python a secure programming language for cryptography?

I know Python is a powerful programming language but is it secure for cryptography? I mean is it possible to reverse engineer the program (written in python) and discover the algorithm of cryptography ...
0
votes
0answers
87 views

Is a RSA 2048 bits public key secure [duplicate]

I realize servers such as Google, Yahoo, which use RSA has 2048 bits public key. After comparing those keys, I realize that the public keys share a common property, that is first 9 bytes and last 5 ...
1
vote
1answer
86 views

Why do we need password in a server which uses TLS?

Suppose a server uses TLS to protect communication between us and the server. I observe that in the TLS handshake protocol, password is not mentioned anywhere. Then why do we need to have a ...
1
vote
1answer
257 views

Crypto libary with Commutative Encryption

I want to implement Mental Poker in JavaScript as a toy program and lead in to a larger serious project so I did my research and found Massey-Omura cryptosystem and the Shamir three-pass protocol ...
2
votes
1answer
419 views

Can public key be recovered from ciphertext & encrypted private key?

I'd like to implement something like a write-once public/private encrypted shared secret (no better quick description for the lack of terminology knowledge). I guess, I'm trying to implement HSM. The ...
3
votes
1answer
214 views

Security of RSA with $\gcd(pq, (p-1)(q-1))\ne 1$

The Congress of ThéOùÇa enacted that civilian use of any public-key encryption system is authorized on the territory of ThéOùÇa, subject to meeting certain security requirements published by the ...
0
votes
1answer
59 views

When homomorphic encryption goes wrong?

Consider I have two ciphertext $c_1$ and $c_2$ encrypted using RSA encryption. By definition if I multiply them I'd get $c_1.c_2 \ modN$. My question is what would happen if $c_1.c_2 >N$. Can we ...
0
votes
1answer
178 views

Show that the equal difference property exits for a modified DES encryption system

My cryptology professor gave us this problem on a past homework assignment and I only managed to get one of the 3 parts correct. Needless to say, I want to know how to do the other two parts as well. ...
3
votes
2answers
214 views

What, cryptographically speaking, is a “long message”?

I have read about long message attacks on some cryptographic hash functions. However, I don't quite understand what is being referred to as a "long message". Also, do long message attacks only apply ...
1
vote
2answers
346 views

CRC32 vs. low 32 bits of cryptographic hash

I was having a discussion with a colleague yesterday whose education and experience exceeded mine. He said something yesterday that sounded incorrect to me intuitively, but I don't have the knowledge ...
0
votes
2answers
98 views

what is contained in a public key certificate

Public key certificate is a digitally signed document which verifies the sender is indeed the person. May I know how can the receiver tell the sender is indeed the person solely based on information ...
-1
votes
1answer
471 views

Simplest code for 64-bit block RSA-like encryption/decryption and key generation

Looking for the simplest code in C. Need a set of functions that will first generate a public/private 64-bit key pair, and then the function to code/decode a given 64-bit block, no built-in checksum ...
1
vote
0answers
164 views

Type of cipher used where ciphertext has no discernible pattern, spaces. Type?

What type of cipher could give ciphertext where for example random ASCII chars between say F-z (symbols and numerals inclusive), but with only a few spaces? Frequency of chars shows some similarities ...
1
vote
2answers
442 views

RSA Decryption given n, e, and phi(n)

my cryptography professor gave us this problem for extra credit a while back and I attempted it but I didn't get it correct. I have gone back to it, but I'm even more lost now than I was the first ...
1
vote
1answer
360 views

AES— Brute force attack versus Known plain text attack

I am taking a codes and cryptology course and the following is a questions on a past exam that I could not and still can't solve: ...
1
vote
0answers
79 views

Why is it hard to calculate Logarithm on Diffie Hellman?

i read something about Diffie Hellman. What i don't understand: Alice selects a randomly generated Number, calculates X = g^x mod p and sends X to Bob. If she calculates g^x, she needs to calcluate ...
0
votes
1answer
53 views

RSA signature scheme

In RSA signature scheme, it is a common practice to 'sign' the hash value of the message so that the length can be fit. Question: If we have $s=m^d \bmod n$ where $d$ satisfies $ed \equiv 1 ...
5
votes
2answers
492 views

Are there any digital signature algorithms in common use that result in 32-byte signatures?

I don't consider myself to be an expert in this field, so forgive me if there is an obvious answer. I am having a tough time finding an algorithm that can sign data and output a 32-byte signature, ...
0
votes
0answers
86 views

Low exponent attack against RSA

According to this: http://www.cims.nyu.edu/~regev/teaching/lattices_fall_2004/ln/rsa.pdf One can calculate the message m, if there was no padding scheme involved. My question: is it possible to find ...
0
votes
1answer
124 views

Symmetric vs non-symmetric pairing based crypto

I am trying to find a comparison of how different pairing-friendly elliptic curves perform (in terms of security) in real world applications; I am using PBC library, and it has type A curves and type ...
3
votes
1answer
90 views

Why develop new stream ciphers when block ciphers can be trivally made into streams?

I've just been reading about a new drop-in replacement for the RC4 stream cipher, but why develop new stream ciphers when AES can be made into a stream with a little XORing?
1
vote
1answer
82 views

Is equal length of primes in Paillier cryptosystem is mandate for security reasons?

In continuation to this question about length of primes , I am in doubt about the restriction on length of primes itself . In Paillier cryptosystem , equal length of primes are used . My doubt is ...
1
vote
0answers
61 views

DLOG in $\mathbb{F}_{p^n}^*$?

Assume that we are given an element $g\in \mathbb{F}_{p^n}^*$ and $g$ does not belong to any of the smaller subfields contained in $\mathbb{F}_{p^n}$. If the degree of $g$ is some number $q$, how much ...

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