2
votes
1answer
151 views

What is the best current way to cryptographically secure databases?

I'm currently working on a proposal for some secure complete system and one of the things currently lacking is the database security. However I don't want to roll my own crypto there and thereby need ...
2
votes
1answer
107 views

Would SHA-1 be safe for certificates with short validity?

There are articles floating around the topic of SHA-1 deprecation. The gist of it is that in (mostly) developing countries, people are still using mobile/computing devices that are 5 years old (or ...
2
votes
2answers
177 views

Given a pseudorandom function F, is $(F_k(r) \; | \; F_k(r + 1))$ also a PRF?

Given: F is a pseudorandom function, G is a pseudorandom generator with $l(n) = n+1$. The following schemes should be classified as being insecure, IND-COA secure, IND-CPA secure. To encrypt $m \in \...
2
votes
3answers
98 views

2 Part Encryption

Can anyone tell me if an encryption / decryption scheme like the following exists? Encrypted1 = SomeCryptoFunction(Data, Key1) ...
2
votes
1answer
127 views

Does DES support different keys that lead to the same result?

While bruteforcing a ciphertext, I've found multiple keys which produce the same result. Mode is DES with ECB and PKCS5 padding. ciphertext is ...
2
votes
1answer
91 views

Problem reproducing AES results

First of all, I just implemented AES because I wanted to understand how it works and as a challenge to see if I could do it and I won't use to encrypt anything important, ever. The (German) Wikipedia ...
2
votes
1answer
95 views

Why can you reverse a modulo function when knowing its primes

We are dealing with cryptography in school right now and superficially went over the Rabin cryptosystem with the (apparently usual) example of p=7 and q=11 etc (we didn't do RSA). I understand that ...
2
votes
2answers
120 views

Given PRNG $G(s)$, why is $G(s) || G(s+1)$ not a PRNG?

I have given a pseudorandom Generator $G(s)$, $|s|=n$ whose expansion $l(n)$ is $>2n$. I also know that $G^\prime(s) := G(s_1,\ldots,s_{\lfloor\frac{n}{2}\rfloor})$ is a pseudorandom generator. Now ...
2
votes
2answers
95 views

Securely generating auth tokens

(Disclaimer: I'm an experienced server-side Java programmer, but with little crypto experience.) Objective: I've got a login server which, given a login+password pair, should issue a unique auth ...
2
votes
1answer
298 views

RSA vs ECDSA/ECDH

So we've been using RSA for a while now. I wonder, is it still secure? I'm wondering whether surveillance agencies can at this point read traffic encrypted with say, TLS_ECDH_RSA_WITH_AES_128_GCM? ...
2
votes
3answers
614 views

Prevent replay attack without storage

I am designing a set of low-power sensing motes. Each mote will communicate to a central base over RF. I want the mote to be able to authenticate itself with the base, and send its data without being ...
2
votes
1answer
88 views

What is the difference between “securely realizes” and “securely implements”?

In some security proofs it is stated that "a protocol securely realizes an ideal functionality" while in some others "a protocol securely implements an ideal functionality". Is there a meaningful ...
2
votes
1answer
151 views

Single bit error in CBC

Why does a single bit error when using the CBC block cipher mode of operation affect the decryption of a block (Oj) with a probabilty of 50%? And in the following block, why is the one bit error in ...
2
votes
2answers
46 views

What is the correct way to notate elliptic curve properties

When looking through elliptic curve and modulus posts i can see many examples of people referencing $p$ and $n$, in upper and lower case, and sometimes $Q$ is written instead of $p$ or $P$, and I ...
2
votes
2answers
115 views

Inverting RSA function

I am in high school and I am writing a paper on RSA. I want to show that low values of the public key exponent can make it easy to 'invert' the function so that the encrypted message can be recovered. ...
2
votes
2answers
73 views

Diffie-Hellman secret key choices

I'm trying to understand why the secret keys used by Alice and Bob in Diffie-Hellman are $a,b ∈ ℤ∗p$. Say $a$ is $p - 1$, wouldn't the transmitted $g^a$ be 1 mod $p$ by $FLT$? Now anytime a ...
2
votes
2answers
75 views

Is it safe to use single-block AES for mutual authentication?

I read the question Symmetric mutual authentication with client using a derived secret and its answer which, if I'm not mistaken, assert that it should be safe to use the proposed protocol for mutual ...
2
votes
2answers
102 views

Using related pair of cryptographic keys to open/seal plaintext

I am using curve25519xsalsa20poly1305/fn.seal from sodiumoxide crate written in Rust language which is a wrapper over libsodium ...
2
votes
2answers
223 views

Authenticating code securely and generating a certificate

I'm working on a product with strong security. Essentially there is an App, downloaded from the iTunes App Store. When the App starts up, it generates a strong RSA keypair and stores it in the ...
2
votes
2answers
94 views

How strong can multiple encryption be?

Suppose I encrypted a homophonic substitution cipher at the level of syllables, trigrams, digraphs, and individual letter with a Vigenere cipher using the keyword cryptography. I would then encrypt ...
2
votes
2answers
123 views

Digital Signature Attack

In a typical digital signature scheme in which in order to sign we compute: hash of the message: $h(m)$ resulting hash signed with the private key $[h(m)](private key)$ If there were a collision ...
2
votes
1answer
245 views

Any reason to use Shamir given faster XOR threshold secret sharing algos?

TL;DR: Is the Kurihara algorithm really what it purports to be (dramatically faster but equally secure replacement for Shamir Secret Sharing)? https://scholar.google.com/scholar?q=kurihara+secret+...
2
votes
1answer
168 views

Extension of a password hashing algorithm using Fibonacci

I am right now taking a class named Applied Cryptography and our final project is to create a password hashing method using at least one existing algorithm and then add additional steps to make it ...
2
votes
1answer
179 views

Is there a secure source of entropy on a typical microcontroller?

On a device that does not have a hardware RNG, what is the best source for entropy? Some options and pitfalls floating around: Use the ADC to read something analog: can become deterministic if ...
2
votes
2answers
254 views

Is Checksum to file back decoding possible?

So, I was having this weird thought. If the checksums(MD5 or SHA...) are unique to any file and are modified if any part of the file is edited, why cant the checksums be decoded back to get the ...
2
votes
1answer
76 views

Permuting Small Sized Set in Practice

Imagine we have a set $S$ of $m$ elements and we wants to permutes the set elements. Thus the original position of each element should be unknown after permuting. If we define a permutation function ...
2
votes
2answers
195 views

Transforming Gaussian random $[0,1] $ numbers to uniform $[0,255] $

I am not exactly sure if this is for math stackexchange or crypto: A TRNG outputs numbers in $[0,1]$ in a Gaussian distribution. I would like to convert them into uniform random bytes ($[0,255] $) to ...
2
votes
2answers
52 views

Correctness of ideal protocol of MPC in presence of malicious adversary

In presence of malicious adversaries in ideal protocol of Multi Party Computation, how can honest parties get the correct output? i.e., corrupted parties modify their inputs and give to the trusted ...
2
votes
1answer
151 views

Ring-LWE elliptic gaussian distribution

I am currently trying to understand this Ring-LWE article: http://www.cims.nyu.edu/~regev/papers/ideal-lwe.pdf and I have a question. Firstly, it is mentioned in the paper that we can view the ...
2
votes
2answers
132 views

Inner product with homomorphic encryption

I want to do a very simple thing: Given two vectors, I want to encrypt them and do some calculation, then decrypt the result and get the inner product between both vectors. I want to do this as fast ...
2
votes
1answer
140 views

Proving membership of a group without revealing identity

I have an interesting problem for which I've failed, so far, to find an elegant solution. Imagine that a user needs to repeatedly prove to public observers that they are a member of a trusted set ...
2
votes
1answer
349 views

Attack for RSA 1024 bit with Low Public Exponent

I am facing a challenge at university. Our teacher give us the challenge to try to break an RSA 1024 bit. We have public modulus N and public exponent e (0x03), we don't know the padding. We have a ...
2
votes
2answers
222 views

RSA private key d knowing e,n

I need to find RSA private key $(d, N)$ knowing $(e, N)$. It's "own" RSA implementation. As i know $p$ is random 70 bit number, then $q$ is $p-2^{10} < q < p+2^{10}$ $d$ is max 16 bit long with ...
2
votes
1answer
81 views

Is “Bit Independence” of SHA-2 hashes secure?

I know bit independence is good in SHA2 function output, but is it truly 100% secure? For example: Y = SHA512(secretKeyNonce256bit) A = first 32ytes / 256bits of Y, used as message encryption key B ...
2
votes
1answer
128 views

Is randomsound for increasing entropy pool not doing what it is supposed to do?

I am using randomsound because I thought it would be a good idea to inject some additional entropy into the entropy pools of my linux machines (clearly those machines have a corresponding sound card). ...
2
votes
1answer
79 views

Is it right about an example of bilinear map $e$?

The equation for the elliptic curve is $y^{2} = x^{3} + x$ and is defined over the field $F_{q}$ for some prime $q\equiv 3 \pmod 4$, and set $q=307$. Choose random generator $g=[182, 240]$. My ...
2
votes
1answer
166 views

How do we guarantee plaintext is coprime in RSA?

The specifications for RSA state: $P^{\phi(N)} \equiv 1 ~mod~N$ if and only if $P$ and $N$ are coprime. Here $P$ is the plaintext and $N$ is the product of two suitable primes $x_1, x_2$. My question ...
2
votes
2answers
387 views

Elliptic curve brute forcing

I have elliptic curve of equation $y^2 \equiv x^3 -x $. And the coordinate of points $Q$ and $P$. I want to solve $Q=[k]P$ (where $k$ is the unknown) by testing all possible $k$. Is this the right ...
2
votes
1answer
170 views

What's the differences among Blind Computation, Secure Multi-Party Computation, Secure Circuit Evaluation and Homomorphic Encryption

We know that Blind Computation, Secure Multi-Party Computation, Secure Circuit Evaluation and Homomorphic Encryption all can process the encrypted data, but I am puzzled by them. What are their ...
2
votes
1answer
487 views

Why is diffie-hellmangroup1-sha1 used instead of diffie-hellman?

For SSH why is diffie-hellmangroup1-sha1 used instead of just diffie-hellman? In other words, why is the hash function used?
2
votes
1answer
302 views

Concatenation of two strong hashes may have striking weakness

For any hash functions $H_0$ and $H_1$, it is easily proved that their concatenation $H_0\|H_1$, defined by $(H_0\|H_1)(X)=H_0(X)\|H_1(X)$, is at least as resistant as the strongest of $H_0$ and $H_1$ ...
2
votes
1answer
227 views

Differential Fault Analysis of AES

Let's say: an error is induced into an implementation of the AES-128 to produce a faulty ciphertext. The error is a one-byte eror and is always induced on the last state byte, during round9, before ...
2
votes
2answers
159 views

How obvious is it to decrypt numerics encrypted with a reused one time pad?

For instance say you encrypt text using the one time pad and you end up with some scrambled text that appears illegible. If you reused the key for multiple times for enough text, someone could ...
2
votes
1answer
106 views

Hash “Preimage by product” resistance

Let H() be a hash function that achieves collision resistance as well as first and second preimage resistance. Let's equip the output set of H of a multiplicative group structure, more precisely a ...
2
votes
2answers
192 views

Equivalent key size between HMAC and AES?

I have seem comparison between AES and RSA, e.g., AES 128 bit key is equivalent to RSA modulus 3072 bits. Is there such comparison between AES key size and HMAC?
2
votes
1answer
701 views

How to accurately calculate Unicity Distance for English?

The Unicity Distance for the DES cipher is around $8.6$ characters, and can be calculated using the $U=H(k)/D$ formula, where $D = R - r$, and where $R = 8$ is the number of bits in a byte (ASCII is 7 ...
2
votes
2answers
489 views

Explanation of each of the parameters used in ECC

I'm having a very difficult time finding a clear explanation of the parameters used elliptic curve cryptography. I know for certain that $p$ is the number or order or whatever of the given field that ...
2
votes
2answers
880 views

Proving the semantic security of the One Time pad

Currently hearing a lecture on cryptography, and the professor gave us the definition of semantic security, which is roughly the following (formally not quite complete, but you get the idea): ...
2
votes
2answers
159 views

I don't care about replay attacks. What should I do with the nonce in nacl?

My system forwards encrypted and/or signed messages on a gossip network. Replay is part of the design. What should I do with the nonce? I'm tempted to just set it to the same number always. Is this a ...
2
votes
1answer
140 views

what are multi-primes and how are they different from semiprimes?

I came to know of semiprimes recently. The simplest explanation of semiprimes is you take any two prime numbers and you multiply them, say 3*11 = 33 in which case 33 would be a semiprime. The numbers ...

15 30 50 per page