2
votes
3answers
342 views

Implementing a one-time pad without binary?

This is a program that I found which takes a purely alphabetical message, converts the letters to their ASCII values and combines them with the ASCII values of an alphabetical key (wrapping around ...
3
votes
1answer
261 views

Generating an IV for ESP 3DES-CBC

I have an application written in C, running in Linux. It uses IPsec (ESP) (manually putting the IPSec packet together) to send certain packets. The algorithm used ...
7
votes
6answers
346 views

Do ciphertexts leak information about their algorithmic creators?

If an adversary holds thousands of encrypted files that were encrypted with the same cipher, can he determine which cipher method had been used on the files? Assume that the adversary has no prior ...
-1
votes
1answer
72 views

Is size Q equal to size SHA(Q)? [closed]

Assume d is a 128 bit random integer and P is base point of an elliptic curve and Q = dP is a point on the elliptic curve and SHA is a hash function with 128 bit output, my question is: Is size Q ...
8
votes
4answers
270 views

Is there a public key encryption scheme with optimal key size?

Symmetric encryption schemes such as AES have known security levels equal to their key sizes (i.e. breaking an encryption with an $n$ bit key needs about $2^n$ work steps). Elliptic curve encryption ...
1
vote
2answers
368 views

Quadratic residue problem on composite integers

Its believed that the quadratic residue modulo $n=p·q$ for large primes $p$ and $q$ is intractable, which forms the basis of some cryptosystems. However, it is solvable if the factors of $n$ are ...
4
votes
1answer
192 views

hardware and software optimizations for Salsa20

I'm using the Crypto++ implementation of Salsa20 for a software project we are working on and I'd like to know if there are any SSE or software optimizations that will increase the speed of the CSPNG? ...
3
votes
2answers
243 views

Is it possible that two distinct RSA moduli share both of their prime factors?

I am using an algorithm (can be found here1) that can compute efficiently the GCD of multiple RSA keys. It intended for RSA keys that were generated with low entropy and may have one of their primes ...
7
votes
2answers
237 views

Why have hashes when you have MACs?

It would seem to a naive eye that if you have a MAC, you have a hash function: use a key that all the parties know (such as all-bits-zero). A potential application would be a resource-constrained ...
1
vote
1answer
178 views

Does CBC encryption of a hash provide authenticity?

Given a message $M$ and a cryptographic hash function $H$, let $f(M) = E_K(M || H(M))$ where $E_K$ is AES-128-CBC encryption with PKCS#5 padding. Take $H = \textrm{SHA-256}$ if it matters. In other ...
1
vote
0answers
405 views

Keepass Twofish plugin security

Keepass is a well known open-source password manager program, with plugin support. One of the offered plugin is a twofish encryption mode of operation in lieu of the build-in AES algorithm ...
5
votes
1answer
320 views

What signature schemes allow recovering the public key from a signature?

It seems to be possible to retrieve the (public) key used for creating an ECDSA signature just from the signature alone. This seems like an interesting property; as far as I know, RSA doesn't share ...
1
vote
1answer
112 views

Three-way key exchange with elliptic curves without pairing

Assume that there are three users, each with their own secret key $d_i$ and the corresponding public key $Q_i = d_i \cdot P$, such that $Q_i$ is a point on an elliptic curve and $P$ is a base point on ...
-2
votes
1answer
111 views

what is pairing in cryptography? [closed]

Let $G_1, G_2$ be additive groups and $G_T$ a multiplicative group, all of prime order $p$. Let $P $ in $G_1, Q $ in $G_2$ be generators of $G_1$ and $G_2$ respectively. A pairing is a map: $e:( ...
5
votes
1answer
238 views

What does ''latency'' really mean when a block cipher is partially unrolled?

Typically,I think latency should mean the time from the first plaintext input to the first ciphertext output, when the block cipher is not totally unrolled (such as AES unrolled with 2 rounds). If I ...
-1
votes
1answer
70 views

The specification of modern, non-communicating cipher machinery [closed]

I'm looking for references, papers or guidance on a class of system which I have not seen widely discussed. Consider powerful electronic machinery which remains in the custody of communicating ...
1
vote
1answer
7k views

What is the “shared secret” used for in IPSec VPN?

Can somebody explain what the "shared secret" and "password" do when opening/creating a VPN tunnel? In this specific case I setup a VPN to my Fritz!Box and I had to provide a shared secret (which was ...
2
votes
1answer
138 views

SHA256 Round Equivalence

I have calculated the average number of operations in 1 round of SHA256 as follows: Additions: 9.25 Bitwise Rotations: 9 Bitwise Shifts: 1.5 Bitwise AND: 5 Bitwise XOR: 10 I have certain ...
4
votes
0answers
326 views

Reasons for Chinese SM2 Digital Signature Algorithm

In the IETF RFC draft named "SM2 Digital Signature Algorithm" a signature algorithm is specified. The RFC does however not mention why this signature algorithm has been defined. Nor does it specify ...
2
votes
1answer
140 views

Multiple parties must encrypt and get the same result

Hopefully this question is not too simple - I did some research but with encryption I really don't want to make a mistake. Our scenario is that multiple groups need to encrypt a number and arrive at ...
1
vote
1answer
272 views

Is the salt value a secret or can it be stored in cleartext just like the IV? [duplicate]

From Wikipedia I read that the IV is used to randomise the mapping of cleartext to cipher text and that the IV is usually stored (in cleartext) together with the encrypted record. ...
0
votes
2answers
98 views

Create a field in PBC

Edited (I removed the emphasize on Integers): My question is partly cryptography and partly programming, I would appreciate any help on any aspect of it :) I want to use PBC library to do the ...
4
votes
5answers
521 views

Is it theoretically possible to construct a string that contain its own hash value?

After saw the xkcd comic self-description, I wonder is it theoretically possible to construct a self-descriptive string that contains its own hash value? Let's say the string's md5 value is ...
3
votes
1answer
542 views

Is there any implementation of scrypt that allows a specific limit on memory?

The answerer has commented that scrypt's memory use is "only a function of r". $\:$ However, he has not addressed my argument that it also depends on N, in one of my comments from over 5 days ago. I ...
1
vote
0answers
119 views

Can anyone explain most popular RSA attacks like I'm 5?

Suppose I implement RSA myself in C and I use just the formulas from number theory. What attacks would my implementation be vulnerable to? Can anyone explain this to me like I'm 5?
5
votes
1answer
840 views

RSA random prime generator

What is the current standard of random bit generators? RSA relies on two large prime numbers, and I am wondering what is the algorithm used to generate such numbers?
7
votes
2answers
1k views

Why is the P-521 elliptic curve not in Suite B if AES-256 is?

In the NSA's document, "The Case for Elliptic Curve Cryptography", we have ...
6
votes
2answers
1k views

Will our app be FIPS 140-2 compliant if we use our own AES algorithm implementation?

We are in the processing to understand if our software applications is FIPS 140-2 compliant or not. Currently in our application, we are using our own implementation of AES algorithm. AES is a FIPS ...
8
votes
1answer
6k views

How does RSA signature verification work?

I understand how the RSA algorithm works for encryption and decryption purposes but I don't get how signing is done. Here's what I (think) I know and is common practice: If I have a message that I ...
1
vote
1answer
155 views

Understanding the “cube-root math” behind an RSA signature forgery

I'm trying to understand the math outlined in this paper on a RSA signature forgery attack. I understand it except for one aspect of how the cube root (that makes the forged signature) is computed. ...
1
vote
2answers
212 views

How resilient to attackers with extreme resources available is this encryption method?

How could the following scheme be made more resilient to attacks capable of utilizing massive amounts of resources? Assume all random values are cryptographically secure. Key derivation: scrypt ...
1
vote
1answer
182 views

Brute force attack on RSA - success criteria?

In a hypothetical discussion we ended up with a concrete question I'd like to find the answer to: If you try to brute force an RSA encryption, but the original vale which was encrypted was just ...
4
votes
2answers
1k views

Is a 1024-bit DSA key considered safe?

I created my PGP key in 2000. I’ve revoked the older, weaker sub-keys in favor of a 4096-bit RSA one, but the primary key is 1024-bit DSA. I read on Wikipedia that… NIST 800-57 recommends lengths ...
6
votes
2answers
584 views

Strength of CBC with Ciphertext Stealing

Is CBC with Ciphertext Stealing (CTS) considerably weaker than CBC with padding such as PKCS7? I would imagine the most common situation where CTS is necessary would be due to some size constraint of ...
6
votes
1answer
210 views

How relevant are hardware implementations of crypto algorithms?

All of the SHA-3 finalists discussed speed and efficiency of a hardware implementation of their algorithms. How relevant are such details? I'm curious about who commercializes hardware that ...
2
votes
3answers
328 views

Identification of correct plaintext after decryption in Rabin cryptosystem

In the Rabin cryptosystem, decrypting a message can produce four different outputs, of which only one is the correct plaintext. How can one know which of the outputs is the correct one?
4
votes
1answer
179 views

OMAC/CMAC constant for different block sizes

OMAC/CMAC only specifies constants for 64-bit (0x1B) and 128-bit (0x87) block size. I would like to know how to get constants ...
4
votes
6answers
624 views

Generate Elliptic Curve Private Key from User Passphrase?

I'd like to generate a private elliptic curve key from user input like pass phrase. Is the best way to do this with a key derivation function like PBKDF2? Is there a better way? Edit (based upon ...
2
votes
1answer
843 views

Am I insecurely implementing AES in Python? [closed]

My name is Pat, I'm a rising high school senior interested in Comp Sci. I've taken interest in cryptography following the NSA scandal. Since this is the first time I've ever implemented encryption ...
6
votes
1answer
158 views

Is there a security proof for the Triple-DES construction in the ideal cipher model?

Suppose one has an ideal block cipher $E \: : \: \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^k \times \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^w \: \to \: \{0,\hspace{-0.04 in}1\hspace{-0.03 in}\}^w ...
6
votes
2answers
356 views

Why are HOTP and TOTP implementations all using 6 digits and not more?

I was checking the RFC's after wondering for some time. In RFC 4226 - HOTP: An HMAC-Based One-Time Password Algorithm, it states on the appendix: A simple enhancement in terms of security would be ...
2
votes
1answer
350 views

Textbook-RSA meet-in-the-middle attack against other RSA based schemes?

A “meet-in-the-middle” (not “man-in-the-middle”!) attack on textbook-RSA was presented to me. The only requirements for it was that the attacker gets the output of RSA and the public key, and that the ...
8
votes
3answers
627 views

Are there cryptographic hash functions that can be computed using only paper and pen without leaking any information about the plaintext?

I am looking for a cryptographic hash function that can be computed by a human using only paper and pen without ever leaking any information about the plaintext on the paper. The cryptographic hash ...
1
vote
1answer
189 views

Relationship between Elliptic Curve Discrete Log, Integer Discrete Log, and Integer Factorization

I am trying to look into a relation between the following three problems which are widely used to build public crypto systems: Integer Discrete log Elliptic Curve Discrete log Integer Factorization ...
8
votes
2answers
207 views

Voting scheme where the votes become public when a threshold is reached

Does there exist a voting scheme where voters cast private encrypted votes that automatically become public only after the threshold number of votes is cast? It needs to be done without a central ...
6
votes
3answers
769 views

Any practical uses of machine learning for cryptography?

I am about to go study for my masters in machine learning, data mining and high performance computing, but have recently become very interested in cryptography after taking Dan Boneh's Cryptography ...
0
votes
2answers
345 views

One Time Pad Question

I have a ciphertext encoded with One Time Pad. I do not know the key. How can I find the possible keys which when decoded, will result in a meaningful plain text?
10
votes
3answers
2k views

MIT says: mathematical theory behind encryption is wrong. What are the consequences?

A friend shared with me the following link: Encryption is less secure than we thought I'm not a security expert and could understand great part the article, except the section about noise, but what I ...
3
votes
2answers
135 views

Could this be a valid variation of the Schnorr protocol?

The Schnorr protocol is a 3-steps proof of knowledge of a discrete logarithm, whose interactive version works as follows. Let $p$ and $q$ be two public primes, such that $q \mid (p-1)$, and let $G$ ...
1
vote
2answers
187 views

What security flaw exists in MAC authentication scenario?

What security flaw exists (if any) in the solution of this non-encrypted authentication scenario? An unencrypted message passes one-way from computer A to B. Its transmission is viewable by the ...

15 30 50 per page