All Questions

11 views

What Does This Symbol Mean? (Hardcore Predicates for One-Way Functions)

I am studying Pseudorandom Number Generators and when reading the discussion on One-Way Functions and Hardcore Predicates, I came upon this equation. $$b(x,r)=\displaystyle \bigoplus_jx_jr_j$$ I ...
18 views

Big type-I Feistel as memory-hard function

I'm wondering, if something like block cipher with big block size is memory-hard function? All memory-hard key derivation functions I've seen look more complex than that, which made me question my ...
913 views

RSA & DH at risk due to math advances, will this eventually affect elliptic curves too?

I was looking into the predictions by some researchers that RSA and Diffie-Hellman may not be secure in the next few years due to advances in math and being able to calculate the discrete logarithm ...
37 views

Are there comprehensive alternatives to RSA?

If we wished to, is there a comprehensive alternative to RSA? I say comprehensive as I wonder if there is one which does both encryption and digital signature like RSA? If not, simply what ...
26 views

How to force an adversary to call a certain oracle?

Consider there is a protocol in real world, which uses a random oracle $\mathcal{H}$. In the ideal world, after the calling of $\mathcal{H}$ by some parties, intuitively I want the simulator gets some ...
13 views

How do a user register his verifier at host in SRP(Secure Remote Password) protocol?

I read RFC 2945, 5054 decribed about SRP. But there is no coment about registraion... How can i know the method of registration of SRP. plz, introduce some paper, or give me some advice.
25 views

Why does the time complexity of RSA encryption and decryption depend on the size of the modulus?

I would think that the time complexity would depend on the exponent, not the number of bits in the modulus. For example, if the exponent were 5, using the "naive" method, we would perform 5 ...
25 views

Cryptographic operations for NISTP256 can be implemented using montgomery method?

I need to implement cryptographic operations starting with the curve NISTP256. I have been told to implement it using Montgomery method. I read a pfd from ...
59 views

Cryptographic hash with ability to ignore specific bits based on a hidden pattern?

I'm looking to use password-style hashing to validate an environment, where some parts may be irrelevant. For example: ...
28 views

Is the RC4 keystream random or not?

I have cause to use the PRNG half of RC4, but am seriously confused as to the randomness of its output. (Only the PRNG half.) On the one hand, there is a large body of literature finding ever ...
38 views

S boxes in Blowfish

I know how the s-boxes in blowfish are initialized, but how is the output sorted, I mean which bit from the input goes where in the box ? and what do mean they have 256 entries if they are 32-bit ...
34 views

More rounds after AES related key attack?

In his blog Schneier discusses that there is a new related key attack on 10 rounds of AES-256 "Another attack can break a 10 round version of AES-256 in 245 time, but it uses a stronger type of ...
33 views

May I use Random Oracle for Inversed Look-up?

Consider there is a protocol in real world calling a random oracle $\mathcal{H}$ for a priavte input $k$. Then in the ideal world, after the calling of $r \leftarrow \mathcal{H}(k)$ by a honest party, ...
65 views

Muchomor cipher

I've been given a task to research and possibly implement so called 'Muchomor' cipher. Has anybody ever heard of this cipher? I've found only one article about it and it was in Russian. I'm quite ...
40 views

What is the difference between LCG and Affine cipher?

What is the difference between LCG and Affine cipher? More specific: What are they used for, and what are the structural differences between them?
28 views

TPM authorization Digest calculation

I am going through Steven Kinney's book; "Trusted Platform Module Basics", and pp 90 - 92 discuss how to calculate the authorization digest. He talks about 1H1, 2H1, 3H1, and 4H1 fields which I do not ...
73 views

RSA: must $d$ be an integer?

I am only taking baby steps in RSA. If $p=11$, $q=7$ and $e=3$, $$\phi(n) = 10*6 = 60$$ Then: $$d = (2 (\phi(n)) + 1 ) / 3 = 121/3$$ Should $d$ be kept as a non-integer or is such a $d$ invalid? ...
6 views

Generate non-random EC private key with openssl [migrated]

I'm trying to generate a deterministic private key for the EC secp384r1using the Unix command openssl. What I mean is, instead ...
16 views

Implementation specific differences between RDRAND and RDSEED

I've read Intel's The Difference Between RDRAND and RDSEED, but I have some open questions that are specific to usage in an application. I work with Wei Dai's Crypto++, which is a C++ class library of ...
70 views

RSA: Most significant key bit always 1?

Is it possible to say that the most significant bit of an RSA private exponent is always 1? Wouldn't that weaken the key strength by exactly that one bit? I refer to the paper "Timing Attack: What ...
99 views

Simple digital signature example that one could compute without a computer?

I am working on a document to explain Bitcoin to students. But I am having a hard time translating the principle described in §2 of the Bitcoin whitepaper in layman's terms. There is a great question ...
18 views

bank websites using AES_256_CBC vs AES_128_GCM/CBC [duplicate]

Hello i have just recently started learning about cryptography, so i was doing some little research on what kind of encryption techniques and modes that were used in bank web pages. I have noticed ...
88 views

(Lightweight) Multicast one-way Authentication

Problem: I'm thinking about a lightweight solution to provide source authentication (only one source) to multiple receivers (multicast message). Context: Taking the problem to ground, we can think ...
32 views

Reusing same source for single-source randomness extractor

Let $ext$ be a single-source randomness extractor which takes a $d$-bit seed and a $n$-bit source as input and produces a $m$-bit output. Suppose we have a source $X$ with min-entropy $k$. Is it ...
55 views

Which hash function is usually used in RSA?

I know there are several available, however I can't seem to find whether there is one standard one or not. I think I understand the process of digital signatures, just wondering which has function is ...
28 views

Rogue CA Certificate MD5 Collision Control

Papers from Marc Stevens et al show that X509 certificates that rely on MD5 signatures can break the assumed security model, that is, it allows for a forged certificate to have the same signature as a ...
54 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 ...
52 views

paradox on fully homomorphic equality checking

Imagine, a client encrypts a corpus of data (say documents of text) with the public key of a Fully Homomorphic Encryption scheme (FHE) and outsources the data to an untrusted server.Now the client ...
29 views

Using HMAC as a nonce with AES-CTR encrypt-and-MAC

Suppose I use the following encrypt-and-MAC construction: $E(k_1, k_2, n, m) = E_\text{AES256-CTR}(k_1, n, m) \| \text{HMAC-SHA256}(k_2, m)$, where: $k_1$ and $k_2$ are 256-bit keys $n$ ...
32 views

How can there be AES-256-GCM, when GCM is defined for 128-sized blocks?

In both node.js and OpenSSL, I am seeing cipher "aes-256-gcm". However, in NIST Special Publication 800-38D, that defines GCM, I am reading: The underlying block cipher shall be approved, the ...
19 views

Bitlocker on windows 10 [on hold]

How much does using Bitlocker on windows 10 slows the file processing on the drive? (I am planning on activating bitlocker on my C drive where my OS is present) and is it recommended to use bitlocker ...
12 views

Probabilistic Disjoint Verification [on hold]

Let $r_1,...,r_n$ be routers in the same organization, and let $h_{CO}$ be the least significant 32 bits of the hash of data packet $CO$. Router $r_i$ verifies $CO$ if $h_{CO} ≡ i \bmod n$. Assuming ...
19 views

Multiple NTRU public keys for the same private key?

An NTRU public key is generated essentially by multiplying the inverse of a polynomial $f$ by a polynomial $g$. The polynomial $f$ is the private key; $g$ is discarded. My question is: Is it insecure ...
23 views

Fully homomorphic encryption arbitrary functions formulation

I am currently studying the interesting field of homomorphic encryption. I read that from a fully homomorphic encryption function that supports both addition and multiplication you can perform any ...
38 views

Unbreakable encryption [duplicate]

I am a newbie, I know that I must be wrong, but I need a good explanation. How is it possible to break a cryptographic algorithm created by me, when only I know the algorithm and the key for ...
41 views

Multi-Party Encryption for a Shared Document

Is there an encryption algorithm/protocol where any of a pre-defined set of keys/passwords will succeed in decrypting a document? The number of keys can be fixed, say, 10 or 20 possible passwords. ...
12 views

StoredKey in Salted Challenge Response Mechanism (SCRAM)

In SCRAM (RFC5802, page 8) the client generates ClientKey to server, which is a derivation of the original password. This is communicated to the server in a secure ...
116 views

What are the steps to decrypt a TLS 1.1 record?

My question is related to another question in Cryptography about TLS 1.1 and 1.2. I have read both RFC 2246 The TLS Protocol Version 1.0 and RFC 4346 The TLS Protocol Version 1.1. What I know is that ...
28 views

Help understanding basic Franklin-Reiter related message attack

I am trying to understand this attack at the most basic level. I set up the following basic scenario: Let the public encryption exponent, e = 3. Let p, be some arbitrary but known (to the ...
185 views

Autocorrelation in Autokey

I know that Vigenère can broken using auto-correlation (as explained at cryptool-online.org). Now my question is: Why does this also work with autokey (tested it using crypttool)? To prove that I ...
15 views

key scheduling in rc4

Found this pseudocode of RC4 key scheduling in wiki : ...
25 views

User revocation in Identity Based Encryption

I read several papers about user revocation in IBE recently. A common point is that when a user is revoked, some other valid users should also update their private keys. Does this mean that one ...
13 views

Edwards / Montgomery ECC over binary extension fields

I recentely had a discussion about the redesign of our ECC code for the library I'm collaborating on and the person I was discussing with came up with Edwards and Montgomery curves over binary ...
18 views

need guidance to decrypt php base 64 [on hold]

i have code encrypted using base 64 i need help to decrypt it , below is attached code , some hacker converted whole code to base 64 below is hint i see all pages i need help to decrypt it ...
232 views

PGP String-to-Key specifiers

I've been reading through the PGP Standard and here I'm a little confused. This section is discussing converting string data to a session key. I'm confused about the paragraph in bold. First off, what ...
25 views

need help to decrypt js encrypted using some aes [on hold]

I have few js code that run on browser and in encrypted using some aes. I think sjcl. below i code format ...
28 views

Bilinear map assumpion

Is there an assumption that says from a tag $k\cdot e(g,g_1)^{rx}$ ($k,r$ are secret) it is difficult to forge it with some x': $k\cdot e(g,g_1)^{rx'}$, as long as you cannot solve DL in ...
26 views

Lattice attacks against Multilinear Maps [CLT13]

I am currently studying an article on a construction of Multilinear maps. There are some attacks on the scheme presented by the authors and I got stuck at the one in section 5.1. I will try to ...