All Questions

1
vote
2answers
90 views

What is primary security in ECC?

I read the following paragraph in a book about Elliptic Curve Cryptography, but didn't understand it: The primary security in ECC is the parameter $n$; where $n$ is Order of point $G$, that is $n$ ...
0
votes
1answer
62 views

Fairness in cryptography

Two users A and B decided to share a file of same size and transfer data bit by bit. And at the end of exchange, A will have B's data and B will have A's data. Assuming, A starts to transfer the ...
0
votes
1answer
53 views

Best practices (if any) to add metadata to encrypted files

I am encrypting files using AES/CBC/PKCSPadding, with 256 bits long keys. So far the first 16 bytes of each encrypted file are the IV. I would like to store some more information regarding the ...
21
votes
6answers
12k views

How does asymmetric encryption work?

I've always been interested in encryption but I have never found a good explanation (beginners explanation) of how encryption with public key and decryption with private key works. How does it ...
0
votes
0answers
28 views

The Inhomogeneous Short Integer Solution (ISIS) problem with a clue

The Inhomogeneous Short Integer Solution (ISIS) problem is as follows: given an integer $q$, a matrix $A \in \mathbb Z^{n\times m}_q$, a vector $b\in \mathbb Z^n_q$, and a real $\beta$, find an ...
7
votes
1answer
76 views

Verifiable, Distributed Secret Santa Assignments

My family was planning a secret santa and I thought about how I might write a little web app to dole out these secret assignments. But the downsides to this approach are obvious: there's no way for ...
0
votes
1answer
64 views

Key management protocol for end-to-end security on Advanced Metering Infrastructure

I am currently working on a research on end-to-end security implementation for Advanced Metering Infrastructure (AMI). Pardon me if I a bit off topic or not asking the right question as I am ...
3
votes
2answers
87 views

Strange MAC algorithm

I'm working with a payment provider which uses the following algorithm for signing messages: The merchant is securely given a secret key k, known to them and the ...
0
votes
0answers
25 views

Where can I get a security audit for a crypto app storing files on the cloud? [closed]

We are completing a new app the encrypts files (AES 26-bit) prior to sending them to cloud storage services (ex. OneDrive, Google Drive, DropBox, etc.). We want to find a consultant who can do a ...
1
vote
1answer
61 views

What is the use of segments in Cipher Feedback Mode (CFB)

In NIST SP800-38A: Recommendation for Block Cipher Modes of Operation CFB can be used with a parameter s - the size of a data segment in bits - which determines the ...
2
votes
0answers
64 views

Consequences of AES without any one of its operations

Suppose AES-$128$. There are $4$ operations in AES's encryption, they are SubByte, Shift Row, MixColumns and AddRoundKey. Question: If I remove one of the following opearations, what will happen to ...
1
vote
2answers
33 views

Condition on Vector Boolean Function to be Bijective

Suppose the vector boolean function be $$\begin{align} f:F^n_2 \longrightarrow F_2^n \\ (x_1,\dots ,x_n) \longrightarrow (x_2,\dots x_n,g) \\ \\ g:F^n_2 \longrightarrow F_2 \\ (x_1,\dots ,x_n) ...
-1
votes
0answers
25 views

example of predicate encryption explaining what is attributes with ciphertext and what predicate with key is

I know that predicate encryption schemes are encryption schemes in which each ciphertext is associated with a binary attribute vector and keys are associated with predicated. I want to ask what is the ...
5
votes
1answer
951 views

What is Attribute Based Encryption?

Can someone explain what attribute based encryption is? I was searching for a book or something that can help me in this regard but so far I have found none. Google also returns practically nothing ...
-1
votes
0answers
47 views

Different Encryption schemes i have no idea to achieve [on hold]

I want to find examples for encryption schemes that: are resistant to a total break but not against universal break are resistant to universal break but not partial break are resistant to partial ...
3
votes
1answer
258 views

AES with weak keys

Suppose that the key generation is insecure; each key bit is independently generated, but the value of each key bit is '$1$' with probability $0.90$. These keys are used in AES. What is an efficient ...
2
votes
2answers
84 views

RSA-KEM construction

"Create a random key for CCPA2 scheme, encrypt m, send it along with a PK encryption of the symmetric key. " Say in the process, the KDF is HMAC, then: get a random key (128-bit) C1 = encrypt ...
1
vote
3answers
88 views

How a file is encrypted?

I thought encryption algorithms(like AES) are used to encrypt texts,so how a file or folder(containing pictures,videos,...) is encrypted?What is encrypted exactly?
9
votes
3answers
3k views

What is the most secure hand cipher?

By "hand cipher", I mean a symmetric cipher for which encryption and decryption can can both be performed with a pencil on graph paper, consuming about 10-20 seconds per character by a proficient ...
0
votes
1answer
36 views

Blowfish ECB mode: Tools for known-plaintext attack?

I'm currently dealing with multiple blowfish-encrypted files that share the same key. All are encrypted using ECB mode judging from their appearance. I don't know what the key is but I know 64 byte ...
1
vote
3answers
111 views

Are modified implementations of cryptographic algorithms a good idea?

Are modified implementations of standard cryptographic algorithms better that the standard versions? Since the algorithm is not standard, is it harder to break? Is it safer?
0
votes
1answer
17 views

CSPRNG's (ELI5) What's the purpose of multiple seeds/ regenerating sources of entropy (i.e. /dev/random)?

Why is there a need to generate more than one high entropy seed? It would seem like if the original source of entropy is high quality, than some 512 bits should be more than enough to seed a CSPRNG ...
0
votes
0answers
36 views

Permutation parity after cycle-walking

Let $E$ be a random even permutation of the set $\{0\dots n-1\}$. We construct a permutation $P$ of the set $\{0\dots m-1\}$, for some $m\le n$, using cycle-walking; that is, computing $P(x)$ is as ...
2
votes
1answer
65 views

Are post-quantum cryptographic ciphers *also* secure if the P=NP conjecture holds true?

First of all, I only understand the P versus NP debate on a rather shallow level as I am not a computer scientist. So perhaps the answer to the question is straightforward but if not, I would be ...
0
votes
0answers
14 views

Sources Which Discuss The Truncation Of Hash Values And Whether Or Not It Is Safe To Do So [closed]

I came across a question which asked whether or not it is considered secure to truncate the output of a hash function to a given length. One of the answers provided for the question stated that is was ...
2
votes
6answers
484 views

Can hashing become encrypting?

hashing some data and encrypting data share some similar attributes. Surely this is why "Difference between encrypting something and hashing something" has been asked. The point of this question is ...
0
votes
0answers
15 views

Cannot decrypt message [closed]

How i recognize which algoritm is used for encrypted message ? For example this message vZ_fMYcihQ0U6en02kT-7LwNq78fT2gD63tKcyw_m-2b3Zo=
0
votes
2answers
47 views

Using bcrypt derived keys for encryption?

Sorry for this ignorant question but I am currently weighing up the advantages and disadvantages of BCrypt over PBKDF2 and from what I have read BCrypt is considered more secure but from what I have ...
0
votes
0answers
39 views

ASP.NET MembershipProvider uses passwordSalt when encrypting [migrated]

I've a question about the ASP.NET Membership (from .NET 2.0), and more specifically the way it encrypts passwords (when you choose to encrypt them, and not hash then), and the way it verifies them. I ...
0
votes
0answers
18 views

Hokkaido (proof-of-Work system) and pseudo-random permutation table

This question is regarding a proof-of-work system suggested in this article "Cryptology ePrint Archive: Report 2005/356". The outset goal of the Hokkaido algorithm is to provide a task to somebody's ...
2
votes
1answer
45 views

what are the security benefits of LUKS?

Aremed with only basic crypto knowledge, I'm trying to understand the security benefits of LUKS over plain-mode dm-crypt. Hopefully this is a good place to ask. Given the LUKS header contains ...
0
votes
1answer
41 views

Why has SSL v3 not yet been upgraded to a higher version with stronger principles, what are the dependencies and issues to do so?

SSLv3 is almost 18 years old; why has it not been updated to a more advanced version with stronger rules and structure. What have been the issues and dependencies in doing so till now???
-2
votes
0answers
54 views

Algorithm of Big Integer class Multiplication in visual studio [closed]

As you know, There is a class in Microsoft Visual Studio with Framework 4, 4.5, for working with big integers. What is the Algorithm name which used for multiplication in "BigInt" class? (montgomery ...
0
votes
1answer
74 views

RSA: Fermat-Euler Theorem - coprimality of message and modulus [duplicate]

I understand the implication of the Fermat-Euler theorem and how it applies to RSA and the detailed explanation by user Ninefingers at What is the relation between RSA & Fermat's little ...
1
vote
1answer
27 views

IPsec authentication and encryption lgorithms

I am looking for the implementation of IPsec security algorithms for both authentication and Encryption. Is there any open source implementation available for the same ? And if someone supposed to ...
12
votes
3answers
45k views

How secure is AES-256?

The cipher AES-256 is used among other places in TSL/SSL across the Internet. It's considered among the top ciphers. In theory it's not crackable since the combinations of keys are massive. Although ...
-1
votes
1answer
141 views

Extending key sizes in Salsa20 and ChaCha?

I've written implementations of Salsa20 and ChaCha that accept 384 and 448 bit keys. It was fairly trivial to implement, the 'sigma' constant is replaced with key material, and the counter, (which was ...
2
votes
2answers
211 views

Can RSA signing be implemented on top of RSA encryption/decryption?

I need to use RSA-SHA256 signing. Unfortunately not all Microsoft CryptoAPI providers support that. It's possible that I might get a handle to a CryptoAPI provider that can just encrypt/decrypt with ...
2
votes
1answer
30 views

ASCII input to HMAC weaker than raw bytes?

In various cryptographic programs I've written (most have been toy problems, but this current one is not) I have taken a slothful approach to performing a message digest (hash) of numerical input. I ...
32
votes
5answers
5k views

How big an RSA key is considered secure today?

I think 1024 bit RSA keys were considered secure ~5 years ago, but I assume that's not true anymore. Can 2048 or 4096 keys still be relied upon, or have we gained too much computing power in the ...
2
votes
1answer
79 views

Why is this cryptosystem insecure?

Can someone help me see the flaw in this cryptosystem? Note: This is homework and it is due today at 1:30pm. An answer before that is not expected; I'd just like to understand what the flaw is. ...
13
votes
2answers
633 views

Attacks of the MAC construction $\mathcal{H}(m||k)$ for common hashes $\mathcal{H}$?

Consider a common practically-collision-resistant hash function $\mathcal{H}$ (e.g. SHA-1, SHA-256, SHA-512, RIPEMD-160), perhaps based on the Merkle–Damgård construction as are the first three. We ...
0
votes
1answer
34 views

TLS - self encrypting to avoid tls setup, secure?

I am in doubt : of course one can create a tl connection between a client and a server. But what if the client sends self encrypted with, say, blowfish, data to the server? The goal is that the ...
1
vote
1answer
56 views

Random Permutation polynomial

I need to know, please: (1) Is there anyway to pick uniformly at random permutation polynomial in a field of prime order? (2) Are there many permutation polynomials in a field? (3) In a finite ...
1
vote
0answers
29 views

Pros and cons between HOTP and TOTP [duplicate]

I'm reading the RFC6238 (TOTP) and RFC4226 (HOTP) standards and can't get which one is to prefer? I've searched around a bit and it seems like TOTP is the one that is most used, but some argue that ...
1
vote
0answers
30 views

Why HMAC=H(message|key) is unsafe? [duplicate]

As mentioned in wikipedia, HMAC=H(message|key) is not safe, but I don't know the reason. Anyone can tell me why? or give me an example? Thank you in advance.
0
votes
0answers
14 views

openssl - Recommended way to encrypt and sign S/MIME messages using openssl

OpenSSL has two command line tools, cms and smime, that can encrypt and sign S/MIME messages. Both can specify ciphers and ...
0
votes
0answers
9 views

java.security.spec.InvalidKeySpecException and Inappropriate key specification error in java program [migrated]

As a part of project implementation,I have done: 1. Generete DSA keys 2. Encrypt the private key using AES 3. Save into the file 4. Open the file and read the encrypted private key 5. I tried to ...
0
votes
0answers
17 views

Validity of ElGamal signature variation

I'm trying to solve excersise 7.6 from Hoffstein - Introduction to Mathematical Cryptography page 459 (http://goo.gl/oRyInT) Let $p$ be a prime and let $i$ and $j$ be integers with $gcd(j, p − 1) = ...
1
vote
0answers
38 views

Encryption in which ciphertext is bigger than plaintext?

Is there an encryption which would produce a ciphertext longer than the plaintext? (please ignore block-chaining IV stuff, which would result in a data being generated from the plaintext). The point ...

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