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
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 ...
0
votes
2answers
48 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 ...
2
votes
1answer
31 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 ...
2
votes
2answers
216 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
48 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 ...
3
votes
3answers
181 views

How to perform frequency analysis of a substitution cipher using a Base64 alphabet

Let's imagine a cipher that works like the following: Plaintext is encoded to Base64. The characters in the encoded plaintext are substituted with a randomly shuffled character set(A-z, 0-9, -, _, ...
1
vote
0answers
22 views

Hybrid fair exchange protocol

A gradual fair exchange (layman term) is a form of fair exchange protocol where Alice will transfer 1 bit to Bob then Bob will transfer 1 bit to Alice. The flaw with this protocol is that the party ...
0
votes
0answers
15 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
18 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) = ...
2
votes
1answer
80 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. ...
1
vote
0answers
39 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 ...
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
1answer
37 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
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 ...
0
votes
0answers
32 views

Test framework for hash functions for collision resistance?

I have two questions about the assessment of collision resistance in hash functions. Given a hash-function what would be the next step to inquiry about it's collision resistance / probability of ...
0
votes
1answer
24 views

What is “electronic” in electronic codebook (ECB)?

This is an honest question regarding terminology. I believe that I understand why one mode to use a block cipher is called a codebook. But I wonder why electronic as a work appears here? Is it fair ...
0
votes
2answers
54 views

Are all block ciphers FPE (format preserving encryption)?

A FPE preserves the format. There is a correspondence between the format of the ciphertext and the plaintext. Given that a message in some binary enconded format can easily be divded in some ...
2
votes
6answers
487 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 ...
1
vote
1answer
29 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 ...
0
votes
1answer
47 views

Storing AES encrypted RSA private keys on a server

I'm thinking about creating an encrypted messaging web application where users create RSA key pairs, they store the public key on the server for others to see and also store an AES encrypted private ...
0
votes
1answer
64 views

Handbook of Applied Cryptography as an entry point - is it ok book? [on hold]

I recently chose to make an entry to Cryptography and encryption by starting to read the book Handbook of Applied Cryptography. I come from computer science background. To be honest, I have forgot ...
1
vote
0answers
74 views

Opinion on my idea for storing credit cards securely

I've been thinking of ways to store credit cards securely, I thought of this: Take the users credit card info Put the card info in a standard format "Full Name/Card Num/Security Num/Expiry ...
1
vote
3answers
112 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
0answers
40 views

How can I calculate the size of an encryption key?

I have encryption algorithm that has two variables are used as encryption key. How can I calculate the size of the encryption key. I will show an example of what the variables can be: ...
-1
votes
1answer
30 views

what is SALSA20 Nonce and its requirements [duplicate]

what is the source of nonce in SALSA20 algorithm. basically who provides the value of nonce in SALSA20 algorithm
0
votes
1answer
36 views

Storing salts and iteration number?

I have a function that derives two sub-keys from one passphrase using PBKDF2 one which is used as a encryption key the other for HMAC generation, because these two sub-keys will need to be regenerated ...
2
votes
0answers
62 views

Does the SSH protocol preserve integrity if an endpoint is cloned?

I am trying to find out if the SSH protocol preserves integrity of the transferred data in the following scenario: The SSH client is running on a virtual machine, at some point in the middle of the ...
0
votes
0answers
76 views

How can I prove CPA secure by using a new scheme gen,enc,dec from GEN,ENC,DEC?

Given public key encryption scheme $(gen; enc; dec)$, we now construct a new scheme $(Gen; Enc; Dec)$ as follows: The key generation algorithm $Gen$ is the same as $gen$. Each ciphertext for a ...
-1
votes
1answer
143 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 ...
0
votes
1answer
81 views

Determining message given cipher-text and public key [duplicate]

Consider the following scenario: Suppose A and B have set up their RSA public keys, namely $(e_a, n)$ and $(e_b, n)$, where the n-value is the same. Also, it happens that the $\gcd (e_a, e_b) ...
0
votes
1answer
75 views

Why is there an extra block when encrypting?

I am passing input data 20 bytes long and java AES-CBC returns 48 bytes instead of 32 which is what I think it should output because of padding. My key is 16 bytes long. ...
0
votes
0answers
24 views

Do OpenPGP SmartCards have the same or better security than an air-gapped machine?

Are OpenPGP SmartCards, such as the OpenPGP SmartCard V2, suitable enough to have secure communications? Meaning, if I connect my smart card to my Mac which is connected to the internet and always ...
0
votes
1answer
78 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 ...
0
votes
0answers
18 views

The number of surviving key after “Meet in the middle stage” in 3-subset MITM attack

In 3-subset Meet in the middle attack, how can we calculate the number of surviving key after meet in the middle stage? and how can we calculate the complexity of Key testing stage? I have read about ...
0
votes
1answer
48 views

Signature scheme doesnt seem to hold

I can't seem to verify this signature scheme. Taking this as an example: $p = 23$, $g = 7$, Private Key : $(12$, $20$, $3$, $18)$, $y = 16$ and $q = 2$ This will give me: $y_1 = 7$12$*16$20 $= ...
-1
votes
1answer
75 views

What does $\mathbb Z_p^*$ contain?

I have a prime $p = 7$ and was tasked to select a random value in $\mathbb Z_p^*$ in my signature scheme. What does the full range of $\mathbb Z_p^*$ contain in this case? Is it $\{0...7\}$ or ...
2
votes
0answers
126 views

As a cryptographer, what are the things I should care about in my implementation of pairing functions?

As a beginner in cryptography, I do not know anything about different pairing types more than their names. So far, I know these names: Ate pairing, tate pairing, eta pairing, and r-ate pairing. I am ...
0
votes
1answer
38 views

Why is g is less than p in Diffie-Hellman?

In non-authenticated DH, p and g are made as public record. p needs to be a large prime number and g should be smaller than p. Why does g need to be smaller than p?
0
votes
4answers
71 views

Why do we need to compute message digest of a message first while signing it?

Why it is more efficient to compute a message digest of message and digitally sign it then, rather than sign the message directly?
0
votes
0answers
27 views

recommendation to see documentaries about history of cryptography

Can anybody recommend any good documentaries which go into some history about cryptography and state of cryptography as of date ? I am not asking for favorites or subjective good documentaries but ...
1
vote
1answer
71 views

What is the value of Q such that Q|P-1 where P is a prime number?

For my crypto assignment, I'm asked to enter a prime P and generate Q such that Q|P-1 Can anyone guide me what is Q|P-1?
2
votes
2answers
241 views

Which attacks are possible against raw/textbook RSA?

The PKCS#1 standard defines multiple padding schemes for signature generation/verification (EMSA-PSS and EMSA-PKCS1-v1_5), and encryption/decryption (EME-OAEP and the less safe EME-PKCS1-v1_5). ...
1
vote
1answer
59 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 ...
0
votes
1answer
31 views

Available programs that can verify the working of a simple substitution cipher

Is there any tool available that can test whether a simple substitution cipher is working. I will put my scenario in detail. Lets say I built a simple substitution cipher that maps 8 bit data to 16 ...
0
votes
0answers
44 views

Franklin-Reiter related message attack m2 = a(m1)+b

As shown in their paper, https://www.cs.unc.edu/~reiter/papers/1996/Eurocrypt.pdf, if one is given an equation relating the two messages m1 and m2 as well as other information one can crack both the ...
3
votes
1answer
65 views

Are there some problems to use pseudo-random number generator in Smart Card?

A Smart Card is a kind of secure device, with limited storage capacity and computational resource. If we use a Pseudo-Random Number Generator to generate random numbers in a Smart Card, then is there ...
0
votes
1answer
72 views

Repeated XOR decryption [closed]

I have this message in Hex: ...
0
votes
1answer
42 views

Davies-Meyer Hash Function

So the Davies-Meyer Hash Function is: Hi = Hi−1 ⊕ exi (Hi−1) Say I pick H0 = 1110 0011 And the message x1 = "5" or "0000 0101" Is this the correct way to compute H1? H1 = 1110 0011 ⊕ (0000 0101 ⊕ ...

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