6
votes
2answers
963 views

Do I really need to use the same private/public key pair in RSA?

So I'm making an Android application, I need my application to be only able to scan my own generated QR codes, and I want to make sure that nobody else can generate fake ones. The data isn't ...
5
votes
0answers
54 views

Using a single Ed25519 key for encryption and signature

The libsodium documentation contains a function crypto_sign_ed25519_pk_to_curve25519 that converts an Ed25519 key into a Curve25519 one, so it can be used for both ...
2
votes
1answer
50 views

When is AES chosen instead of a stream Cipher (e.g., RC4) during an SSL connection?

During an SSL handshake, the browser sends a list of cipher suites to the server, from which the server selects one option. For data encryption, two of the several possibilities for the ciphers in ...
2
votes
2answers
33 views

Homomorphic Encryption operation for regression

I must be missing something, and I am sorry if this is a novice question... I have seen in places (eg. https://crypto.stanford.edu/~dwu4/talks/SecurityLunch0214.pdf page 13) that linear regression is ...
1
vote
1answer
30 views

Acceptable condition for dictionary search

I am trying to write a program to break transposition cipher using dictionary search. But I cannot understand the finishing condition of the search. Is there any theory that the maximum number of ...
4
votes
2answers
76 views

On the security definition of password-authenticated key exchange

I found in all PAKE papers, the security is defined as something like this: Let $Succ(A)$ be the probability that an attacker $A$ successfully distinguished the session key from a random string. Then ...
4
votes
0answers
60 views

Replacing signer with simulator

Assume we can prove security of digital signature scheme against key-only (no message) attacks. Now we want to prove security against adaptive chosen message attack. We use random oracle model. The ...
1
vote
2answers
252 views

Verifying Without Knowing Key

Say user Bob sends an encrypted message to a server. People can download the message from this server and later get the key directly from Bob. Is it possible for the server to somehow verify that ...
3
votes
0answers
37 views

ED25519 and hierarchical deterministic wallet

I'm building a solution based on the stellar codebase and using the ED25519 curve for the signatures. One of the features I've been adding to the system is a support for hierarchical deterministic ...
3
votes
1answer
65 views

PRNG output with truly random noise

I am considering a situation where an adversary does not have access to the $n$-bit output string of a PRNG, but instead receives a noisy version of it, where each bit of the string is flipped with ...
6
votes
1answer
73 views

How to forge signatures in the Schnorr scheme if $r=g^k$ is eliminated?

I need some help to demonstrate how to forge signatures in the Schnorr scheme if I eliminate the random string $r=g^k$ used in the hash – using $H(M)$ instead of $H(M||r)$. How would one be able to ...
8
votes
1answer
304 views

Salary Negotiation Problem

Imagine Alice is applying for a new job. Alice has an idea of the minimum salary that she is willing to accept—let's call this value A. Bob, the hiring manager for ...
1
vote
1answer
35 views

Generating passwords using Password-Based Key Derivation Function

I was thinking of using different and independent password for different websites, but not storing them in some password manager so I don't need to backup the passwords. I thought I could use some ...
1
vote
0answers
23 views

Is manually 'salting' my passwords a safe alternative to having a different password for each site? [duplicate]

It is highly recommended to use a different password for each site to prevent the breach of security of one site from compromising the user accounts on all other websites that have the same username - ...
2
votes
0answers
37 views

How does Bluetooth pairing (SSP with numeric comparison) work?

I have a question concerning the pairing of two Bluetooth devices using Simple Secure Pairing with numeric comparison. The NIST document I am looking at states on page 14: Numeric Comparison was ...
3
votes
1answer
125 views

What do they mean when saying that a certain value should be “super-logarithmic”?

What do they mean when saying that a certain value should be “super-logarithmic”? I've found the Wikipedia definition of a “super-logarithm”, but I'm having trouble understanding how a given value ...
6
votes
5answers
5k views

How do ciphers change plaintext into numeric digits for computing?

For example, in RSA, we use this for encryption: $ciphertext = (m^e \mod n)$ and for decryption. If our message is "hello world", then what number do we have to ...
0
votes
0answers
277 views

Changing plaintext for encryption in RSA [duplicate]

In the RSA crypto scheme, the message $x$ (plaintext), is encrypted to produce ciphertext ($y$), by computing $x^e \bmod n$. Of course, that means that $x$ has to be a numeric value for this to work, ...
-1
votes
1answer
66 views

How to calculate this binary operation? [closed]

I found this binary operation, however It is the first time that I found this operator '.' : That is the equation: 02 • 63 = 00000010 • 01100011 = 11000110 I don't understand how 0 • 0=1 I ...
0
votes
0answers
4 views

OpenSSL: Generate ECDSA key and CSR [migrated]

I know how to generate an RSA Private Key and CSR: openssl genrsa -out my.key.pem 2048 openssl req -new -sha256 -key my.key.pem -out my.csr But, How do I do the ...
-1
votes
0answers
28 views

Anyone know of a portion of the Enigma Code? [closed]

I was reading about it today and it sounds like it would be a fun thing to try to decode. Problem is that I can't find a portion anywhere. Is it classified or am I not looking in the right spots
3
votes
2answers
185 views

Is the security of MAC function is based on HASH function

It is widely known, generally, that a MAC is a HASH with key. I just want to ensure that my understanding is correct to avoid base further assumptions on wrong conception. So, if I used MAC that uses ...
1
vote
1answer
34 views

Randomized functions cannot increase statistical distance

In these lecture notes instructor Chris Peikert states the following lemma without a proof Let $f$ be a (randomized) function on the domain of $X$, $Y$. We have $\triangle (f(X), f(Y)) \leq \...
5
votes
1answer
77 views

Problem with LLL reduction on truncated LCG schemes

I am struggling to apply Freize et al. paper to break a truncated LCG. A truncated LCG is a pseudo random generator that outputs the $n$ leading bits $y_i$ of $x_i$, where $(x_i)$ is such that $x_{...
0
votes
1answer
31 views

Easily reversible hash functions as a method of data transmission [duplicate]

I've been looking through the literature because I want to see if anyone has implemented this idea I have. I know data compression algorithms work by removing redundancy in data. I was wondering ...
6
votes
1answer
580 views

Is unusual (non power-of-two) RSA key size more secure?

On this blog https://blog.josefsson.org/2014/06/23/offline-gnupg-master-key-and-subkeys-on-yubikey-neo-smartcard/ there is a following sentence Generate master key Below I will use a 3744 bit ...
2
votes
1answer
473 views

DES S-Box properties

Two of the properties that lead to the design of DES S-Boxes are: For any non-zero 6-bit difference between inputs, no more than 8 of the 32 pairs of inputs exhibiting that difference may result in ...
3
votes
1answer
63 views

How to create reduction functions in rainbow tables?

I have been trying to understand rainbow tables lately and one part is giving me trouble to understand here. Let's say I want to generate a table where the chains are 100 000 hash/plaintext long. I ...
10
votes
4answers
2k views

Desirable S-box properties

What desirable properties should an S-box have? My current standard selection process is to just pick them at random and verify that they fit the following criteria: The probability that any random ...
5
votes
2answers
89 views

Is the difference distribution table of AES S-box uniform?

I am studying about various block ciphers and their weaknesses, so I have a doubt about AES S-boxes, Is the difference distribution table of AES uniform ?
0
votes
1answer
47 views

Can I discard a specific X509 signature from file?

I'm writing a program to sign files using X.509 certificates and .NET framework classes. My users can sign the same file more than once without any problem (like a revision process). So, a file may ...
1
vote
1answer
23 views

Time complexity of looking up in a rainbow table

It is mentioned in the famous paper Making a Faster Cryptanalytic Time-Memory Trade-Off (pdf) by Philippe Oechslin that: The total number of calculations we have to make is thus $\frac{t(t−1)}{2}...
1
vote
0answers
25 views

Mitigating weaknesses in RC4 [duplicate]

I've been researching RC4 and implementing it, and I was wondering, from the perspective of a cryptographer (a real one, not a fake one like me), what could be added to the RC4 algorithm to improve on ...
3
votes
0answers
27 views

Computational Randomized Encoding in the hybrid proof

A computational randomized encoding scheme $(\textrm{RE.Encode}, \textrm{RE.Decode})$ works as follows: $\textrm{RE.Encode}(1^\lambda, C, x, r)$: takes as input the security parameter $\lambda$ in ...
3
votes
1answer
73 views

How does one practically calculate the non-linearity of a multi-output boolean function like the AES s-box?

I am working on multi-output boolean function i.e. a function that takes an $n$-bit input and gives an $m$-bit output for all possible inputs (i.e. $2^n$ inputs). To be more exact: I am trying to do ...
-2
votes
0answers
56 views

Help with a ctf im stuch on, base64 encryption [closed]

So my friend and I were trying to do this ctf challenge here labyrenth .com and when we were trying to solve the first part of the "Threat" challenges we stumbled upon a challenge we have no idea how ...
2
votes
1answer
64 views

SEAL Homomorphic multiplication

In SEAL homomorphic encryption library, there is an internal procedure to decompose a polynomial with large coefficients into a vector of polynomials with smaller coefficients. The procedure is ...
3
votes
1answer
36 views

How to distribute system parameters in identity-based encryption

Identity-based encryption papers describe that system parameters are declared as public. However,in real scenario, how to distribute system parameters to users?
1
vote
1answer
21 views

Time efficiency of Bitcoin Multi-signature Vs. threshold signature

I read this paper (Securing Bitcoin wallets via a new DSA/ECDSA threshold signature scheme) that illustrated that threshold signature is the best solution to avoid single point of failure but I think ...
-3
votes
2answers
61 views

Why are asymmetric keys represented as base 64? [closed]

When one generates a public and private key with say a total of 4096 bits, why does the program output what I assume to be base 64 instead of base 10 or binary?
6
votes
1answer
113 views

Designing Secure Multi-Party Computation Sub-Protocols Based on Homomorphic Encryption

When designing SMPC protocols using secret-sharing, it is a common approach to compose a protocol from several sub-protocols (each proven secure under the formal definition of security w.r.t. semi-...
1
vote
1answer
69 views

How to choose key from string?

do you know any methods for choosing specific position in text for a key? Background: Lets suppose, that I want to encode message to friend: Text1 (not too long - max 1000 chars). I have made ...
6
votes
1answer
5k views

Can I remove newlines in a public key?

Can I remove new lines from the RSA public key file to get a one line string? So the question is if the key looks like this AAA BBB CCC or ...
1
vote
0answers
15 views

Unique decentralized ID systems

We are all familiar with the standard decentralized ID system, the web of trust, e.g. for PGP keys. However, normal web of trust systems are unable to guarantee uniqueness — there's no practical limit ...
6
votes
0answers
80 views

Are there any signatures based on matrix multiplication with noise?

Are there any signatures based on matrix multiplication with noise? Representing the message as a matrix and multiplying with some randomness coming from another matrix such that the signature itself ...
5
votes
2answers
750 views

Would it be better to split a file and then encrypt, or vice versa?

Assuming that you are paranoid before storing your file (distributed across a shared location), which will be the best case scenario: splitting the file first and then encrypting or encrypting first ...
7
votes
1answer
494 views

Timing attack on RSA as used by CryptoLocker?

So far I have researched timing attacks on RSA, We all know the ransomware named CryptoLocker uses RSA 2048 bit encryption. Now, is it possible to break the encryption using a timing attack. I have ...
5
votes
1answer
409 views

Toy encryption system that provides “hints”

I'm looking for a toy encryption system that has a specific property that when decrypting it with a key that is close enough to the key used in the encryption, it will produce some of the original ...
0
votes
1answer
73 views

Key Hierarchy and key Encryption

If i have two 56-bit DES keys, and I use these two key to encrypt a 256-bit AES key. Like this $K_{AT}$ encrypts $K_{BT}$ and $K_{BT}$ encrypts $K$ What is the effective security of key $K$? Is it $...
-1
votes
0answers
23 views

Meaning of Policy matches when signing SSL certificates

I was going over the process of doing a self-signed SSL certificate. The config file here is one of the inputs to this process (see: https://www.phildev.net/ssl/opensslconf.html) I have a question ...

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