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In three different, highly reputable sources (e.g. "Introduction to Modern Cryptography" by Katz and Lindell, 2007), the definition of CCA attack doesn't allow the adversary to decrypt the challenge, but also doesn't require the adversary to send never-before seen messages.
I'm assuming that this is a mistake, and that... |
safe to say I'm a complete beginner when it comes to cryptography... I believe the example output below is some sort of RSA (or RS256) encrypted string, and was just curious whether it'd be possible to re-create that encryption with any random text I enter based on the information that I have below.
Example output (wha... |
Some of the encrypted messenger apps and password managers use extended version of Bernstein's ciphers and some of them not.
Viber-Salsa20
Wire-ChaCha20
Threema-XSalsa20
Sid-Salsa20
Nordpass-XChaCha20
Keepass-ChaCha20
Why? Does larger nonce make extended version more secure? if it is then why some of them not using ext... |
For DSA, if the same message is signed multiple times on different occasions, the signatures will differ because the random value k is generated for each signature. This is not true of RSA signatures. What is the practical implication of this difference?
|
The compliance department is asking me for recommendations on encrypting data before Saas-solutions. Meaning that the Saas-solution should not be able to see the data when stored and processed.
Reading about Fully Homomorphic Encryption seems like it would solve the issue, but i can't seem to really find out how widesp... |
I am studying the vulnerability of DES algorithm.
Let there be a DES system with 5 keys, 56bits each. Encryption works as follows: (It's in this order on purpose)
$C=DEC_{k1}(ENC_{k2}(ENC_{k3}(DEC_{k4}(DEC_{k5}(M)))))$
With k2=k3 and k4=k5
Where C = Cipher,
M = plain text
DEC = Decryption
ENC = Encryption
-kn = Is the... |
I see many papers that compare the latency of the signature schemes in terms of clock cycles by two-three numbers. I don't know why they write 2-3 numbers instead of one number to represent clock cycle. For example consider the following table from this paper link: https://eprint.iacr.org/2019/122.pdf
|
As title I have a password-like passphrase (8 chars at least) that is then hashed with argon2(with the salt is SHA256 of that passphrase).
Then use it as AES256 key along with a random IV generated by CryptoJS.lib.WordArray.random(256 / 8);
Is it okay?
Or should I use the IV as a key?
|
Let's say I have two binary messages ($m_0$ and $m_1$) of length $n$ which are bitwise complements of each other such that $$m_0 \xleftarrow{r} \{0,1\}^n \text{ and } m_1 = \overline{m_0}$$
If I perform a one-time pad encryption of $m_0$ and $m_1$ with the same key, I would only leak that the messages are bitwise com... |
Lets say I know a secret value x.
The hash of x, y = H(x) is public.
Is there any zk way to prove to a verifier that I know x without revealing x and only revealing y?
|
Mike Hamburg proposed the Ed448-Goldilocks curve and submitted a software implementation for it to the SUPERCOP project.
Below you can see that MH picked a generator (or base point) that has a y-coordinate equal to 19.
Why was this generator chosen?
(I would guess that points with y=0..18 are somehow not suitable and t... |
Can I use Diffie-Hellman over, say, $GF(2^{128}) \bmod$ irreducible poly in $GF(2^{128})$ instead of $GF(p)$?
If not, why?
Or increase it to $GF(2^{2^{\text{whatever}}})$.
|
I came across 2 older answers (2 different but similar questions on the small cofactor attack) which cover this attack.
https://crypto.stackexchange.com/a/12614/3941
Here the attacker replaces the $bG$ Bob sends to Alice with $H$ where $H$ is a point of smaller order.
https://crypto.stackexchange.com/a/26844/3941
H... |
In the dieharder test suite there are things like:-
diehard_3dsphere| 3| 4000| 100|0.56011310| PASSED
and in the NIST IID (brief mode) and randomness test suites there are things like:-
** Passed IID permutation tests
and:-
1 2 1 1 0 2 2 0 0 1 0.739918 10/10 Universal
1 ... |
On KeePass help center it's stated that:
... if the header of the database (first few bytes) is corrupted, you're out of luck, too: the repair functionality won't be able to restore any entries (because the header contains information required to decrypt the database).
I wonder if header corruption (or maybe other ty... |
Let's say that Alice is the administrator of a group. For each message generated by a group member, Alice uses an administrator's private key ($sk$) to sign it, indicating that this message has been checked by her. One day, Bob takes over from Alice. Therefore, Alice sends Bob the $sk$ in a secure channel. But the secu... |
I have a need for the following encryption properties: $f(g(v_\text{plaintext}) = v_\text{ciphertext}$ needs to be decryptable by $f^{-1}(g^{-1}(v_\text{ciphertext}))$ and $f$ and $g$ need to be different.
The idea goes like this.
A user is going to encrypt some plaintext (DB credentials) with a private key they contr... |
As some password manager, such as KeyPassXC allows a user to create a master password using a HMAC response from a YubiKey concatenated with a password entered by user, I was wondering something.
Assuming that:
*The encryption key is created with PBKDF2 HMAC-SHA256 from the YubiKey HMAC result and a user-provided input... |
To valiate integrity
or
To verify if the software is digitally signed
The question seems wrong to me. I do not see any reason to publish(make public) a hash. But it is in the material I am studying.
|
Is it safe to use CTR encryption mode and authenticate it with HMAC(message, key), where key is the cipher encryption key, and the key is unique for each message? Would it be safer if I change the key a little? For example, flip a lower bit. Or I need to have independent secret for HMAC?
|
I think I understand snowball consensus algorithm with exception of 1 think.
Node polls 5-10 random nodes N times and choose color. Is it querying always same list of nodes? Or it is changed after some iteration? Or everytime it queries it chooses a new set of nodes?
|
Is it safe to truncate HMAC? What is the minimum length of a truncated HMAC so that HMAC is still considered to be safe to use? Are there any standards on when it comes to shortening HMAC?
In my case, the hash function is SHA-256. Would the answer also be applicable for any other hash function?
|
I'm reading the Signal specification and they suggest to use EC keys, in particular with X25519 or X448 curves, both for the initial X3DH agreement and the DH ratchet.
I've noticed that languages and libraries seems to have a better support for RSA (for example the two curves recommended by Signal are not available usi... |
We have a smart contract containing encrypted data that should remain encrypted till a specified timeLimit.
Then, the decryption key would be made public, for everyone to read that data.
We want to achieve this in a trustless manner, as anyone with knowledge of this data before the timeLimit can use it to exploit the s... |
Hi I struggling to find the answer of my schhol exam, can anyone help me .
In a Diffie-Hellman key exchange the multiplicative group of integers modulo
p is used with the parameters p = 59, g = 3 mod 59. The public keys A = 28 and
B = 36 are exchanged. One of the private keys is relatively small. Find this key
and comp... |
When implementing and testing my own EdDSA program I found out that the old RFC7748 gives wrong parameters for Ed448/Edwards448.
There is currently a new Draft were this is clarified:
https://datatracker.ietf.org/doc/draft-ietf-lwig-curve-representations/
(page 109)
IMPORTANT NOTE: the supposed base point of Ed448 spe... |
So, I'm taking Cryptography I by Dan Boneh on Coursera and I was reviewing the definition of security for a PRF while solving exercises, and I stumbled upon this question from a homework Dan Boneh gave for a winter class of 2020. Where it's cleared stated that F1 is not a secure PRF, but I can't get my head over it.
I... |
I have a problem where I have to find mod N in a RSA cipher.
I am given the following information:
The public key (e)
Plaintext (M)
Cipher text (C)
How can I reverse the equation C = (M^e) mod N to find N?
|
I have been learning about AES-GCM and AES in general lately and founding:
The key is the secret and both sender and receiver keep it hidden forever.
The IV and auth tag are public and sent along with the ciphertext which means they are public to the world.
So what can these give other people hints or information about... |
Is there any standard solution to the colluding problem in Shamir's secret sharing i.e. How should I prevent my k friends from colluding and recovering my secret?
|
I'm trying to solve a crypto RSA problem from my last exam in a clean way, but I'm stuck in the last step...
First of all, we are using an alphabet with 27 characters (i.e. spanish alphabet: A-Z + Ñ). We will code each char as A=0, B=1, ..., N=13, Ñ=14, O=15, ..., Y=25, Z=26.
We have d=7, n=33, e=3.
As 271 < 33 < 272 w... |
To quote Ilari on the CFRG mailing list:
e.g. the vile mess that is ECDSA with SHA-3
I have some ideas what he might mean but I couldn't find the discussion so what is that mess?
|
This is the attack I am talking about - Why are the lower 3 bits of curve25519/ed25519 secret keys cleared during creation?
An elliptic curve group of order $8p$ where $p$ is a prime.
Let $G$ be the generator of the subgroup of order $p$. For ECDH, Alice sends $aG$ to Bob & Bob sends back $h$ instead of $bG$ where $h$ ... |
Terms:
Client: Browser, mobile app or desktop application written using using JavaScript, HTML, CSS and packaged with Capacitor / Tauri.
Server: NodeJS based API.
Data: Username / password
Vendor: Third party integration
Background:
I am writing an integration with various vendors that requires users to enter their ven... |
I am trying to figure out if there is an authority like FIPS, NIST, NSA, or DOD that has recommendations or standards for implementing AES such as key derivation algorithms and iterations as well as CSPRNG for keys but I can't seem to find anything. Is there any authoritative documentation for "current" AES implementat... |
for example, I have an encryption program like this:
Input: a message, M; my public key Kpub
Step 1: randomly generate a symmetric (e.g., AES) key, K
Step 2: use K to encrypt M
Step 3: use Kpub to encrypt K
Step 4: destroy K
In step 4, how to destroy K? Can we just assign a random value (e.g., 0) to the variable? Is th... |
The Spritz cipher is a "sponge-like" construction that the authors show can be used as a hash, MAC, stream cipher, re-seedable pseudo random number generator, and/or an authenticated cipher.
Apart from some internal control variables, there is an array of size N (call it the state : I set N = 256 for this discussion).
... |
The Spritz stream cipher algorithm has been shown to have a special class of states that can be used to do a full state recovery attack better than brute force.
While the authors of the paper clearly show what states are special, the behaviour of the cipher when in one of these states, and how to exploit them, they do ... |
I'm sorry if I'm going horribly wrong - I am new to this stuff.
My question is：
KDFC1,KDFC2,KDFC3 is defined by myself.
Key1 is come from outside .
Is it possible to use the aes-ecb-256 decryption algorithm to generate an aes key?
If I'm going horribly wrong , Is there any relevant information that can be provided f... |
Before looking at the textbook ZKP for discrete log, I tried to construct one myself. This turned out quite different to the textbook one, and I've been wondering what might be wrong with it? (I was unable to refute any of the ZKP requirements, so I guess I'm missing something).
The original problem:
Given $g,h \in \m... |
I'm creating an application that requires message authentication on the payload of a QR-code. Because of the maximum length of an error-correcting (H) QR-code (368 bits) and the original size of my payload (128 bits), I have to limit the size of the MAC.
This leaves me with several options. I can use basically any HMAC... |
I'm currently trying to implement a PEKS scheme for my master's thesis and got stuck on a check I have no clue how to implement.
The equation looks like this:
$$
\hat{e}\left(P_1, T_3\right)\stackrel{?}{=}\frac{\hat{e}\left(T_1,T_2\right)}{\hat{e}\left(T_1,T_3\right)}
$$
Note: $\hat{e}$ is a bilinear pairing function $... |
i would like to implement a custom Encrypt than HMAC scheme instead of using AES-GCM can anyone share resource to do it correctly . are there any common pitfalls i should be aware of for secure implementation ( i browsed internet but got shady sites like medium.com , i couldn't trust hence asking here , sorry for poor ... |
Problem
I have a central server to store content. A user can create content and control who can decrypt this content. This needs to be secure using E2EE.
How another user knows whether to fetch this content to try decrypt it is out of the scope of this question.
My initial solution
Requirements:
Content must be encryp... |
I am trying to find a good implementation of Merkle Tree generation in Golang, and I need the tree to be resilient to Second Preimage Attack
I have found this standard implementation in the golang docs, but it looks to me like it is susceptible to Second Preimage Attacks, since it only uses 1 hashing algorithm for the ... |
According to video from Dr. Pound, password managers (LastPass in particular) holds encrypted image of your data on their servers and then with master password you authenticate to get encrypted image to client side where decryption is done.
How is this handled when you login to lastpass website with browser?
Is your b... |
Can setting random indexes (and hiding them from the parties) in Shamir's secret sharing solve the colluding problem?
Here, Colluding problem is defined as if the threshold number of fraud parties combine and recover the secret without the knowledge of the dealer and Indexes are the x-coordinates of their respective sh... |
The Skein hash function family defines stream cipher and message authentication code modes of operation.
While these two modes can be used together to perform authenticated encryption with associated data, there is no mention of a single mode of operation to do this.
Ideally, a mode would be defined that would support ... |
I'm searching for ways of replacing a Merkle-tree with something more space-efficient.
I don't need any kind of authentication embedded - the accumulator value can be signed via a separate procedure.
Thanks!
|
I'm currently reading this classic paper "How To Simulate It" and on most of the definitions it is using the term probability ensemble to represent the message space. From my understanding a probability ensemble is like a stochastic process and a probability distribution is an instance of a stochastic process. For exam... |
When reading about the comparison of interactive and non-interactive Zero-Knowledge-Proofs, I came across the statement that non-interactive Zero-Knowledge-Proofs are not deniable compared to interactive ones.
What makes an interactive Zero-Knowledge-Proof deniable, and how is that property lost when transforming it in... |
When verifying a (HMAC) authentication tag it is often indicated that a constant-time comparison is required for security. I can see how leaking information about a password hash can introduce a mild vulnerability as the password hash may become known. However, we're talking here about a calculation over a known and ra... |
Most real-world RSA implementations add padding and such that break the multiplicative homomorphism of raw RSA. However, this multiplicative homomorphism can be useful.
I haven't seen any existing schemes that make RSA semantically secure but maintain the multiplicative homomorphism properly. The only scheme that I h... |
I am developing an implementation of OpenPGP, and I'm using Kleopatra to test my generated messages.
After generating a signature for a message, I compress both the message and signature, but upon decrypting it in Kleopatra, it's treated as an unsigned document, returning to me decrypted and decompressed message with t... |
I was recently trying to gain a better understanding of the SHA-512/256 algorithm and on this NIST example they use the word "abc" as the input. In the Block Contents, it shows the expected hexadecimal 616263 (abc), although why is it directly followed by 0x80 and 0x18 at the very end?
Block Contents:
W[ 0] = 616263800... |
Suppose there is a popular system that is widely used by a huge amount of people. Its security protocol provides a finite group with a generator $g$, and users need to choose a random number $r$ and calculate $h=g^r$ in a certain phase. This is commonly seen in many schemes.
Since this system is widely used by many peo... |
For use use in Encrypt then MAC scheme i am considering using HMAC-SHA256 with 256 bit key, i am wondering if i should use HMAC-SHA512 to be post quantum secure, will simply using HMAC with 256 bit key alone irrespective of hash function will be post quantum secure?
|
Assume to neglect:
The man in the middle attack.
The efficiency of symmetric encryption over asymmetric
I can't understand the usefulness of TLS, with respect to the security, if both parties exchange encrypted and signed messages (i.e <ciphertext, signature>) without TLS.
Is the security communication using TLS the... |
AES uses 256 bit keys. Newer symmetric ciphers like Salsa20 still use at most 256 bit keys. But everyone talks about the security level after quantum computers so they say 128 bit key will provide 64 bit key, 256 bit will be 128 bit. So in the post quantum world we'll have no longer 256 bit security, right? So why don'... |
Public nonces can be problematic for privacy when they can be considered metadata. They can also be troublesome for security if you do things like using a hash of the message as the nonce.
PASETO now derives the nonce alongside the key using HKDF on the input keying material with a 256-bit salt. Thus, the actual nonce ... |
I have two PRGs:
$$G: \{0,1\}^l \rightarrow \{0,1\}^{3l}$$
$$G': \{0,1\}^m \rightarrow \{0,1\}^n , n \gg m$$
I also have a PRF:
$$F: \{0,1\}^{3l} \times\{0,1\}^m\rightarrow \{0,1\}^m $$
Is:
$$\operatorname{F}'(k, x) = G'(F (G(k), x))$$
a PRF?
How can I actually prove this? I was trying defining two different hybrid... |
Background of the question:
I’m working on constructing a cryptosystem to achieve a specific goal that could utilize partially homomorphic schemes. (details of the cryptosystem are out of the scope of this post)
Are there any production-grade usages of any partially homomorphic scheme (ElGamal, Paillier, etc) that mig... |
Background:
I've seen that the value of plain text should be lesser than p*q as per this slide.
I was reading Tanenbaum's Computer Network book the next night, and I saw this thing that I'm not sure that I understood!
I feel he's telling that a PlainText should be less than $$p*q$$.
I'm not getting $$2^k < n$$ thing.
... |
I'm currently building an implementation of the dynamo paper, yottastore. Imagine it as a huge, distributed, hash map.
To find the node holding a key, I use rendezvous hashing (an improvement over consistent hashing), which requires 4 hashes. In order to avoid hash flooding attacks I'm using a keyed hash function, usin... |
As I understand, the one-time pad can be generalized to any finite group. So, for example, if you consider $\mathcal{P} := \mathcal{C} := \mathcal{K} := \{0, 1, ..., 2^{n}-1\}$ for an integer n, and you draw one-time keys $k$ uniformly from $\mathcal{K}$, then encrypting a plaintext $p$ by modular addition $c = p + k\;... |
I'm looking for a way for a single individual to sign or otherwise provide proof of ownership of two private keys from keypairs $A$ & $B$.
Simultaneous ownership is important. Alice can't do part of the proof with $A$, then pass the proof to Bob to finish with $B$. The proof requires both keys in a single step. E.g. Si... |
I have been considering an approach to incentivize cryptocurrency miners to verify claims of quantum computational supremacy. Briefly, miners find collisions $f(x_1)=f(x_2)=y$ of some known $f:m+1\mapsto m$-bit hash function $f$. I envision that a quantum computer broadcasts and commits to $y$ and to another sting $d... |
For a project I'm working on, I need to perform addition, subtraction and dot operations on relatively large encrypted 2x2 dimensional matrices.
The project is written in python and I am using the numpy library for matrix operations.
In order to be able to encrypt the data and perform mathematical operations, I receive... |
I was asking myself the following question but I'm not really sure if it's in this way:
I have a first $PRG$:
$$G_1: \{0,1\}^{\lambda} \rightarrow \{0,1\}^{\lambda+1}$$
Now I want to construct a second $PRG$ that is structured as follows:
$$G: \{0,1\}^{\lambda} \rightarrow \{0,1\}^{2\lambda}$$
Such that ($||$ is the co... |
Contemplating using YubiKey’s challenge-response feature to hash public passphrases.
By public, I mean an attacker could potentially exfiltrate passphrases but, not having YubiKey*, passphrases would be useless.
Is such as scheme secure in 2022 and is it quantum-computing safe?
Thanks for helping out!
*HMAC is computed... |
Given an integer $b$ modulo a prime $q$, one can define a `rounding’ function $\lfloor b\rceil_p$ for a prime $p$, $p<q$, as follows: $$\lfloor b\rceil_p = \lfloor \frac{p}{q}\cdot b\rceil\bmod p.$$ In the paper Pseudorandom Functions and Lattices, it is claimed that the statistical distance between the uniform distrib... |
I have been trying to solve the following:
Given a scheme that is perfectly correct but not perfect secrecy. It satisfies computational security, however, in that, if Q = Pr[Adv wins no query semantic security game], then
$$Pr[Q] \leq \frac{1}{2} + \epsilon$$
for some negligible $\epsilon$ in $n$ which is the security ... |
I have a question about symmetric message authentication codes (MACs).
Say Bob sends encrypted messages to Alice using a symmetric cipher. As I understand it:
(1) Their threat model could or should include the risk of an active attacker sending Alice maliciously crafted ciphertexts for the purpose of exploiting bugs in... |
I'm reading an article "A Tweakable Enciphering Mode" by Halevi and Rogavay and wondering about one statement. On page 6 there are 3 inequalities:
$$
\begin{equation}
\begin{split}
\mathbf{Adv}_{\mathbb{CMC}[\text{Perm}(n)]}^{\pm\text{prp}}(n\sigma) & \leq
\frac{5 \sigma ^ 2}{2 ^ n} \\
\mathbf{Adv}_{\te... |
Given some intervals of long integers (64 Bits). I need to generate alphanumeric strings which:
should be used like passwords(known only by few individuals)
must always be the same for the same integer
must always be different for different integers
must not be easily to be created for another integer if they are know... |
I just came across this question, but it does not really answer my main concern that I have regarding password tokens.
To authenticate a client who is not logged in; I generate two random tokens and then use one as the DB selector, the other one as the validator, to authenticate an unknown client for a given operation,... |
I have the public key, the string itself (not a file), and I am trying to figure out the SHA256 fingerprint, as in the image attached. The default key generated by PuttyGen is SSH-2 RSA with a SHA256 fingerprint. This would help me identify the keys by their fingerprints in the AWS S3 containers, given that I stored on... |
Not sure about the security implications of making HMAC SHA1 message and corresponding hash public (secret would remain… secret)?
Evaluating if that would help an attacker crack algorithm.
|
I have been playing with AES256-GCM in NodeJS crypto library and it shows that the original message can be decrypted without caring about the auth tag.
So can a non-tag verified decryption be secure? Only send the ciphertext+iv to the attaker and assuming he/she knows the ecryption method(in an open source github)?
Upd... |
I wanna create from several inputs/sources should be formed into one hash value for controlling of different thinks later.
Example:
String + File
String + String
File + File
String + File + String
From the logic now there a different ways to do that:
CREATE HASH [(HASH(String)) + (HASH(File))] = HASH-RESULT
CREATE H... |
I am still studying for my crypto 101 and I have a problem with one exercise that I can't find where I'm wrong...
We have p=11 and q=19 (so n=p*q=209) and e=17. I need to encrypt m=5 with RSA system.
So: Crypt_Msg = me mod n = 517 mod 209 = 80
Ok... now I want to decrypt that value (Crypt_Msg=80)...
First of all d = in... |
I am tasked with creating a practical demonstration of a random number.
This means, generating a random number, then showing something practical with it.
Does anyone happen to know something practical to do with it, or use it in a software, or a communication demonstration?
|
This question was originally asked on Reverse Engineering SE, but I
felt that the main part of my question doesn't relate to RE directly,
and it's more about a fundamental understanding of cryptography, hence
why the original question has been removed and re-asked here.
I'm trying to analyze the UDP packets of a P2P ... |
I thought I understood cofactor clearing before I read this write-up which generally seems quite popular (lot of other sites link to it) - Cofactor Explained: Clearing Elliptic Curves' dirty little secret
Let's say you have a group of non-prime order like say $44$. Now, $44 = 11 * 4$. We are interested in working in th... |
I looked into this paper on privacy-preserving aggregation by Marc Joye and Benoit Libert (https://www.ifca.ai/fc13/proc/3-3.pdf). A key element in their scheme is a hash function defined as $$H: \mathbb{Z} \mapsto (\mathbb{Z}/N^{2}\mathbb{Z})^{*}$$ without giving an example of such a construction, which left me puzzle... |
The paper Efficient Schemes for Committing Authenticated Encryption introduces a framework for committing security notions that includes:
CMT-1: commit to the key.
CMT-3: commit to the key, nonce, and associated data.
CMT-4: commit to all inputs, so the message as well.
Then there are D-notions referring to decryptio... |
For some time now, we have been assessing the risks from a GDPR perspective when data (data-at-rest) in the Google Cloud is fully encrypted using native means. This means that we create both the KEK and the DEK completely with Google Cloud KMS and encrypt the storage buckets with it.
Also, we are not currently subject ... |
I was just watching this video on the Double ratcheting protocol.
at around 31:37, the presenter says that the protocol only provides weak forward secrecy.
I've only ever heard about a distinction between Perfect forward secrecy, and "normal" forward secrecy. Where the perfect version is resistant to leakage of long te... |
In some contexts (ZKP of the validity of a decryption key without revealing the message in public, section 3.3 of CAO21), one wants to emit a proof that the encryption of a message with a public key cryptosystem $Enc(m)$ satisfies some properties. Examples of such properties are "$m$ is a private key associated with a ... |
Is it possible that there is a cryptographic hash function that outputs a c-membered subset of the n-membered set?
In other words, can the set of the binary representation of c-membered subsets of the n-membered set, be the range of a hash function?
The hash function will look like below (for 2-membered subset of the 4... |
I have got 4 variables $n$, $x$, $y$, and $z$:
Here, $n = p\cdot q$ with $p$ and $q$ are distinct primes
\begin{align}
x &= m^p \bmod n\\
y &= m^q \bmod n\\
z &= m^n \bmod n\\
\end{align}
How can I find $m$?
|
Is there a special limit in the range of the hash function?
More specifically, is it possible that there is a cryptographic hash function that outputs c-membered subsets of the n-membered set?
In other words, can the set of the binary representation of "all" c-membered subsets of the n-membered set, be the range of a h... |
My question is whether it is possible to use "another" algorithm than the sha256 to hash data but end up with the identical sha256 hash (obviously without using the sha256 algorithm)?
|
I'm implementing a content-addressable file store - similar to a key/value store, but the key is always a hash of the value.
I'd like to build an encryption layer for it, to hide what data is being stored on the server device. Encrypting the data is easy and doesn't need anything special - it'd be just like encrypting ... |
I'm trying to understand Merkle–Damgård construction. We can hash as many blocks of data as we want, if I understand it right. But then it looks like when input is bigger, then also time to compute hash is longer, isn't it?
So is it true that SHA-256 would also calculate the hash longer if input is bigger? Therefore ar... |
Let E be some IND-CPA public key encryption scheme. Given two users with public keys $pk_0,pk_1$ respectively, each user $i$ selects a nonce $r_i$ at random and computes an encryption $c_i = E_{pk_i,r_i}(b_i)$ of some secret bit $b_i\in\{0,1\}$ selected by the user. Is it possible to construct an algorithm A such that
... |
In my open source with offline client side encryption application, I plan to use AES-CTR or ChaCha20 without MAC instead of GCM or Poly1305 since:
There is no database, the ciphertext, nonce, tag stored and encryption happened completely on the user's device, no need to verify authenticity or integrity with any API en... |
Are there any deterministic commitment schemes? What are their security properties, if so? Most ones I see are randomized.
|
I want to understand the difference between randomized encodings and indistinguishability obfuscation (iO).
Are randomized encodings a special type of iO?
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A symmetric key schedule is a key schedule of the form $(k_1,\dots,k_{n-1},k_n,k_{n-1},\dots,k_1)$ or of the form $(k_1,\dots,k_{n-1},k_n,k_n,k_{n-1},\dots,k_1)$. A skew symmetric key schedule is a key schedule of the form $(k_1,\dots,k_{n-1},k_n,g(k_{n-1}),\dots,g(k_1))$ or of the form $(k_1,\dots,k_{n-1},k_n,g(k_n),g... |
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