instruction stringlengths 15 30k |
|---|
Does removing just last bit from output of one way function change its one wayness? |
If $g(x)$ if length preserving one way function, is there a scenario where $h(x) := g(x)_{1\ldots |x|−1}$ . I.e., $h$ returns all bits that g returns, except for the last bit., is not a one way function.
I think it has to be one way because the probability of inverse just doubles at most. If the probability of inve... |
P256 parameter generation seems to never have been verified: https://credelius.com/credelius/?p=97 |
The seed used in the pre-hash of the SHA1 function for P256 parameter generation seems to never have been verified. If a large chunk of randomly generated curves are "weak", this could be a disaster. The seed was not some simple constant like 0 or 1.
https://credelius.com/credelius/?p=97
There are some additional ... |
It is possible to simply calculate the amount of possibilities and then take the $\log_2$ to get the number of bits that you are using. In this case that means $\log_2(62^{16}) \approx 95$.
However, that is assuming that there is no bias in the chosen values. If you choose a value of 0..255 and you then take the mod... |
> Is there any (open) standard for converting text to numbers before encrypting?
Well, yes and no.
There is the Unicode standard which converts each character as a single code point. But that's not what you are after, you want to encode a complete text into a number.
---
To do this the standard way to opera... |
I am working on improving my grasp on applied cryptography. Following question is just for learning/understanding purposes..
Lets say I want to generate a 16 byte key that I want to use for some symmetric encryption (leaving aside the specific algorithm, IV etc.) which of the following two is better and for what rea... |
First of all a couple of things:
I am aware that cascade encryption tries to solve a problem that isn't present often. Attacks are more likely to be mounted against implementation details instead of creating a pure cryptoanalytic break on modern crypto.
I am also aware that cascade encryption has at least the secur... |
In order to design and analyze a cipher, we have to establish what a cipher is supposed to accomplish. Put simply, we would like to be able to transform information in such a way that only those who are authorized may perform or invert the transformation. We can refer to this transformation as "encryption". Unauthorize... |
I (and many others for that matter) have always been fascinated by the inner workings of _the_ modern building block of cryptography: block ciphers.
Now, the resources on the "black art" of design and analysis of these ciphers are sparse; especially for the entry level. Available information like [the Schneier guide... |
**This is a complementary answer to the others, focusing on theory as well:**
*Step 1*
The Heys' "Tutorial on linear and differential cryptanalysis" [available here][1] which uses 4 rounds of an SPN network with 16 bit block length and four 4x4 Sboxes is a very nice introduction to cryptanalysis where it is possi... |
[This][1] paper suggests the following approach to oblivious transfer (OT), using asymmetric encryption:
1. Receiver generates keypair $(pk_b, sk)$, selects random $t$, and set $pk_{1 - b} = pk_b \oplus \mathsf{H}(t)$;
2. Receiver gives sender $pk_0, t$, and sender challenges receiver to confirm it knows how to dec... |
I don't understand whether they are different or not. Would you mind explaining them all?
- MK-AC, MK-SMI, MK-SMC
- MDK Encryption Key, MDK MAC, MDK AC
- IMK-AC, IMK-SMI, IMK-SMC
For example, in the generation of ICC Master Key(=**U**nique **D**erived **K**ey), EMV Book 2 on page 129, Option A uses *IMK* [wh... |
**1. G known - how to decrypt**
Referring to this question: https://crypto.stackexchange.com/questions/17708/basic-attacks-on-mceliece-finding-s-and-p (nobody answered)
Take a McEliece cryptosystem with public generator matrix $G′=SGP$ where $G$ is a generator matrix of a secret code with known fast decoding (not n... |
In the normal McEliece proposal, the public key
G' = SGP is used, with S beeing non-singular, G Generator Matrix and P permutation Matrix
In the White Paper on McEliece with Binary Goppa Codes by Michiel Marcus and the lecture of Tanja Lange it says that you do not need P because you can just permute the support L... |
I am quite new to ruckack cryptosystems (specifically the merkle-hellman cryptosystem) and don't quite understand what exactly is the density $d(a) = \frac{n}{max_i a_i}$ defined [here][1] among other things. The denominator of the formula of $d(a)$ is the largest element of the weights (i.e. the public key)? What exac... |
I am quite new to knapsack cryptosystems (specifically the merkle-hellman cryptosystem) and don't quite understand what exactly is the density $d(a) = \frac{n}{max_i a_i}$ defined [here][1] among other things. The denominator of the formula of $d(a)$ is the largest element of the weights (i.e. the public key)? What exa... |
I am quite new to knapsack cryptosystems (specifically the merkle-hellman cryptosystem) and don't quite understand what exactly is the density $d(a) = \frac{n}{\log_2max_i a_i}$ defined [here][1] among other things. The denominator of the formula of $d(a)$ is the largest element of the weights (i.e. the public key)? Wh... |
```
slope (s) = 75359724952757581356787150982223137069297282952438962440225639443485944634025
Qx = 112711660439710606056748659173929673102114977341539408544630613555209775888121
Qy = 25583027980570883691656905877401976406448868254816295069919888960541586679410
```
**Derived x and y-coordinate from performing poi... |
Ok, let me preface this by clarifying that I am not a cryptographer by trade, but I've been using cryptographic suites in the context of signing w3c Verifiable Credentials, and I am not sure if this is the right place to ask this question.
In the European framework, eIDAS requires Qualified eSeals for legal entities... |
I'm building an app that will primarily be iOS or Android based. My plan is for every user to have their own key pair. The public key will be stored on the server along with a 128 bit UUID which is used to identify each user. The private key will obviously stay on the device.
When a message is sent to other people t... |
```
slope (s) = 75359724952757581356787150982223137069297282952438962440225639443485944634025
Qx = 112711660439710606056748659173929673102114977341539408544630613555209775888121
Qy = 25583027980570883691656905877401976406448868254816295069919888960541586679410
```
**Derived x and y-coordinate from performing poi... |
```
slope (s) = 75359724952757581356787150982223137069297282952438962440225639443485944634025
Qx = 112711660439710606056748659173929673102114977341539408544630613555209775888121
Qy = 25583027980570883691656905877401976406448868254816295069919888960541586679410
```
**Derived x and y-coordinate from performing poi... |
Given $Q = (Q_x, Q_y)$ the doubling formula under the condition that $Q_y \neq 0$
\begin{align}
s & =\frac{3 Q_x^2+a}{2Q_y} &(1)\\
R_x & = s^2 -2 Q_x \mod p & (2)\\
R_y & = s\cdot (Q_x-R_x) -Q_y \mod p & (3)
\end{align}
So, basically asking;
- given $s, G_x, G_y, p$, and $R_x$ **find** $R_y$;
Then, c... |
Suppose a prover computes a non-interactive proof which is composed of $k$ parallel repetitions of a sigma protocol with binary challenges (and knowledge error $\frac{1}{2}$), composed in parallel and transformed into a non-interactive proof by Fiat-Shamir.
The verifier samples a random subset of $m$-out-of-$k$ of t... |
**PORS** (**PRNG to ORS**) is a secure variant of the **HORS** few-time signature scheme. In **PORS**, instead of using a hash function, it uses a message (and salt) as a seed of PRNG and query it until obtains **k** distinct indices.
As stated in 6.2 [Security of PORS](https://eprint.iacr.org/2017/909.pdf)
**H... |
```
slope (s) = 75359724952757581356787150982223137069297282952438962440225639443485944634025
Qx = 112711660439710606056748659173929673102114977341539408544630613555209775888121
Qy = 25583027980570883691656905877401976406448868254816295069919888960541586679410
```
**Derived x and y-coordinate from performing poi... |
I want to know the state of the art result for proving knowledge of graph isomorphism. As described [here](https://web.cs.ucla.edu/~rafail/PUBLIC/03.pdf), the classical Goldreich-Micali-Wigderson (GMW) protocol is a $\Sigma$-protocol with soundness error $\frac{1}{2}$, so it requires repetition. They then showed a $5$-... |
**Little history;**
- 1997 Peter L. Montgomery introduced the Montgomery curves in 1987 for [speeding up the Speeding the Pollard and Elliptic Curve Methods of Factorization][1]
- 1996 the Montgomery Curve power increased with [the introduction of the side-channel attack][2] circa 1996 by Paul C. Kocher.
Thi... |
I see in many discussion on differential cryptanalysis of SBOX (and others boolean functions, see SIMON-like round functions, SPECK-like round function) the idea of reasoning in terms of *weights* associated with differentials. *Weigth* defined as minus the logarithm of the probability of a transition. Some seem to imp... |
**Little history;**
- 1997 Peter L. Montgomery introduced the Montgomery curves in 1987 for [speeding up the Speeding the Pollard and Elliptic Curve Methods of Factorization][1]
- 1996 the Montgomery Curve power increased with [the introduction of the side-channel attack][2] circa 1996 by Paul C. Kocher.
Thi... |
A (interactive) proof system for a language $\mathcal{L}$ is defined by two algorithms $\mathcal{P}$, a prover, and $\mathcal{V}$, an efficient verifier, with the following requirements:
- Completeness: For $x\in \mathcal{L}$, $\Pr[\mathcal{V}(x, \mathcal{P(x)}) = 1] \geq c$, for some fix constant $c \in (0,1]$.
... |
```
slope (s) = 75359724952757581356787150982223137069297282952438962440225639443485944634025
Qx = 112711660439710606056748659173929673102114977341539408544630613555209775888121
Qy = 25583027980570883691656905877401976406448868254816295069919888960541586679410
```
**Derived x and y-coordinate from performing poi... |
I see in many discussion on differential cryptanalysis of SBOX (and others boolean functions, see SIMON-like round functions, SPECK-like round function) the idea of reasoning in terms of *weights* associated with differentials. *Weight* is defined as minus the logarithm of the probability of a transition. Some seem to ... |
How many distinct sequences can a 128-bit Fib LSFR (considering 4 taps set for the maximum period) generate? Will all 2^128 - 1 distinct seeds produce distinct sequences?
Also, let's say I discard the first 128 bits and only consider the bits that occur after the MSB of the seed has come out of the output end (to a... |
Can the KangarooTwelve Keccak-p[1600,12] be used to create a CSPRNG in which there is random access to an element (or a small group of outputs) of the generated list (instead of sequential generation)?
Perhaps the k-th group of L outputs can be generated as:
* K12(*inputMessage*=seed || k, *customizationString*="... |
We want to implement an encryption / decryption module that we want to provide to different internal components of our system (internal library for internal components).
The component will provide (authenticated) Encryption & Decryption based on state-of-the art algorithms (AES-GCM-256).
Furthermore we have a Pas... |
**Little history;**
- 1997 Peter L. Montgomery introduced the Montgomery curves in 1987 for [speeding up the Speeding the Pollard and Elliptic Curve Methods of Factorization][1]
- 1996 the Montgomery Curve power increased with [the introduction of the side-channel attack][2] circa 1996 by Paul C. Kocher.
Thi... |
**Little history;**
- 1997 Peter L. Montgomery introduced the Montgomery curves in 1987 for [speeding up the Speeding the Pollard and Elliptic Curve Methods of Factorization][1]. This work is now famous due to the Montgomery Ladder that works on Montgomery curves ( there is [Joye Ladder][2] for other curve, however,... |
Why is the Initial Permutation Step necessary in DES? How does it strengthen the cipher since we are reversing the permutation in the output? |
> Why is the Initial Permutation Step necessary in DES? How does it strengthen the cipher since we are reversing the permutation in the output?
The initial permutation doesn't strengthen the cipher at all. Because it is a public unkeyed operation (that is, the adversay can predict exactly how it would transform any... |
How many distinct sequences can a 128-bit Fib LFSR (considering 4 taps set for the maximum period) generate? Will all 2^128 - 1 distinct seeds produce distinct sequences?
Also, let's say I discard the first 128 bits and only consider the bits that occur after the MSB of the seed has come out of the output end (to a... |
I am trying to implement a TRNG on Windows and among other entropy sources, I want to extract raw bytes from various kinds of CPU and process info.
As per my knowledge, BCryptGenRandom is a CRNG in the Windows API that uses this kind of noise to generate entropy. Do files like /dev/random exist on Windows and if so ... |
Is there a counterpart of /dev/random and /dev/urandom in Windows NT systems? |
May I ask that in section 2.7 challenge space in the paper [Lattice-Based Zero-Knowledge Proofs and Applications:
Shorter, Simpler, and More General][1]
[![enter image description here][2]][2]
[1]: https://eprint.iacr.org/2022/284.pdf
[2]: https://i.stack.imgur.com/hIRCD.png
What is rot(c), why does ro... |
The problem of applied machine learning techniques on serious ciphers is that you don't have some good property like continuity which tells you when you are too far, a bit far or close to your solution. Take a look of this polynomial curve over a finite, How do you get the order of the polynomial based on the shape of ... |
The problem of applied machine learning techniques on serious ciphers is that you don't have some good property like continuity which tells you when you are too far, a bit far or close to your solution. Take a look of this polynomial curve over a finite, How do you get the order of this polynomial based on the shape of... |
This answer focus on 3 things:
> 1. K12 hash vs Keccak-p[1600,12].
Although K12 is a concurrent high-throughput hash function, using it for PRNG doesn't necessarily offer the best performance, since its output is serial. Keccak permutation on the other hand, can be run in some special mode of operations to provid... |
According to my understanding a public key is made up of x and y coordinate and a compress public key is made up of the y-coordinate since it's possible to directly calculate the uncompress public key using the compress public key.
Using the below **secp256k1 elliptic curve** coordinate what formula can I use to de... |
I'm trying to figure out why Mersenne Twister use exactly Mersenne prime numbers but not regular primes. What makes Mersenne prime numbers more appropriate for this role than regular primes? |
So I have a set of coordinates and I will hash these with a random salt with SHA256.
Coordinate range is 0,100.
```
salt = abc
[1, 5] = "sZv6eqPT9bqGiXbjvO8yrb4wuFjl0Z1CwSHdnIgGqEI="
[3, 4] = "8XgDJ/rrDELExVflBfDOLjqV5SB//8urxN5I6hxK9Mo="
[6, 3] = "FTzCfctBaBKp/wmopgMw7YFRpo1z2p6/IdHVujFliGs="
[1, 6] = "t2WE+b... |
The problem of applied machine learning techniques on serious ciphers is that you don't have some good property like continuity which tells you when you are too far, a bit far or close to your solution. Take a look of this polynomial curve over a finite, How do you get the order of this polynomial based on the shape of... |
I'll answer a simplified question:
> Why does the [Mersenne Twister][1] use a [Mersenne prime][6]?
The Mersenne Twister is a [Linear-Feedback Shift Register][2]. A LFSR with $n$-bit state generates a [Maximum-length sequence][3] that repeats for the first time after $2^n-1$ steps (starting from any non-zero state) ... |
I'll answer a simplified question:
> Why does the [Mersenne Twister][1] use a [Mersenne prime][6]?
The Mersenne Twister is a [Linear-Feedback Shift Register][2]. A LFSR with $n$-bit state generates a [Maximum-length sequence][3] that repeats for the first time after $2^n-1$ steps (starting from any non-zero state) ... |
I'll answer a simplified question:
> Why does the [Mersenne Twister][1] use a [Mersenne prime][6]?
The Mersenne Twister is a [Linear-Feedback Shift Register][2]. A LFSR with $n$-bit state generates a [Maximum-length sequence][3] that repeats for the first time after $2^n-1$ steps (starting from any non-zero state) ... |
I'll answer a simplified question:
> Why does the [Mersenne Twister][1] use a [Mersenne prime][2]¹?
The Mersenne Twister is a [Linear-Feedback Shift Register][3]. A LFSR with $n$-bit state generates a [Maximum-length sequence][4] that repeats for the first time after $2^n-1$ steps (starting from any non-zero state)... |
I'll answer a simplified question:
> Why does the [Mersenne Twister][1] use a [Mersenne prime][2]¹?
The Mersenne Twister is a [Linear-Feedback Shift Register][3]. A LFSR with $n$-bit state generates a [Maximum-length sequence][4] (M-sequence) that repeats for the first time after $2^n-1$ steps (starting from any no... |
**Background information:**
I need to encrypt 168bit messages, the ciphertext should, preferably, match the plaintext size. Message Authentication and Integrity is not a must, but a really important should. My first idea was using AES-GCM-SIV, but performance is a thing. the software will run on a mini PC (Older Ras... |
I'm researching cryptographic libraries for a project I'm working on, and I'm particularly interested in the BearSSL Library due to its lightweight nature. But I'm not sure if it supports ECC (Elliptic Curve Cryptography) encryption/decryption functionality.
Can someone provide information on whether the BearSSL Lib... |
Does BearSSL Library Support ECC Encryption and Decryption Functionality? |
I'm researching cryptographic libraries for a project I'm working on, and I'm particularly interested in the BearSSL Library due to its lightweight nature. But I'm not sure if it supports ECC (Elliptic Curve Cryptography) encryption/decryption functionality.
Can someone provide information on whether the BearSSL Lib... |
Does BearSSL Library Support ECC Encryption/Decryption Functionality? |
How many distinct sequences can a $128$-bit Fibonacci LFSR (considering $4$ taps set for the maximum period) generate? Will all $2^{128} - 1$ distinct seeds produce distinct sequences?
Also, let's say I discard the first $128$ bits and only consider the bits that occur after the MSB of the seed has come out of the ... |
**Background information:**
I need to encrypt 168bit messages, the ciphertext should, preferably, match the plaintext size. Message Authentication and Integrity is not a must, but a really important should. My first idea was using AES-GCM-SIV, but performance is a thing. the software will run on a mini PC (Older Ras... |
Sorry, this is sort of a beginner question.
But providing that it is possible to find the same options, can I verify a message with Openssl if it was sign with .Net System.Security.Cryptography ?
Let's say I need to do this for sha1, are the underlying algorithms similar enough to be able to verify the signature... |
Can I verify a message with Openssl if it was sign with .Net System.Security.Cryptography? |
I'll answer a simplified question:
> Why does the [Mersenne Twister][1] use a [Mersenne prime][2]¹?
A Mersenne Twister is a [Linear-Feedback Shift Register][3]. A LFSR with $n$-bit state generates a [Maximum-length sequence][4] (M-sequence) that repeats for the first time after $2^n-1$ steps (starting from any non-... |
A Mersenne Twister is a [Linear-Feedback Shift Register][3] and other characteristics, including period a Mersenne prime¹. In essence, the question asks why that's so.
A LFSR with $n$-bit state generates a [Maximum-length sequence][4] (M-sequence) that repeats for the first time after $2^n-1$ steps (starting from an... |
Your background information and initial research are well laid out, and I'll address your queries point by point.
1. **Ciphertext Sizes:** Your observations are correct.
- **ChaCha20-Poly1305**: The addition of the Poly1305 tag does increase the overall size of the ciphertext.
- **AES-GCM-SIV**: The ciphert... |
Suppose we have two sets of ElGamal cipher texts encrypted with the same public key $y$ in a prime order group:
$C_i = (g^{r_i}, a_i y^{r_i}) $ for $ i \in \{1 ... n\}$
and
$D_j = (g^{s_j}, b_j y^{s_i}) $ for $ j \in \{1 ... m\}$
Bob own the private key $x$ to $y$ such that $g^x = y$
Alice wants to know... |
Have any good 8-bit S-boxes made using ARX principles been found yet? I found [Alzette](https://eprint.iacr.org/2019/1378), but it's a huge S-box at 64 bits.
I know that with a combination of addition, rotation, and XOR that any S-box permutation can be achieved, but working backwards would be way too hard for the e... |
Various papers in the literature (such as https://eprint.iacr.org/2022/322.pdf, https://eprint.iacr.org/2013/850.pdf) use the sign, exponent, and significand values to additively secret share the original floating point secrets and later perform arithmetic operations on the shares of sign, exponent, and significand val... |
**Background information:**
I need to encrypt 168bit messages, the ciphertext should, preferably, match the plaintext size. Message Authentication and Integrity is not a must, but a really important should. My first idea was using AES-GCM-SIV, but performance is a thing. the software will run on a mini PC (Older Ras... |
**Background information:**
I need to encrypt 168bit messages, the ciphertext should, preferably, match the plaintext size. Message Authentication and Integrity is not a must, but a really important should. My first idea was using AES-GCM-SIV, but performance is a thing. the software will run on a mini PC (Older Ras... |
Note that your first linked paper open-sourced their code [here](https://github.com/mpc-msri/EzPC). The second paper doesn't have code that is nearly as easy to track down. It mentions using `Sharemind` and `secrec`. I can find the paper on Sharemind (which seems to be some sort of company?)'s website [here](https://sh... |
Quote from https://en.wikipedia.org/wiki/RSA_(cryptosystem)#Operation
> A basic principle behind RSA is the observation that it is practical
> to find three very large positive integers $e$, $d$, and $n$, such
> that with modular exponentiation for all integers $m$ (with $0 ≤ m < n$)
>
> $$ (m^e)^d \equiv m \pm... |
Quote from https://en.wikipedia.org/wiki/RSA_(cryptosystem)#Operation
> A basic principle behind RSA is the observation that it is practical
> to find three very large positive integers $e$, $d$, and $n$, such
> that with modular exponentiation for all integers $m$ (with $0 ≤ m < n$)
>
> $$ (m^e)^d \equiv m \pm... |
$\left(\epsilon,\delta,\gamma\right)$-Random Differential Privacy as defined in [rubenstein17][1]:
$$Pr\left[\forall S \subset \mathbb{R}, Pr\left(A(D) \in S\right) \leq e^{\epsilon} \cdot Pr\left(A(D') \in S\right) + \delta\right] \geq Pr\left[|f(D) - f(D')| \leq \Delta\right] \geq 1 - \gamma$$
$\Delta \text{is ... |
$\left(\epsilon,\delta,\gamma\right)$-Random Differential Privacy as defined in [rubenstein17][1]:
$$\begin{align*}Pr\left[\forall S \subset \mathbb{R}, Pr\left(A(D) \in S\right) \leq e^{\epsilon} \cdot Pr\left(A(D') \in S\right) + \delta\right] &\geq Pr\left[|f(D) - f(D')| \geq \Delta\right] \\ &\geq 1 - \gamma\end... |
Setting all 48 ChaCha state bytes (key, nonce, initial counter) from one result of strong hash function like sha3-384 or blake2b - correct usage? or bad practice?
|
Setting all 48 ChaCha state bytes (key, nonce, initial counter) from one result of strong hash function like sha3-384 or blake2b - correct usage? or bad practice?
PS: using original chacha20 (8bytes nonce/8bytes counter) for encrypting one long file or one-way tcp stream, not multiple small files/messages. |
I am currently working on a cryptography challenge. The program uses AES-GCM to encrypt and decrypt strings.
Let's say I have the following:
- IV which is reused
- cipher text
- authentication tag
Is it possible to uncover the plaintext even if I don't have the key? I've read somewhere that IV reuse ... |
Is it possible to uncover the plaintext if IV is used twice but the key is different? |
A Mersenne Twister is a [Linear-Feedback Shift Register][3] with other characteristics, including period a Mersenne prime¹. In essence, the question asks why that's so.
A LFSR with $n$-bit state generates a [Maximum-length sequence][4] (M-sequence) that repeats for the first time after $2^n-1$ steps (starting from a... |
Suppose I have the following secret, calculated by concatenating and hashing the results of two random strings:
secret = H( H( random_string1 ) || H( random_string2 ) )
Let's assume that the adversary knows one of these strings but not the other. In this case, can the adversary recover the secret in a practical m... |
assuming there is a web service that returns the following to an unauthenticated user:
```
SHA-1(known_prefix + user_input + backend_secret)
```
where `+` is string concatenation, `known_prefix` is known to the attacker, `user_input` can be specified almost arbitrarily (maybe only printable ascii characters, but ... |
> Is there an intelligent way, by specifying different `user_input` strings and analyzing the returned SHA-1 hash, how an attacker could extract the `backend_secret`?
There is no known way.
SHA-1 has two known weaknesses:
- The length extension attack (where, given $SHA(\text{unknown})$, you can compute $SHA(... |
> Is there an intelligent way, by specifying different `user_input` strings and analyzing the returned SHA-1 hash, how an attacker could extract the `backend_secret`?
There is a possible way to get some information on `backend_secret` (at least, the value of the first byte); this might speed up the follow-up brute ... |
I am currently working on a cryptography challenge. The program uses AES-GCM to encrypt and decrypt strings.
Let's say I have the following:
1. IV which is reused
2. only 1 cipher text
3. authentication tag
4. AAD data
Is it possible to uncover the plaintext even if I don't have the key? I've read so... |
> Is there an intelligent way, by specifying different `user_input` strings and analyzing the returned SHA-1 hash, how an attacker could extract the `backend_secret`?
There is a possible way to get some information on `backend_secret` (at least, the value of the first several bytes); this might speed up the follow-... |
A Boolean cardinality constraint
$$\sum_{j=0}^{n-1}x_j=k,$$
where $x_j$’s are Boolean
variables, and $k$ is a non-negative integer.
How to express the Boolean cardinality constraint to CNF formulas? |
Assuming there is a web service that returns the following to an unauthenticated user:
```
SHA-1(known_prefix + user_input + backend_secret)
```
where `+` is string concatenation, `known_prefix` is known to the attacker, `user_input` can be specified almost arbitrarily (maybe only printable ascii characters, but ... |
$\left(\epsilon,\delta,\gamma\right)$-Random Differential Privacy as defined in [rubenstein17][1]:
$$\begin{align*}Pr\left[\forall S \subset \mathbb{R}, Pr\left(A(D) \in S\right) \leq e^{\epsilon} \cdot Pr\left(A(D') \in S\right) + \delta\right] &\geq Pr\left[|f(D) - f(D')| \geq \Delta\right] \\ &\geq 1 - \gamma\end... |
Suppose I encrypt a file, of, say, 10 MB, with a secure, suitable passphrase, and the command:
```sh
gpg --symmetric my_file.txt
```
What level of expertise and hardware would be required, in broad terms, to break the encryption? |
How secure is a file encrypted with GnuPG, a strong passphrase, and the symmetric option? |
I'm diving into SHAKE256's XOF (Extendable Output Function), and I've got a bit of a head-scratcher.
I'm wondering if there's any difference between incrementally absorbing bytes and absorbing everything in one go when it comes to generating the digest. I've scoured the web but couldn't find an answer.
## Scenar... |
In [this question on `sha1(known_prefix + user_input + backend_secret)`](https://crypto.stackexchange.com/q/107983/111411), [an answer states that is realistically possible to find the first few bytes of `backend_secret` quicker than brute force](https://crypto.stackexchange.com/a/107984/111411).
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**Changing o... |
In [this question on `sha1(known_prefix + user_input + backend_secret)`](https://crypto.stackexchange.com/q/107983/111411), [an answer states that is realistically possible to find the first few bytes of `backend_secret` quicker than brute force](https://crypto.stackexchange.com/a/107984/111411).
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**Changing o... |
> Are the results of these two scenarios the same
For $\textrm{SHAKE256}$, both cases result in exactly the same final internal state.
> are there any quirks I should know about?
The [canonical][1] meaning of the inputs to hash and XOF functions should be reflected in a change to their internal states & out... |
$\left(\epsilon,\delta,\gamma\right)$-Random Differential Privacy as defined in [rubenstein17][1]:
$$\begin{align*}Pr\left[\forall S \subset \mathbb{R}, Pr\left(A(D) \in S\right) \leq e^{\epsilon} \cdot Pr\left(A(D') \in S\right) + \delta\right] &\geq Pr\left[|f(D) - f(D')| \leq \Delta\right] \\ &\geq 1 - \gamma\end... |
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