instruction stringlengths 15 30k |
|---|
I'm a RSA n00b when it comes to the mathematics for RSA. After spending some time reading, watching lectures, etc. I pretty much have everything down, except for how to figure out the equation for determining the private key (d).
Reading this very Q/A forum, a person said, "There are better ways to find d from e i... |
I'm a RSA n00b when it comes to the mathematics for RSA. After spending some time reading, watching lectures, etc. I pretty much have everything down, except for how to figure out the equation for determining the private key $d$.
Reading this very Q/A forum, a person said, "There are better ways to find $d$ from $e$... |
I'm a RSA n00b when it comes to the mathematics for RSA. After spending some time reading, watching lectures, etc. I pretty much have everything down, except for how to figure out the equation for determining the private key $d$.
Reading this very Q/A forum, a person said, "There are better ways to find $d$ from $e$... |
Using the L-notation, integer factorization of an integer $n$ has the best known complexity of $L_n[1/3,c]$ using general number field sieve. Would discovery of an algorithm with complexity $L_n[1/4,c]$ be of any consequential significance to security of RSA-2048? If my computation is correct, for $c \approx 2$, it sho... |
Using the L-notation, integer factorization of an integer $n$ has the best known complexity of $L_n[1/3,c]$ using general number field sieve. Would discovery of an algorithm with complexity $L_n[1/4,c]$ be of any consequential significance to security of RSA-2048? If my computation is correct, for $c \approx 2$, it sho... |
Using the L-notation, integer factorization of an integer $n$ has the best known complexity of $L_n[1/3,c]$ using general number field sieve. Would discovery of an algorithm with complexity $L_n[1/4,c]$ be of any consequential significance to security of RSA-2048? If my computation is correct, for $c \approx 2$, it sho... |
How about using something similar to [Zobrist hashing][1] and generate the look-up table by coin flips?
Let's say you want to commit to a 64-bit integer and you are able to deliver the look-up table in person and later communicate a 256-bit hash.
Flip the coin 256 x 64 times, with 2 seconds / flip it takes 9.1 ho... |
How about using something similar to [Zobrist hashing][1] and generate the look-up table by coin flips?
Let's say you want to commit to a 64-bit integer and you are able to deliver the look-up table in person and later communicate a 256-bit hash.
Flip the coin 256 x 64 times, with 2 seconds / flip it takes 9.1 ho... |
Alice holds a secret $a \in X$. Bob holds a secret $b \in X$. Is there a protocol that accomplishes the following?
If $a=b$, then Alice and Bob can be sure they indeed have the same secret number.
If $a \neq b$, then Alice learns nothing about $a$, except that $b$ is different from $a$. Likewise Bob learns nothin... |
Is it safe to XOR parameters like domain, length of the message or block counter into sponge's capacity or that gives attacker control over capacity?
For example NORX XORs domain into capacity.
Does this break sponge security proofs?
What about adding bit into capacity to denote that there was no padding since... |
Alice holds a secret $a \in X$. Bob holds a secret $b \in X$. Is there a protocol that lets them compute
$f(a, b) = \begin{cases}
1 & \textrm{if } a = b \\
0 & \textrm{else}
\end{cases}$
If $a \neq b$ they should not learn anything else about each others secret.
---
If $|X|$ is sufficiently large, then t... |
Alice holds a secret $a \in X$. Bob holds a secret $b \in X$. Is there a protocol that lets them compute
$f(a, b) = \begin{cases}
1 & \textrm{if } a = b \\
0 & \textrm{else}
\end{cases}$
If $a = b$ the protocol must always succeed.
If $a \neq b$ they should not learn anything else about each others secret.
... |
How about using something similar to [Zobrist hashing][1] and generate the look-up table by coin flips?
Let's say you want to commit to a 64-bit integer and you are able to deliver the look-up table in person and later communicate a 256-bit hash.
Flip the coin 256 x 64 times, with 2 seconds / flip it takes 9.1 ho... |
How about using something similar to [Zobrist hashing][1] and generate the look-up table by coin flips?
Let's say you want to commit to a 64-bit integer and you are able to deliver the look-up table in person and later communicate a 256-bit hash.
Flip the coin 256 x 64 times, with 2 seconds / flip it takes 9.1 ho... |
Let $E$ be the elliptic curve and $\alpha,\beta$ are two points of $E$ and $a$ is a private key such that $\beta=a\cdot\alpha$. We choose random integer $k$ and plain text $x\in E$. Encryption and decryption methods are as follow:
>$Enc(x,k)=(k\cdot\alpha,x+k\cdot\beta)$
>$Dec(y_1,y_2)=y_2-a\cdot y_1$
How we c... |
I am studying reductions to prove security of crypto systems. Generally are used "games" for the proves. For example, the next image is extracted from the page 91 of the book [Postquantum Cryptography][1]. Here, is constructed an adversary against Lamport-Diffie signature using a Forger with access to an oracle. My que... |
Let $E$ be the elliptic curve and $\alpha,\beta$ are two points of $E$ and $a$ is a private key such that $\beta=a\cdot\alpha$. We choose random integer $k$ and plain text $x\in E$. Encryption and decryption methods are as follow:
>$Enc(x,k)=(k\cdot\alpha,x+k\cdot\beta)$
>$Dec(y_1,y_2)=y_2-a\cdot y_1$
How we c... |
Let $E$ be an elliptic curve; $\alpha,\beta$ two points of $E$; and $a$ a private key such that $\beta=a\cdot\alpha$. We choose random integer $k$ and plain text $x\in E$. Encryption and decryption methods are as follows:
>$\operatorname{Enc}(x,k)=(k\cdot\alpha,x+k\cdot\beta)$
>$\operatorname{Dec}(y_1,y_2)=y_2-a\... |
Is IPsec IND-CCA secure provided the used block cipher is a pseudorandom function? |
I am not aware about a software doing what you're asking. Moreover I think it would be quite difficult to have a software testing for a generic implementation. It would be possible if there was a standard interface to run a specific operation (just think about the symmetric encryption: you have few variables and parame... |
I was reading a proof to the statement:
> Perfect privacy implies that `|K| = |M|`
where I am pretty sure that `K` is the set of keys and `M` is the set of messages.
The proof is the following, but I don't understand it (maybe because of the notation).
> Assume not, i.e., assume we have fewer keys than mes... |
Is it possible to construct a hash function with the following property?
If you have hash(A) and hash(B) with A and B being integers, you can tell if A is greater than B -- without however knowing the actual values of A and B.
Even better: If you have hash(A) and hash(B) with A and B being ordered sets of strings... |
Hash function that allows to decide if A > B if you only have hash(A) and hash(B)? |
I was reading a proof to the statement:
> Perfect privacy implies that $|K| = |M|$
where I am pretty sure that $K$ is the set of keys and $M$ is the set of messages.
The proof is the following, but I don't understand it (maybe because of the notation).
> Assume not, i.e., assume we have fewer keys than mes... |
A wants to buy a company from B. Before A and B enter negotiations, they want to make sure that there actually is a zone of potential agreement. Obviously, they don't want to communicate their reservation prices to the other party (A only buys for less than 100m, B only sells for at least 90m). So they both communicate... |
Protocol to identify zone of potential agreement without revealing reservation prices and having to trust third parties? |
Assume that Alice has a file $F$ which she is going to send, in encrypted form to Bob. Alice possesses $F$ and an encryption key $K$. She sends to Bob the encryption of $F$ using $K$, $E(F,K)$ as well as a hash of the file $H = {\rm hash}(F)$ which is used as a unique blinded identifier of the file. It's assumed that... |
I'm reading [this article][1] and I have a doubt in the page 7. First I going to describe the required definitions and next I formulate my question.
Let be $$F(n)=\{f_k: \{0,1\}^n\rightarrow \{0,1\}^n| k\in \{0,1\}^n\}$$ a family function.
**Definition:** The upper bound $\kappa$ is defined as follows: For each... |
I'm reading [this article][1] and I have a doubt in the page 7. First I going to describe the required definitions and next I formulate my question.
Let be $$F(n)=\{f_k: \{0,1\}^n\rightarrow \{0,1\}^n| k\in \{0,1\}^n\}$$ a family function.
**Definition:** The upper bound $\kappa$ is defined as follows: For each... |
Is it safe to XOR parameters like domain, length of the message or block counter into sponge's capacity or that gives attacker control over capacity?
For example NORX XORs domain into capacity.
Does this break sponge security proofs?
What about adding bit into capacity to denote that there was no padding since... |
Do you allow Bob to ask all the users having $F$ to encrypt, then to upload the file with a same secret key deriving from F ?
Here would be the principle of the tweaked protocol : all the users must encrypt the file with the same key which depends on the file (calculated via another hash). The key would be a kind o... |
Do you allow Bob to ask all the users having $F$ to encrypt, then to upload the file with a same secret key deriving from $F$ ?
Here would be the principle of the tweaked protocol : all the users must encrypt the file with the same key which depends on the file (calculated via another hash). The key would be a kind... |
Is it safe to XOR parameters like domain, length of the message or block counter into sponge's capacity or that gives attacker control over capacity?
For example NORX XORs domain into capacity.
Does this break sponge security proofs?
What about adding bit into capacity to denote that there was no padding since... |
> Is there a protocol that A and B can use to find out the same thing
> without having to trust the other and any third parties?
There is. Even more than one.<br>
Your problem actually is equivalent to [**Yao's Millionaire's Problem**][1].<br>
You have two numbers which two parties want to keep secret and you wan... |
I'm using 4096-bit RSA to encrypt a 256-bit AES key generated client-side. The RSA ciphertext is then sent to the server, and the server decrypts the RSA ciphertext to acquire the AES key. Information is then exchanged between the server and client using the AES key in CBC mode.
I generate a unique IV using a secu... |
Should I be concerned about padding oracle attacks if the lifespan of my key is ~1 minute? |
- [Spartacus](http://crypto.stackexchange.com/users/30267/spartacus): Maybe i came out with the solution, since the cryptosystem described above is not **CCA-secure**, an adversary **A** can intercept **(A,B)** and compute a new ciphertext $$C = 2B\bmod N = 2^er^e \bmod N$$ Since he's carring out a CCA-attack he has ac... |
> Is there a protocol that A and B can use to find out the same thing
> without having to trust the other and any third parties?
There is. Even more than one.<br>
Your problem actually is equivalent to [**Yao's Millionaire's Problem**][1].<br>
You have two numbers which two parties want to keep secret and you wan... |
In Javscript code in one of our application,I am trying to change Math.random to secure random.I am not sure ,how to change.can anybody help? |
I have two prime numbers:
p = 37
q = 41
And I need to find whether any of these prime numbers, 5, 7 or 11, can be used as a valid encryption key e?
My working so far:
Computer their product:
n = p * q = 1517
Compute Euler totient:
m = (p - 1)(q - 1) = 1440
Find greatest common ... |
Is it safe to XOR parameters like domain, length of the message or block counter into sponge's capacity or that gives attacker control over capacity?
For example NORX XORs domain into capacity.
Does this break sponge security proofs?
What about adding bit into capacity to denote that there was no padding since... |
In crypto protocols that contains calculus on elliptic curves I can often see $\dfrac{m}{q}$$Q$ where $m$ stands for order of EC points group and $q$ is the order of corresponding subgroup of $m$. $Q \in q$.
What is the possible sense of this multiplication speaking mathematically?
It's possible that protocol exa... |
What is th purpose of m and q in elliptic curve cryptography protocols? |
Suppose I have two values to be hashed, $x$ and $y$. Is there a function $H$ with the following properties?
$H(x) = H(y), \; H(m(x)) \neq H(m(y)), \; \forall \; x \neq y$
Where $m$ is a permutation function that may depend on $H$. |
how to encrypt decrypt string using MACTripleDES? and is there any difference between MACTripleDES and TripleDES? |
how to encrypt decrypt string using MACTripleDES? |
Sorry for spamming answers but this is an interesting and practical topic :)
I think it is viable to execute GSM's [A5/1][1] algorithm manually by preparing roughly 40 to 50 pieces of `1`s and `0`s or 80 to 100 in total (assuming that out of 64 bits of state roughly 50% are `1`s and 50% `0`s).
The 64-bit commitme... |
Suppose I have two values to be hashed, $x$ and $y$. Is there a hash function $H$ with the following properties?
$H(x) = H(y), \; H(m(x)) \neq H(m(y)), \; \forall \; x \neq y$
Where $m$ is a permutation function that may depend on $H$. |
Suppose I have two values to be hashed, $x$ and $y$. Is there a hash function $H$ with the following properties?
$H(x) = H(y), \; H(m(x)) \neq H(m(y))$
Where $m$ is a permutation function that may depend on $H$.
**Edit**: The corrected question is, if $H(x) = H(y)$, them is it possible to make any permutation ... |
I was asked to encrypt/decrypt a string using MACTripleDES. Is there any difference between *MACTripleDES* and *TripleDES*? If, where exactly is the difference between both? |
What is the difference between MACTripleDES and TripleDES? |
Steven Wolfram of Mathematica uses a pseudorandom number generator based on Rule 30 for applications in Mathematica software but I would like to know if a pseudorandom generator based on Rule 30 is cryptographically secure? Can anyone weigh in on this? |
The IV used in schemes such as CBC has to be random and unpredictable. But at the same time it does not have to be kept secret.
If the IV does not have to be secret, why does it have to be random then? I fail to make sense out of these seemingly contradicting requirements.
I have seen descriptions of attacks ... |
>A Padding Oracle attack due to my use of CBC Cipher Mode
CBC in and of itself does not directly result in a padding oracle. It is when you abuse the padding after decryption to decide whether or not decryption was successful and then communicate (maybe not even directly) the results of that padding check.
Based ... |
I understand that "anagramming" is often used after frequency analysis of a traditional substitution cipher, but anagramming requires prior frequency analysis to provide a starting point. Is there any technique other than frequency analysis for a cipher-text only attack on a traditional substitution cipher? |
Is frequency analysis the only attack on a simple substitution cipher? |
I'm working on a true random number generator, and I came across this phrase in the American NIST [guide][1], in section 6.4.1 Non-Approved Conditioning Components :
"The entropy rate provided shall be no greater than the entropy rate provided by the input to the conditioning component; full entropy shall not be pro... |
What is an impure NIST true random number generator? |
OK, so lots of questions get asked about RC4 but I want to make mine specific and hopefully answerable.
RC4 Design as I'm sure anyone reading this knows, uses self permutation in stage 1 of the KSA.
Is this KSA any better? Can we know easily? Is there proof from a security point of view, this is actually worse, c... |
Do we have anyway of knowing if avoiding self-permutation in RC4 makes it any stronger? |
I took the p&q value as 61 & 53 and n=3233
e=17
d=?
How to find it?
Plz help me... |
How to calculate d in RSA for my number? |
I'm writing a tool to do security posture assessments of SSL/TLS services, and ran into an interesting result. I ran through all defined cipher suites to test which could be negotiated (like sslscan does) and found that an unusual PCT-related cipher suite, `PCT_SSL_CIPHER_TYPE_1ST_HALF` (0x830004) appeared to be accept... |
What is PCT_SSL_CIPHER_TYPE_1ST_HALF? |
I am trying to make a simple 2 way encryption function that currently uses substitute cipher for the encryption and then just swaps via the same base "algorithm" (if you can call it that...).
I want to move away from the sub cipher so my question is as follows:
What things do I need to look out for when creating... |
I am trying to make a simple 2 way encryption function that currently uses a substitute cipher for the encryption and an inverse substitution for the decryption.
I want to move away from this substitution algorithm, so my question is as follows:
What things do I need to look out for when creating a custom encrypt... |
I'm working on a true random number generator, and I came across this phrase in the American NIST [guide][1], in section 6.4.1 Non-Approved Conditioning Components:
> The entropy rate provided shall be no greater than the entropy rate provided by the input to the conditioning component; full entropy shall not be pro... |
I'm doing some research into attacks on the RSA cryptosystem and have stumbled across Wiener's attack. Within the proof there exists the statement "$p+q-1 < 3\sqrt{N}$".
No proof is given for this, and I can't seem to figure out why this statement holds. Could anyone help me figure this out or point me towards the ... |
RSA: Proving that $p+q-1 < 3 \sqrt{N}$, where N = pq and p,q are prime? |
Assume that Alice has a file $F$ which she is going to send, in encrypted form to Bob. Alice possesses $F$ and an encryption key $K$. She sends to Bob the encryption of $F$ using $K$, $E(F,K)$ as well as a compact message authentication code which could be the hash of the file $H = {\rm hash}(F)$, which is used as a u... |
Is it safe and secure to use bin2hex() on output of openssl_random_pseudo_bytes
and mcrypt_create_iv to have them as hexit instead of binary raw data? or this is a security risk and not recommended?
|
Is it secure to use bin2hex() on output of openssl_random_pseudo_bytes? |
studying for CISSP these choices seemed limited
What is the advantage of digital signatures over message authentication codes?
a Digital Signature provides integrity verification while message authentication code can not
b. Digital Signature provides confidentiality while message authentication code can not
c. D... |
What is the advantage of digital signatures over message authentication codes? |
studying for CISSP these choices seemed limited
What is the advantage of digital signatures over message authentication codes?
1. Digital Signature provides integrity verification while message authentication code can not
2. Digital Signature provides confidentiality while message authentication code can not
3.... |
studying for CISSP these choices seemed limited
What is the advantage of digital signatures over message authentication codes?
<code>
1. Digital Signature provides integrity verification while message authentication code can not
2. Digital Signature provides confidentiality while message authentication code can... |
studying for CISSP these choices seemed limited
What is the advantage of digital signatures over message authentication codes?
1. Digital Signature provides integrity verification while message authentication code can not
2. Digital Signature provides confidentiality while message authentication code can not
3.... |
Is it safe and secure to use a function like `bin2hex` (which converts binary data to hexadecimal) on the binary output of functions like `openssl_random_pseudo_bytes` and `mcrypt_create_iv`?
Meaning: can I use the hexadecimal output instead of the raw binary data, or is there some kind of security risk involved whe... |
Studying for CISSP these choices seemed limited:
> What is the advantage of digital signatures over message authentication codes?
> 1. Digital Signature provides integrity verification while message authentication code can not
2. Digital Signature provides confidentiality while message authentication code can no... |
I am trying to find the definitions to several terms related to digital currencies. Unfortunately, I am always ending up on Bitcoin-oriented pages and websites which only take Bitcoin itself into consideration. So far, I managed to understand (actually, *“guess”* would be more appropriate) the following:
1. **Digita... |
Is it secure to use hexadecimal data for IV instead of raw binary? |
Based on [NIST SP 800-38D][1] section 5.2.1.1, it seems that the maximum length of plaintext is 2^39-256 bits ~ 64 GB. We've got 100+GB files in genomics that need to be GCM encrypted so are concerned about hitting this.
So two questions:
* What's the source of this rather low limitation?
* What happens (mathe... |
Plain text size limits for AES-GCM mode just 64GB? |
I am looking at why certain public keys in RSA can't be used, such as:
- 2 and all other even numbers (since $\gcd(\phi,e)$ must equal 1)
- 1 (since the cipher text would equal the message)
- 0 (since the cipher text would be 1. Also because 0 has no
multiplicative inverse)
Let's say we have a message $m... |
Why can the public key exponent in RSA not be negative? |
I am looking at why certain public keys in RSA can't be used, such as:
- 2 and all other even numbers (since $\gcd(\phi,e)$ must equal 1)
- 1 (since the cipher text would equal the message)
- 0 (since the cipher text would be 1. Also because 0 has no
multiplicative inverse)
Let's say we have a message $m... |
Wanted to expand on my [comment](https://crypto.stackexchange.com/questions/31770/do-we-have-anyway-of-knowing-if-avoiding-self-permutation-in-rc4-makes-it-any-st?noredirect=1#comment73835_31770) as an answer.
The KSA in RC4 permutes the bytes [0,1,...,255] using a key, say $k_u$. For any permutation of these bytes,... |
I know that – within the elgamal cryptosystem – the values of $a$ and $b$ are public. But which values are used to create public keys? |
Which values are used for an elgamal cryptosystem public key? |
I am looking at why certain public keys in RSA can't be used, such as:
- 2 and all other even numbers (since $\gcd(\phi,e)$ must equal 1)
- 1 (since the cipher text would equal the message)
- 0 (since the cipher text would be 1. Also because 0 has no
multiplicative inverse)
Let's say we have a message $m... |
Why can’t the public key exponent in RSA be negative? |
I am trying to encrypt the word `Hello` using RSA. When encrypting `Hello`’s integer representation, is each letter encrypted separately, or is the whole thing encrypted? Furthermore, am I correct in assuming that `Hello` is to be represented in binary form for RSA encryption?
|
> Why can the public key exponent not be negative?
Technically, it *can* be. There's just no point to using such negative exponents in general, since for every valid negative RSA exponent, there is an equivalent positive one that is easier to calculate with.
Specifically, for any exponent $e$, message $m$ and mo... |
> Why can the public key exponent not be negative?
Technically, it *can* be. There's just no point to using such negative exponents in general, since for every valid negative RSA exponent, there is an equivalent positive one that is easier to calculate with.
Specifically, for any exponent $e$, message $m$ and mo... |
I have this large number:
1728098743723095094470726818328193358068864405124007684733613106475812450278961107574624070107782941006379
which is the multiplication of two unknown large prime numbers. I try to factorize it with the "Yafu" tool, but i get an error of "time exceeded.
How can I factorize it? How many... |
How can I factorize a 350 bit (106 decimal digits) number in two prime factors? |
I (for a test) just randomly altered a private RSA key by opening it up in vim and changed a few bytes. It is the private part of an SSH key pair used for logging in on a remote system. Puzzlingly, it still allows me to login.
I did some research and found that it is a base64 encoded ASN.1 container, so I pulled all... |
Why does my SSH private key still work after changing some bytes in the file? |
I'm happy to have a crack at this one, providing I've understood your question correctly.
Firstly I wouldn't say the cipher *possibly exhibits low level bias* at any point. It experiences plenty of bias and I'll attempt to explain how we can use it to launch practical attacks. As I'd imagine you know, [the strongest... |
Given the cipher `E(k, m) = m xor k xor rev(k)` where `rev(k)` is the reversed binary of k, how would one prove that the cipher is not perfectly secret.
I know that the definition of perfect secrecy is `P(M = m | C = c) = P(M = m)` for all m and c and that each key is only used once.
Clearly the intuition comes ... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.