instruction stringlengths 15 30k |
|---|
Could a one-way accumulator be used in a manner to replace a digital signature? |
Can a one-way accumulator be used in place of a digital signature? |
Could a one-way accumulator be used in a manner to replace a digital signature? Can it provide a way to -1- verify that the data has not been tampered with, and -2- verify that the message is in fact sent/signed by the one who claims to have done.
|
I've implemented the md5 source from a crypt lib from http://sourceforge.net/projects/libcrypt/
The string I'm passing to md5 is `ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890.`
From the md5 provided by my system I receive this hash `26756d7b34ff23859568262596dc159d` but from what I've implement... |
I've implemented the md5 source from a crypt lib from http://sourceforge.net/projects/libcrypt/
The string I'm passing to md5 is `ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890.`
From the md5 provided by my system I receive this hash `26756d7b34ff23859568262596dc159d` but from what I've implement... |
Could a one-way accumulator be used in a manner to replace a digital signature? Can it provide a way to:
1. verify that the data has not been tampered with, and
2. verify that the message is in fact sent/signed by the one who claims to have?
|
I am auditing some software that includes compiled in Diffie–Hellman parameters (2048 bits).
- I can't be sure who generated the DH parameters or how they were generated.
Question:
- Can DH parameters be weak if they were generated improperly or
made intentionally weak?
- Is it possible to *test* DH pa... |
I have read [a paper on Bit Slicing and Lightweight crypto][1] but cannot understand how bitslicing makes encryption scheme faster.
Please can someone explain with an example exactly how bit slicing makes the code faster (even a single xor example will suffice)? Can bitslicing be applied to any encryption scheme?
... |
I'm educating myself about cryptography. I know this is a long one, but please, bear with me. :) Now I have a scenario in my mind and I'd like to ask if what I've thought is sound (enough), what more to take into account and possible pointers.
**Describing the scenario**
1. Let's assume there are *producers*, *P... |
When looking through elliptic curve and modulus posts i can see many examples of people referencing **p** and **n**, in upper and lower case, and sometimes **Q** is written instead of **p** or **P**, and i think i've seen **N** written as **Q** once.
examples i've seen for sepc256k1
> p = 0xffffffffffffffffffffff... |
I want to implement a FHE scheme based on NTRU, namely the scheme described here https://eprint.iacr.org/2014/039.pdf . How to test the security of my implementation ? Do I have to implement the attacks against NTRU-FHE by myself or there are already some programs that do this? |
How to test a FHE implementation? |
I'm quite novice in security, and all examples I saw seem to salt the password by adding it before, or by applying a simple binary OR or XOR.
If I'm right, a hacker should know how the password has been salted in order to retrieve a user password. So, can the complexity of the salting method improve the overall secu... |
Can the salting function complexity improve the hash robustness? |
I'm quite novice in security, and all examples I saw seem to salt the password by adding it before, or by applying a simple binary OR or XOR, so the hash is based on "salt + password", "salt | password", etc.
If I'm right, a hacker should know how the password has been salted in order to retrieve a user password. So... |
I'm quite novice in security, and all examples I saw seem to salt the password by concatenating it, or by applying a simple binary OR or XOR. So the hash is based on "salt + password", "salt | password", etc.
If I'm right, a hacker should know how the password has been salted in order to retrieve a user password. So... |
Lets consider Secure Multiparty Computation based on Secret Sharing schemes (rather than Garbled Circuits approach). If we have to do regular expression matching on secret shares of words of texts. Trivial solution is to secret share each letter of the word and distribute to different parties and later each party execu... |
I'm trying to find a good algorithm for generating authorization codes, access tokens and refresh tokens in an API.
Currently, I am looking into the following setup:
Tokens are generated using the [`RNGCryptoServiceProvider`][1] class in C#. (I have limited the allowed chars to the following set: `abcdefghijkmno... |
Lets consider Secure Multiparty Computation based on Secret Sharing schemes (rather than Garbled Circuits approach). If we have to do regular expression matching on secret shares of words of texts. Trivial solution is to secret share each letter of the word and distribute to different parties and later each party execu... |
Alice and Bob want to play a coin flipping game. Alice wins if the coin flips head.
They choose to trust a independent third party that generates a random beacon (such as NIST). There is no communication only before the random beacon is generated. After it is generated, there may be communication.
Alice has a me... |
When looking through elliptic curve and modulus posts i can see many examples of people referencing $p$ and $n$, in upper and lower case, and sometimes $Q$ is written instead of $p$ or $P$, and I think I've seen $N$ written as $Q$ once.
For example, this is one of the things I've seen for sepc256k1:
> $p$ = 0xfff... |
You can see a little background about this on this [bitcointalk post](https://bitcointalk.org/index.php?topic=3238.0) by the late Hal Finney.
> $\beta$ and $\lambda$ are the values on the secp256k1 curve such that:
$$\begin{align}
\lambda^3 &= 1 \mod N \\
\beta^3 &= 1 \mod P \\
\end{align}$$
As seen [here](ht... |
You can see a little background about this on this [bitcointalk post](https://bitcointalk.org/index.php?topic=3238.0) by the late Hal Finney.
$\beta$ and $\lambda$ are the values on the secp256k1 curve such that:
$$\begin{align}
\lambda^3 &= 1 \mod N \\
\beta^3 &= 1 \mod P \\
\end{align}$$
As seen [here](http... |
**Note:** This question was [reposted from Bitcoin Stack Exchange](http://bitcoin.stackexchange.com/questions/35814/how-do-you-derive-the-lambda-and-beta-values-for-endomorphism-on-the-secp256k1-c), where it received alike answers.
---
You can see a little background about this on this [bitcointalk post](https://... |
The following is more or less a copy-paste of a comment I made on the related ArsTechnica thread. Indeed, StackExchange is probably one of the better places to debate this.
A few reminders first:
- there are approximately $p$ elliptic curves over the finite field of integers $\pmod{p}$;
- of these curves, on... |
Take the lifted ElGamal as an example: suppose the original ciphertext is $<g^y ~mod~q,~g^m~mod~q>$. After some calculations, $m$ could be large enough to do modular. But I don't want $m$ to be reduced to a small value. So I was considering whether I can expand the modular $q$ (e.g., multiply it with another prime $p$)... |
Can I expand the modular of an encryption scheme? |
i am studying about differential cryptanalysis, and found one metric to measure the resistance of a sbox to it, but to use it, it is necessary to build a difference distribution table, like the one in [this link][1], this is is the table of sobox s1 of des, how do I build the table for AES sbox for example?
[1]:... |
How to build a difference distribution table? |
Why does a single bit error in CBC cipher block affects the decryption of a block (Oj) with probabilty of 50% and in the following block why is the one bit error in the exact position as in cipher block? (1 bit error propagation 1:1) |
The basic idea of bitslicing, or [SIMD within a register](https://en.wikipedia.org/wiki/SWAR), involves two parts:
1. expressing the cipher in terms of single-bit logical operations (AND, OR, XOR, NOT, etc.), as if you were implementing it in hardware, and
2. carrying out those operations for *multiple instances ... |
Please, could someone explain to me how KFB mode works and what for the IV in output block stands for? |
Curve25519 - Alice can decrypt her own message to Bob? |
I understand why you need to hash the data before signing it, but don't you need to communicate what hash algorithm you use to whoever will need to verify the signature? How does that normally work? |
How do you communicate the hash function used with RSA signing? |
When it comes to RSA signing, I understand why you need to hash the data before signing it, but don't you need to communicate what hash algorithm you use to whoever will need to verify the signature? How does that normally work? How do you communicate the hash function used with RSA signing? |
Why does a single bit error when using the CBC block cipher mode of operation affect the decryption of a block (Oj) with a probabilty of 50%? And in the following block, why is the one bit error in the exact position as in cipher block? Differently worded: why is the 1 bit error propagation 1:1? |
I'm running into very contradictory opinions when try to understand if weak elliptic curves exist. I'm not interested in the case when a curve's weakness is attributed to properties of an EC's prime, because those cases have been already explored, e.g. here: http://wstein.org/edu/2010/414/projects/novotney.pdf
I wan... |
The following is more or less a copy-paste of a comment I made on the related ArsTechnica thread. Indeed, StackExchange is probably one of the better places to debate this.
A few reminders first:
- there are approximately $p$ elliptic curves over the finite field of integers $\pmod{p}$;
- of these curves, ... |
Concerning private key (symmetric) IND-CPA game definition:
1. Attacker $A$ queries the encryption oracle polynomial number of times.
2. $A$ sends the challenger $C$ a message pair $m_0$ and $m_1$. $C$ picks a random bit $b$ and sends back to $A$ a cyphertext $Enc(m_b)$.
3. $A$ makes further queries to the encrypt... |
I'm running into very contradictory opinions when try to understand if weak elliptic curves exist. I'm not interested in the case when a curve's weakness is attributed to properties of an EC's prime, because those cases have been already explored, e.g. here: http://wstein.org/edu/2010/414/projects/novotney.pdf
I wan... |
As it is discussed [here][1] that the highest security any homomorphic encryption scheme is at most IND-CCA1, Is there any known fully homomorphic encryption scheme that achieves this security level? Out of many schemes mentioned [here][2] (or otherwise) which of them are IND-CCA1 secure ? (not necessarily practical th... |
Which is the strongest known Fully Homomorphic Encryption scheme? |
Which is/are the strongest known Fully Homomorphic Encryption scheme(s)? |
I'm educating myself about cryptography. I know this is a long one, but please, bear with me. :) Now I have a scenario in my mind and I'd like to ask if what I've thought is sound (enough), what more to take into account and possible pointers.
**Describing the scenario**
1. Let's assume there are *producers*, *P... |
Please, could someone explain to me how the [Key feedback mode (KFB)][1] mode works and what the IV in output block stands for? And what properties does the "constant input" has to provide? Should it be random / unpredictable / fixed ?
Then it's encrypted with K which is previous output and then it's xored with the ... |
Please, could someone explain to me how the [Key feedback mode (KFB)][1] mode works and what the IV in output block stands for? And what properties does the "constant input" has to provide? Should it be random / unpredictable / fixed ?
Then it's encrypted with $K$ which is previous output and then it's xored with th... |
Please, could someone explain to me how the [Key feedback mode (KFB)][1] mode works and what the IV in output block stands for? And what properties does the "constant input" has to provide? Should it be random / unpredictable / fixed ?
Then it's encrypted with $K$ which is previous output and then it's xored with th... |
The j-invariants classify the elliptic curves up to isomorphisms (if we suppose to work in the algebraic closure). Is this classification used in some way to decide whether or not an elliptic curve can be used in cryptography?
- If j-invariants *can not* be used for classification, is there an other classification ... |
Can j-invariants be used to decide which elliptic curves are suiteable for cryptography? |
If I have a block-cipher like for example AES,
a plaintext x, we use different function to crypt and decrypt
: crypt(x)=y , decrypt(y)=x
Now, if we build a function with a permutation P(x) with P(P(x))=x :
F(x)=decrypt(P(encrypt(x)) , we have F(F(x))=x , a function that crypt and decrypt.
Does this reduce... |
Concerning private key (symmetric) IND-CPA game definition:
1. Attacker $A$ queries the encryption oracle polynomial number of times.
2. $A$ sends the challenger $C$ a message pair $m_0$ and $m_1$. $C$ picks a random bit $b$ and sends back to $A$ a cyphertext $Enc(m_b)$.
3. $A$ makes further queries to the encrypt... |
Concerning private key (symmetric) IND-CPA game definition:
1. Attacker $A$ queries the encryption oracle polynomial number of times.
2. $A$ sends the challenger $C$ a message pair $m_0$ and $m_1$. $C$ picks a random bit $b$ and sends back to $A$ a cyphertext $Enc(m_b)$.
3. $A$ makes further queries to the encrypt... |
I've recently asked a [question][1] about RSA encryption. One of the things that I don't understand is the usage of two public keys.
In the example on Wikipedia, a message is encrypted like:<br>
`c(m) = m ^ e % n`
This means that I need `e` *and* `n` to do an encryption. Also, in the article `m` is defined as pl... |
How to convert RSA public keys to one key to use for text hashing? |
As I understand, your question is about using an involutive function $F$ as a block cipher. This function is constructed as $F(x) = D(P(E(x)))$, for some (let's assume secure) block cipher represented by $(E, D)$. I will assume the encryption and decryption keys are equal such that the same holds for $F$.
Below is a g... |
got a question as follows -
how to decrypt below in to letters knowing that crypting language is 469 and it base ofcourse on mathematic.
46781! 9063376290 3222011 677 80322429 67538 14805394, 6880326 677 63378129 337011 72683 149630 4378! 453 639 578300 986372 2953639! I know it’s rather short, but still, this poem... |
how to decrypt hidden text under numbers? |
I am going through Steven Kinney's book; "Trusted Platform Module Basics", and pp 90 - 92 discuss how to calculate the authorization digest. He talks about 1H1, 2H1, 3H1, and 4H1 fields which I do not even see in the corresponding diagram. Can anyone explain this process, or point me to a document which does? If you ar... |
If I have a block-cipher like for example AES,
a plaintext $x$, we use different function to encrypt and decrypt
: $\text{encrypt}(x) = y$ , $\text{decrypt}(y)=x$.
Now, if we build a function with a permutation $P(x)$ with $P(P(x))=x:$
$F(x)=\text{decrypt}(P(\text{encrypt}(x))$ , we have $F(F(x))=x$, a function th... |
How do I combine $e$ and $n$ to be one public key?
---
The two *components* of the public key are indeed the modulus and the public exponent. It doesn't really matter how they are stored together, as long as the two components can be reconstructed afterwards.
The most common way is probably using the ASN.1 speci... |
Concerning private key (symmetric) IND-CPA game definition:
1. Attacker $A$ queries the encryption oracle polynomial number of times.
2. $A$ sends the challenger $C$ a message pair $m_0$ and $m_1$. $C$ picks a random bit $b$ and sends back to $A$ a cyphertext $Enc(m_b)$.
3. $A$ makes further queries to the encrypt... |
First post on Crypto SE, so I've attempted to search the term "English" and looked through the first 10 pages of results, to see if this was a common question, I couldn't find a suitable answer.
I'm currently attempting the [Matasano Crypto Challenges](http://cryptopals.com/) as a basic intro to cryptography. For s... |
First post on Crypto SE, so I've attempted to search the term "English" and looked through the first 10 pages of results, to see if this was a common question, I couldn't find a suitable answer.
I'm currently attempting the [Matasano Crypto Challenges](http://cryptopals.com/) as a basic intro to cryptography. For s... |
First post on Crypto SE, so I've attempted to search the term "English" and looked through the first 10 pages of results, to see if this was a common question, I couldn't find a suitable answer.
I'm currently attempting the [Matasano Crypto Challenges](http://cryptopals.com/) as a basic intro to cryptography. For s... |
XTS, as given by the below equation, is a mode of operation primarily targeting full-disk encryption scenarios.
By the way it works it also doubles the keylength although a meet-in-the-middle attack applies (by enumerating all the whitening values). However one only needs to calculate the whitening value once per se... |
Is XTS basically the cheapest form of (secure) double-encryption? |
The details about what an RSA key is made up of are explained succinctly [here][1].
Is it possible to reduce the amount of data that's usually packaged with the key and then derive it later?
[1]: http://stackoverflow.com/a/5404947/356778 |
Is it possible to reduce the size of an RSA key? |
The details about what an RSA key is made up of are explained succinctly [here][1].
Is it possible to reduce the amount of data that's usually packaged with the (private) key and then derive it later?
[1]: http://stackoverflow.com/a/5404947/356778 |
I've recently asked a [question][1] about RSA encryption. One of the things that I don't understand is the usage of two public keys.
In the example on Wikipedia, a message is encrypted like:<br>
`c(m) = m ^ e % n`
This means that I need `e` *and* `n` to do an encryption. Also, in the article `m` is defined as pl... |
"the only thing the simulator can do in the ideal model is to choose the corrupted parties' inputs." [Yehuda Lindell said][1].
1- what will happen when the corrupted parties have no inputs to the protocol? e.g. in cases that the corrupted party/parties are just some computing servers with no input.
2- in these ca... |
how does the simulator work when the corrupted party has no input? |
The basic idea of bitslicing, or [SIMD within a register](https://en.wikipedia.org/wiki/SWAR), involves two parts:
1. expressing the cipher in terms of single-bit logical operations (AND, OR, XOR, NOT, etc.), as if you were implementing it in hardware, and
2. carrying out those operations for *multiple instances ... |
XTS, as given by the below equation, is a mode of operation primarily targeting full-disk encryption scenarios.
By the way it works it also doubles the keylength although a meet-in-the-middle attack applies (by enumerating all the whitening values). However one only needs to calculate the whitening value once per se... |
I've read recently the paper ["Minimalism in Cryptography: The
Even-Mansour Scheme Revisited" by Dunkelman, Keller and Shamir][1] where it is claimed that the following construction is secure:
$$C=K\oplus E(P\oplus K)$$
with $E$ being a publicly known fixed permutation.
**Is there any reason not to use the ab... |
Is there any reason not to use AES-XEX with a constant key? |
I am writing a high-school paper on textbook RSA (the mathematical aspect only). Many definitions of the RSA method start off with saying that one should:
> Generate two large random (and distinct) primes *p* and *q*, each roughly the same size
>(http://cacr.uwaterloo.ca/hac/about/chap8.pdf, page 286)
My quest... |
I've read recently the paper ["Minimalism in Cryptography: The
Even-Mansour Scheme Revisited" by Dunkelman, Keller and Shamir][1] where it is claimed that the following construction is secure:
$$C=K\oplus E(P\oplus K)$$
with $E$ being a publicly known fixed permutation.
**Is there any reason not to use the ab... |
> My question is: what does 'large' imply? How many digits - is there a
> 'limit' to the amount of digits for an suitable prime?
A prime $p$ is called large in this case if factoring the multiplication $pq$ with a similar-sized prime $q$ prime is considered infeasible. <br> Usual sizes of the primes include $2^{102... |
> My question is: what does 'large' imply? How many digits - is there a
> 'limit' to the amount of digits for an suitable prime?
A prime $p$ is called large in this case if factoring the multiplication $pq$ with a similar-sized prime $q$ prime is considered infeasible. <br> Usual sizes of the primes include $2^{102... |
There is one such signature scheme designed specifically for cryptocurrencies:
https://bitcointalk.org/index.php?topic=1129388.0
It is based on ECDSA and works by committing to $k$ (a number used to create the signature, see https://en.wikipedia.org/wiki/ECDSA) in advance by making $k$ x $G$ part of public key. ... |
I've read recently the paper ["Minimalism in Cryptography: The
Even-Mansour Scheme Revisited" by Dunkelman, Keller and Shamir][1] where it is claimed that the following construction (Single-Key EM) is secure:
$$C=K\oplus E(P\oplus K)$$
with $E$ being a publicly known fixed permutation.
**Is there any reason n... |
I want to implement the ATV-FHE scheme as it is described here https://eprint.iacr.org/2014/039.pdf. How to generate the public key ?
Should I compute it as indicated in section 2 :
h(i) = 2g(i)*[ ( f(i) )^(-1) ]
or should I sample the public key as indicated in section 3 Parameter selection in NTRU_FHE :
... |
How to generate public key for ATV-FHE scheme? |
Is there any reason not to use Single-Key EM with AES and a constant key? |
I want to implement the ATV-FHE scheme as it is described here https://eprint.iacr.org/2014/039.pdf. How to generate the public key?
Should I compute it as indicated in section 2 :
> $h(i) = 2g(i)*[ ( f(i) )^{(-1)} ]$
or should I sample the public key as indicated in section 3 Parameter selection in NTRU_FHE... |
In adaptive attacks, if we design poorly, adversary can modify his queries and break the given pseudo random generator (that is distinguish it from uniform randomness).
Is there a poor way to design a PRF such that in one round of query, the adversary cannot distinguish but in two rounds the adversary can?
How ab... |
In adaptive attacks, if we design poorly, adversary can modify his queries and break the given pseudo random function (that is being able to distinguish it from uniform randomness).
Is there a poor way to design a PRF such that in one round of query, the adversary cannot distinguish but in two rounds the adversary c... |
In adaptive attacks, if we design poorly, adversary can modify his queries and break the given pseudo random function (that is being able to distinguish it from uniform randomness).
Is there a poor way to design a PRF such that in one round of query, the adversary cannot distinguish but in two rounds the adversary c... |
PRF that can be distinguished after $k$ queries? |
> So is there any way to break XTS or a double application thereof in less time and/or space than expected?
> The expected time for standard XTS is time $2^{512}$ for 256-bit AES and $2^{513}$ time and $2^{512}$ space for double encryption.
Yes, there are better attacks than that.
With XTS a single sector is e... |
> So is there any way to break XTS or a double application thereof in less time and/or space than expected?
> The expected time for standard XTS is time $2^{512}$ for 256-bit AES and $2^{513}$ time and $2^{512}$ space for double encryption.
Yes, there are better attacks than that.
With XTS a single sector is e... |
I am trying to encrypt the word 'Hello' using RSA. When encryption '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?
|
Encrypt letters separately? |
I am wondering whether e = 2 can be used in unpadded RSA...
It seems like it is not possible to use it: the value of e needs to be coprime with tot(n). tot(n) = (p - 1)(q - 1) where p and q are prime numbers.
The way I see it, there are two scenarios.
1) Neither p nor q are equal to 2. This means they are odd.... |
Can e = 2 be used in unpadded RSA? |
Alice has a secret `S` and publishes some public information `P`, about `S` which is insufficient to recreate `S`.
Is there a way that Bob can use `P`, and an arbitrary integer `I` to create an (EC?) public key for which Alice can subsequently calculate the private key, given `I`?
Does this requirement already ... |
I try to implement the ATV-FHE scheme as described in this paper https://eprint.iacr.org/2014/039.pdf.
How do I choose the bound for the probability distribution chi?
How do I choose standard deviation for this distribution? |
What is the bound for the probability distribution for ATV-FHE scheme? |
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