instruction stringlengths 15 30k |
|---|
Well, there's always the generic option:
- the GM generates a common reference string for a stand-alone
[computationally NIZK argument of knowledge](http://www0.cs.ucl.ac.uk/staff/J.Groth/NIZKJournal.pdf) system
- the GM generates a two inner key-pairs, one for a standard signature scheme
and one for an... |
> How many keys are required for secure communication among 1000 person if:
> 1. Symmetric key encryption algorithm is used?
2. Asymmetric key encryption algorithm is used?
**My guess:**
For symmetric they each need to maintain and transfer their own key, so probably 1000*1000, and for asymmetric maybe just ... |
Well, there's always the generic option:
- the GM generates a common reference string for a stand-alone
<br>
[computationally witness-indistinguishable](http://www0.cs.ucl.ac.uk/staff/J.Groth/NIZKJournal.pdf) system that is [co-sound](http://books.google.com/books?id=DIxCPUBmzlAC&pg=PA288) as
<br>
a stand-alone... |
I just migrated CodesInChaos' C# implementation of Ed25519(ref10) to Java, and everything works fine. (I.e. I get the same results for key generation, signature and verification.)
Now, I would like to do a Diffie-Hellman key exchange directly on Ed25519. Therefore I am examining the functions for point addition, dou... |
Point addition and doubling in Ed25519 (ref10)? |
I just migrated CodesInChaos' C# port of Ed25519(ref10) to Java, and everything works fine. (I.e. I get the same results for key generation, signature and verification.)
Now, I would like to do a Diffie-Hellman key exchange directly on Ed25519. Therefore I am examining the functions for point addition, doubling and ... |
I could not find any mention on the Internet of a proven/known cryptographically secure keyed rolling hash function (ie rolling MAC). Has the question been studied, is it possible to build one ?
By cryptographically secure I mean properties equivalent to HMAC with a cryptographic hash function :
- without knowin... |
Suppose that $N=pq$ where $p$ and $q$ are [safe primes][1]. $\mathbb{QR}_N$ is the group of quadratic residues which is a cyclic group with order $\frac{\phi(N)}{4}$. Let $g$ be the generator of $\mathbb{QR}_N$.
The computational Diffie-Hellman problem is defined as : given $U=g^u\in\mathbb{QR}_N$ and $V=g^v\in\math... |
(If members "expiring" is the _only_ reason for revocation, then you could just skip the whole "standard signature scheme" part of the following, encode the expiration dates into the IDs, and have the signers' arguments include that issue too.)
<br><br><br>
Well, there's always the generic approach:
- the GM gene... |
So the other day, I was piqued by a ciphertext that was trivially encoded through substitution. Solvable only because we can use our eyes to determine word boundary word detection, etc. Trawling the net, there didn't seem to be any automated way of doing this, other than of course to generate a key the size of the alph... |
How to retrieve the plaintext of a substitution ciphertext? |
The results should be the same as you have noted. Although I would think that most people would have a function more akin to `ScalarMult(int, point)` instead of `dbl`. Perhaps you could look at `dbl` and check if it is really a doubling function.
Another check you could perform is to look at the $x$-coordinates of e... |
One simple cryptographically secure rolling hash function is the following:
$$F_k(x) = E_k(R(x))$$
where $R(\cdot)$ is any non-cryptographic rolling hash function (e.g., Rabin-Karp), and $E_k$ represents encryption with a block cipher (e.g., AES).
Why is this a rolling hash, you ask? Well, given $y=F_k(x)$, i... |
I could not find any mention on the Internet of a proven/known cryptographically secure keyed rolling hash function (ie rolling MAC). Has the question been studied, is it possible to build one ?
By cryptographically secure I mean properties equivalent to HMAC with a cryptographic hash function :
- without knowin... |
One simple cryptographically secure rolling hash function is the following:
$$F_k(x) = E_k(R(x))$$
where $R(\cdot)$ is any non-cryptographic rolling hash function (e.g., Rabin-Karp), and $E_k$ represents encryption with a block cipher (e.g., AES).
Why is this a rolling hash, you ask? Well, given $y=F_k(x)$, i... |
I could not find any mention on the Internet of a proven/known cryptographically secure keyed rolling hash function (ie rolling MAC). Has the question been studied, is it possible to build one ?
By cryptographically secure I mean properties equivalent to HMAC with a cryptographic hash function :
- without knowin... |
Consider the [Triple DES](//en.wikipedia.org/wiki/Triple_DES) encryption calculated as:
$$C= E_{K_1}(D_{K_2}(E_{K_1}(P))).$$
For a chosen plaintext attack, given plaintext $P$, we compute the result of $D_{K_2}(E_{K_1}(P))$ and store it as a table of length $2^{112}$, then decrypt the cipertext $C$ using $2^{56}... |
Why is Triple DES not vulnerable to meet in the middle attacks? |
In the ElGamal cryptosystem, I was wondering whether the $m$ (message) should be less than $p$ (large prime). Because on decryption, we are getting $m \bmod p$. For $m \bmod p$ to be equal to $m$, shouldn't $m$ be less than $p$? So what should be the size of $p$? Should it be a very very large prime number if I need to... |
Size of p in ElGamal cryptosystem? |
I just migrated CodesInChaos' C# port of Ed25519(ref10) to Java, and everything works fine. (I.e. I get the same results for key generation, signature and verification.)
Now, I would like to do a Diffie-Hellman key exchange directly on Ed25519. Therefore I am examining the functions for point addition, doubling and ... |
One simple cryptographically secure rolling hash function is the following:
$$F_{k1,k2}(x) = E_{k1}(R_{k2}(x))$$
where $R_{k2}(\cdot)$ is a non-cryptographic rolling hash function (e.g., Rabin-Karp), and $E_{k1}$ represents encryption with a block cipher (e.g., AES). By $R_{k2}(\cdot)$, I mean that the parameter... |
One simple cryptographically secure rolling hash function is the following:
$$F_{k1,k2}(x) = E_{k1}(R_{k2}(x))$$
where $R_{k2}(\cdot)$ is a non-cryptographic rolling hash function (e.g., Rabin-Karp), and $E_{k1}$ represents encryption with a block cipher (e.g., AES). By $R_{k2}(\cdot)$, I mean that the parameter... |
I just migrated CodesInChaos' C# port of Ed25519(ref10) to Java, and everything works fine. (I.e. I get the same results for key generation, signature and verification.)
Now, I would like to do a Diffie-Hellman key exchange directly on Ed25519. Therefore I am examining the functions for point addition, doubling and ... |
I just migrated CodesInChaos' C# port of Ed25519(ref10) to Java, and everything works fine. (I.e. I get the same results for key generation, signature and verification.)
Now, I would like to do a Diffie-Hellman key exchange directly on Ed25519. Therefore I am examining the functions for point addition, doubling and ... |
I was reading the paper [Fully Homomorphic Encryption over the Integers](https://eprint.iacr.org/2009/616.pdf), and started
<br>
wondering if there is a known quantum attack on their main scheme, because
<br>
There is an efficient quantum attack on their "even slightly simpler scheme", as follows:<br>
[complet... |
FHE over the integers - Is that paper's scheme known to be insecure against quantum adversaries? |
I am currently using the ElGamalEngine of bouncy castle to implement exponential ElGamal for the purpose of making ElGamal additively homomorphic. To do this i raise the message to be encrypted to the generator *g* and modulo it with the group parameter *p*, like this:
private BigInteger g;
private BigInteg... |
Why is ElGamalEngine in bouncy castle restricting input data to be less than the length of the group parameter p? |
I could not find any mention on the Internet of a proven/known cryptographically secure keyed rolling hash function (ie rolling MAC). Has the question been studied, is it possible to build one ?
By cryptographically secure I mean properties equivalent to HMAC with a cryptographic hash function :
- without knowin... |
We know there is a man in the middle vulnerability with unauthenticated DH key establishment. And the way to negate that is to use authenticate the keys used. But what if I only verify the signature of one end. Is there any vulnerability then? |
I have ten piece of ciphered texts. I know that they ciphered with same length key Any idea How can i decrypt the texts? what kind of algorithms should i use?
What are the points of taking care of 'xoring' these tags with each other and space character? |
how to decrypt a text which is ciphered same length key? |
I have ten piece of ciphered texts. I know that they ciphered with same length key Any idea How can i decrypt the texts? what kind of algorithms should i use?
What are the points of taking care of 'xoring' these texts with each other and space character?
(text ciphered with the asymmetric key) |
> …what if I only verify the signature of one end?
Bob would not be able to know if he is looking at a signature by Eve, or if it’s a valid signature coming from Alice. In case if Eve is messing with the exchange, Eve would be able to inject her own (as it is handled non-authenticated) **and** Eve would be able to v... |
> …what if I only verify the signature of one end?
Bob would not be able to know if he is looking at a signature by Eve, or if it’s a valid signature coming from Alice. In case if Eve is messing with the exchange, Eve would be able to inject her own (as it is handled non-authenticated) **and** Eve would be able to v... |
> …what if I only verify the signature of one end?
Bob would not be able to know if he is looking at a signature by Eve, or if it’s a valid signature coming from Alice. In case if Eve is messing with the exchange, Eve would be able to inject her own (as it is handled non-authenticated) **and** Eve would be able to v... |
I have ten piece of ciphered texts. I know that they ciphered with a same-length key. Any idea how I can decrypt the ciphertexts? What kind of algorithms should I use? What are the points of taking care of 'XORing' these texts with each other and space character?
(text ciphered with the asymmetric key) |
How to decrypt a text which is ciphered same length key? |
We know there is a man in the middle vulnerability with unauthenticated DH key establishment. And the way to negate that is to use authenticate the keys used. But what if I only verify the signature of one end. Is there any vulnerability then?
EDIT: To be clear, I am not referring to the fact that the authenticated ... |
Let $X\in \Bbb F_2^p$ be some information.
How do I create $Y_1,\dots,Y_n \in \Bbb F_2^q$ so that having less than $n-1$ of the $Y_i$s gives you no information on $X$ but having $n-1$ of them allows you to recover $X$?
----------
I first though of error correcting codes, but I don't think those would be able t... |
I **want** to:
1. **Encrypt** my whole HDD with a **keyfile and** a **password** (meaning that both are required to decrypt it)
2. Be able to **back up** pieces of the **keyfile** in several distant locations using **secret sharing**
3. Be able to **change** the **password** often and easily
---
**Notes**:
... |
I **want** to:
1. **Encrypt** my whole HDD with a **keyfile and** a **password** (meaning that both are required to decrypt it)
2. Be able to **back up** pieces of the **keyfile** in several distant locations using **secret sharing**
3. Be able to **change** the **password** often and easily
---
**Notes**:
... |
### I want to:
1. Encrypt my whole HDD with a keyfile and a password (meaning that both are required to decrypt it),
2. Be able to back up pieces of the keyfile in several distant locations using Secret Sharing,
3. Be able to change the password often and easily.
### Notes:
- The keyfile is made of 4096 rand... |
I am looking for a good pseudo-random number generation algorithm for passwords.
My scenario is that I have to generate 5K pseudo-random bits from a user-supplied password (6 characters). What are possible options and which one would be able to cover for my purposes? |
One simple cryptographically secure rolling hash function is the following:
$$F_{k1,k2}(x) = E_{k1}(R_{k2}(x))$$
where $R_{k2}(\cdot)$ is a non-cryptographic rolling hash function (e.g., Rabin-Karp), and $E_{k1}$ represents encryption with a block cipher (e.g., AES). By $R_{k2}(\cdot)$, I mean that the parameter... |
I have ten piece of ciphered texts. I know that they ciphered with a same-length key. Any idea how I can decrypt the ciphertexts? What kind of algorithms should I use? What are the points of taking care of 'XORing' these texts with each other and space character?
(text ciphered with the asymmetric key)
should we use ... |
Let's say that we have a cryptosystem where Forward Secrecy and Man-In-The-Middle attacks are *not an issue,* purely hypothetically.
Would it be correct for a key exchange with any given public-key algorithm to simply work as follows?
1. Alice calculates public & private key
2. Alice sends the public key to Bo... |
I read about Asymmetric key cryptography like EG-ECC , RSA, ECDH. I understand the concept of mathematics to these algorithms. But I have wondered about the public key for sender and private key for recipient. In other words,
Any other user who wants to send an encrypted message can get the intended **recipient's pu... |
Is it necessary to generate a private key for each encryption process? |
In Merkle Signature, it also requires one-time signature to be used once for a message. The signature in Merkle scheme is even longer compared to Lamport one time signature. The verifier also has more work to do.
Hence, what is the advantages of Merkle compared the one-time (Lamport) signature? |
It's still common to come across implementations of KDF1 and KDF2. Basically these are KDF's that simply derive multiple keys from the key seed and a counter:
$K_i = KDF(K_{master}, i) = H(K_{master} | c)$
In this function $|$ means concatenation and $c$ is the encoded value of $i$ in 4 bytes using an unsigned bi... |
So far as I can find, every method for producing a hash collision in cryptographic hashes involves finding some metric for the distance between two messages' hashes and calculating alterations to each that will iteratively reduce that distance.
And further, unless I'm misreading it, none of the existing attacks is a... |
Hash collision attacks that don't involve iteratively reducing a distance metric? |
If the public key (e,n) and the private key (d,n) are known, how can I find the p and q primes by the easiest way?
When n and fi(n) are given was easy to solve, but this issue I can't manage.
Thanks for any help. |
If the public key (e,n) and the private key (d,n) are known, how can I find the primes p and q in the easiest way?
When n and phi(n) are given was easy to solve, but this issue I can't manage.
Thanks for any help. |
I am curious, is there any paper where SHA-3 competitors are compared in terms of energy efficiency? |
So far as I can find, every method better at producing a hash collisions in cryptographic hashes than exhaustive search involves finding some metric for the distance between two messages' hashes and calculating alterations to each that will iteratively reduce that distance.
And further, unless I'm misreading it, non... |
So far as I can find, every method better at producing hash collisions in cryptographic hashes than exhaustive search involves finding some metric for the distance between two messages' hashes and calculating alterations to each that will iteratively reduce that distance.
And further, unless I'm misreading it, none ... |
Eventually though, unless you're doing it through human intervention, there will be instances where a non fully formed word occurs and the program needs to decide on the relevancy of that word. It seems like you'd have to run the plaintext, after a sufficiently far enough iteration of determining the key, through a lex... |
So the other day, I was piqued by a ciphertext that was trivially encoded through substitution. Solvable only because we can use our eyes to determine word boundary word detection, etc. Trawling the net, there didn't seem to be any automated way of doing this, other than of course to generate a key the size of the alph... |
Ive looked around this site and the web quite a bit, but cant find a definitive answer on whether or not the secret key $k$ used in the AES cryptosystem has to be a prime number? Or can you just use any random values for the $128,192$ or $256$ bit long keys?
As a personal educational exercise, im working on my own i... |
Does the secret key used in AES have to prime? |
I’ve looked around this site and the web quite a bit, but can’t find a definitive answer on whether or not the secret key $k$ used in the AES crypto-system has to be a prime number? Or can you just use any random values for the $128,192$ or $256$ bit long keys?
As a personal educational exercise, I’m working on my o... |
If the decrypting key is 448, then what is the key size? Suppose I am encrypting a plain text with a key by choosing some random numbers between `0` to `1000` then how I can calculate the key size? |
So far as I can find, every method better at producing hash collisions in cryptographic hashes than exhaustive search involves finding some metric for the distance between two messages' hashes and calculating alterations to each that will iteratively reduce that distance.
And further, unless I'm misreading it, none ... |
If the public key $(e,n)$ and the private key $(d,n)$ are known, what is the easiest way to find the primes $p$ and $q$?
When $n$ and $\phi(n)$ are given this is easy to solve. But I can't manage it given just $(e,d,n)$.
Thanks for any help. |
If the decrypting key is `448`, then what is the key size? Suppose I am encrypting a plain text with a key by choosing some random numbers between `0` to `1000` then how I can calculate the key size? |
Is it possible to figure out what $arg1 is if I know both $arg2 and $arg3?
`$hash = hash('sha512', $arg1 . $arg2 . $arg3);` |
Is it possible to figure out what $\$$arg1 is if I know both $\$$arg2 and $\$$arg3?
`$hash = hash('sha512', $arg1 . $arg2 . $arg3);` |
Is it possible to figure out what `$arg1` is if I know both `$arg2` and `$arg3` in addition to `$hash`?
`$hash = hash('sha512', $arg1 . $arg2 . $arg3);` |
I have read numerous times that the RC4 cipher itself is considered broken in TLS. Still many websites are using the *tls_rsa_with_rc4_128_sha* configuration even to date.
Now I know that sometimes different uses of a cipher mitigate different attack scenarios, so my question is straightforward:
Is this particular... |
Is tls_rsa_with_rc4_128_sha still a secure cipher to use? |
I have read numerous times that the RC4 cipher itself is considered broken in TLS. Still many websites are using the *TLS_RSA_WITH_RC4_128_SHA* configuration even to date.
Now, I know that sometimes different uses of a cipher mitigate different attack scenarios, so my question is straightforward: Is this particular ... |
Is TLS_RSA_WITH_RC4_128_SHA still a secure cipher to use? |
Recently I have surveyed a few research papers related to roaming authentication protocol for wireless networks, for example, “**Efficient Privacy-Preserving Authentication in Wireless Mobile Networks**” by Hyo Jin Jo, Jung Ha Paik, and Dong Hoon Lee and “**Secure and Efficient Handover authentication Based on Bilinear... |
Recently, I have surveyed a few research papers related to roaming authentication protocol for wireless networks. For example: [“Efficient Privacy-Preserving Authentication in Wireless Mobile Networks”](http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6636293) by Hyo Jin Jo, Jung Ha Paik, and Dong Hoon Lee an... |
Use case: I have a random number generator that can generate random numbers in a range that is limited by a number $x$, say $x$ ranges from $2$ to $2^{(n - 1)} - 1$ exclusive. In this case $n$ is $16$, i.e. we can generate a number from $0$ to $32767$ exclusive. Programmers will directly identify the upper bound to be ... |
Sure you can depending on the entropy contained in <code>$arg1</code>.
For example, say you know <code>$arg2=Will you marry me?</code>
and
<code>$arg3=\r\n\r\nBob</code>.
If Bob has been dating two girls, say Alice and Trudy, you could guess that either <code>$arg1=Alice,\r\n</code>
or <code>$arg1=Trud... |
I’ve looked around this site and the web quite a bit, but can’t find a definitive answer on whether or not the secret key $k$ used in the AES crypto-system has to be a prime number? Or can you just use any random values for the $128,192$ or $256$ bit long keys?
As a personal educational exercise, I’m working on my o... |
Sure you can depending on the entropy contained in <code>$arg1</code>.
For example, say you know <code>$arg2=Will you marry me?</code>
and
<code>$arg3=\r\n\r\nBob</code>.
If Bob has been dating two girls, say Alice and Trudy, you could guess that either <code>$arg1=Alice,\r\n</code>
or <code>$arg1=Trud... |
Vigenere's weakness is Kasiski's test and index of coincidence. However, if you put columnar transposition on top of Vigenere, that weakness is gone. The text is now shuffled and you can't search for digrams/trigrams, because they will give you wrong key length pattern.
You also can't solve Columnar Transposition. ... |
How to solve cipher encrypted with Vigenere + Columnar Transposition? |
Vigenère's weakness is Kasiski's test and index of coincidence. However, if you put columnar transposition on top of Vigenère, that weakness is gone. The text is now shuffled and you can't search for digrams/trigrams, because they will give you wrong key length pattern.
You also can't solve Columnar Transposition. ... |
How to solve cipher encrypted with Vigenère + Columnar Transposition? |
I could not find any mention on the Internet of a proven/known cryptographically secure keyed rolling hash function (ie rolling MAC). Has the question been studied, is it possible to build one ?
By cryptographically secure I mean properties equivalent to HMAC with a cryptographic hash function :
- without knowin... |
Im looking into "bitcoin like" mining processes. Say a security process uses a hash of data as proof that the data was known at some point in time.
from what I understand, hash functions are pseudorandomly generated based on the initial seed (the raw data).
if the hash function is chaotic, then the seed data sh... |
are deterministic pseudorandom based hash functions chaotic? |
Use case: I have a random number generator that can generate random numbers in a range that is limited by a number $x$, say $x$ ranges from $2$ to $2^{(n - 1)} - 1$ exclusive. In this case $n$ is $16$, i.e. we can generate a number from $0$ to $32767$ exclusive. Programmers will directly identify the upper bound to be ... |
I am implementing ring signatures as a part of an authorization system. Since the number of users could get high enough to make computation on end-user devices infeasible, I am thinking of "subgrouping" them.
My idea is the following:
There are $n$ users and there is an **untrusted** third party, the server $S$ whi... |
So far as I can find, every method better at producing hash collisions in cryptographic hashes than generic collision search involves finding some metric for the distance between two messages' hashes and calculating alterations to each that will iteratively reduce that distance.
And further, unless I'm misreading it... |
On page 21 of the Rivest's [Cryptology][1] chapter, he defines a trapdoor predicate as a boolean function for which it is easy to choose an `x` such that `B(x) = v`, but hard for an adversary to compute `B(x)` given `x`, without the trapdoor information.
He goes on to say that Alice's public key contains a **descri... |
What constitutes a "description of B" for probabilistic encryption as defined in Cryptology 6.3.4? |
For our privacy-preserving protocol, an encrypted channel is established. In order to protect our system from man-in-the-middle attacks, signature-based approach is used. After we've implemented it with RSA, we decided to optimize the protocol a bit by using ECDSA. The result was very surprising: signing and verifying ... |
For our privacy-preserving protocol, an encrypted channel is established. In order to protect our system from man-in-the-middle attacks, signature-based approach is used. After we've implemented it with RSA, we decided to optimize the protocol a bit by using ECDSA. The result was very surprising: signing and verifying ... |
For our privacy-preserving protocol, an encrypted channel is established. In order to protect our system from man-in-the-middle attacks, signature-based approach is used. After we've implemented it with RSA, we decided to optimize the protocol a bit by using ECDSA. The result was very surprising: signing and verifying ... |
I've encountered this term many times in the fields of Fully-Homomorphic Encryption and Obfuscation.
I want to learn those subject and Cryptographic Linear Maps seems to be an obstacle in the way.
Can you help me with that and explain it in simple words (as much as you can)? |
What are Cryptographic Multi-linear Maps? |
I could not find any mention on the Internet of a proven/known cryptographically secure keyed rolling hash function (ie rolling MAC). Has the question been studied, is it possible to build one ?
By cryptographically secure I mean properties equivalent to HMAC with a cryptographic hash function :
- without knowin... |
RSA primes are 100 bit. You know first 80 bits of one of the primes. In this system, come up with an efficient way to decrypt the cipher-text. This was the question on my quiz. I'm not sure how to go about it. Any hints? |
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