instruction stringlengths 15 30k |
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DES has 8 different S-boxes, and AES has only 1.
What are the negative consequences of such choices? |
How is AES more secure than DES even if it only has one S-box? |
What are the negative consequences for choosing 8 S-boxes for DES vs 1 S-box for AES? |
While Email encryption can protect the content of an email, the metadata are still readable and can be used to gather important information about the sender and the receiver.
There were several news articles about the Darkmail project, which aims to increase privacy in email communication. The initiative is developi... |
How does darkmail (DIME) work to hide email metadata? |
My question is about Key-Policy ABE (KP-ABE). What does it mean when a "Ciphertext is Labeled with set of attribute"? How is it labeled? |
The coefficient for the highest term in a polynomial should not actually be non zero as this results in an imperfect Shamir scheme.
This is because this assumption means that any attacker will know that the polynomial is definitely of a size t-1. Now if said attacker gained t-1 shares it is actually possible for hi... |
Currently I am learning about [Hybrid Encryption](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) but I was not able to find any good study material.
*Below is my understanding:*
One of the reason why we use `Hybrid Encryption` because `public-key cryptosystems` often rely on complicated mathematical computat... |
Currently I am learning about [Hybrid Encryption](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) but I was not able to find any good study material.
*Below is my understanding:*
One of the reason why we use `Hybrid Encryption` because `public-key cryptosystems` often rely on complicated mathematical computat... |
Currently I am learning about [Hybrid Encryption](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) but I was not able to find any good study material.
*Below is my understanding:*
One of the reason why we use `Hybrid Encryption` because `public-key cryptosystems` often rely on complicated mathematical computat... |
Wiki definition :
> A cryptosystem is considered secure in terms of indistinguishability
> if no adversary, given an encryption of a message randomly chosen from
> a two-element message space determined by the adversary, can identify
> the message choice with probability significantly better than that of
> rand... |
In addition to the [other answer][1].
The _Steps of Hybrid Encryption_ in the question really are steps of one form of hybrid encryption, built on top of asymmetric encryption.
There are other forms of hybrid encryption, including some
- resistant to passive eavesdropping (attacks where the adversary can't sen... |
In addition to the [other answer][1].
The _Steps of Hybrid Encryption_ in the question really are steps of one form of hybrid encryption, built on top of asymmetric encryption.
There are other forms of hybrid encryption, including some
- resistant to passive eavesdropping (attacks where the adversary can't sen... |
Currently I am learning about [Hybrid Encryption](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) but I was not able to find any good study material.
*Below is my understanding:*
One of the reason why we use `Hybrid Encryption` because `public-key cryptosystems` often rely on complicated mathematical computat... |
Why is hybrid encryption more effective than other encryption scheme? |
In addition to the [other answer][1].
The _Steps of Hybrid Encryption_ in the question really are steps of one form of hybrid encryption, built on top of asymmetric encryption.
There are other forms of hybrid encryption (at least for the meaning of that in protocols), including some
- resistant to passive eave... |
In addition to the [other answer][1].
The _"Steps of Hybrid Encryption"_ in the question really are steps of one form of hybrid encryption, built on top of asymmetric encryption.
There are other forms of hybrid encryption (at least for the meaning of that in protocols), including some
- resistant to passive ea... |
I was working on affine coordinates and struggling with the computation time taken for operations and then I was advised to use projective coordinates so that mul-inverse operation can be avoided
Can somebody tell me how to compute 'z'?...I read at some places that z can be assumed as (1,1). If so then can it be use... |
How to compute projective cordinate Z in elliptic curve cryptography? |
The string (32 ASCII characters) is entered by a human, and considered truly random. Should a key derive from this string, or it is secure to use this string as a key directly? In other words, does deriving a key from this string makes the encryption more secure? |
On AES, is a true random string enough for a key? |
Which algorithm would be ideal for ephermal key generation followed by DH key exchange? |
Imagine such protocol.
Client and server initially share secret K[0].
1. When client wants to contact server she sends server K[0] and her ID.
2. Server accepts request, and generated new random K[1] and sends it to client which should use this in next communication.
3. Again, if client wants to authenticate with... |
i want to ask you a question. I have WPA 2(enterprise) network. Also called as 802.1x. I use Linux Zeroshell distribution, which is optimalized for these services. Linux Zeroshell is Radius server. I have also router. I have entered accounts to Zeroshell, which can access network. Each human, which want to connect must... |
Imagine such protocol.
Client and server initially share secret K[0].
1. When client wants to contact server she sends server K[0] and her ID.
2. Server accepts request, and generated new random K[1] and sends it to client which should use this in next communication.
3. Again, if client wants to authenticate with... |
I want to ask you a question.
I have WPA-2 (enterprise) network. Also called as 802.1x.<br>
I use the Linux Zeroshell distribution, which is optimized for these services. Linux Zeroshell is provides a radius server. I also have a router.<br>
I have entered accounts to Zeroshell, which can access the network. Each ... |
Imagine such protocol.
Client and server initially share secret K[0].
1. When client wants to contact server she sends server K[0] and her ID.
2. Server accepts request, and generated new random K[1] and sends it to client which should use this in next communication.
3. Again, if client wants to authenticate with... |
Is the motivation for this a copy protection scheme?
If so, the most obvious problem is that if $K[n]$ is _transmitted_ by the server but not _received_ by the client, then synchronisation is lost.
This could happen if there is a proxy in between as is often the case in corporate networks with HTTP (or more cont... |
Are there any (recent) estimates of cost of attack on DSA with attack on DLP? I'm especially interested in attacks that use Pollard rho algorithm.
Are there any efficient implementations of Pollard rho algorithm that can be used to estimate such costs? |
Are there any (recent) estimates of cost of attack on DSA with attack on DLP? I'm especially interested in attacks that use Pollard rho algorithm.
Are there any optimized implementations of Pollard rho algorithm that can be used to estimate such costs? |
I have a strong interest in one time pads, and I would suggest that your scheme is a poor substitute for two reasons:-
1. What is the key to decode the message? It would have to be related (however indirectly) to the start position in the pi sequence. For example, you can decode my "Hello Joshua" message by start... |
I'm a hobby programmer and very new to this field.
I opened a bank account recently and got two pins. One for the girocard and the other for a creditcard. And I needed two more pins for the online banking account, that I could choose by myself. Just for fun I tried to come up with an algorithm, that generates each pin... |
Is my pin algorithm secure? |
Are there any (recent) estimates of cost of attack on DSA by solving the discrete logarithm? I'm especially interested in attacks that use Pollard's rho algorithm.
Are there any optimized implementations of Pollard's rho algorithm that can be used to estimate such costs? |
Imagine such protocol.
Client and server initially share secret K[0].
1. When client wants to contact server she sends server K[0] and her ID.
2. Server accepts request, and generated new random K[1] and sends it to client which should use this in next communication.
3. Again, if client wants to authenticate with... |
Here is a video on youtube titled "How to launch a nuclear missile", taken in the Titan Missile Museum mentioned by Cort Ammon.
https://www.youtube.com/watch?v=knDIENvBTgw
The message contains a seven character string.
The personnel in the shelter have a set of envelopes with the first two letters on the outsid... |
Assuming that someone discovers your encrypted PINs, knows about your algorithm, but does not know $n$ or $k$, then it is more secure than if they discovered the plan PINs. As you normally only get a few attempts at guessing a PIN
However, there are some features of your algorithm that make it less than perfectly s... |
Assuming that someone discovers your encrypted PINs, knows about your algorithm, but does not know $n$ or $k$, then it is more secure than if they discovered the plain PINs. As you normally only get a few attempts at guessing a PIN
However, there are some features of your algorithm that make it less than perfectly ... |
First, if $e$ is the public key exponent, then the private key exponent $d$ is the (unique) multiplicative inverse modulo $\phi(n)$, or alternatively $ed \equiv 1 \pmod{\phi(n)}$. The reason we want $d$ to have this property is because by Euler's theorem, which says $a^{\phi(n)} \equiv 1 \pmod{n}$ for essentially all v... |
I am currently studying an article on a construction of [Multilinear maps][1]. There are some attacks on the scheme presented by the authors and I got stuck at the one in section 5.1.
I will try to summarize the ideas presented there and ask the questions in the end:
<tex>
Consider the product of $n$ secret dist... |
I am trying to decrypt a RSA encrypted text file. I have a 2048 bit public key.
Analyzing the public key with `openssl` reveals the exponent used is 3.
openssl rsa -pubin -inform PEM -text -noout < publickey.pub
Public-Key: (2048 bit)
Modulus:
00:c7:d6:bc:a5:80:22:35:a5:6d:f4:fa:f0:8d... |
How to determine if padding has been used while encrypting a message with RSA? |
Assuming that someone discovers your encrypted PINs, knows about your algorithm, but does not know $n$ or $k$, then it is more secure than if they discovered the plain PINs. As you normally only get a few attempts at guessing a PIN
However, there are some features of your algorithm that make it less than perfectly ... |
As [explained by Cort Ammon](http://crypto.stackexchange.com/a/31254), they mostly relied on physical, rather than mathematical processes.
[Here is a video on Youtube titled "How to launch a nuclear missile"](https://www.youtube.com/watch?v=knDIENvBTgw), taken in the Titan Missile Museum mentioned by Cort Ammon.
... |
First, if $e$ is the public key exponent, then the private key exponent $d$ is the (unique) multiplicative inverse modulo $\phi(n)$, or alternatively $ed \equiv 1 \pmod{\phi(n)}$. The reason we want $d$ to have this property is because by Euler's theorem, which says $a^{\phi(n)} \equiv 1 \pmod{n}$ for essentially all v... |
First, if $e$ is the public key exponent, then the private key exponent $d$ is the (unique) multiplicative inverse modulo $\phi(n)$, or alternatively $ed \equiv 1 \pmod{\phi(n)}$. The reason we want $d$ to have this property is because by Euler's theorem, which says $a^{\phi(n)} \equiv 1 \pmod{n}$ for essentially all v... |
On a related note of [building my own RNG](http://crypto.stackexchange.com/questions/21186/how-to-roll-my-own-hardware-rng), as someone suggested to use several commericial solutions how can I check if it is rigged against me? (although I am still strongly biased to a homebrew solution that is designed to be hard to su... |
How to tell if a hardware RNG is rigged? |
I have read a lot of summaries of block ciphers particularly with regards to the NIST competitions stating that reduced-round block ciphers are – for example – vulnerable to differential cryptanalysis.
I have a general idea that the application of differential cryptanalysis is to look at the difference between input... |
[Bitcoin](http://www.bitcoin.org/) addresses are RIPEMD-160 hashes of the public portion of a public/private ECDSA keypair (along with an abbreviated hash of the hash to provide a check code, as @pulpspy notes in a comment). They are generally base-58-encoded. See [Address - Bitcoin](https://en.bitcoin.it/wiki/Addres... |
RSA is not designed to be used on long blocks of plaintext like a block cipher. Nevertheless, I need to use it to send a large (encrypted) message.
How can I do this? |
What are the main weaknesses of a [Playfair cipher][1], if any?
I know that they depend on none of the letters missing, but that is an easy fix if a letter gets dropped. Besides that, are there any other problems with it?
[1]: http://en.wikipedia.org/wiki/Playfair_cipher |
What are the main weaknesses of a Playfair cipher, if any? |
I'm trying to learn how RSA works. From what I found online, I'm supposed to
generate private key using Extended Euclidean algorithm.
I've managed to generate the public key, but don't know how to use EEA to generate the private key. How should I exactly input into EEA, and how to process the output?
|
can someone help me in coding of linear cryptanalysis of PRESENT block cipher?
How should I start with 64 bit of plaintext and 80 bits of key? |
The Snowden situation raises an intereting cryptograpic problem. At present, how can something be sent confidentially to Snowden?
**Claim:**
I have no particular political orientation. The above question is merely a cryptographic challenge. The meta assumption is…
1. You trust someone, denoted as Snowden, bu... |
Could anyone tell me what the difference is between a ***theoretical attack*** (Like the one done on SHA-1) and an actual, ***practical attack*** (Like the one done on SHA-0)? Is a theoretical attack a proposed method of attacking, that no one has ever done due to lack of resources (like computing power)? |
I am working towards building a format-compliant encryption system for pictures. The aim of it is to be able to obscure specific areas of a picture (i.e. faces, car license numbers...) while keeping the rest unaltered. The aim would be, for instance, being able to publish a picture on any given social network, making t... |
After spending more than two weeks reading well over 750 pages while checking the following (PDF) documents…
- [Sponge Functions](http://sponge.noekeon.org/SpongeFunctions.pdf)
- [Cryptographic sponge functions](http://sponge.noekeon.org/CSF-0.1.pdf)
- [Security Analysis of Extended Sponge Functions](http://ww... |
I would like to know which method can provide better security: using identity based signature or hashing the identities and message (using SHA-1) for authentication? |
Can someone help me implement linear cryptanalysis of the [PRESENT](https://en.wikipedia.org/wiki/PRESENT_%28cipher%29) block cipher?
How should I start with 64 bits of plaintext and 80 bits of key? |
How to apply linear cryptanalysis to PRESENT? |
We know that it's possible to create a hash using a stream cipher (for instance, RC4 or AES in Counter Mode). As stated [here][1]: "*A Pseudo Random Generator (PRG) and a hash function are both Pseudo Random Functions (PRFs), but they have different security considerations*". Whether or not it's advisable to do so, is ... |
I will be very grateful if someone has an implementation of Sthe atoh algorithm (Fast Elliptic Curve Point Counting). Can someone point me to practical algorithm implementations or provide some examples? Everything I can find is just an article.
|
**[PRESENT](https://en.wikipedia.org/wiki/PRESENT_%28cipher%29)** is an "ultra-lightweight block cipher" developed in 2007. It has a 64-bit block size and an 80 or 128 bit key, and internally uses 31 rounds of a substitution-permutation network based on a single 4-bit S-box. It is included (together with CLEFIA) in t... |
I would be very grateful if someone has an implementation of the [Satoh algorithm](http://www.sciencedirect.com/science/article/pii/S1071579702000138) (Fast Elliptic Curve Point Counting). Can someone point me to practical algorithm implementations or provide some examples? Everything I can find is just an article.
|
We know that it's possible to create a hash using a stream cipher (for instance, RC4 or AES in Counter Mode). As stated [here][1]: "*A Pseudo Random Generator (PRG) and a hash function are both Pseudo Random Functions (PRFs), but they have different security considerations*". Whether or not it's advisable to do so, is ... |
There is a lot of confusion in this question. Hash functions provide collision resistance. However, under a pretty reasonable assumption, they can be used to obtain a PRG or a PRF. Thus, hash functions and stream ciphers can be used to obtain a pseudorandom generator. This is true. (Although RC4 is broken and CANNOT be... |
*Note: I originally posted this as an answer to [another question](http://crypto.stackexchange.com/questions/31031/what-type-of-encryption-scheme-can-prevent-cheating-in-this-coin-flip-protocol) before realizing that it was a duplicate, so I'm reposting it here.*
As already noted, any scheme that lets $B$ choose $c_... |
I am working on this exercise but can't work out the answer to the question b.
I have solved the question (a) by decrypting the ciphertext $C = 2$ using the formula:
$$
M = C^d \bmod n = 2^{17} \bmod 21 = 11
$$
> Alice and Bob agree to communicate using the RSA cryptosystem. Alice has a private key ($n = 21$, $... |
Imagine such protocol.
Client and server initially share secret K[0].
1. When client wants to contact server she sends server K[0] and her ID.
2. Server accepts request, and generated new random K[1] and sends it to client which should use this in next communication.
3. Again, if client wants to authenticate with... |
I have two secret values $a$ and $b$ (i.e. they are arbitrary values). I mask them as follow:
$v_1=r_1a+r_2$
$v_2=r_1(b-a)$
where $r_1$ and $r_2$ are uniformly random values. I send $v_1$ and $v_2$ to a malicious server, and ask him to compute $v_1+v_2=r_1b+r_2$
-----------------------------------
**Questi... |
I have two secret values $a$ and $b$ (i.e. they are arbitrary values). I mask them as follow:
$v_1=r_1a+r_2$
$v_2=r_1(b-a)$
where $r_1$ and $r_2$ are uniformly random values. I send $v_1$ and $v_2$ to a malicious server, and ask him to compute $v_1+v_2=r_1b+r_2$
-----------------------------------
**Questi... |
I am doing a DES problem by hand and I want to know how you calculate the inverse of the initial permutation. I know what the permutation is, but how do you find it based off the given initial permutation? |
DES: How to find the Inverse of the Initial Permutation? |
> Given $v_1$ and $v_2$, can the server learn anything about $a$ and $b$?
Yes, they can (with high probability) determine whether $a = b$; if $v_2 = 0$, then either $r_1 = 0$ or $a = b$; given that $r_1 = 0$ occurs with probability $1/p$, the attacker can conclude that $a = b$.
Now, that's the only thing the atta... |
Is it fine to XOR length of the message into sponge's capacity or that gives attacker control over that part of capacity?
What about adding bit into capacity to denote that there was no padding since message was multiple of rate and therefore reducing number of permutation function executions?
For example NORX XO... |
> Which PRG would be faster? A stream cipher (like AES in Counter Mode) or a Hash Function like SHA-1?
While it is correct to say that it depends on the function, the practical answer is that stream ciphers, including AES in CTR mode, are usually faster at generating output than hash functions. In particular SHA-1. ... |
We know that it's possible to create a hash using a stream cipher (for instance, RC4 or AES in Counter Mode). As stated [here][1]: "*A Pseudo Random Generator (PRG) and a hash function are both Pseudo Random Functions (PRFs), but they have different security considerations*". Whether or not it's advisable to do so, is ... |
I've been learning about RSA and wrote my own implementation. I don't pretend to have intuitive understanding of RSA or that I understand *why* it works, but I believe to have some basic understanding of *how* it works, and believe that my implementation is valid. Due to time penalty of key generation, I set extremely ... |
In regular ElGamal and DSA, we choose large primes $p$ and $q$ such that $p\equiv 1\pmod{q}$, and a group element $g$ of order $q$ by computing $a^{(p-1)/q}$ for some random $a$. This is to prevent smooth group order which can then be factorized, and the discrete log problem can be solved by Polhig-Hellman algorithm.
... |
In regular ElGamal and DSA, we choose large primes $p$ and $q$ such that $p\equiv 1\pmod{q}$, and a group element $g$ of order $q$ by computing $a^{(p-1)/q}$ for some random $a$. This is to prevent smooth group order which can then be factorized, and the discrete log problem can be solved by Pohlig-Hellman algorithm.
... |
In regular ElGamal and DSA, we choose large primes $p$ and $q$ such that $p\equiv 1\pmod{q}$, and a group element $g$ of order $q$ by computing $a^{(p-1)/q}$ for some random $a$. This is to prevent smooth group order which can then be factorized, and the discrete log problem can be solved by Pohlig-Hellman algorithm.
... |
Are textbook RSA signatures secure if an Adversary does not have access to ask signing oracle queries?
|
Unbalanced Feistel networks can be homogenous (F-function identical in each round), or they can be heterogeneous (F-function not always identical in each round).
The advantage of heterogeneous UFNs is, that its internal properties change each round, making it more difficult to find specific characteristics which pro... |
Is there any area where AES-CBC cannot be used ? If so, why? |
In Diffie-Hellman key agreement between Alice and Bob, Alice computes and sends $g^a$ to Bob, and Bob computes and sends $g^b$ to Alice. Alice then computes $(g^b)^a$, and Bob computes $(g^a)^b$; $g^{ab}$ is their shared key. But this is vulnerable to man-in-the-middle attack.
To overcome the man-in-the-middle, supp... |
Why use Diffie-Hellman key exchange over RSA (or any public-key encryption)? |
In Diffie-Hellman key agreement between Alice and Bob, Alice computes and sends $g^a$ to Bob, and Bob computes and sends $g^b$ to Alice. Alice then computes $(g^b)^a$, and Bob computes $(g^a)^b$; $g^{ab}$ is their shared key. But this is vulnerable to man-in-the-middle attack.
To overcome the man-in-the-middle, supp... |
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I'm an embedded systems researcher, and new in crypto field. Actually,
I need to know if there are any lightweight asymmetric encryption algorithm especially from time needed for key generation.
I found that NTRU is considered one of the most lightweight asymmetric crypto system, is this ri... |
I'm an embedded systems researcher, and new in crypto field. Actually, I need to know if there are any lightweight asymmetric encryption algorithm especially from time needed for key generation.
I found that NTRU is considered one of the most lightweight asymmetric crypto system, is this right?
Many thanks In ad... |
I am looking for a modern cipher to encode morse code, ie. input is [A-Z 0-9] and output is the same, one character at a time. The old enigma does a good job at doing this, but is obviously broken.
The cipher doesn't necessarily have to be usable "by hand" (as the "classic ciphers" per definition do), yet it would b... |
Best modern cipher for morse code? |
I'm an embedded systems researcher, and new in the crypto field. Actually, I need to know if there are any lightweight asymmetric encryption algorithm especially considering the time needed for key generation.
I found that NTRU is considered one of the most lightweight asymmetric crypto systems, is this correct? |
When an embedded device needs asymmetric crypto to _encrypt_, (e.g. measurements it makes) or _check authenticity_ (e.g. of commands or firmware updates it receives), there is no need for a private key or key generation in the device, and nothing beats [RSA][1] and [Rabin][2] on simplicity and speed (for RSA: with $e=3... |
I'm a student and I don't know how to solve the following problem :
- Alice is proposing **a 10 questions list** to Bob.
- Bob choose **only 1 question** and wants to know the answer **without Alice knowing the question**.
- Alice wants that Bob can only have **1 correct answer**.
Is it possible ? I... |
>Alice could just generate a random number (to be their shared key), sign it, encrypt it with Bob's public key, and send it to Bob.
I, as an eavesdropper, can capture this exchange. In fact, I can capture many of these as I want with other people communicating with Bob. Then, fast **forward** to some point in the fu... |
I am looking for a modern cipher to encode morse code, ie. input is [A-Z 0-9] (`base36` as I learned in the comments below) and output is the same, one character at a time. The old enigma does a good job at doing this, but is obviously broken.
The cipher doesn't necessarily have to be usable "by hand" (as the "class... |
Is it fine to XOR length of the message or block counter into sponge's capacity or that gives attacker control over that part of capacity?
What about adding bit into capacity to denote that there was no padding since message was multiple of rate and therefore reducing number of permutation function executions?
Fo... |
Are there AES128 keys such that first round key equals last round key? |
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