instruction stringlengths 15 30k |
|---|
How can one sign with NTRU? |
I have a personal project in mind in which I plan to use cryptography in order to let the users be confident in the fact that, even if all data get's stolen, it would be virtually impossible to crack in the next few decades.
I would like some advice on the way I planned it until now:
All data resides in two key/v... |
given a CBC ciphertext and IV, How can I find the encryption key ?
We are limited with an 8 chars key, each char in the range of [a..h], so I can generate every possible key. How would I go about finding the correct one though ?
Thanks
|
Given a CBC ciphertext and IV, how can I find the encryption key?
We are limited with an 8 chars key, each char in the range of [a..h], so I can generate every possible key (these are only $8^8 = 2^{24}$ (about 4 million) different possible keys).
How would I go about finding the correct one though? |
How can I do a brute force (ciphertext only) attack on an CBC-encrypted message? |
I can't really understand MixColumns in Advanced Encryption Standard, can anyone help me how to do this?
I found some topic in the internet about MixColumns, but I still have a lot of question to ask.
ex.
|d4| |02 03 01 01| |04|
|bf| . |01 02 03 01| = |66|
|5d| |01 01 02 03| |81|
|... |
Well, it sounds like you're close.
The multiplications implicit within the MixColumns operation are $GF(2^8)$ multiplication operations, using the same field representation as they use in the inverse within the sbox.
However, because they're multiplying by the fixed constants 1, 2 and 3, it's easier to implement ... |
Well, it sounds like you're close.
The multiplications implicit within the MixColumns operation are $GF(2^8)$ multiplication operations, using the same field representation as they use in the inverse within the sbox.
However, because they're multiplying by the fixed constants 1, 2 and 3, it's easier to implement ... |
I can't really understand MixColumns in Advanced Encryption Standard, can anyone help me how to do this?
I found some topic in the internet about MixColumns, but I still have a lot of question to ask.
ex.
$$
\begin{bmatrix}
\mathtt{d4} \\
\mathtt{bf} \\
\mathtt{5d} \\
\mathtt{30} \\
\end{bmatrix}
\cdot
... |
> Textbooks say the one-way function is merely two primes...
Yes, that's the key part.
It turns out that if you have a number that's a product of two large primes, deducing which primes factor that number is quite difficult.
So, what we understand from this is that if you have $n = pq$, and you know $p$ and ... |
I am confused about how keys in asymmetric encryption are generated and what the implications for open communications are. Textbooks say the one-way function is merely two primes (with some critical constraints) -- so how do the two primes generated get turned into keys? Does this mean that having a public key is sim... |
I am confused about how keys in asymmetric encryption are generated and what the implications for open communications are. Textbooks say the one-way function is merely two primes (with some critical constraints) -- so how do the two primes generated get turned into keys?
Does this mean that having a public key is ... |
Well, it sounds like you're close.
The multiplications implicit within the MixColumns operation are $GF(2^8)$ multiplication operations, using the same field representation as they use in the inverse within the sbox.
However, because they're multiplying by the fixed constants 1, 2 and 3, it's easier to implement ... |
I am confused about how keys in RSA asymmetric encryption are generated and what the implications for open communications are. Textbooks say the one-way function is merely two primes (with some critical constraints) -- so how do the two primes generated get turned into keys?
Does this mean that having a public key... |
How are the primes used to generate RSA keys? |
I'm a total noob when it comes to cryptography but I believe this falls under the "zero knowledge" category.
I have two associated pieces of information:
1. **tag** - Known by both parties. Unique per scenario.
1. **identity** - Known by only one party. Potentially associated to multiple tags. Comes from a pool ... |
Can a digital money system exist, that's secure, anonymous and allows offline transactions? |
I'm a total noob when it comes to cryptography but I believe this falls under the "zero knowledge" category.
I have two associated pieces of information:
1. **tag** — known by both parties. Unique per scenario.
1. **identity** — known by only one party. Potentially associated to multiple tags. Comes from a pool ... |
Well, it sounds like you're close.
The multiplications implicit within the MixColumns operation are $GF(2^8)$ multiplication operations, using the same field representation as they use in the inverse within the sbox.
However, because they're multiplying by the fixed constants $\mathtt{1}$, $\mathtt{2}$ and $\math... |
I have written a C implementation of the [Berlekamp-Massey algorithm][1] to work on finite fields of size any prime. It works on most input, except for the following binary GF(2) sequence:
0110010101101 producing LFSR $\langle{}7, 1 + x^3 + x^4 + x^6\rangle{}$
i.e. coefficients $c_1 = 0, c_2 = 0, c_3 = 1, c_4 = 1... |
I am looking to see if this one-way communication protocol is secure. Assume Alice wants to send Bob a message (and doesn't need Bob to reply in the same session/channel - think email). Bob knows Alice's public key $A_{public}$, and Alice knows Bob's public key $B_{public}$. Assume ideal cryptographic primitives for th... |
Is this authenticated one-way communication protocol secure? |
I think you are right, the non-identifiability of Alice and Bob by an attacker is the problematic point. For this to work, you need some requirements on your public-key encryption and signature scheme(s):
* An encrypted message (i.e. your field 1) does not allow any clues on the public key used to encrypt it.
* A s... |
I have a question about RCON
here is my illustration...
this is the 128 bit key..
[2b] [28] [ab] [09]
[7e] [ae] [f7] [cf]
[15] [d2] [15] [4f]
[16] [a6] [88] [3c]
and then I will get this..
[09]
[cf]
[4f]
[3c]
and then I will put down the first 8bit(1byte) where it is the 09
0= 0000... |
I have a question about RCON
here is my illustration...
this is the 128 bit key..
[2b] [28] [ab] [09]
[7e] [ae] [f7] [cf]
[15] [d2] [15] [4f]
[16] [a6] [88] [3c]
and then I will get this..
[09]
[cf]
[4f]
[3c]
and then I will put down the first 8bit(1byte) where it is the 09
0= 0000... |
Is it true that there is no feasible attack on Advanced Encryption Standard? all of them are infeasible, according to my research, there is one known attack that was developed by some Microsoft researcher but it is not really a threat. |
I have a question about RCON
here is my illustration...
this is the 128 bit key..
[2b] [28] [ab] [09]
[7e] [ae] [f7] [cf]
[15] [d2] [15] [4f]
[16] [a6] [88] [3c]
and then I will get this..
[09]
[cf]
[4f]
[3c]
and then I will rotate down the first 8bit(1byte) wh... |
I have heard a lot about the [biclique](http://research.microsoft.com/en-us/projects/cryptanalysis/aes.aspx) cryptanalysis research on AES, which as far as I know is the closest anyone has got to breaking AES.
Exactly how close did they get? Does this attack propose a credible risk to my using AES today? Exactly how... |
Does the Biclique attack on AES pose a credible risk to its security? |
I realize that this isn't a site for reviewing code, but I created a basic file encryption method, that seems pretty secure to me, but one of my colleagues claims that it can be cracked if you know the length of the password.
The way the encryption works, is that it reads the byte value of the file, puts it into an... |
How crackable is the following file encryption? |
I realize that this isn't a site for reviewing code, but I created a basic file encryption method, that seems pretty secure to me, but one of my colleagues claims that it can be cracked if you know the length of the password.
The way the encryption works, is that it reads the byte value of the file, puts it into an... |
I realize that this isn't a site for reviewing code, but I created a basic file encryption method, that seems pretty secure to me, but one of my colleagues claims that it can be cracked if you know the length of the password.
The way the encryption works, is that it reads the byte value of the file, puts it into an... |
How crackable is the Vigenère cipher in file encryption? |
I have a question about RCON
here is my illustration...
this is the 128 bit key..
[2b] [28] [ab] [09]
[7e] [ae] [f7] [cf]
[15] [d2] [15] [4f]
[16] [a6] [88] [3c]
and then I will get this..
[09]
[cf]
[4f]
[3c]
and then I will rotate down the first 8bit(1byte) wh... |
I am confused, How can I encrypt File using 128 Bit Advanced Encryption Standard.
Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it?
ex. I want to encrypt a ms word file or a pdf file. |
I'm looking into blind signature schemes for use as digital cash. I have come across blinded RSA, and [Lucre](http://anoncvs.aldigital.co.uk/lucre/)(DSA based). Are there other schemes available, and how do they compare? I suspect there should be a ECDSA scheme, which might have better performance than the other scheme... |
Which blind signature schemes exist, and how do they compare? |
I am confused, How can I encrypt File using 128 Bit Advanced Encryption Standard.
Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it? ex. there is something that I will extract to the file to encrypt it.
ex. I want to encrypt a ms word file or a pdf file. |
You are right to be confused, because you could you just as well have asked "How can I encrypt a file using a CPU that supports xor, shifts and rotates?" The answer is that of course you can, but there is obviously a lot more to it, if you are going to do it right.
AES is just a standard block cipher primitive. The ... |
I'm looking into blind signature schemes for use as digital cash. I have come across blinded RSA, and [Lucre](http://anoncvs.aldigital.co.uk/lucre/)(DH based). Are there other schemes available, and how do they compare? I suspect there should be a elliptic curve scheme, which might have better performance than the othe... |
I am confused, How can I encrypt File using 128 Bit Advanced Encryption Standard.
Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it? ex. there is something that I will extract to the file to encrypt it.
ex. I want to encrypt a ms word file or a pdf file.
... |
I am confused, how can I encrypt a file using 128 Bit Advanced Encryption Standard?
Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it? Is there something that I will need to extract to the file to encrypt it?
For example, I want to encrypt a ms word fil... |
How to perform file encryption using 128-Bit AES? |
I'm looking into blind signature schemes for use as digital cash. I have come across blinded RSA, and [Lucre](http://anoncvs.aldigital.co.uk/lucre/)(DH based). Are there other schemes available, and how do they compare? I suspect there should be a elliptic curve scheme, which might have better performance than the othe... |
Depends on what you mean by secure. If you merely want the ability to detect and then presumably punish double spending, you can do that in a way that is secure and anonymous: double spending reveals enough information to provably identify the user. Since honest users don't double spend, they are still anonymous. This ... |
I created a basic file encryption method, that seems pretty secure to me, but one of my colleagues claims that it can be cracked if you know the length of the password.
The way the encryption works, is that it reads the byte value of the file, puts it into an array, and then takes the password, encrypts it with MD5... |
How crackable is the Vigenère cipher in file encryption when encrypting the password with MD5 first? |
I created a basic file encryption method, that seems pretty secure to me, but one of my colleagues claims that it can be cracked if you know the length of the password.
The way the encryption works, is that it reads the byte value of the file, puts it into an array, and then takes the password, encrypts it with MD5... |
How secure is the Vigenère cipher in file encryption if you encrypt the password first? |
**Note:** *If you decide to downvote this question, I would appreciate it if you could leave a comment as to why, so I can fix the question accordingly*
----
I created a basic file encryption method, that seems pretty secure to me (based on an answer below, it seems to be an implementation of the Vigenère cipher)... |
I know that Elgamal algorithms have fallen out of fashion, and they are not included in any widespread cryptographic standard nowadays. However, they are still present in several popular crypto libraries (bouncy castle, botan, cryptopp, etc). One disturbing thing I found is that such libraries have no or very limited t... |
RSA was there first. That's actually enough for explaining its preeminence. RSA was first published in 1978 and the [PKCS#1][1] standard (which explains exactly how RSA should be used, with unambiguous specification of which byte goes where) has been publicly and freely available since 1993. The idea of using elliptic ... |
I created a basic file encryption method, that seems pretty secure to me (based on an answer below, it seems to be an implementation of the Vigenère cipher) , but one of my colleagues claims that it can be cracked if you know the length of the password.
The way the encryption works, is that it reads the byte value ... |
Can a proof be constructed to show there is no distinguisher? |
I'm trying to find faster ways to solve this:
http://cryptogram.org/solve_cipher.html
Actually lists of common words are good, but they are often limited to 1000 words.
http://wordlist.sourceforge.net/12dicts-readme.html
I found this, but I'm not sure which one to use, but the word list still seems too large
D... |
Existing dictionnaries of popular words to help solve a random substitution cipher? |
If we have a hash function h(x) and then a hash function H(X) = h(h(X_0) + h(X_1)) where X_0 is the first half of X, X_1 is the second half of X and + is concatenation. Then assuming we can easily find a collision for H, then it would be easy to find a collision for h as well - Therefore finding a collision for H is as... |
I showed my friend this post, and wrote a program to crack it. (this is assuming the password is exactly 3 characters long though). Here is the code he wrote (it's in java):
import java.util.Scanner;
import java.io.*;
import java.util.ArrayList;
public class Test {
/**
* @param args
*... |
My friend (Jerome Kelman (he wanted me to quote him as the author when I posted this)), wrote a program to crack it. (this is assuming the password is exactly 3 characters long though). Here is the code he wrote (it's in java):
import java.util.Scanner;
import java.io.*;
import java.util.ArrayList;
... |
If we have a hash function $h(x)$ and then a hash function $H(X) = h(h(X_0) || h(X_1))$ where $X_0$ is the first half of $X$, $X_1$ is the second half of $X$ and $||$ is concatenation. Then assuming we can easily find a collision for $H$, then it would be easy to find a collision for $h$ as well - Therefore finding a c... |
An asymptotic lower bound such as exponential-hardness is generally thought to imply that a problem is "inherently difficult". Encryption that is "inherently difficult" to break is thought to be secure.
However, an asymptotic lower bound does not rule out the possibility that a huge but finite class of problem insta... |
Are asymptotic lower bounds relevant to cryptography? |
The practical security of any cryptosystem ultimately depends on the separation of the complexity classes P and NP. Until that day comes, and let's not hold our breath waiting for someone to prove the P vs NP conjecture either way, no cryptosystem can be said to be so "complex" as to be unbreakable. For example, say y... |
*. I'm talking on a cipher text only attack - I got as input only the Initialize vector and one cipher text.
Hi all, I know the key domain: letters "a-h", and the padding is zero's (don't know if that helps).
Problem is that after XORing (as part of the CBC schema) most of the remaining letters are not part of the ... |
cipher text only attack - how to know when to stop when brute-force attack? |
This question is an extension of http://crypto.stackexchange.com/questions/1534/families-of-public-private-keys-in-elliptic-curve-cryptography
As described above, bitcoin "type 2" deterministic wallets use a root private/public key pair, where subsequent keys take advantage of the fact that in elliptic curve cryptog... |
One nice way to generate a word list is distilling it from a large amount of texts.
There are a few interesting effects with this creation method:
* The word frequency depends a lot on the chosen texts. For example when feeding it wikipedia the language is rather formal, and common every-day words are pretty rare... |
My question is about a cipher text only attack - I have as input only the initialization vector and one cipher text.
I know the key domain: letters "a-h", and the padding is zero's (don't know if that helps).
Problem is that after XORing (as part of the CBC schema) most of the remaining letters are not part of th... |
I'm trying to find faster ways to solve this:
http://cryptogram.org/solve_cipher.html
Actually lists of common words are good, but they are often limited to 1000 words.
I found [this][1], but I'm not sure which one to use, but the word list still seems too large.
Do you know lists of 10k, 20k, 30k words, or t... |
Existing dictionaries of popular words to help solve a random substitution cipher? |
> **Possible Duplicate:**
> [How can I do a brute force (ciphertext only) attack on an CBC-encrypted message?](http://crypto.stackexchange.com/questions/2394/how-can-i-do-a-brute-force-ciphertext-only-attack-on-an-cbc-encrypted-message)
<!-- End of automatically inserted text -->
My question is about a cipher tex... |
There are a number of distinguishers that it it would be easy to prove are not present in a hash function.
For example, I can easily prove that Skein does not have the distinguisher "the 2nd bit in the output is equal to the first bit of the output with probability 1". The proof would be a simple example of a messag... |
It seems that the RSA Problem stands alone (at least for now, right?). The paper pointed to by Henrick outlines the following.
1. The RSA Problem is no harder than factoring, but (especially for small encryption exponents) it is likely "easier" than factoring.
2. Computing the private key from the public key has ... |
My understanding is that a KDF is a function that takes a master secret and generates multiple keys. It is secure as long as the keys are "independent". If this is true, the following definition would generate a secure KDF, right?
> Assuming we have access to a completely random function, $R:
\mathcal{K} \rightarro... |
Let's start with a general secure KDF construction, as follows. Let $F(k,x) \rightarrow \{0,1\}^n$ be a secure PRF. Then choose $L$ such that $L \times n$ provides as many output bits as you need for all of your generated keys. Let $S$ be your original secret key/entropy. Generate the following string:
$KDF(S,N,L) :... |
Let's start with a general secure KDF construction, as follows. Let $F(k,x) \rightarrow \{0,1\}^n$ be a secure PRF. Then choose $L$ such that $L \times n$ provides as many output bits as you need for all of your generated keys. Let $S$ be your original secret key/entropy. Generate the following string:
$KDF(S,N,L) :... |
Let's start with a general secure KDF construction, as follows. Let $F(k,x) \rightarrow \{0,1\}^n$ be a secure PRF. Then choose $L$ such that $L \times n$ provides as many output bits as you need for all of your generated keys. Let $S$ be your original secret key/entropy. Generate the following string:
$KDF(S,N,L) :... |
Assuming I already have a D, P, Q, etc of an RSA key: How do I now sign a message? If it matters – the message is around 100 bits.
I don't know much about cryptography, but I can get these numbers generated by a computer. Unfortunately, in my scenario – I can't use the built-in functions to use these numbers. |
How to sign cryptographically? |
How to sign a message using RSA? |
IMO implementing RSA yourself is a bad idea. While textbook signing is pretty easy, if you have access to a `BigInteger` class, you also need to get the padding right. In some use-cases timing attacks are also a problem.
But if you want to go that route, [PKCS #1](http://www.rsa.com/rsalabs/node.asp?id=2125) is the ... |
I'm trying to decrypt a message that is encrypted using a LUC encryption scheme and running into roadblocks. I know that with RSA if Alice and Bob use the same public modulus but different encryption exponents, with $\gcd(n_A,n_B)=1$ then you can find the plaintext $M$.
I'm provided $R$ (public modulus), $n_A$ (A... |
I'm conceiving an application that uses cryptographic tools and concepts for securing data. I know that's difficult and risky, therefore I prefer to ask around before implementing anything.
When using generic length-extension for hash functions, such as SHA256d where, if I'm correct, "d" stands for the number of t... |
Is a random length-extension worth the effort? |
A lot of hash functions, including the SHA-2 family(but not the SHA-3 candidates and SHA256d) are vulnerable to length extension attacks. But when is this property a problem?
I guess certain naive MAC implementations might have issues. Are there also some situations where length-extensions cause problems for unkeyed... |
In which situations is a length-extension attack a problem? |
I am considering attacks on Two-Key Triple-DES Encryption assuming $2^{32}$ known plaintext/ciphertext pairs (that's a mere 32 Giga Bytes of ciphertext) by methods analog to that devised by [Paul C. van Oorschot and Michael J. Wiener][1].
As a synthetic information for decision makers, I am looking for an independen... |
Duration for attacking Two-Key Triple-DES Encryption using all RAM ever built? |
I am considering attacks on Two-Key Triple-DES Encryption assuming $2^{32}$ known plaintext/ciphertext pairs (that's a mere 32 Giga Bytes of ciphertext) by methods analog to that devised by [Paul C. van Oorschot and Michael J. Wiener][1].
As a synthetic information for decision makers, I am looking for an independen... |
I am considering attacks on Two-Key Triple-DES Encryption assuming $2^{32}$ known plaintext/ciphertext pairs (that's a mere 32 Giga Bytes of ciphertext) by methods analog to that devised by [Paul C. van Oorschot and Michael J. Wiener][1].
As a synthetic information for decision makers, I am looking for an independen... |
I am considering attacks on Two-Key Triple-DES Encryption assuming $2^{32}$ known plaintext/ciphertext pairs (that's a mere 32 Giga Bytes of ciphertext) by the method devised by [Paul C. van Oorschot and Michael J. Wiener][1], or another published method.
As a synthetic information for decision makers, I am looking ... |
IPSec recommends rekeying SA's figuring in both time and amount of data sent. Even when using AES-256 in CBC mode, the key and IV commonly get re-negotiated after 100MB.
My case isn't using IPSec, the above is just for comparison.
Assuming a plaintext is encrypted and stored to disk using AES-256 in CBC mode, i... |
CBC key lifetime, or, "how big is too big?" |
I need MGF1 and OS2IP functions, as defined in the [PKCS #1 v2.1: RSA Cryptography Standard][1].
Is there anything available in openssl, or any other open C library?
[1]: http://www.rsa.com/rsalabs/node.asp?id=2125 |
are there any openssl MGF1 and OS2IP functions available? |
are there any MGF1 and OS2IP functions available in C? |
IMO implementing RSA yourself is a bad idea. While textbook signing is pretty easy, if you have access to a `BigInteger` class, you also need to get the padding right. In some use-cases timing attacks are also a problem.
But if you want to go that route, [PKCS #1](http://www.rsa.com/rsalabs/node.asp?id=2125) is the ... |
I've seen an example of how to sign using RSA. Besides the signing itself (s = m^d mod n) it also hashes and adds an IV.
Why is that needed?
|
Why hash or salt when signing? |
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