instruction stringlengths 15 30k |
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Why are cryptography algorithms not exported to certain countries? |
**Re: *"So why limit the export?"***
The laws you're talking about are generally part of the laws that control the export of weapons and of dual-use goods. Dual-use goods are things that can be used both for a military and for a civil purpose… cryptography is such a dual-use good.
In fact, the classification as d... |
**Re: *"So why limit the export?"***
The laws you're talking about are generally part of the laws that control the export of weapons and of dual-use goods. Dual-use goods are things that can be used both for a military and for a civil purpose… cryptography is such a dual-use good.
In fact, the classification as d... |
**Re: *"So why limit the export?"***
The laws you're talking about are generally part of the laws that control the export of weapons and of dual-use goods. Dual-use goods are things that can be used both for a military and for a civil purpose… cryptography is such a dual-use good.
In fact, the classification as d... |
I've done research about this subject, but I can't find the answer I'm looking for.
The background:
> I'm making a network service that is used to transfer small amounts of data (less than 100bytes 90% of the time), to a small amount of users. When a known users connects it will generate a new RSA key-pair and send... |
Your problem boils down to the following:
- Client shows $v$ (his certificate).
- Server wants to know whether $v$ is the same one as previously. He may store $v$ itself, but $v$ is somewhat bulky, so the server would like to store $h(v)$ only, for a hash function $h$.
So can an attacker show up with a value $... |
I've done research about this subject, but I can't find the answer I'm looking for.
The background:
> I'm making a server (using xinetd) that is used to transfer small amounts of data (less than 100bytes 90% of the time), to a small amount of users. When a known users connects the server will generate a new RSA key... |
In most sites the exponent of the RSA public key is 24 bits. but the modulus can get to 4096 bits size.
I have an accelerator that can get max 2112 bit size modulus. it calculates a^e mod n.
Is there a way to separate n (maybe bit wise) and use the accelerator in several iterations to calculate the wanted a^e mod... |
In most sites the exponent of the RSA public key is 24 bits. But the modulus can get to 4096 bits size. I have an accelerator that can get max. 2112 bit size modulus. It calculates `a^e mod n`.
Is there a way to separate $n$ (maybe bit wise) and use the accelerator in several iterations to calculate the wanted `a^e... |
I was recently wondering - would RSA be useful if we brought it to, say, medieval times? Could you choose the keys so that you could encrypt/decrypt messages quite easily, but factoring the private key would, say, take over 1000 days for 1000 people, provided that they used paper and pencil only and wouldn't make any m... |
Would RSA make sense if we used no computers? |
Quoting the article [Gone in 60 Months or Less](http://www.infosecisland.com/blogview/23407-Gone-in-60-Months-or-Less.html):
>The National Institute of Standards and Technology (NIST) has disallowed the use of 1024-bit keys after 31 December 2013 because they are insecure. Rapid advances in computational power and c... |
When NIST disallows the use of 1024-bit keys, what effect will that have on SHA-3 (with max. 512 bits)? |
Having taken [The Design of Rijndael][1] from the library just yesterday, I had a look on this problem, too. Fixee wrote in a comment:
> However, my question is not so much about security implications, but rather
> "how does omissions of MixColumns make the inverse cipher similar to the cipher?"
> and "how does th... |
Quoting the article [Gone in 60 Months or Less](http://www.infosecisland.com/blogview/23407-Gone-in-60-Months-or-Less.html):
>The National Institute of Standards and Technology (NIST) has disallowed the use of 1024-bit keys after 31 December 2013 because they are insecure. Rapid advances in computational power and c... |
Quoting the article [Gone in 60 Months or Less](http://www.infosecisland.com/blogview/23407-Gone-in-60-Months-or-Less.html):
>The National Institute of Standards and Technology (NIST) has disallowed the use of 1024-bit keys after 31 December 2013 because they are insecure. Rapid advances in computational power and c... |
What about using Shamir's secret share over the real numbers leaks information? I know there is a problem with random number generation, and someone suggested it leaks the parity of the polynomial, but I can't see very many other problems. |
The best answer is almost certainly to use a cryptographic hash.
Your reason for avoiding a cryptographic hash makes no sense to me. Your problem does not explain the motivation for your question, but I suspect you've fallen prey to [the XY problem](http://meta.stackoverflow.com/questions/66377/what-is-the-xy-prob... |
I am trying to create a social network, in which I want to use **attribute based cryptography**. One professor told me it is possible to do it only in J2EE, but he can barely code!! Some friends of mine suggested using .NET.
I know through research that both are feasible, but since it is going to be a web based app... |
I am trying to create a social network, in which I want to use attribute-based cryptography. One professor told me it is possible to do it only in J2EE, but he can barely code! Some friends of mine suggested using .NET.
I know through research that both are feasible, but since it is going to be a web-based applicat... |
For those who didn't notice yet, here's a little heads-up on the fact that one of the most trusted institutions related to cryptography — NIST — has been shut down and is currently closed.
The text at their site reads:
> **NIST Closed, NIST and Affiliated Web Sites Not Available**
> Due to a lapse in governmen... |
NIST closed — will that have a negative impact the future of cryptography? |
For those who didn't notice yet, here's a little heads-up on the fact that one of the most trusted institutions related to cryptography — NIST — has been shut down and is currently closed.
The text at their site reads:
> **NIST Closed, NIST and Affiliated Web Sites Not Available**
> Due to a lapse in governmen... |
For those who didn't notice yet, in the USA, the National Institute of Standards and Technology(NIST) has been shut down temporarily because of the poor fiscal situation of the USA.
The text at their site reads:
> **NIST Closed, NIST and Affiliated Web Sites Not Available**
> Due to a lapse in government fundi... |
NIST temporarily closed — will that have a negative impact the future of cryptography? |
I am just reading the DAA paper (http://eprint.iacr.org/2004/205.pdf, Appendix A). A party $\mathcal{I}$ generates two group elements $g' \in \mathrm{QR}_n$ and $h = g'^r \bmod n$ with $r \in_R \left| \mathrm{QR}_n \right|$. Now $\mathcal{I}$ wants to prove in zero-knowledge that $h$ has been created correctly, i.e. th... |
can you please list the pros and cons of Paillier crypto system you have encountered or found?? |
Paillier Crypto System : Pros and Cons? |
I'd like to extract the entropy of data without injecting "pseudo" entropy (eg, by encrypting with AES-CTR). For example, let's say I have a series of bytes, but only the low bit is changing (or something is changing that I'm not aware of beforehand).
Is there a known way to extract the random part of the data witho... |
(I cleaned up the question a bit, It was previously titled "extracting entropy without hashing" .. thus some of the comments / answers)
I'd like to extract the entropy of data without injecting "pseudo" entropy. For example, let's say I have a series of bytes, but only the low bit is changing (or something is changi... |
I have two secret keys. One is a secret key generated by openssl(Primary secret key). Second key is generated by performing one way hash operation to GPS co ordinates and time parameters(Geo secret key). Now I want to combine this two keys to be used for an AES encryption. I have two options.
1. Encrypt twice by usi... |
Can you please list the pros and cons of the Paillier crypto system you have encountered or found? |
Ok, so my crpto lecturer in Uni posed this question at the end of the RSA key generation lecture as a brain teaser.
I have been thinking about this and I think I have come up with a way ( I am aware its not practical and very vulnerable - But I would love for you guys to punch holes through it ):
Use RSA to gener... |
Apologies, for a totally newbie question. I've been reading [this][1], and was wondering if there is a way to generate an RSA private/public key-pair based on some cryptographically secure input, so that if the input stays the same we keep getting the same key pair on the output.
The guys on the linked web-site use ... |
Is it possible to generate a key pair based on certain input? |
I have two secret keys. One is a secret key generated by openssl(Primary secret key). Second key is generated by performing one way hash operation to GPS co ordinates and time parameters(Geo secret key). Now I want to combine this two keys to be used for an AES encryption. I have two options.
1. Encrypt twice by usi... |
I've been reading [this][1], and I'm wondering if there is a way to generate an RSA private/public key-pair based on some cryptographically secure input, so that if the input stays the same we keep getting the same key pair on the output.
The linked web-site uses elliptic curve cryptography to achieve this property.... |
I've done research about this subject, but I can't find the answer I'm looking for.
The problem is that the string I want to send doesn't fit into the RSA key that the client have, and during encryption getting `ValueError: Plaintext is too long.`
The proposed solution is to do hybrid encryption by generating a s... |
I've done research about this subject, but I can't find the answer I'm looking for.
The problem is that the string I want to send doesn't fit into the RSA key that the client have, and during encryption getting `ValueError: Plaintext is too long.`
The proposed solution is to do hybrid encryption by generating a s... |
I've done research about this subject, but I can't find the answer I'm looking for.
The problem is that the string I want to send doesn't fit into the RSA key that the client have, and during encryption getting `ValueError: Plaintext is too long.`
The proposed solution is to do hybrid encryption by generating a s... |
The question has several aspects:
- it asks about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link when doing hybrid encryption with 2048-bit RSA used to transfer a 256-bit AES key;
- it asks how much slower 2048-bit RSA is for bulk encryption, com... |
The question has several aspects:
- it asks about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link when doing hybrid encryption with 2048-bit RSA used to transfer a 256-bit AES key;
- it asks how much slower 2048-bit RSA is for bulk encryption, com... |
Folks, I am undertaking a crypto course in Uni. Our professor asked us to try and design some authentication schemes which are resistant to active attacks. This was just a in class exercise to get us interested in the topic. It did the trick, I have been trying to come up with something using what we have learned so fa... |
The question has several aspects:
- it asks about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how much slower 2048-bi... |
Folks, I am undertaking a crypto course in Uni. Our professor asked us to try and design some authentication schemes which are resistant to active attacks. This was just a in class exercise to get us interested in the topic. It did the trick, I have been trying to come up with something using what we have learned so fa... |
Folks, I am undertaking a crypto course in Uni. Our professor asked us to try and design some authentication schemes which are resistant to active attacks. This was just a in class exercise to get us interested in the topic. It did the trick, I have been trying to come up with something using what we have learned so fa... |
The question has several aspects:
- it asks about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how much slower 2048-bi... |
The main problem with OTP's is the fact that they can only be used once (duh). Would it be possible to use a random number that's, say, 512 digits, then use 256 of those for the (non-random) message, the 256 remaining ones to send half of the new pad (to be able to send a message back), then re-use those last 256 to se... |
Re-using parts of a one time pad to encrypt a new one? |
The main problem with OTP's is the fact that they can only be used once.
Would it be possible to use a random number that's, say, 512 digits, then use 256 of those for the (non-random) message, the 256 remaining ones to send half of the new pad (to be able to send a message back), then re-use those last 256 to send... |
I've been reading ["SQRL Secure QR Login" at Gibson's website][1], and I'm wondering if there is a way to generate an RSA private/public key-pair based on some cryptographically secure input, so that if the input stays the same we keep getting the same key pair on the output.
The linked web-site uses elliptic curve ... |
The question has several aspects:
- it asks about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how much slower 2048-bi... |
If I have to encrypt a 32 bit plaintext in each of Paillier, SSE and OPE, how can I make an estimate of the ciphertext sizes respectively in order to reserve the amount of space in a database? |
Folks, I am undertaking a crypto course in Uni. Our professor asked us to try and design some authentication schemes which are resistant to active attacks. This was just a in class exercise to get us interested in the topic. It did the trick, I have been trying to come up with something using what we have learned so fa... |
I am implementing in C++ the Scream stream cipher. The Scream family is composed of Scream-0, Scream-S and Scream-F. For this question, assume that I'm using Scream-S.
The specifications of the Scream cipher are given [here][1]. I have many questions about it. Also, I have to precise that I didn't find any code for ... |
Best ways to estimate avg bits of entropy in a byte stream.
I know there are different statistical tests out there (nist, dieharder, nsa, etc), which all do different ways of analyzing entropy.
What I'm having a hard time finding is any particular literature which describes how to go from those tests to actual b... |
I am implementing in C++ the Scream stream cipher. The Scream family is composed of *Scream-0*, *Scream-S* and *Scream-F*. For this question, assume that I'm using *Scream-S.
The specifications of the Scream cipher are given in the paper ["Scream: a software-ecient stream cipher"][1], but I didn't find a reference ... |
I am implementing in C++ the Scream stream cipher. The Scream family is composed of *Scream-0*, *Scream-S* and *Scream-F*. For this question, assume that I'm using *Scream-S*.
The specifications of the Scream cipher are given in the paper ["Scream: a software-efficient stream cipher"][1], but I didn't find a refere... |
This question is about [Tyche](http://eden.dei.uc.pt/~sneves/pubs/2011-snfa2.pdf), a non-cryptographic PRNG. While the PRNG is not cryptographic the analysis and this question surely is heavily involved with cryptography, so I think it's on-topic here.
In short, Tyche is a nonlinear PRNG based on the ChaCha quarter-... |
How should I interpret this note on diffusion of the internal state of a PRNG? |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
I would expect a complicated answer for what seems like a simple question about Elliptic curve cryptography. I've read several entries here such as this: http://crypto.stackexchange.com/questions/2440/elliptic-curve-cryptography-related-key-attacks and afterwards I am still left wondering what the primary attack vecto... |
In RSA public-key material (e, N), why must the encryption exponent e be relatively prime to f(N)? Why must any public key encription algorithm resist CPA? |
In RSA public-key material (e, N), why must the encryption exponent e be relatively prime to $\phi(N)$? Why must any public key encryption algorithm resist CPA? |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
How to know how much space to reserve? There are two ways:
1. Take an implementation of the scheme, encrypt a 32-bit plaintext, and see how long the resulting ciphertext is. This is the simplest approach.
2. Understand the scheme at a conceptual level, and then use your understanding of the algorithm to predict... |
I am given 5 different encryption modulus, N, each ranging from 78 to 88 numbers long. Then for the encryption exponent, each has the same which is 5. Then I am given 5 different encrypted messages, E, which also ranges from 76 to 88 numbers long. I am trying to decrypt the message without having to discover the privat... |
How to know how much space to reserve? There are two ways:
1. Take an implementation of the scheme, encrypt a 32-bit plaintext, and see how long the resulting ciphertext is. This is the simplest approach.
2. Understand the scheme at a conceptual level, and then use your understanding of the algorithm to predict ... |
I see no issue here about bit diffusion; if $\textit{MIX-i}$ has a problem, so does $\textit{MIX}$.
The reason is simple, $\textit{MIX-i}$ is precisely $\textit{MIX}$, but backwards. Hence, if $\textit{MIX}$ starting at initial state $S_0$ and ending at final state $S_n$, would generate the output:
$B_0, B_1, ... |
I made this small tool for make & read easily an encrypted message without nothing to install, just a simple private key like a word or a couple of words to share. (Without say it directly of course but with a guess, like a place gone together with the correspondent, renembered).
I think the result message and the sys... |
I see no issue here about bit diffusion; if $\textit{MIX-i}$ has a problem, so does $\textit{MIX}$.
The reason is simple, $\textit{MIX-i}$ is precisely $\textit{MIX}$, but backwards. Hence, if $\textit{MIX}$ starting at initial state $S_0$ and ending at final state $S_n$, would generate the output:
$B_0, B_1, ... |
A cryptographic [salt][1] is additional input other than message itself for a hash function so that it prevents attacker from launching dictionary attacks . Usually the salt is stored along with the hash of say the password etc.
Keyed Hashing is secret key is used as input for hashing along with message like HMAC .
... |
Difference between salted hash and keyed hashing? |
I would expect a complicated answer for what seems like a simple question about Elliptic curve cryptography. I've read several entries here such as "http://crypto.stackexchange.com/questions/2440/elliptic-curve-cryptography-related-key-attacks" and afterwards I am still left wondering what the primary attack vector wou... |
This question is about [Tyche](http://eden.dei.uc.pt/~sneves/pubs/2011-snfa2.pdf), a non-cryptographic PRNG. While the PRNG is not cryptographic the analysis and this question surely is heavily involved with cryptography, so I think it's on-topic here.
In short, Tyche is a nonlinear PRNG based on the ChaCha quarter-... |
I cannot see it having a negative effect, only a positive effect.
[Let's read the Reddit AMA][1] of Glenn Greenwald. Here's the relevant comments:
> There are **hundreds of encryption standards compromised** by the program the Guardian, NYT and PP all reported on. I have never seen any list of those standards and... |
According to the birthday paradox we need approx. $O(|T|^{1/2})$ samples from the tag-space to find a collision for a hash function $h:K\times M \to T$. But hoe many samples are needed to find a three-way collision, i.e. $h(a) = h(b) = h(c)$ for three messages $a,b,c \in M$ hashed with same key $k\in K$ ?
I thought... |
I am given 5 different encryption modulus, $N$, each ranging from 78 to 88 numbers long. Then for the encryption exponent, each has the same which is 5. Then I am given 5 different encrypted messages, $E$, which also ranges from 76 to 88 numbers long. I am trying to decrypt the message without having to discover the pr... |
The question has several aspects:
- it asks about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how much slower 2048-bi... |
The question has several aspects:
- it asked ([initially][1]) about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how m... |
The question has several aspects:
- it asked ([initially][1]) about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how m... |
The question has several aspects:
- it asked ([initially][1]) about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how m... |
The question has several aspects:
- it asked ([initially][1]) about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how m... |
NIST FIPS 180-4. “5.1. Padding the Message.”
> Suppose that the length of the message, M, is bits.
Is there any library that can receive a message of length (in bits) which is not a multiple of 2^3? |
NIST FIPS 180-4. “5.1. Padding the Message.”
> Suppose that the length of the message, $M$, is $l$ bits.
Is there any library that can receive a message of length (in bits) which is not a multiple of $2^3$? |
The question has several aspects:
- it asked ([initially][1]) about any security issue in breaking a piece of data into separately RSA-encrypted chunks;
- it asks what's the weak link in the security chain when doing hybrid encryption with a 256-bit AES key transfered enciphered using 2048-bit RSA;
- it asks how m... |
I think you have to specifically define what you're trying to do. Just "authentication" doesn't quite make sense from a practical stand point.
I can thinking of saying "hello" to someone for the purpose of "ok, if you get a hello from me then attack!!", but that protocol would look differently than what you're t... |
I think you have to specifically define what you're trying to do. Just "authentication" doesn't quite make sense from a practical stand point.
I can thinking of saying "hello" to someone for the purpose of "ok, if you get a hello from me then attack!!", but that protocol would look differently than what you're t... |
It seems that GCM mode encryption has a clear advantage over CBC + HMAC in the sense that it only requires a single key. But it seems that there are some experts here that do not trust it enough to recommend it. This question is a call to those experts to clearly define those concerns.
Are there any properties of GC... |
I think you have to specifically define what you're trying to do. Just "authentication" doesn't quite make sense from a practical stand point.
I can thinking of saying "hello" to someone for the purpose of "ok, if you get a hello from me then attack!!", but that protocol would look differently than what you're t... |
I think you have to specifically define what you're trying to do. Just "authentication" doesn't quite make sense from a practical stand point.
I can thinking of saying "hello" to someone for the purpose of "ok, if you get a hello from me then attack!!", but that protocol would look differently than what you're t... |
I think you have to specifically define what you're trying to do. Just "authentication" doesn't quite make sense from a practical stand point.
I can thinking of saying "hello" to someone for the purpose of "ok, if you get a hello from me then attack!!", but that protocol would look differently than what you're t... |
I'm playing around with a package that does Elliptic Curve Cryptography from http://jecc.sourceforge.net/
Every time I encrypt a value it produced a different result (same private key). However I'm always able to decrypt this result with the related public key. For a 1 byte result the resulting data is 34 bytes, 2 b... |
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... |
Considering a stream cipher that produces a ciphertext $c$ from a message $m$ and a key $k$ is it possible to apply operations (multiplication and/or addition) directly to $c$ without knowing the key ?
Example : $m$ > encrypt > $c$ > $c+5$ > decrypt > $m+5$
I can not manage to get a valid $m$ at the end. I tried ... |
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