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Q: How long shall the RSA key be in order to be secure against _practical_ attacks?
---
A: **Impractically large**. This does not imply that RSA is unsafe against practical attacks; only that some of these attacks must be prevented by ways other than increasing the key size.
That's because key size is not a parame... |
Q: How long shall the RSA key be in order to be secure against _practical_ attacks?
---
A: **Impractically large**. This does not imply that RSA is unsafe against practical attacks; only that some of these attacks must be prevented by ways other than increasing the key size.
That's because key size is not a parame... |
Q: How long shall the RSA key be in order to be secure against _practical_ attacks?
---
A: **Impractically large**. This does not imply that RSA is unsafe against practical attacks; only that some of these attacks must be prevented by ways other than increasing the key size.
That's because key size is not a parame... |
I was looking at PBKDF2, bcrypt and scrypt as options for key derivation; and would like to try using them all together in order to get the cryptographic strength of the strongest one (which seems to be scrypt so far unless something novel is discovered).
My first thought was to apply the first kdf to the password, t... |
I was looking at PBKDF2, bcrypt and scrypt as options for key derivation; and would like to try using them all together in order to get the cryptographic strength of the strongest one (which seems to be scrypt so far unless something novel is discovered).
My first thought was to apply the first kdf to the password, t... |
I'm starting to play with PGP and I don't understand how if your key pair is RSA you can encrypt a message with someone whose key is for example ElGamal. How the asymmetric key exchange works if the key crypstosystem are different? |
How RSA and ElGamal are compatible in PGP? |
I'm starting to play with PGP and I don't understand how if your key pair is RSA
<br>
you can encrypt a message for someone whose key is for example ElGamal.
<br>
How does the asymmetric key exchange work if the crypstosystems are different? |
How are RSA and ElGamal compatible in PGP? |
In the beginning SSL handshake, the client sends a list of supported ciphersuites (among other things). The server then picks one of the ciphersuites, based on a ranking, and tells the client which one they will be using.
This step is the one that determines whether or not the future connection will have perfect fo... |
I want to encrypt credit card number. I want to apply AES-CTR mode. Is it suitable for that? how to store nonce and counter value for an individual credit card number? How to send counter value (clear/cipher text). shall we use fresh key for every credit card number? |
I want to encrypt credit card numbers. I want to apply AES-CTR mode. Is it suitable for that?
<br>
How can I store nonce and counter values for an individual credit card number?
<br>
How can I send the counter values (clear/cipher text)?
<br>
Should we use a fresh key for every credit card number? |
Say I want to encrypt the following text: "Today is March the 22nd, 2015". And say want to encrypt 8-byte blocks of data using the following permutation [6,3,0,1,5,7,2,4] to swap characters at those indexes.
[T|o|d|a|y| |i|s| |M| a| r| c| h| | t| h| e| | 2| 2| n| d| ,| | 2| 0| 1| 5]
0 1 2 3 4 5 6 7 8 9 ... |
Is it safe to encrypt data by simply randomizing chunks based on a permutation? |
I'm encrypting some of my (not so much important) files with `PBEWithMD5AndDES`. Is it a strong method or it can be de-crypt easily without knowing my selected `password`?
I'm new to crypto, thanks in advance. |
Is it safe to use PBEWithMD5AndDES? |
Okay this is how I understood it according to [this][1]:
- Alice A establishes a connection to KDC and prepares for session key Exchange R1
- A encrypts the request with her key kA(A, B) meaning "*need a session key to communicate with Bob B*"
- KDC decrypts the message, genereates kA(R1, kB(A, R1)) and sends it t... |
Okay this is how I understood it according to [this][1]:
- Alice $A$ establishes a connection to $KDC$ and prepares for session key Exchange $k_{ses}$
- $A$ encrypts the request with her key $k_A(A, B)$ meaning "*need a session key to communicate with Bob $B$*"
- $KDC$ decrypts the message, genereates $k_A(k_{se... |
Long question but I am starting to lose sight of all the HASH algo's there are.
I know SHAKE128 and 256 are part of the SHA-3 standard but is the SHA3 standard officially released yet? i can only find a [draft][1] of the publication, does this mean it's not official and therefor not proven to be secure?
I have no... |
What is the best hash for HMAC? |
Should I remove these uses of MD5/SHA1 within my program? |
Should I remove these use cases of MD5/SHA1 from my program? |
Do you know the article [If You’re Typing the Letters A-E-S Into Your Code You’re Doing It Wrong](http://chargen.matasano.com/chargen/2009/7/22/if-youre-typing-the-letters-a-e-s-into-your-code-youre-doing.html)? This is basically the same, but with a focus on hashes.
There is a quite important misconception in your ... |
Do you know the article [If You’re Typing the Letters A-E-S Into Your Code You’re Doing It Wrong](http://chargen.matasano.com/chargen/2009/7/22/if-youre-typing-the-letters-a-e-s-into-your-code-youre-doing.html)? This is basically the same, but with a focus on hashes.
There is a quite important misconception in your ... |
> I know SHAKE128 and 256 are part of the SHA-3 standard but is the SHA3 standard officially released yet? i can only find a draft of the publication, does this mean it's not official and therefor not proven to be secure?
No, SHA-3 has not been formally approved. On the other hand, what do you mean "not proved to b... |
What is this cryptosystem called? |
Long question but I am starting to lose sight of all the HASH algo's there are.
I know SHAKE128 and 256 are part of the SHA-3 standard but is the SHA3 standard officially released yet? i can only find a draft of the publication, does this mean it's not official and therefor not proven to be secure?
I have not fou... |
No, sorry, this is the bad case in zero knowledge proofs. Can it be done? Yes. Can it be proven to another party? No. |
Using Wireshark, I found these data exchanged with google.com over TLS:
1. Client Hello
- possible cipher suites and possible curve types (eg. secp256r1) sent
2. Server Hello
- cipher suite selected
3. Certificate
- RSA certificate signatures exchanged, etc. (hopefully, not important for me)
4. Client Key ... |
How does ECDHE_RSA key exchange mechanism work? |
Why do testing suites calculate pi using the Monte Carlo method to determine if a series of numbers are random? As far as I can tell, the Monte Carlo method can be used to estimate pi itself (as a numeric means of calculating it). It just so happens to use random numbers.
Why does it have to be pi if you're testin... |
Why calculate pi to estimate randomness? |
From a paper _Outsourcing Large Matrix Inversion Computation to A Public Cloud_ ([IEEE Transactions on Cloud Computing, Vol. 1, N°1, 2013][1]; alternate [source][2] requiring registration; [preprint][3]), I got to know about an encryption-decryption system. As I know only the basics of cryptography, I can't just figure... |
I did found an [old question][1] which answers exactly this but it is from 2 years ago and i was wondering if there were any changes. I have not been able to find any new information on the cipher and am quite curious seeing as it's extremely fast.
I've tested it against a very fast (fastest I have found so far) AES... |
Is the SEED blockcipher still secure? |
Here $g$ is some fixed generator of a discrete log group. I don't want the group to be bilinear for efficiency and BDH-skepticism reasons.
Is anyone aware of a discrete log accumulator? What I mean specifically is some function $f(x, A)\mapsto A'$ (that is, $A$ is the accumulator value; $f$ adds $x$ to the accumulat... |
Suppose we have bit commitment scheme:
$n=p*q$ and $t \in QNR_n$, with Jacobi $(\frac{t}{n})=1$
Commitment(P), random $x\in \mathbb{Z}_n$, $y=x^2t^b$, where $b$ is bit.
Ok, suppose we have $y_1$ and $y_2$ blobs containing same $b$
How P can prove that both blobs contain same bit without revealing it? |
Bit commitment, two blobs with same bit, without revealing it? |
I am building a small embedded system of two nodes that communicate wirelessly. The microcontrollers I'm using are very limited: they only have 256 bytes of RAM. I would like to be able to authenticate messages sent and received between the nodes, but traditional methods such as HMAC aren't possible because of the co... |
I am building a small embedded system of two nodes that communicate wirelessly. The microcontrollers I'm using are very limited: they only have 256 bytes of RAM. I would like to be able to authenticate messages sent and received between the nodes, but traditional methods such as HMAC aren't possible because of the co... |
Actually, it's not a hare-brained idea at all; you certainly can do integrity checking using a one-time pad. However, I believe that you'll need to use the one-time pad bits a bit faster than you'd expect, to achieve a forgery probability of at most $2^{-32}$, I believe you'll need at least 64 pad bits per packet (ass... |
In the recommendations, it seems cycles is used usually as in "CPU Cycles", but, that's not what I mean here.
What I mean, is this: Let's say I start with a particular 256 bit value. Call this v. I then hash that value, and get another 256 bit value. Call this SHA256(v). I take this value and get another 256 bit val... |
Actually, it's not a hare-brained idea at all; you certainly can do integrity checking using a one-time pad. However, I believe that you'll need to use the one-time pad bits a bit faster than you'd expect, to achieve a forgery probability of at most $2^{-32}$, I believe you'll need at least 64 pad bits per packet (ass... |
Suppose to have a function for numbers expressed in 8-bit $\in [0,2^8-1]$ defined as:
$$f(x)=x||x||x||x$$ where $|f(x)|$ is exactly 32 bits.
e.g., suppose x=2 (00000010) so $f(x)=2+2^9+2^{17}+2^{25}=33686018$ (00000010000000100000001000000010)
Given **N** and **x** I'd like to find **y,z,w** s.t.
$$f(x)*f(... |
I suspect the answer is no, but I am not able to either prove it, or provide an example. In Katz and Lindell's book, it is only said that with a perfectly secret encryption scheme, the plain and ciphertext distributions are *independent*. But when I try to construct an example with a non-uniform ciphertext distribution... |
Does perfect secrecy imply uniform ciphertext distribution? |
zendo is a new mobile phone app which encrypts messages using a one-time pad:
http://techcrunch.com/2015/03/24/one-time-pads-ride-again/
users have to meet in person and exchange a key via a qr code. the one-time pad data is then initialized on both phones using this key to make a secure transfer. however, accord... |
zendo is a new mobile phone app which encrypts messages using a one-time pad:
http://techcrunch.com/2015/03/24/one-time-pads-ride-again/
users have to meet in person and exchange a key via a qr code. the one-time pad data is then initialized on both phones using this key to make a secure transfer. however, accord... |
I took a cryptography class back in college, and now that I am working my 1st career one of the things currently on my plate is coming up with an algorithm to encrypt data before it's placed on the server (In this case it's pretty sensitive info). I remember different modes of operation from that class like cipher bloc... |
Are modes of operation algorithms practical? |
>I know that some of them are pretty hard to crack, but since they are so commonly known is it even practical to consider using something like that as an encryption method considering the algorithms for encryption and decryption are commonly known (from a security perspective)?
In fact, this is exactly what we want.... |
Lets say we have 2 primes, $p=q\equiv3(mod 4)$, and we make $n=p*q$ public.
I can, without revealing factors, show that $n$ has two prime factors. How can i zero knowledge prove that those are Blum primes, as described before? |
Blum primes [x=3(mod 4)] zero knowledge proof? |
Lets say we have 2 primes, $p \equiv q \equiv 3 \pmod{4}$, and we make $n=p \times q$ public.
I can, without revealing factors, show that $n$ has two prime factors. How can i zero knowledge prove that those are Blum primes, as described before? |
Please help me. It's using EUclidian inverse. you can show it step by step .Tks
e.g. N=7, q=11, a = 3+2X2 -3X4 +X6 , the inverse of a modulo 11 is
A=-2+4X+2X2 +4X3 -4X4 +2X5 -2X6
Why we have A? |
I'm studying for random number generators(RNG) and I saw about machine learning a few days ago.
So I searched analysis of RNG using machine learning.
But I couldn't find such fields.
Are there such examples for analysis of RNG using machine learning?
No matter some papers of articles.
|
Can machine learning analyze random number generator? |
Please help me. It's using Euclidian inverse. Can you show it step by step .Tks
e.g. $N=7, q=11, a = 3+2X^2 -3X^4 +X^6$ , the inverse of a modulo $11$ is
$A=-2+4X+2X^2 +4X^3 -4X^4 +2X^5 -2X^6$.
How do we compute A? |
Please help me. It's using Euclidian inverse. can you show it step by step. Tks
e.g. $N=7, q=11, a = 3+2X^2 -3X^4 +X^6 , the inverse of a modulo 11 is
$A=-2+4X+2X^2 +4X^3 -4X^4 +2X^5 -2X^6
how do we compute A? |
It's using Euclidian inverse. Can you show it step by step?
$$N=7, q=11, a = 3+2X^2 -3X^4 +X^6$$
the inverse of $a \pmod {11}$ is
$$A=-2+4X+2X^2 +4X^3 -4X^4 +2X^5 -2X^6$$
How do we compute $A$? |
I have a short (32-bit) message that needs to be authenticated. Due to the constraints of my platform, I would like to use [Speck32/64](https://en.wikipedia.org/wiki/Speck_%28cipher%29) (32-bit block, 64-bit key) with a [Matyas-Meyer-Oseas](https://en.wikipedia.org/wiki/One-way_compression_function#Matyas.E2.80.93Meye... |
Is it secure to transmit a short plaintext with its MAC? |
I have a short (32-bit) message that needs to be authenticated. Due to the constraints of my platform, I would like to use [Speck32/64](https://en.wikipedia.org/wiki/Speck_%28cipher%29) (32-bit block, 64-bit key) with a [Matyas-Meyer-Oseas](https://en.wikipedia.org/wiki/One-way_compression_function#Matyas.E2.80.93Meye... |
A normal security notion for MAC's is that of unforgeability. So given some set of message,tag pairs $(m_0,t_0),\ldots,(m_k,t_k)$ is should be hard to create a tag for a new message not among the $\{m_0,\ldots,m_k\}$, stated informally.
In your case, you could just use $E_k(m_0)$ with the secret MAC key $k$ ($H_0$ ... |
zendo is a new mobile phone app which encrypts messages using a one-time pad:
http://techcrunch.com/2015/03/24/one-time-pads-ride-again/
users have to meet in person and exchange a key via a qr code. the one-time pad data is then initialized on both phones using this key to make a secure transfer. however, accord... |
After doing a good amount of research, it's become fairly obvious that I ought to be using the extended Euclidean algorithm to calculate d from the data that I already have.
However, this isn't an area of mathematics I'm very familiar with, and the algorithm both takes and outputs multiple integers instead of just o... |
RSA: If I know n, e, p, and q, how do I calculate d using the extended euclidean algorithm? |
Suppose i have a 128 bits random binary string (128 bits of entropy), then i hash it using SHA-256, then i take the first 128 bits of the output hash. Does the taken bit string still have (almost) 128 bits of entropy or the entropy is reduced to 64 bits? (I mean another 64 bits of entropy probably lies in the second 12... |
After reading [this document][1] about MD5 collision attacks, I still don't understand how collisions can make digital signatures insecure. In the paper, the researchers created two files with the same hash, one innocent and one malicious. The malicious party first sends the good file, gets it signed, and then copies t... |
After reading [this document][1] about MD5 collision attacks, I still don't understand how collisions can make digital signatures insecure. In the paper, the researchers created two files with the same hash, one innocent and one malicious. The malicious party first sends the good file, gets it signed, and then copies t... |
After reading [this document][1] about MD5 collision attacks, I still don't understand how collisions can make digital signatures insecure. In the paper, the researchers created two files with the same hash, one innocent and one malicious. The malicious party first sends the good file, gets it signed, and then copies t... |
NTRU has some homomorphic properties modulo q, supporting both addition and multiplication. Due to its nature, it cannot support many of them. My main focus currently is in the addition, so the question is how many additions could it support to consider the result reliable? I believe that a naive bound would be $q/2$ b... |
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I read about 3DES Cryptography but i don't understand exactly what is the specific meaning of Key size? for example
<br
> i found that 3des support 64,128,192,256 bits key size
what is all possible key size supported by 3des ?
there is any function to calculate if a key is valid ... |
I read about 3DES encryption but I don't understand exactly what the specific meaning of key size is. For example I found that 3DES supports 64, 128, 192, and 256 bits key size. What are all the possible key sizes supported by 3DES?
Is there any function to determine if a key is valid for 3DES or not ?
|
In brute-force attack calculations cryptographers say we should assume an attacker will find the key after 2^(n/2) tries. If n=128, then n/2=64. We know that this is practical (A 64 bit key is already found via brute-force by distributed.net). Then why 128 bit encryption is considered practically secure at present?
... |
In brute-force attack calculations cryptographers say we should assume an attacker will find the key after 2^(n/2) tries. If n=128, then n/2=64. We know that this is practical (A 64 bit key is already found via brute-force by distributed.net). Then why 128 bit encryption is considered practically secure at present?
... |
In brute-force attack calculations cryptographers say we should assume an attacker will find the key after $2^{(n/2)}$ tries. If n=128, then n/2=64. We know that this is practical (A 64 bit key is already found via brute-force by distributed.net). Then why 128 bit encryption is considered practically secure at present?... |
`n` is the exponent. So when `n` is doubled from 64 to 128 it doesn't mean that you have to try twice as many values. It means that you have to try $2^{64}$ times the amount you were already trying (as $2^{128} = 2^{2\times64} = 2 ^{64+64} = 2^{64}\times2^{64}$).
It is required to only search half of the key space o... |
In brute-force attack calculations cryptographers say we should assume an attacker will find the key after $2^{(n/2)}$ tries. If n=128, then n/2=64. We know that this is practical (A 64 bit key is already found via brute-force by distributed.net). Then why 128 bit encryption is considered practically secure at present?... |
`n` is the exponent. So when `n` is doubled from 64 to 128 it doesn't mean that you have to try twice as many values. It means that you have to try $2^{64}$ times the amount you were already trying (as $2^{128} = 2^{2\times64} = 2 ^{64+64} = 2^{64}\times2^{64}$).
It is required to only search half of the key space o... |
[Here][1] I overconfident in myself state that I can show, that n has two factors.
This is not completely true, can possibly show $n$ is composite - prover generates RSA key with modulo $n$, and gives $e$ to verifier.
Verifier takes random number $x$, and checks if $x^{e*d}=x$, where $d*e=1$ (mod $n-1$). If it i... |
[Here][1] I overconfident in myself state that I can show, that n has two factors.
This is not completely true, can possibly show $n$ is composite - prover generates RSA key with modulo $n$, and gives $e$ to verifier.
Verifier takes random number $x$, and checks if $x^{e*d}=x$, where $d*e=1$ (mod $n-1$). If it i... |
Let's say Alice wants to talk securely to Bob over the internet, and Eve is not only eavesdropping, but has managed to get into a MITM position.
In this scheme Alice and Bob exchange $n$ (example $n = 2$) plaintext questions, at least one for both parties:
> Alice, what brand of car did I ride you to the airport ... |
Is this a valid scheme to authenticate through a 'human-readable' certificate? |
Let's say Alice wants to talk securely to Bob over the internet, and Eve is not only eavesdropping, but has managed to get into a MITM position.
In this scheme Alice and Bob exchange $n$ (example $n = 2$) plaintext questions, at least one for both parties (these are toy example questions):
> Alice, what brand of ... |
Let's say Alice wants to talk securely to Bob over the internet, and Eve is not only eavesdropping, but has managed to get into a MITM position.
In this scheme Alice and Bob exchange $n$ (example $n = 2$) plaintext questions, at least one for both parties (these are toy example questions):
> Alice, what brand of ... |
New to cryptographic, weak in math.
I have designed a PRG which consist of 33 LFSR's, each 32 bits wide.
I use one of the LFSR's as "selector", using the 5 LSB from this register to select one of the other 32 registers, from which I grab one byte and use as output. So each requested byte will thus come from one ... |
Stacked LFSR - why not used? |
I've developed a bit of Mathematica code that can find primes within a range of numbers. For example, if I wanted all the primes between one million and two million, it could do that. Of what use is this code I invented ?
The only thing I could think of was that if one wanted to find two primes of a certain size fo... |
[QKD](http://en.wikipedia.org/wiki/Quantum_key_distribution) aims at exchanging key material to be used with encryption based on [OTPs](http://en.wikipedia.org/wiki/One-time_pad) between two parties and thus to achieve perfect secrecy for transmitted messages.
There are, however, several drawbacks for practical use... |
I have to come up with a design for a cryptography system by combining a block cipher and a stream cipher. I can't seem to come up with anything on my own. Can someone point me in the right direction with helpful resources and information to tackle this problem? Thank you |
I'm reading through Bernstein's [The Poly1305-AES message-authentication code](http://cr.yp.to/mac/poly1305-20050329.pdf).
The MAC is predicated on 16-byte block ciphers like AES and produces 16-byte authentication tags. However, Bernstein does not really discuss the block cipher's key sizes, other than to state its... |
Can Poly1305-AES be used with AES-256? |
Is there any proof of correct work of RSA algorithm, if p is not a prime number? For example: n = p*q, p = p1*p2, where p1 and p2 are primes. |
Is there any proof of correct work of RSA algorithm, if p is not a prime number? For example: n = p*q, p = p1*p2, where p1 and p2 are primes.
Edit:
I found that it's called Multiprime RSA, but i didnt find proof of Correctness for it. |
I want to create a smart house project, and in that i bought some simple
RF modules. Those modules don't support crypto out of the box but i want to connect them to a device that i would program to use crypto (For example AES).
Now the question is since i would be sending allot of same messages (digital I/O Pins... |
I can attempt to define the term 'pepper' as:
> In cryptography, a pepper is a something that is added to another
> value (for example a password) prior to a the value being hashed using
> a [[Cryptographic_hash_function|cryptographic hash function]]. A
> pepper can be added to a password in addition to a [[Salt
... |
I can attempt to define the term 'pepper' as:
> In cryptography, a pepper is a something that is added to another
> value (for example a password) prior to a the value being hashed using
> a cryptographic hash function. A pepper can be added to a password in
> addition to a salt value. A pepper performs a similar... |
Let's say Alice wants to talk securely to Bob over the internet, and Eve is not only eavesdropping, but has managed to get into a MITM position.
In this scheme Alice and Bob exchange $n$ (example $n = 2$) plaintext questions, at least one for both parties (these are toy example questions):
> Alice, what brand of ... |
I'm using openssl library and I've a problem with RSA_private_encrypt() and RSA_public_decrypt(). I'm using a key size of 256 bit with no padding of the input message. I've noted that when my input message ( random generated ) has 248 bit or less the functions fail with the following error :
> Error code : error:04... |
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