instruction stringlengths 15 30k |
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How can synchronization of counters is achieved in HOTP.Server increments its counter value only if a match(of otp value) is found.What happens at client side??
Suppose server verifies 50 successful attempts from client which implies counter value at server is 50.What if a fresh request comes from a client(different) ... |
Can we use Elliptic curve cryptography in Wireless Sensors . If we use how to map points to message chracters? |
Can we use Elliptic curve cryptography in Wireless Sensors If we use how to map points to message chracters? |
Can we use elliptic curve cryptography in wireless sensors?
If so, how do you map points to message characters? |
Can we use elliptic curve cryptography in wireless sensors? |
How is synchronization of counter values achieved in the HOTP protocol?
As I understand it, the server increments its counter value only if a match (of the OTP value) is found. What happens at client side?
Suppose server verifies 50 successful attempts from client which implies counter value at server is 50. Wha... |
Of course wireless sensors can use elliptic curve cryptography, why wouldn't they be able to? [TinyECC][1] provides elliptic curve crypto for TinyOS. If you are on another OS, you'll have to find a library that will work for your platform.
As for mapping a message to points, the problem is the same whether you are o... |
Let n = $p^a$$q^b$ where p and q are distinct primes and a and b are positive integers. How to construct a zero knowledge proof that n is of such form?
This is actually a homework problem with a hint that if a n = $p^a$$q^b$ then exactly half of the elements in $Z_n$ with jacobi symbol +1 are quadratic residues mod... |
Let $n = p^a$$q^b$ where p and q are distinct primes and a and b are positive integers. How to construct a zero knowledge proof that n is of such form?
This is actually a homework problem with a hint that if a $n = p^a$$q^b$ then exactly half of the elements in $Z_n$ with jacobi symbol +1 are quadratic residues mod... |
Actually, it is not necessary for the prover to show that "exactly half" of elements with Jacobi symbols being +1 are, in fact, QR. Instead, here are some hints:
- Assuming that n is not of that form (and also n is not of the form $n = p^a$, which is easy test for), the probability that a random element with Jacobi... |
My current textbook (Information Security: Principles and Practice by Mark Stamp) discusses how to determine the CRC of data via long-division, using XOR instead of subtraction to determine the remainder.
If our divisor has N-bits, we append (N-1) 0 bits to the dividend (the data) and then use long-division with XOR... |
What **anonymous offline** electronic money systems exist and what are they based on? I know only one currently - [eCash][1], based on [RSA blind signatures][2].
[1]: http://en.wikipedia.org/wiki/Ecash
[2]: http://en.wikipedia.org/wiki/Blind_signature |
From [here][1] they define the $\ell$-Diffie Hellman inversion problem as:
> Given $g^{a},g^{a^2}\ldots,g^{a^{\ell}} \in G$, compute $g^{a^{-1}}$
Would this problem become easy if the generator $g$ is also known?
[1]: http://www.ecrypt.eu.org/wiki/index.php/Discrete_Logarithms "here" |
Is the l-Diffie Hellman Inversion easy when g is known? |
Do you know about the paper [Variants of Diffie-Hellman Problem][1]? The problem you stated is the generalization of the inversion problem stated in that paper. You can use their technique to prove the relation.
[1]: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.104.3007 |
Do you know about the paper [Variations of Diffie-Hellman Problem][1]? The problem you stated is the generalization of the inversion problem stated in that paper. You can use their technique to prove the relation.
[1]: http://www.google.ca/url?sa=t&rct=j&q=diffie%20hellman%20inversion&source=web&cd=5&ved=0CEMQ... |
I just discovered on the eprint server of the IACR the [paper](http://eprint.iacr.org/2012/097.pdf) mentioned in the title. Scanning quickly over the paper I didn't find anything spectacular, so I doubt that their new(?) approach will be any good. But as I'm not an expert in the field of factorization, and as the proof... |
Is the new preprint "An Algorithm For Factoring Integers" by Yingpu Deng and Yanbin Pan worth reading? |
I want to encrypt a truly random plaintext (a key file) based on a user password. I'll use PBKDF2-HMAC-SHA256 to generate an encryption key from the password, but I'm wondering if I even need to both with AES or some other cipher: can I expect good security if I just use PBKDF2 to generate a key equal in length to the ... |
Can PBKDF2 be used to create an OTP to encrypt random plaintext? |
Do you know about the paper [Variations of Diffie-Hellman Problem][1] ([PDF][2])? The problem you stated is the generalization of the inversion problem stated in that paper. You can use their technique to prove the relation.
[1]: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.104.3007
[2]: http://ci... |
Is the $\ell$-Diffie Hellman Inversion easy when g is known? |
If I encrypt a message with AES-GCM, is it safe to use the MAC as the hash in a DSA/RSA signature? That is, if someone knows the AES key and nonce, will they be able to generate a different message with the same key/nonce that results in the same MAC?
How about other modes like CCM/OCB or authenticated stream cipher... |
In a Diffie-Hellman exchange, the parties need to agree on a prime `p` and a base `g` in order to continue. Assuming some application that's going to want to initiate handshakes with some large portion of its users, each of which only need to be realistically secure for a few hours,
- Approximately how large should ... |
How large should a Diffie-Hellman p be? |
Well, to answer your questions in order:
- How big should $p$ be? Well, it should be large enough to defend against the known attacks against it. The most efficient attack is NFS; that has been used against numbers on the order of $2^{768}$ (a 232 digit number). It would appear wise to pick a $p$ that's considera... |
You want to obtain a 74-bit secret $K$. There is an oracle that will provide you with the following value for several values of $T$:
$$(\mathrm{MD5}(T_{\mathrm{dec}}||K_{\mathrm{hex}}))_{\mathrm{hex}}[0..5]$$
* $T_{\mathrm{dec}}$ is the number of seconds since 1970 divided by 10 (i.e. it's the current time in un... |
Actually, from my examination of the paper, I don't know if the result is of even academic interest.
One generic way to factor a value $n$ is to take a function $F$ and define:
for i = 1 to some_upper_limit do
temp = F( n, i )
factor = gcd( temp, n )
if 1 < factor and factor < n
... |
As I understand it, the RSA algorithm is based on finding two large primes (p and q) and multiplying them. The security aspect is based on the fact that it's difficult to factor it back into p and q. Now, since RSA keys are so large (often 1024 bits and above), the primes have to be at least half that (at least 512 bit... |
How are primes generated for RSA? |
As a followup to a [previous question][1] I asked which was more related to Fully Homomorphic Encryption (FHE), what other cryptographic methods are available for computing a private function on public and/or private input? And, what are the benefits/limitations when compared to FHE?
In specific I am interested in [... |
I just discovered on the eprint server of the IACR the [paper](http://eprint.iacr.org/2012/097.pdf) mentioned in the title. Scanning quickly over the paper I didn't find anything spectacular, so I doubt that their new(?) approach will be any good. But as I'm not an expert in the field of factorization, and as the proof... |
I'm implementing the SRP6 protocol, which relies on discrete logarithms for it's security (essentially diffie-hellman).
The RFC documents state that "The private values a and b SHOULD be at least 256-bit random numbers, to give approximately 128 bits of security against certain methods of calculating discrete logari... |
Size of a Diffie-Hellman private key? |
When it comes to lattice based cryptographic systems, all the literature talks about, good bases and bad bases.
How does one define what a good basis is and what a bad basis is? |
In a lattice, how can one define a good basis and a bad basis? |
I think 1024 bit RSA keys were considered secure ~5 years ago, but I assume that's not true anymore. Can 2048 or 4096 keys still be relied upon, or have we gained too much computing power in the meanwhile?
Edit: Lets assume an appropriate padding strategy. Also, I'm asking both about security of signatures and secur... |
How big an RSA key is considered secure today? |
Suppose the Hill cipher were modified to something like a one-time pad cipher, where Alice wants to send a message to bob, and she chooses a key matrix randomly every-time a new message is sent (and the inverse of the key matrix is sent to bob by other means everytime - just as in the one-time pad). would this yield pe... |
Oh, and while you did not specifically ask about this, there is another point I believe that is important to highlight; DH and SRP are different protocols, and have different requirements on the generator they use. **In particular, taking a generator that is designed to be used securely within DH can void the security... |
Suppose the [Hill cipher][1] were modified to something like a one-time pad cipher, where Alice wants to send a message to Bob, and she chooses a key matrix randomly everytime a new message is sent (and the inverse of the key matrix is sent to Bob by other means everytime - just as in the one-time pad). Would this yiel... |
I'm implementing the SRP-6 protocol, which relies on discrete logarithms for it's security (essentially Diffie-Hellman).
The [RFC documents][1] state:
> The private values $a$ and $b$ SHOULD be at least 256-bit random numbers, to give
> approximately 128 bits of security against certain methods of calculating di... |
What should be the size of a Diffie-Hellman private key? |
Imagine a Ring homomorphism from Z10 --> Z10 given by g(x) = 5x .
What if a client planning to outsource his computations to server , translates every possible x as 5 times x and sends to server and once he gets the result divides the response by 5.
Since the above mapping is homomorphic , additions and mult... |
What is the flaw in this model for homomorphic encryption ? |
If I'm hashing alphanumeric strings (chars in the set `0`-`9`, `a`-`z`, and `A`-`Z`) with a CRC-64 hashing function, how long can my strings be while guaranteeing no hash collisions?
Stated differently: If I have a set of all CRC-64 checksums computed from alphanumeric strings $0$ to $N$ bytes, how large can $N$ be... |
Imagine a Ring homomorphism $g : \mathbb Z_{10} \to \mathbb Z_{10}$ given by $g(x) = 5·x$.
Assume a client is planning to outsource his computations to server, translates every possible $x$ as $5$ times $x$ and sends to server and once he gets the result divides the response by $5$.
Since the above mapping is hom... |
What is the flaw in this model for homomorphic encryption? |
Imagine a Field Isomorphism $g : \mathbb F1 \to \mathbb F2$ given by some $g(x)$
Assume a client is planning to outsource his computations to server, translates every possible $x$ as $g(x)$ and sends to server and once he gets the result he translates g inverse to get the answer.
I know the above is straw man ... |
What is the computaional cost of a certificate signature verification in terms of exponentiation, multiplication and other computaion operations ? |
What is the computational cost of a public key certificate signature verification? |
What is the computational cost of a certificate signature verification in terms of exponentiation, multiplication and other computation operations? |
What is Implicit Authentication, in the context of authentication methods?
I searched the Web but could not find any article that describes this. If anyone can describe, it would be a great help.
Thanks. |
What is Implicit Authentication? |
I'm wondering if breaking the DLP, that is the basis for ElGamal and DSA, would automatically break RSA. The way I see it, RSA is based on the following three assumtpions, please correct me if I'm wrong.
1. **The hardness of integer factorization**. This is obvious, if this would be possible, we could find p and q f... |
RSA security assumptions - does breaking the DLP also break RSA? |
> **Possible Duplicate:**
> [Would the ability to efficiently find Discrete Logs have any impact on the security of RSA?](http://crypto.stackexchange.com/questions/802/would-the-ability-to-efficiently-find-discrete-logs-have-any-impact-on-the-secur)
<!-- End of automatically inserted text -->
I'm wondering if bre... |
In the first decade of the 21th century, and counting, on a given $Year$, no RSA key bigger than $(Year-2000)\cdot 32+512$ bits has been openly factored [other than due to a failure of the key generator][1]. This linear estimate of _academic_ factoring progress should be used neither for long-term predictions, nor for ... |
In the first decade of the 21th century, and counting, on a given $Year$, no RSA key bigger than $(Year-2000)\cdot 32+512$ bits has been openly factored [other than due to a failure of the key generator][1]. This linear estimate of _academic_ factoring progress should be used neither for long-term predictions, nor for ... |
The main difference between your two algorithms is that the second one takes longer because of your additional hashing of the "public key". Also, by the truncation of this hash to 3 characters (are this bytes, hex digits, base64 digits?) could lead to collisions of different public keys to the same hash, which is much ... |
Let me ask about my toy passwords generator program X5 which I want to improve.
X5 uses a secret key and a public key to generate a password.Where any public key is supposed to be known to hackers in the worst case.
pwd = sK + pk
To describe details, let me define some expressions.
1. each of K and k den... |
How to take SHA-1 safely for my particular case? |
I was wondering if the prime numbers defined for use with Diffie-Hellman in RFC 3526 are more trustworthy than generating one's own, especially considering the recent Arjen Lenstra paper ([*Ron was wrong, Whit is right*][1]) which criticized the similarities detected in public keys and prime numbers across the Internet... |
Is it safer to generate your own Diffie-Hellman primes or to use those defined in RFC 5526? |
Is it safer to generate your own Diffie-Hellman primes or to use those defined in RFC 3526? |
I was wondering if the prime numbers defined for use with Diffie-Hellman in [RFC 3526][1] are more trustworthy than generating one's own, especially considering the recent Arjen Lenstra paper ([*Ron was wrong, Whit is right*][2]) which criticized the similarities detected in public keys and prime numbers across the Int... |
i'm looking into implementing a private SILC server for friends (and possibly their friends)..
and after visiting the wikipedia entry for [SILC protocol][1]
it seems all the official page linked at the bottom is dead with only a few anon servers here and there..
my main question in what happened mainly focuses o... |
whatever happened to SILC? |
In the first decade of the 21th century, and counting, on a given $Year$, no RSA key bigger than $(Year-2000)\cdot 32+512$ bits has been openly factored other than by [exploitation of a flaw of the key generator][1]. This linear estimate of _academic_ factoring progress should be used neither for long-term predictions ... |
In the first decade of the 21th century, and counting, on a given $Year$, no RSA key bigger than $(Year-2000)\cdot 32+512$ bits has been openly factored other than by [exploitation of a flaw of the key generator][1]. This linear estimate of _academic_ factoring progress should be used neither for long-term predictions ... |
Let me ask about my toy passwords generator program X5 which I want to improve.
X5 uses a secret key and a public key to generate a password.Where any public key is supposed to be known to hackers in the worst case.
pwd = sK + pk
To describe details, let me define some expressions.
1. each of K and k den... |
I am curious, is there any paper where SHA-3 competitors are compared in terms of energy efficient? |
Energy efficient of SHA-3 competitors? |
I just read this article on Wikipedia: [Certificate signing request][1]
I'm not a PKI/Crypto expert. As I understand, a CSR (certification request) is always signed by the PKCS#10-Request creator.
What I don't understand is why the CA, which receives and processes the CSR, then removes this signature (I mean, wi... |
X.509 CSR: Why does CA remove signature? |
How does the energy consumption of the SHA-3 finalists compare? |
I just read this article on Wikipedia: [Certificate Signing Request][1]
I'm not a PKI or Crypto expert. As I understand, a CSR (certification request) is always signed by the PKCS#10-Request creator.
What I don't understand is why the CA, which receives and processes the CSR, then removes this signature (I mean,... |
For a project I wonder if there exists some kind of fixed-size checksumming/fingerprinting function in which based on this fingerprint given data block 1, it is easy to generate more data blocks that share the same fingerprint/hash key.
Therefore this is unlike an MD5 sum. (In that I don't know how to easily go back... |
For a project I wonder if there exists some kind of fixed-size checksumming/fingerprinting function in which based on this fingerprint given data block 1, it is easy to generate more data blocks that share the same fingerprint/hash key.
Therefore this is unlike an MD5 sum. (In that I don't know how to easily go back... |
I'm looking into implementing a private SILC server for friends (and possibly their friends).
And after visiting the Wikipedia entry for [SILC protocol][1], it seems all the official pages linked at the bottom are dead with only a few anon servers here and there.
Is it still being used nowadays?
And if it is ...... |
Is the SILC protocol still used? |
I need to implement the HASH algorithm (MD5 & SHA-1) on an 8 bit MCU. I hear it can only be implemented on 32bit and sometimes 16bits MCU. Is that possible? I will appreciate link where possible. A program in C language most preferred. |
This might be out of ignorance, I apologize, but how complex of a problem might it be to *generate* a file of size N whose md5sum is X?
For example,
ls -l wczasp.rb
-rwxrwxrwx 1 master master 7273877 2011-01-30 17:13 wczasp.rb
md5sum wczasp.rb
acf3602b5eb9a2db3e365d3043682faf wczas... |
For a project I wonder if there exists some kind of fixed-size checksumming/fingerprinting function in which based on this fingerprint given data block 1, it is easy to generate more data blocks that share the same fingerprint/hash key.
Therefore this is unlike an MD5 sum. (In that I don't know how to easily go back... |
I'm looking into implementing a private SILC server for friends (and possibly their friends).
And after visiting the Wikipedia entry for [SILC protocol][1], it seems all the official pages linked at the bottom are dead with only a few anon servers here and there.
Is it still being used nowadays?
And if it is ...... |
I found the answer [here][1]
[1]: http://books.google.de/books?id=QsUOEOSiy6cC&lpg=PA102&ots=NvBZX2knmp&dq=sha-3%20competitors%20comparison%20energy&pg=PA102#v=onepage&q=sha-3%20competitors%20comparison%20energy&f=false |
In the first decade of the 21th century, and counting, on a given $Year$, no RSA key bigger than $(Year-2000)\cdot 32+512$ bits has been openly factored other than by [exploitation of a flaw of the key generator][1]. This linear estimate of _academic_ factoring progress should be used neither for long-term predictions ... |
Suppose Alice would like to obtain the product of two mXn matrices i.e. A and B. Alice has A, whereas Bob has B.
Since Alice does not want to reveal A to Bob, she chooses a mXn random invertable matrix R. She sends R*A to Bob over a secure channel.
Bob obtains R*A, and calculates R*A*B, and sends it to Alice ove... |
In the first decade of the 21th century, and counting, on a given $Year$, no RSA key bigger than $(Year-2000)\cdot 32+512$ bits has been openly factored other than by [exploitation of a flaw of the key generator][1]. This linear estimate of _academic_ factoring progress should be used neither for long-term predictions ... |
I was wondering why the Fujisaki-Okamoto construction (or one of its variants) is not (at least commonly) used with RSA to achieve CCA2 security? Does anyone know of any speed comparisons between RSA w/ F-O and RSA-OAEP? Perhaps the reason is simply historical since F-O is newer. |
I'm not sure I understand really the implications of proofs of security in the random oracle model. Does a proof of security in ROM translate to a reduction of security of the crypto-system to the security of the hash function in the standard model? If not, then this would imply that the meaning of the ROM proof in the... |
Does security under ROM imply exactly what? |
Suppose Alice would like to obtain the product of two mXm matrices i.e. A and B. Alice has A, whereas Bob has B.
Since Alice does not want to reveal A to Bob, she chooses a mXm random invertable matrix R. She sends R*A to Bob over a secure channel.
Bob obtains R*A, and calculates R*A*B, and sends it to Alice ove... |
Why over a secure channel? Wouldn't this work pretty well if you take A and B not invertible also in the presence of an eavesdropper? Then Bob could use a similar trick to get AB by sending BS to Alice (where S is invertible) and then recover AB from ABS that Alice sends back. This seems extremely inefficient though. |
Why over a secure channel? Wouldn't this work pretty well if you take A and B not invertible also in the presence of an eavesdropper? Then Bob could use a similar trick to get AB by sending BS to Alice (where S is invertible) and then recover AB from ABS that Alice sends back. This seems extremely inefficient though.
... |
I found the answer in the paper ["Comparison of the Power Consumption of the 2nd Round SHA-3 Candidates"][1] ([PDF version][2]) by Benedikt Westermann, Danilo Gligoroski, and Svein Knapskog, published at the ICT Innovations 2010 Conference.
[1]: http://books.google.de/books?id=QsUOEOSiy6cC&lpg=PA102&ots=NvBZX2knmp... |
Suppose Alice would like to obtain the product of two mXm matrices i.e. A and B. Alice has A, whereas Bob has B.
Since Alice does not want to reveal A to Bob, she chooses a mXm random invertable matrix R. She sends R*A to Bob over a secure channel.
Bob obtains R*A, and calculates R*A*B, and sends it to Alice ove... |
I am a software developer working on an application with the .NET platform. This application needs to provide a secure connection and encrypt all data between the client and the server. It is a standaone app that does not use a web browser and will be using a symmetrical key for the vast majority of the messages for ... |
Does a public key absolutely need to be used to initiate an encrypted session? |
Regard your sub question 4: Your argument is unfortunately flawed. A broken cipher algorithm becomes a security issue if both of the following conditions are true:
1. Your adversary knows how to break the algorithm,
2. You don't known that your adversary knows how to break the algorithm.
Suppose you are choosing... |
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