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We have a multiplicative cyclic group $G$ with generators $g$ and $h$, as in El Gamal. Assume $G$ is a subgroup of $(\mathbb{Z}/n\mathbb{Z})^*$. There are two parties, Alice and Bob:
Alice knows: $g$, $h$, $x_1$, $x_2$ and $(a,b,c)$,
Bob knows: $g$, $h$ and $(a,b,c)$.
Can Alice prove to Bob in zero knowledge that ... |
Possible Duplicate:
CPA Secure Chosen plaintext scheme
The example for IND-CPA secure schemes given is generally:
for a random r,
$Enc_k(m) =(r|| E_k(r)$ $XOR$ $m)$ where $E$ is a $PRF$
But does the role of r and k really matter--i.e. isn't this equally secure?
$Enc_k(m) =(r|| E_r(k)$ $XOR$ $m)$ ?
|
Suppose I want to prove that a given symmetric encryption scheme is not IND-CPA secure. The first thing I do is to define a specific adversary that attacks the scheme. How can I proof neatly, (using the game where A chooses two messages and is given a ciphertext $c$) that the adversary indeed almost always can determin... |
Apologies if this is a stupid question, but I'd be grateful if someone could provide an answer. I'm assuming that you need to use different keys to provide these functions, is that correct?
|
If I encrypt a file with gpg -c file.zip, and change the filename. Is there any way I can restore the filename as I used as a password. or the name encrypted to?
|
In the HOTP protocol after calculating a 20 byte hash it is truncated to 4 bytes.
For this first an offset is calculated (low-order 4 bits of the last byte) which determines the four bytes to be selected:
DT(String) // String = String[0]...String[19]
Let OffsetBits be the low-order 4 bits of String[19]
Offset = StTo... |
The example for IND-CPA secure schemes given is generally:
for a random r,
Enc_k(m) =(r|| E_k(r) XOR m) where E is a PRF
But does the role of r and k really matter--i.e. isn't this equally secure?
Enc_k(m) =(r|| E_r(k) XOR m) ?
|
I have an exercise to do regarding Vigenère encryption.
I've got the cipher text: WNZTNVIEEGTJYKRRWYUELWNZTNV
and a partial plain text: S''''R''R''''R''''PASS'''''
The key length is unknown.
The question is: is it possible to find the key and the plain text?
Regarding what I've seen in class, I don't think it's possibl... |
I'm extremely new to crypto, and very much inexperienced. Lately I've been reading about the Diffie-Hellman key-exchange methods, and specifically about the computational diffie-hellman assumption vs. decision diffie-hellman assumption. Specifically I'm referencing Dan Boneh's paper on DDH problem. However, I'm having ... |
It is known that the two prime factors $p$ and $q$ of an RSA modulus $n$ should not be too close to each other, otherwise an attacker may factor the modulus. In other words, $\Delta = \left| p - q \right|$ should not be too small.
However, "too small" is a somewhat subjective measure. "Too small" with respect to what? ... |
I followed the algorithms 14.4 (computes 1st and 3rd coordinates in (X,Y,Z)#k modulo n) and 14.5 (factorization using ECM) in David Bressoud's book 'Factorization and Primality Testing'. I think the algorithm is similar to Lenstra's, it uses the formula Y^2 - X^3 - aX, where the values for X,Y and a are chosen at rando... |
I have the following requirement for hashing using MD5.
H(A,B,C,X);
Where values A,B & C are given. However X is not given.
I would like to find out what value of X would give a hash beginning with 32 1's bits
meaning H(A,B,C,X) = Begin with 32 '1' bits
I can brute force by testing all kinds of characters of X till i g... |
I've been reading a bit about block cipher modes and I have a relatively straightforward question regarding CTR. In essence, I was hoping you guys would be kind enough to validate my understanding of things.
As I understand it, CTR does the following:
Take the first output of the nonce (let us assume an incrementing ... |
Might it be possible that reversible combinatorial circuits (or some emulating software) are going to be used to get the input of the white box?
I mean if I have constructed a proper reversible circuit then (in theory) I can obtain the input of whatever output I get. Am I missing the point?
Here is the relevant WP link... |
It's interesting to see critical thinking being applied to CryptDB in contrast to all the hoopla around it here. CryptDB is not a major theoretical breakthrough but potpourri of technologies to make it work. But then: I am curious whether there has been a formal security analysis done on CryptDB. All over the web it is... |
Unsure whether this is the right forum for this question, worth a try.
The task im faced with is to implement a poly-time algorithm that finds a nontrivial factor of a carmichael number. Many resources on the web states that this is easy, however, without further explanation why that is?
Furthermore, since miller-rabbi... |
I am looking for a good pseudo-random number generation algorithm for passwords.
My scenario is that I have to generate 5K pseudo-random bits from a user-supplied password (6 characters). What are possible options and which one would be able to cover for my purposes?
|
I'm trying to figure out a suitable encryption technique and after reading a bit, I figured the current AES 128-bit encryption is suitable for what I'm trying to do. However, this is more due to the wide-range use of AES than any other factor. So I need to know how the AES compares to the other finalists Twofish, Serpe... |
I usually choose bcrypt when hashing as I can set the work factor to slow down the calculations of the hash. However, I have to keep a copy of the hash in order to verify it (since it includes the salt) when the same input comes around again.
Are their any A) common and B) slow hashing algorithms that do not require a ... |
The way I understand it, an algorithm is said to be randomized if it uses randomness as part of its logic (quoting Wikipedia). Now, in the case of encryption algorithms, I assume this means that for the same input, different outputs (i.e. ciphertexts) will be produced. The question is, what does "input" mean in this co... |
It is well known that simple m-sequence linear feedback shift registers have a linear algebraic structure and therefore the generator seed can easily be deduced using the Berlekamp-Massey algorithm. Are there any other algorithms that can that can be used to "break" LFSR's and if so how does the algebra of said algorit... |
Preface: here is the official site for the Blowfish algorithm:
http://www.schneier.com/blowfish.html
The Blowfish algorithm uses an s-box, which consists of hex digits of pi (found here: http://www.schneier.com/code/constants.txt). I'm guessing that this s-box serves a very similar purpose to the s-box in AES (right?)
... |
I'm trying to implement modular exponentiation in Java using Lagrange and the Chinese remainder theorem.
The example we've been given is:
Let $N = 55 = 5 · 11$ and suppose we want to compute $27^{37} \pmod N$.
He doesn't give us the answer, but says:
The most efficient way to do it is is using Lagrange's theorem, ... |
It is possible to use a hash function to construct a block cipher with a structure similar to DES? Because a hash function is one way and a block cipher must be reversible (to decrypt), how is it possible?
|
I have a file of my own that I have encrypted using Coder-Abi. Now, I can just remember part of this password. So, would it be possible (much easier) for me to crack it knowing only part of it? I can remember around 20 of them. The files are pictures, excel and word files.
If there's any software (mainly freeware), ple... |
Is there a way to prove/create (or are there known hash functions) two hash functions that never have the same collision? I mean, like provable in way that someone who took one cryptography class in university can prove.
For example, I want hash functions $A$ and $B$ such that if hash function $A$ collides on $X$ a... |
Cryptographic key management involves storing and managing encryption decryption keys , certificates , signatures etc .
If the requirement is just to store and manage object specific keys ( say amazon's s3 store objects ) do we really require a key management solution like the one from porticor or an appliance ?
Instea... |
(i'm just trying to find what am I missing...)
Assuming John have a clear text message , he can create a regular hash ( like md5 , or sha256) and then encrypt the message.
John can now send Paul the message + its (clear text)hash and Paul can know if the message was altered. ( decrypt and then compare hashes).
Even if... |
As far as I know,
when I request a certificate from Verisign (for example), and after they approved that I is me, they create a certificate (for me) that contains the digital signature and public key.
The digital signature is data that was created (not encrypted!) by their private key over my certificate data.
Now, a c... |
I read that
A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time.
(Source: Cryptography and Network Security, William Stallings.)
A block cipher encrypts one block at a time. The block may be of... |
I'm reading the book Network Security Essentials written by William Stallings.
To create a message digest with SHA-512, we have to go through some steps:
append padding bits.
append length
initialize hash buffer
... so on.
In the book is written for step 3:
A 512 bit buffer is used to hold intermediate & final resul... |
I have Montgomery exponentiation working, but it's working quite slow. I suspect there are two reasons for this - I implemented it bit size instead of word size (I didn't realize at the time that software implementation should use word size).
The second is how I select R. Given a modulus N with bit length n, I'm calcu... |
Let $c=E^{RSA}_{e}(w)$ be the ciphertext belonging to the plaintext $w$ if an $RSA$ system is used. Assume that the public exponent $e$ satisfies $e \le 10$. Furthermore, assume there is an oracle that, on input $r>0$, responds with the value $c_{r}= E^{RSA}_{e} (w + r)$.
Can the plaintext be decrypted efficiently, giv... |
After my failed attempt at trying to implement the ECM, I started working on the quadratic sieve. It works, but the bottleneck is finding smooth values over the factor base.
The way I implemented it now, it generates 250,000 values of X, then calculates Y as:
Y = (X + ceil(sqrt(n)))^2 - n
Where n is the number to be f... |
Can anyone explain to me what a trapdoor one-way permutation is? Is RSA a trapdoor one-way permutation?
Context: I was reading about ring signatures. On page 560, it describes steps to implementing a ring signature. I am confused by step 3, where $g()$ is a trap-door permutation. The paper briefly says that $g()$ i... |
NIST recommends Krawczyk's HMAC-based key derivation function (HKDF) in SP-800-56C (PDF). HKDF shall e.g. be used to create keys from shared secrets after Diffie Hellman key establishment.
NIST states in the same doc:
Each call to the randomness extraction step requires a
freshly computed shared secret $Z$, and this s... |
Montgomery described an efficient method to compute a modular multiplication. This works by using a special constant $R$ and assumes the inputs $a$ and $b$ have been made into a special representation (residues $aR\mod N$ and $bR\mod N$) and produces the value $abR^{-1}\mod N$. Thus to pursue the computations, one need... |
I'm guessing they're some kind of standard function but what do they do and what do the names mean? A little explaination or link me to an article would be great.
|
Given $G:\{0,1\}^s \rightarrow \{0, 1\}^n$ a secure PRG, how can one prove that $G'(k_1, k_2) = G(k_1) \cdot G(k_2)$ is secure ($\cdot$ means concatenation)?
In other words, I'd like to show that if there is a distinguisher for $G'$ then this implies that there exists a distinguisher for $G$.
For example, could this di... |
Unkeyed hash functions are, by definition, hash functions computed without a key. SHA-1 is an example. MDCs (message digest codes) are a subclass of unkeyed hash functions. How are unkeyed hash functions secure, when the message is encrypted with a known, open hash function and without a key?
|
Could somebody explain what is the difference between "word-based" stream ciphers and the regular ones? Those last ones use pseudo-random sequences XOR'd bit by bit with the message, as far as I know. How does that change when it comes to "word-based" ciphers?
Examples of word based keystream ciphers include SNOW, PANA... |
I wonder if it's safer to encrypt a plain text with RSA twice than it is to encrypt it just once. It should make a big difference if you assume that the two private keys are different, and that the only way used to crack it is brute force. I submitted these theories to my teacher, but he claims that a double encryption... |
I strive into understanding why OAEP has two rounds of computations and not just one. I.e: Wouldn't it be safe to hash the random number r and XOR it with the original message?What security risks if any that padding scheme violates?
|
There is a paper on ring signatures and a python implementation of it here.
The Step 4 in the paper describes $y_s = v =C_k,_v(y_1, y_2, ... y_r)$ for all $1 \leq i \leq r$ where $i \neq s$. The next step is to find a unique $x_s$ for the signer's computed $y_s$. This is done by solving $x_s = g_s^{-1}(y_s)$
However, i... |
I’ld like to ensure I understand AES key padding correctly…
Is the initial AES key (expanded to the key schedule) byte padded if less than e.g. 16 bytes?
Is there a safe way of determining if decryption was successful (meaning: that the correct key has been used
)?
|
I'm implementing AES in C++, and, inspired by the way words are handled in SHA, I decided this time to handle the state as a one dimensional array of 4byte unsigned integers as opposed to a two dimensional array of bytes. To get the bytes out of each of word, I use shifts and mod. E.g. to get the first byte in state[0]... |
Consider the following problem: given $g_1 \ldots g_i,h_1 \ldots h_i \in G$, $\forall i$ find $x_i$ such that $g_i^{x_i}=h_i$
For $i=1$ this is the discrete log problem and is assumed to to have some level of security based on the order of $G$ for certain groups. Let's call this security level $\lambda$.
What hap... |
So let any secure MAC (message authentication code) be given.
Intuitively, I think it is clear that the probability of getting the same tag on two different messages is very small, i.e. negligible. I want to prove this statement mathematically.
How can we
formulate this in an exact manner (because, negligible in what... |
Let $E$ be a family of Pseudo-Random Permutations of $b$ bits, with $E_K$ indistinguishable from random permutation with effort less than $O(2^b)$, easily computable as well as the inverse permutation, e.g. as instantiated by AES-192 for $b=128$. Let $E_A$ and $E_B$ be two public members of this family.
For an $E_K$ in... |
I need to store several million Payment Card Numbers (PCNs) securely in a mainframe database (that is, 'at rest'). I assume that any attacker will have access to all of the stored data.
I assume the availability of a secure device that can:
Store a unique, constant ('master') key that is to be used for all
PCNs
If nec... |
I have a digital signature that was created using the following algorithm: a SHA-256 hash of the body of the message is calculated. It is then signed using an RSA private key and the result is base64-encoded.
Now, I have the RSA public key corresponding to that private key which was used to encrypt the hash. I want to ... |
So for block ciphers you need a fixed size block.
If the plaintext length is not a multiple of the block length then you need to pad it.
One way you could do this is that for the last block you just pad the blocks with 0s or some random characters except for the last character of the last block which represents the num... |
FIPS 186-3 specifies a method to generate DSA parameters.
Is there anything similar (official standard or widely-accepted recommendation) that shows how to generate the primes for multi-prime RSA?
|
With a standard authenticated encryption scheme (or MAC), Alice and Bob share a symmetric key. When Alice sends something to Bob, Bob can check that it is authentic. At that point, Bob can deduce that the message must have been sent by someone who knows the key, i.e., it must have been sent by Alice or Bob.
How can B... |
What if, instead of using CBC mode in the normal way with a random IV, I used this approach:
Use a fixed IV (like a block of 0's).
Before encrypting, generate a random block and prepend it to the plaintext.
After decrypting, ignore the first block.
Is this exactly the same in terms of security as using a random IV?
A... |
This is a follow-up question to Relative merits of AES ECB and CBC modes for securing data at rest.
I need to store encrypted Personal Account Numbers (PANs) in a database. The only encryption option I have available is CFB mode with a fixed (0x00) IV. I can choose my cipher, and have chosen AES-256.
Encryption and dec... |
Is there a formal security proof in the shape of reduction that states that if an attacker manages to break the collision resistance property of a cryptographic hash function (a random oracle) he will break the pre-image attack as well? To rephrase it: is first pre-image resistance as hard as collision resistance s.t i... |
The scenario in Alice/Bob/Cindy terms:
Alice approaches someone she doesn't know, but thinks is Bob, and asks for some secret information. Bob doesn't know and doesn't trust Alice, but Alice says she knows Cindy.
To prove that, Bob calls Cindy, who does know Bob, and asks for half of an asymmetric key pair. Bob then c... |
Is there anyway to detect that a cipher is encrypted with ROT13 Or Base64 without decrypting it using the algorithm and check that the result means (works)?
I mean does an algorithm exists that test the cipher and tell YES it is ROT13/Base64 (or NO it isn't)?
Thanks
|
Possible Duplicate:
Advantage of AES(Rijndael) over Twofish and Serpent
What is the reason of NIST why Rijndael choose as the Advanced Encryption Standard
|
When having a company computer that is full disk encrypted, it is common that the boss have a master password / backdoor, so the data always can be decrypted.
I have heard some call this for "scrow" or something similar.
Does anyone know the correct name?
|
Also, where do I store my salt (can I just store it at the beginning of the encrypted file)?
|
Is it secure to store the hash of a symmetric cipher key along with data encrypted with that key? Are there any circumstances or algorithms in which this combination could lead to potential weaknesses -- or is it always a bad idea? Assume the cipher is AES-128 or -192 and the hash is SHA-256, and also assume that the k... |
We want to explicitly construct a good (as tentatively defined below) Pseudo-Random Function $F$ with $b$-bit input and output, from (preferably just) one Pseudo-Random Permutation $E$ of $b$-bit, as instantiated in practice by TDEA for $b=64$ or AES-256 for $b=128$, and one fixed random secret key.
I tentatively defin... |
First off, if you're doing William's p+1 test, then also doing Pollard's p-1 is redundant, since the p+1 test covers both cases, right?
Second, why is the recurrence $V_{n+1} = aV_n - V_{n-1}$ used? Using $V_{n+1} = V_n + bV_{n-1}$ instead would give you a provable $\frac{1}{2}$ chance of getting a quadratic nonresidue... |
On page 7 of NIST's views on SHA-3's security requirements and Evaluation of attacks, I see that, at least at this point, NIST planned on offering SHA-3 having eTCR security (defined on page 3):
eTCR: Find $M$ and then for a randomly chosen $r$, find $M’$
and $r’$ s.t. $H_r(M) = H_{r’}(M’), (r,M) ≠ (r’,M’)$ where
... |
I'm wondering if it would make sense to record a whole HTTPS session,
publish its encryption keys and present it to third parties as a proof
that this particular data was sent by a given server identifying
itself with some signed certificate. Could such proof be forged in any
way? Should this proof be convincing to th... |
Is there any easy way to crack a Beaufort cipher?
We have a Vigenère table, and are trying to guess the keyword.
Any easier way?
|
Frequently, we want to send messages that are (a) encrypted, so passive attackers can't discover the plaintext of the message, and (b) signed with a private-key digital signature, so active attackers can't make Alice think that a message came from Bob when it didn't.
Is it better to
generate the digital signature from... |
In Public key infrastructure, the MD5 of a piece of data is encrypted with the private key of a sender and this encrypted MD5 – along with the data – is again encrypted using an algorithm like AES or 3DES.
Here, the private key of a sender is used to encrypt with AES… is that correct?
This is a rough implementation of... |
A recent BBC article entitled WWII code 'may never be cracked' posted a code:
AOAKN HVPKD FNFJW YIDDC
RQXSR DJHFP GOVFN MIAPX
PABUZ WYYNP CMPNW HJRZH
NLXKG MEMKK ONOIB AKEEQ
WAOTA RBQRH DJOFM TPZEH
LKXGH RGGHT JRZCQ FNKTQ
KLDTS FQIRW AOAKN 27 1525/6
According to the article the code was found on the leg of a pigeon in... |
How would you answer the following question (I have to translate it from German):
The existence of a pseudorandom generator implies the existence of a AE-Secure encryption scheme (AE = authenticated encryption)
YES or NO
I would say "NO" because (as far as I understand) AE-secure schemes should use two keys (one for ... |
I'm looking for examples of a proof by reduction. For example:
Let $A=(Gen, H)$ be a hash function. We define a new Hash function $A'=(Gen',H')$ with $Gen=Gen'$ by $H'_s(x)=H_s(H_s(x))$.
It should be shown that if $A$ is collision resistant, then $A'$ is collision resistant too.
I am not looking for a solution for ... |
I have a FPGA and am curious what cryptographic applications I can use with it. I'm just a hobbyist / security researcher and not a professional cryptographer.
Since I'm creating my own curriculum, what cryptographic goals should I have with regards to the FPGA device? (note I'm not looking for FPGA programming advic... |
I have a question about the way to store a key or password that was used for encryption, so that the application can check if the user put in the right key for decryption. If I make a mistake, please advise me and I will try to avoid such a mistake in the future.
Normally, the key that was used for encryption is stored... |
Give a 256 bit key space and 128 message space would AES block cipher as the encryption scheme be CPA secure?
|
In a brute force attack on DES, it seems to me that one plaintext-ciphertext pair suffices to launch the attack. (I.e. suppose we are given a message $x$ and a ciphertext $c$ such that $DES_k ( x ) = c$, where the $56$-bit key $k$ is unknown. Then going through all $2^{56}$ keys will eventually give the result.) I am,... |
I'm looking for a solution to use in a context where I need to be able to generate new asymmetric key pairs quickly (using a widely recognized algorithm, and EC-DSA is not applicable). It sounds like DSA would be the adequate solution.
According to the documentation, just generating DSA parameters once allows then to g... |
I'm designing a messaging system where the sender A sends a message m with a signature s to n Receivers.
A Receiver Ri should then be able to prove to a Verifier V that he is one of the receivers of the message without disclosing m and the identity of the other receivers. He will however disclose A and Ri.
Question: h... |
Shamir's original paper (PDF, 197kb) describing a threshold secret sharing scheme states:
To make this claim more precise, we use modular arithmetic instead of
real arithmetic. The set of integers modulo a prime number $p$ forms a
field in which interpolation is possible. Given an integer valued
data $D$, we pic... |
One of the necessary components to the Schnorr Digital Signature scheme is a pair of prime numbers $p$ and $q$ such that $q$ divides $p-1.$ However, there is never a modular inverse taken of q so why is there an extra constraint on $q$? Couldn't $q$ be a number that divides $p-1$ but not prime?
|
My question relates to the original KP-ABE paper:
http://research.microsoft.com/en-us/um/people/vipul/abe.pdf
I'm having trouble understanding the proof (pages 10–13) that the scheme is secure in the Selective Set Model:
Proof: Suppose there exists a polynomial-time adversary A, that can attack our scheme
in the Se... |
I'm building a small VoIP client which transmits encrypted audio data via UDP, and some packet loss is expected, so each packet will need to be decrypted separately even if others in the stream don't arrive. I also don't enforce strong ordering of data, since re-ordering is done only if a packet is significantly out of... |
I was reading the paper $[1]$ and came across the scheme that I show below. While I understand the scheme well, I don't understand why they prepend a 0 to the block containing $r$ and a 1 to all other blocks. What is achieved by this? They never explain why they do it. Here is the scheme as presented in the paper:
$[1... |
Ok hypothetical scenario. Lets say I want to generate a lot of key material quickly for a one-time pad. This key material will be divided up and used for many different messages in the future.
I select 50-100+ songs out of a custom playlist of all my music. The music has been converted to basic Waveform Audio File For... |
As part of a puzzle I was given an RSA 256-bit public key and an encrypted message.
The key itself is very weak, having exponent e = 65537 and modulus N = 00:c0:fb:55:b3:ed:f5:19:bf:8d:3a:2a:60:e8:bc:6e:1c:94:f0:5c:17:19:f8:38:ff:45:0b:01:0f:47:96:27:fb
I can determine p and q by using an arbitrary precision library an... |
In easy steps, this is how it works:
Convert txt to numbers. mod 1-26.
Generate random numbers (by my other cipher) equal to plain txt.
Write random numbers under txt numbers.
Like this:
txt = LOI - txt number = 12 15 09 - random number = 73 96 14
Encryption system, random numbers under txt numbers
12 15 09 --> txt ... |
I'm just interested in cryptography, so please don't expect me to be an expert. ;) I recently read about AES cache timing attacks and found it very interesting. I read the article Cache-timing attacks on AES by Daniel Bernstein, but I don't seem to understand everything.
How relevant is this to "real-life" network app... |
In the case of password storage, consider the following:
I have an idea that one can exhaust the entropy of input to the MD5 function by using a 128 bit random value as the password (indeed, any hash function, using the output length as input). Is this a correct assumption, or is the entropy exhausted at 123.4 bit, thi... |
I read the paper Cache-timing attacks on AES (by Daniel J. Bernstein), but I don't seem to understand everything. The author dedicates a long section on how to prevent the OS to interrupt an AES computation. But how does this leak any information? Yes, the calculation takes more time than usual, but it is not dependent... |
I'm trying to figure out block ciphers and this is the first time I've encountered the term "oracle adversary". It appears in the context of defining a PRP and a PRF. Can someone please explain what an "oracle adversary" can/cannot do? Or maybe help out with a link or something (I've tried looking it up myself, but I c... |
I need to generate a 1024 bit ElGamal key on Android, and key generation takes forever (~10 minutes on a Galaxy Nexus), I suspect because it take so long to generate a safe prime.
Is it dangerous for me to use the same safe prime p for all devices using my app?
Where can I find a list of 1024 bit and 2048 bit safe prim... |
I know that you can use for example CBC-MAC to verify data integrity and thus the password upon decryption.
But would there be security implications of just adding a constant string to the plaintext and if the first block is identical upon decryption we know the key was correct?
|
In Alice/Bob/Cindy terms (EDIT: and with a little more detail):
Alice and Bob have each securely obtained one key of an RSA keypair from a trusted third party. Alice has one key ($e$ and $n$), Bob has the other ($d$ and $n$, where $d\equiv e^{-1} (mod\ \phi(n))$).
The RSA algorithm technically does not care which of t... |
I have a question about random number generators.
I have read from a real random number generator, based on a webcam ("randcam"). My problem is, that I do not really understand how the generation of the random numbers works. Has anyone heard of this principle before and can give some hints how it could be implemented?... |
I want a script that is running on the client to compute a collision resistant hash and send it to a server. I need to ensure that the script which performs this hash is not altered in any malicious way. Is there any protocol that exists which can ensure that the client script that calculates the hash has not been alte... |
I read briefly over the TSL/SSL key exchange protocol. I have to wonder about the whole pre-master-key procedure. Wouldn't it be sufficient if the client or server encrypted a generated session key with the other sides public key? Why the extra work?
|
Bent functions are Boolean functions with maximum nonlinearity and are widely studied for their potential applications in cryptography. Let's say you want to use a simple $2$-input AND gate as a nonlinear combiner for the outputs of two linear feedback shift registers. Because a $2$-input AND gate is a bent function, i... |
Authentication protocols often rely on humans dealing with large numbers correctly. For example, when a user logs into a remote machine using SSH for the first time, she is prompted to confirm that the fingerprint of the server is the expected fingerprint. The user can phone the owner of the server, and confirm that th... |
I have a client-server application, which is transferring data between its components in a secure way. I currently use AES algorithm with CBC mode to transfer data and file. This is the scenario: Client ask for data(file or plaintext), server takes the request and encrypt data with a iv/key pair and sends encrypted dat... |
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