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I am trying to understand the operation of the Dual_EC_DRBG. I'm reading the formal specification (SP 800-90) and can't seem to find a definition of the $\phi$ function used throughout the definition that I can grasp. The definition I found is on page 65 of SP 800-90A. Just to be clear, I'm referring to the $\phi$ fo... |
I currently am writing a web app and am using two random hashes that are before and after the string and are both 50 char long (alphabet, numbers, and special chars).
strlen($hash1) = 50;
strlen($hash2) = 50;
$sha3pw = sha3($hash1+$password+$hash2);
What are the chances that someone will be able to find a collision fr... |
The RSA signature operation is basically the same as encrypting with the private key. In particular, both operations use the same kind of keys.
Is it safe to use the same RSA keypair both for encryption / decryption and for signing / verification?
|
I have taken elliptic curve $E\colon y^2=x^3-4x+20$, defined over $\mathbb{F}_{29}$.
The number of points on the curve, $\left|E(\mathbb{F}_{29})\right|=37$.
I took base point $P=(1,5)$, and got following results:
I want the results graphically to know the behaviour of the curve.
Is there any tool for this to show res... |
Suppose $h_1$ is collision resistant, and $h_2$ isn't.
Will $h(x)=h_2(h_1(x))$ always be collision resistant?
[Edited:] the output of h2 must be uniformly distributed
|
I was wondering what is the performance bottleneck in RSA algorithm?
Is it the size of message, calculating the modular inverse, exponentiation?
Say I have a fixed value of n to encrypt and decrypt a message would l get a better performace with m being small or large?
|
I wonder if it is possible to devise a function $F(K,S,R_S)\mapsto D$ where:
$K$ is some key (I have freedom on $K$, it could even be generated by a trusted party);
$S$ is in $\{0,1\}^s$, say $s=32$; $S$ is a serial number;
$R_S$ is a random value associated to $S$, in $\{0,1\}^r$, say $16\le r\le48$; $R_S$ is produce... |
I'm an undergraduate Math student currently taking a cryptology course. I have a question about the RSA signature authentication mechanism.
An RSA signature can be authenticated with the public key of the signer. However, I'm wondering why it can ONLY be authenticated with the signer's public key. Why can't it be mist... |
I am a student taking a cryptography course so forgive me if this comes off as a silly question.
This is an assignment question:
$Alice \rightarrow R \rightarrow Bob$
$Alice \leftarrow [R]B \leftarrow Bob$
$Alice \rightarrow [R+1]A \rightarrow Bob$
Why doesn't this protocol provide mutual authentication?
Here's... |
If I proved a scheme's security under GDH assumption, in real-life, if this DDH oracle does exist, then it's good, but what about other side ? In real-life, if this DDH oracle doesn't exist, then what's the meaning of proving?
|
My understanding is that, simply put, a stream cipher is just a CSPRNG such that $R(i,k)$ will produce a deterministic but statistically random sequence, where $i$ is an IV, and $k$ is the session key. The resultant key-stream $K$ is then combined with plaintext (i.e. $C = K \oplus M$).
Now, if we take two messages $m_... |
This is hypothetical as I can't think of any reason to do this, but out of curiosity...
Could I, for example, take the MD5 digest of a message and concatenate it with the SHA-1 digest (not quite broken, but getting close), to form a secure concatenated digest? Intuitively, I would think the chances of finding a collisi... |
I am working on teaching myself basic cryptography. In the process I created a simple substitution cipher based on a single alphabet, and a statically defined offset (no key for now). Now that everything is working, I want to start on another application to "crack" the offset. The key here is my cipher removes all spac... |
Given an elliptic curve with equation $y^2=x^3+ax+b$, and i want to find the number of points $(a,b)\in E(\mathbb{F}_p)$ where the polynomial has repeated roots, how do i do it? I have an intuition it is $p$, but don't know how to rigorously show it.
Thanks
|
If I XOR the output from 2 CSPRNG will the result be better (more random) than the output from either one?
Assume one of the PRNG is biased.
|
Let $E\colon y^2=x^3+ax+b$ be an elliptic curve, and consider its realisation over the finite field of prime order $p$: $E(\mathbb{F}_{p})$.
Then if $0<a,b$ is the following true?
$$\forall x,y\in[0,p) \text{ s.t. }E(x)=y \text{ : }(x_i<x_j)\implies E(x_i)<E(x_j)$$
|
I am a student taking a cryptography course so forgive me if this comes off as a silly question.
This is an assignment question:
Alice ------R--------> Bob
Alice <-----[R]B------ Bob
Alice ------[R+1]A---> Bob
Why doesn't this protocol provide mutual authentication?
Here's a plausible scenario Alice sends R trudy inter... |
If we know for some message $m$ that $H(m) = 0$, how can we forge a DSA signature with only the public key?
I got that $g^s*r = (g^x)^r$ where $x$ is the private key, but that's one equation with 2 unknowns, and since discrete log is hard, I can't substitute a value for either $s$ or $r$ and find the other and satisfyi... |
I was thinking about stretching salt.
Key-stretching is good against brute force guessing and assumes your system isn't compromised.
Salting a one-way makes it so you have to compute * n for each password and assumes your system is compromised.
Assuming the system is compromised, derived salts are found, static keys ar... |
Given an curve with equation $y^2=x^3+ax+b$, I want to find the number of pairs $(a,b)\in \mathbb{F}_p \times \mathbb{F_p}$ NOT on the curve. How do I do it?
I have an intuition that it is $p$, but don't know how to rigorously show it.
|
There are a number of papers in the literature describing secure/fair coin flipping protocols. Unfortunately in my case, I am looking for coins that are epsilon-biased or epsilon-correlated. I am looking for a coin-flipping protocol that is guaranteed to output correlated and/or biased coins to parties for some pre-agr... |
for my hobby tinkering project, I need a mixing function that takes 32-bit input and has 32-bit output (and will, most likely, run in a 32-bit C environment) and the following property (independent of endianness, i.e. it’s enough to only look at either big endian or little endian (or pdp endian) systems):
union u {
... |
Given $n=pq$ for $p,q$ known, I can calculate $\phi(n)$.
$e$ is selected such that $\gcd (e,\phi(n)) = 1$.
Using this, how do I calculate the RSA private key?
Example:
I have $n = 35$, with $(p,q)=(5,7)$.
I have also computed $\phi(n)=24$, and selected $e$ such that $\gcd (e,\phi(n)) = 1$ by taking $e=23$.
Calculat... |
For $d = e^{-1} \mod \phi(n)$
$$d\cdot e \operatorname{mod} \phi(n)=1$$
$$d = (e^{-1} \operatorname{mod} \phi(n))$$
With having $e$ and $n$, we can calculate the value of $d$ , the private key for cracking.
Why do people worry about factoring $d$ when this technique is available?
I would like to know some real insight ... |
I've done a few obvious searches on google and google scholar and not turned up any security analysis of FreeBSD's geli. Is there some out there, or has it gone unanalyzed since its introduction circa 2005? Frustratingly, it seems to have sprung into existence fully-formed and without explanation of the choices in e.... |
I have a hard time understandin which of the following protocols is susceptible to replay attack:
A -----> B username, password
A -----> B username, h(timestamp,password)
A -----> B username timestamp, h(password)
A -----> B username, h(timestamp), h(password)
I think the answer is 1 and 3
I know 2) is sec... |
We have been shown that DE is congruent to 1 mod phi(n). How do we arrive to the real equation for figuring out d that is d = e^-1 mod phi(n). I want to know the entire process. I am just curious, spending the night studying the workings of the RSA.
|
I have a third-party point-of-sale API (Speedflow Pay-N-Get) that I am trying to communicate with over HTTP, but I have a problem with it.
In a nutshell, a request is encrypted using RSA, and the response is encrypted using RSA followed by Rijndael/AES-128. The RSA keys are provided by the vendor, the AES IV is a vend... |
When encryption is done using the AES-CBC algorithm, the encryption can be thought of as chaining the cipher texts with the previous ones and an IV. However, if its on CBC mode, we give our cipher text forward diffusive properties (i.e. if we change but i in our cipher, plaintext is change for all blocks after that). T... |
I'm looking for a slow one-way pseudo-random permutation; or in other words a block cipher $E_K: P\in\{0,1\}^b\mapsto C\in\{0,1\}^b$ with moderate block size $b\approx 64$ bits, wide key $K$, indistinguishable from a random permutation for one not knowing $K$, and additional characteristics:
encryption $E_K$ is contro... |
Due to some platform restrictions our decryption algorithm can only handle up to 1 million bytes. The string we receive is larger, having been generated by AES in cipher block chaining (CBC) mode, with PKCS5 padding.
Is it possible to somehow split the encrypted data and decrypt the parts?
|
How can I tell how many bits of security a secure hash function has?
For example, how would I calculate or tell how many bits of security a secure hash function with 160 bits output would have? Assuming there are no known weaknesses…
|
There are various different modes of operation for block cipher use, some of which provide "encryption" and some of which provide authenticated encryption.
Why should I use an authenticated encryption mode rather than just an encryption mode?
This question does not aim to discuss different modes of authenticated encryp... |
What I want to do is use asymmetric crypto to guarantee that a file comes from a source. I have software that runs on lots of wireless devices, and each of those has a license file with an encrypted date that they expire. I'd like to be able to encrypt it in the office and have the devices decrypt/read the date. The pu... |
Suppose you are running a server with the Diffie-Hellman parameters (so the group G and generator g) generated once. There are many connections made to the server, all using TLS with an DHE cipher suite.
Now, assume an adversary captures all connections and is able to break one key exchange (find the master key). How m... |
Why does RSA use semiprime numbers? Why not just use any big number ??
What is the advantage of the two original numbers being prime?
Because factoring any big number will be difficult
|
I've been given as an exercise to show an encryption scheme that is CCA-secure but is not a secure message transmission scheme.
What is a message transmission scheme, and how does it differ from a regular encryption scheme?
|
I'm now studying the block cipher substitution-permutation network construction and realized that it uses several small pseudo-random permutations instead a big one for saving memory (or that is one of the reasons).
Why does the PRP with input/output of $n$ bits utilize $\log(2^n!)$ memory? (When saving a full table of... |
My understanding is crypto researchers tend to prefer solving a problem in software without the need for secure hardware. Why is this? What is the big problem with using secure hardware if the hardware components are cheap and can be easily made?
|
I have the ciphertext and the plaintext. Is it possible to know the key? If not, what do I need to find it?
|
I'm struggling with some DES variant that I got as an exercise (exercise taken from Katz-Lindell Ex5.14).
The variant is as follows:
The left half of the master key is used to derive all the sub-keys in rounds 1-8, while the right half of the master key is used to derive all the sub-keys in rounds 9-16.
My direction i... |
Given this encryption method:
$$f_{N,e} : Z^{*}_{N} \to QR(N)^{*};\quad f_{N,e}(x) = x ^{2e} \bmod N$$
I need to show that, for any $x_{0} \in Z^{*}_{N}$, there are four elements $x \in Z^{*}_{N}$ such that $f_{N,e}(x) = f_{N,e}(x_{0})$.
This seems like a cross between RSA ($x \mapsto x^{e} \bmod N$) and Rabin ($x \map... |
I once asked a question "Would RSA make sense if we used no computers?". The answer was negative, because finding primes that would make secure keys would prove too hard. Assuming that we had found another way of finding primes without computers, would RSA be usable in, for example, medieval times?
|
I have been reading the Cryptographic sponge functions paper, but I'm still confused.
Does Keccak in authenticated encryption mode absorb ciphertext or plaintext?
Edit: Are there any test vectors to verify implementation of Keccak authenticated encryption?
|
I don't understand how the $E(m)$ turns into $E(mt)$. I mean, I don't know how does that transformation happen and how does the equation occur.
$$E(m) \cdot t^e \bmod n = (mt)^e \bmod n = E(mt)$$
See, $E(m)$ is $m^e \bmod n$, so if you plug in real values, it won't work.
For example:
$c_1 = 17^{23} \bmod 35 = 33$
$c_... |
A weak key for DES is a key $K$ such that $DES_{k_1}(DES_{k_2}(x))=x$ for all $x$.
I don't get why are the 4 keys $k_1||k_2$: $1^{112}$, $0^{112}$, $0^{56}||1^{56}$, $1^{56}||0^{56}$ considered as weak. (Also didn't find some detailed explanation in the web.)
|
I am considering the FNV1a 32 bit hash as part of a simple software security and authentication system. I am aware that FNV1a is NOT ideal but it may suit my needs.
I am aware that FNV1a has rather poor collision behavior, but I would like to know if it may be implemented in such a way as to minimize problems. Assuming... |
Is there a best practice for Diffie-Hellman parameters (p, g, and q) used on a web server?
The server is using ephemeral keys, but should the parameters be rotated on a regular basis? Is it OK for the server to keep them fixed for years (in the source code)? Or should they be generated uniquely for each site?
This serv... |
Edit: My goal is to create a voting scheme that doesn't require a lot of crypto infrastructure to be deployed on the client side. Smartcards, and tokens are impractical for these purposes. I envision a user typing a "code" into a web browser (which is imperfect) and submitting the inputs. The code is either static,... |
I'm reading about Hidden Field Equations Multivariate scheme. My lecture states that the central map is a univariate polynomial $$P(X)=\sum_{i=0}^{r-1}\sum_{j=0}^{r-1}p_{ij}x^{q^i+q^j} \in K[X]$$ where $K$ is a extension field of the finite field $k=\mathbb{F}_q$ of degree $n$ and $r$ is a small constant chosen in a wa... |
I am looking into implementing ECDSA signature and ECDH key agreement in a Xilinx FPGA.
All the examples I have found of VHDL implementations skip over how to construct the low level ECC primitives (e.g. point multiplication, MOD P in prime fields, and specially Inversion.
Can anyone point me to documentation or a si... |
I'm currently reading up on the components of PGP and I am wondering what exactly the PRNG is used for. PGP uses ANSI X9.17 and entropy from a users keystrokes to generate a temporary key.
So, is this temporary key used for the public key encryption? Is it one of the keys in the key pairs? And how does PGP actually gen... |
I know we could possibly be using DH key exchange, that would enable PFS. However, what if we make modifications on our SSL 3.0 handshake such that the only cipher we use is RSA for the achieving PFS? Is it possible to modify SSL handshakes to enable PFS while still using RSA during the handshake?
|
To my understanding, if a server “cert+key” (RSA) is compromised, than the SSL/TLS network traffic can be decrypted.
What about a client “cert+key” (RSA)? Could someone reuse client certificates?
For example: can somebody with the client “cert+key” decrypt (or in otherwise mess with) the traffic of another user? (Ye... |
I'm writing my own cryptosystem that uses One Time Pad and Diffie-Hellman to generate keys for the OTP. I am using Rails on the server side and Javascript for the client side.
Please don't tell me this is insecure and I shouldn't do it. I'm doing this purely for educational purposes and in no way will this be deploye... |
I want to store data encrypted within an Android application. Keeping an encryption key safe outside the app is not an option so I looked into password derived key algorithms.
I found a nice example from Android on the blog-post “Android Developers — Using Cryptography to Store Credentials Safely ”. Let me quote the s... |
In a commitment scheme, are there any differences on using a symmetric cipher versus using a hash?
If at the "opening", I have to reveal $r$ (a random number concatenated with the messaged at the time of hashing) and $m$ (the message), why not reveal the key used for encryption for everybody to decipher the message a... |
One thing I was surprised to learn about AES is that random padding can be added to the message to make it a multiple of block size. What I can not wrap my head around is how this random padding can reliably be removed from the message upon decryption, given that if it is generated by a truly random process, the recipi... |
One of the problems of one-time Lamport signatures is that public keys are disposed after use, so you must generate many keys and store them in a Merkle tree. The root is the "real" public key and each signature is supplied with a Merkle branch from the root public-key to the one-time public key.
I was thinking of usin... |
When choosing the public exponent e, it is stressed that $e$ must be coprime to $\phi(n)$, i.e. $\gcd(\phi(n), e) = 1$.
I know that a common choice is to have $e = 3$ (which requires a good padding scheme) or $e=65537$, which is slower but safer.
I also know that for two primes $p,q$, we have $\phi(pq) = (p - 1) (q - ... |
I'm working with documents encrypted in long term storage. When a client requests the document, the document should be delivered encrypted under a distinct key (distinct from the long term storage key).
For efficiency, I want to avoid decrypting the document under its long term key and then re-encrypting under a client... |
I am trying to understand the AES encryption algorithm. I know that we process 128 bits at a time for a 128 bit key in a 4x4 octet form, but am confused by the following:
How does the substitution subround work, as the size of the Rijndael's S-box is 16x16 Octets and size of the input is 4x4?
How does the mixed column... |
Let $G$ be a group of order $n$ and let $e,d$ be integers such that $ed\equiv 1 \pmod{n}$. Then the exponentiation maps $x \mapsto x^e$ and $y \mapsto y^d$ are inverse maps on $G$.
These maps give us the Pohlig-Hellman exponentiation cipher. The secret key is the two numbers $e$ and $d$. The group $G$ and its order $n... |
If a cipher implementation passes unit tests using test vectors from some trusted source (these for AES, for example), then can we say that it is fully conforming to the specification, and must have been implemented correctly?
Is it possible to backdoor a cipher (or hash function, I suppose) in such a way that it still... |
Is there any new understanding, property, or knowledge that has come from the Number Fields @Home distributed computing project? Has any outcome advanced the study of cryptography, or altered previous recommendations?
If nothing in particular has come from the project as of yet, are there some outcomes a cryptographer... |
Can somebody explain, in simple terms, the difference between Pseudo Random Permutation Ensemble and Super Pseudo Random Permutation Ensemble?
|
Given a message and DES encrypted form of said message, is it possible to efficiently compute the key used to encrypt the data?
|
Simple question. I have a source file and I have encrypted it with a certain public key. If I take this exact same source file, encrypt it with the exact same key a few hours later would the file hash of the two encrypted files be the same?
|
how we can summarize SHA-256 into shorter values when we for example can't handle more than 128 bits on system? its better just use first 128bit and ignore the rest of bits or split full value and XOR them? or use another hash function that produce required bit long hashes to generate a hash from SHA-256's value (e.g S... |
I'm on a crypto app using OpenSSL (I'm more an implementer/cryptographer than a cryptologist), mainly as a hobby, for now.
My app will be able to encrypt a file (not a container) with symmetric or asymmetric or both encryption (sym then asym), and I want to implement "deniable encryption" (I'm in France, you should hav... |
My understanding of ECDSA signature length is that it depends on the key size. So for instance, if a "prime256v1" is used, the signature length will be 64 because (n/8)*2 and for "secp384r1" it will be 96. However, I don't understand why is it for "secp521r1" the signature length is 132 instead of 130?
|
In a hash function, you map an input of arbitrary length to an output of finite length such that the relationship is one-to-one (or at least that's what you are trying to achieve).
Hence, isn't it impossible to have a perfect hashing algorithm? Aren't MD5, SHA-*, all flawed in this respect?
Is an "ideal hash" impossibl... |
I currently have a system which uses two keys sourced from a single key subjected to HKDF. One key is used in the Salsa20 stream cipher and the other is used for a SHA-2 based HMAC.
Given that the stream cipher (Salsa20) is being used for a persistent stream lasting a long time (perhaps hours) with frequent data exchan... |
Can anyone tell me the name of this cipher please?
I know it's a simple substitution cipher, I just don't know the name of it.
Cipher Key:
help
Cipher alphabet:
a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z
h|e|l|p|a|b|c|d|f|g|i|j|k|m|n|o|q|r|s|t|u|v|w|x|y|z
Text:
this is a test
Cipher text:
tdfs fs h tast
I ... |
I’m doing a school assignment about secure communications between a Server and a Client.
Basically, messages are exchanged between the clients and the server and these communications must implement confidentiality, authentication, integrity and non-repudiation.
Imagine I have to send a message from the client to the se... |
I'm developing a new image steganalysis technique, and I'd like to test how effective it is in practice. How could I do this? Are there such things as standard "test vectors" for steganalysis?
|
AES in CBC-MAC mode is proven to be good PRF . But is there any study done on other modes ? how good is ECB mode as PRF ?
|
I'm new in the crypto world and I've just discovered PBKDF (I used to use typed passeword as symmetric key).
When using some crypto mode, you're required to generate an IV which must be completely random and not predictable, the best length is the length of a block size. PBKDF (and hashing functions in general) needs a... |
Suppose I use GnuPG to symmetrically encrypt a file like so:
gpg --no-options -c --cipher-algo AES256 --no-random-seed-file -o my.out my.file
I then provide a passphrase when prompted.
What steps does the software actually take to get from the passphrase I provide as a user, to the actual 256-bit AES key which is use... |
I'm trying to study a simplified TLS-style protocol, including verifying RSA signatures. It's an attempt to verify using only a valid certificate. However, I can't manage to get anything to verify properly. I have a modulus, exponent, signature, and hash of the message. With the following parameters:
modulus = 28459 =... |
I was asked to implement traffic encryption between the game server and clients.
Currently, the traffic is not encrypted in any way, which lets players use cheats to listen to the traffic in order to obtain information about the location of the opponents.
Traffic packets are small (50-70 bytes) and the developers are n... |
I am new to linear cryptanalysis, so I decided to try to break a toy cipher that was designed to be vulnerable to linear cryptanalysis. Unfortunately, I can't get it to work no matter how hard I try. I've read the Wikipedia article and several papers, but they always seem vague on how to turn equations that hold over t... |
I'm building a device that performs a modular inversions using a secret modulus. I would like to know if it is possible to recover all or part of this modulus by side-channels (timing, power, EMR, etc.).
All information I found related to side-channels in modular arithmetic applies to modular exponentiation.
The algori... |
Recently i'm reading "Cryptographically Strong de Bruijn Sequences
with Large Periods" . In the section 2 2.1 Basic Definitions and Properties , property 1 says that $$2n<LS_s\leq2^n-2$$ for a span $n$ sequence. The author claims that this bound comes from "Characterizations of Generators for Modified de Bruijn Sequenc... |
In most of time, what I see is explicit signatures such as ElGamal, it's rare to see the implicit signatures. So I wonder
why it's rare to be seen?
what aspect is it mainly used?
what's the difference between implicit signature and explicit
signature?
P.S. I want a detailed answer, better give some examples of implic... |
I'm using OpenSSL 0.9.8 on OSX Maverick, and I want to use a PBKDF but I can't find any doc/man about it on OpenSSL's website.
I'm working on QCA, an OpenSSL wrapper for Qt, and when I arrived there was PKCS5_PBKDF2_HMAC_SHA1 as PBKDF2, a function I can’t find either on the OpenSSL website. It's marked as DEPRECATED on... |
Typically ad hoc networks do not have a proper infrastructure and the routing is done only through the base stations which are connecting a wired and wireless network. Does quantum cryptography protocols and QKD provide a better security for such ad hoc networks.?
|
I've seen a few puzzles based on a type of cipher in which letters in the plaintext are substituted with groups of characters in the ciphertext. The ciphertext only uses a handful of unique characters. For example:
a -> 154
b -> 53
c -> 12
d -> 41
e -> 153
...
In this example, bead is encoded as 5315315441.
Since no... |
Why are security against eavesdropping and security against CPA equivalent
in the setting of public-key cryptography?
|
I'm currently working on web services which allows to send and retrieve data.
The data belong to a team.
A team is composed of users.
Each authenticated user can send and retrieve data to/from their team.
I need to add encryption to this with the following requirements:
Data are encrypted on the server and the server ... |
I have been working on a Bloom Filter implementation recently and after a discussion with a co-worker about how many hashing functions to use I told him I was limited with using hashing functions that are already implemented and didn't want to risk the loss of distribution if I derive hashing functions from them.
We ca... |
Attack scenario:
SSD physically retrieved from a computer that is turned off. The entire disk is encrypted with AES 256-bit (GNU/Linux, LUKS). The SSD has had TRIM enabled for several years and the file system has seen a lot of use, i.e. a lot of files deleted over time (triggering TRIM). Assume that the key used is su... |
In learning how DH works for cryptography applications, I'm coming across some confusing language. For starters, most of the time DH is discussed in the context of "generating" their shared secret. However, I'm also seeing that it can be used for encryption purposes as well (such as encrypting the shared secret using a... |
Consider the pairing $e: G_1*G_2 \to G_t$.
Why we are mapping element from group $G_1$ and group $G_2$ to an element in $G_t$.
How are they used in cryptography?
What advantages do they provide?
|
Is a one-time pad still breakable on a depth of 2+ if the plaintext is completely random?
I'm assuming this idea is wrong, mostly because it occurred to me, but let me walk you through my logic so you can concisely correct me:
A one-time pad is unbreakable on a depth of 1 because a comprehensive
brute-force attack wil... |
Given the following preconditions:
A plaintext A (~512bit length), that is hashed by using SHA-1 and truncated to (the first) 64 bits.
I know both, the plaintext and the truncated hash, and want to perform a Second Preimage Collision Attack.
Furthermore, a part of the new plaintext B, that should produce the sam... |
Im trying to understand if nowadays using AES is secure or not, after reading some arguments on Schneier’s blog (to be more exact, a comment to “The NSA Is Breaking Most Encryption on the Internet”) it seems like it is not secure:
Now as the NSA GCHQ et al know very well the more efficient you make the implementation ... |
Schneier says:
Fewer and smaller S-boxes. It may be possible to reduce the number of
S-boxes from four to one. Additionally, it may be possible to overlap
entries in a single S-box: entry 0 would consist of bytes 0 through 3,
entry 1 would consist of bytes 1 through 4, etc. The former
simplification would redu... |
Is there a way to setup a hierarchical encryption using public key encryption?
Let's say a higher level user can decrypt messages encrypted by lower level users. Is that possible?
I guess it is only possible to do with hierarchical key management, like the higher level users have access to the lower level user's keys.... |
So finding a pre-image means given the hash value, one tries to find a message that gives this value using the function's standard IV. What about pseudo-preimage?
|
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