instruction stringlengths 32 27.2k |
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To my best knowledge, the Goldreich's pseudorandom generator (PRG) with locality 5 has been considered as one of standard assumptions.
On the other hand, Lin and Tessaro (Crypto'17) provides a new notion, called the block-wise locality PRG. As I know, block-wise locality 2 PRG was broken, but block-wise locality 3 PRG ... |
I'm trying to figure out exactly how solving different generic lattice problems can solve LWE, and in particular, BDD. Everything I've found says that since an LWE sample is $(A,b=As+e\mod q$), then the lattice $L_q(A)=\{v : \exists x:Ax=v\mod q\}$ contains $As$, so $b$ is within distance $\Vert e\Vert$ of that lattice... |
For the chronological categorisation of cryptography, I have proceeded as follows:
Cryptography by hand (e.g. Caesar, Vigenére, etc., till around 1900/1920)
Cryptography using machines (e.g. Enigma, TypeX, etc., till around 1960)
Computational Cryptography (e.g. DES, AES, RSA, etc.)
The Future of Cryptography (e.g. Qu... |
When exchanging a public key I usually receive some compressed form of X,Y coordinates. To use some speed ups I'd need to represent that in the Jacobean x,y,z form.
Z=1 satisfies everything and looking at the speed ups (https://en.wikibooks.org/wiki/Cryptography/Prime_Curve/Jacobian_Coordinates, http://www.hyperellipti... |
As I understand it, RSA works as follows:
Pick two large primes $p$ and $q$
Compute $n = p \cdot q$
The associated group $\mathbb{Z}^*_n$ consists of all integers in the range $[1, n - 1]$ that are coprime to $n$ and will have $\phi(n) = (p-1)(q-1)$ elements
Select the public exponent $e$, which must be coprime to $\p... |
I have been reading the Hasty Pudding Cipher specification and the author make clear that the cipher has some equivalent keys if the keyspace is larger than 8192-bits:
Two keys are equivalent if they expand to the same key-expansion
table. The likelihood is negligible for keys of size < 1/2 the
key-expansion table siz... |
The protocol SRTP uses by default AES in CTR mode with HMAC-SHA1.
For my thesis I want to research if GCM would be a better option.
Therefore I read following discussion.
There the answer was that GCM mode is better among other things because GCM just needs one key for encryption and message authentication and CTR+SHA1... |
It's not clear from the documentation if the sequence of integers produced by these PRNGs belongs to the uniform distribution.
Also it's look like there is a whole family of RNG algorithms called in a similar manner. Personally I'm mostly interested in xoshiro256** - but no information about distribution uniformity as ... |
I have performed the XOR and the result comes as 1001.
Now my confusion is that in standard S-Box (DES) the input is 6 bit where the first and last bit together specifies row and 4-middle bits column. Even if I append two zeros on the left making the XOR result 001001, then row 01 does not exist in the problem. If I d... |
I recently learned of the McCallum-Relyea exchange which allows for a method of key escrow without actually transmitting the key.
It was developed at RedHat and is used by the tang and clevis utilities (and further described here) to allow for automated decryption, in particular for an encrypted root partition for Linu... |
In a public-key system using rsa, you intercept the ciphertext c = 15 sent to a user whose public key is e = 5, n = 35. What is the plaintext m?
In my calculations m=15. But i dont think my calculations are correct
|
Are there any security concerns with using RSA in “CBC mode”?
Specifically: if I use RSA encryption as my block cipher operation, and apply the standard CBC mode operations including a random IV, will the resulting cipher text provide the same level of theoretical security as the underlying RSA problem?
I am only consi... |
These days I found myself thinking about the implications of padding or not padding block cipher modes that act like additive stream ciphers (I meant OFB, CTR, GCM etc). Let's call additive modes.
You know, people hooked on crypto tend to be I little bit paranoid... Well, at some point in my ruminations about the pros ... |
I have a string that generates from SHA-256
x = fea5f97f9ca1e1a0a2ae344f4e12a3ab0c4d9221e6bb5d70bc567e39f8fbc3d5
What's are the first 10 bits are of the value of x?
|
I don't quite understand hashing, for encryption or otherwise.
So, if you have a website, and a user signs up, you store his password as a hash.
When they log in, your website takes the submitted password, hashes it, and compares hashed submission to the stored hash, right?
Say you are hashing a sentence using SHA-256,... |
This from the manuscript of a book on Zero Knowledge Proofs - https://people.cs.georgetown.edu/jthaler/ProofsArgsAndZK.pdf
3.5 Low Degree and Multilinear Extensions Let $\mathbb F$ be any finite field, and let $f : \{0, 1\}^v \rightarrow \mathbb F$ be any
function mapping the v-dimensional Boolean hypercube to $\mat... |
I was studying a protocol that used an OT and suddenly and suddenly I realize that I fail to imagine how a protocol using an OT could be malicious secure.
Suppose we have a protocol P that use an OT as subrotocol. Suppose that the OT is used $N$ times. Each OT has input $x_{0,i}$, $x_{1,i}$, where $i$ denotes the $i-$t... |
I'm doing a performance test on AES with CTR mode and HMAC SHA1 for message authentication and found the openssl speed tool for that.
I run multiple tests with openssl speed -evp sha1 aes-128-ctr aes-128-gcm because I want to compare it to the GCM mode which do encryption and message authentication in a single mode.
No... |
So here I am, googling my brain on the possibilities of impersonation attempts by a MITM attacker on Lamport's one-time password scheme.
Here's my scenario:
Say we have a client and server setup. Given a nonce $n$, and a hash function $h()$, a client computes the hash of $n$ several times (say $100$) and sends at first... |
I am a total newbie to cryptography and I would like to know the meaning of a "uniform n-bit string". Also, why keys of that type are commonly used in private-key encryption?
Thanks!
|
I'm looking for an elegant solution to the might-seem-trivial problem of looking up for specific value in a known set of values without disclosing what value we look for. Let me describe it in a classical way:
Alice will soon celebrate her birthday and she wants to know if anyone in her class has the birthday on the sa... |
Trying to implement a mechanism for one way transmission of encrypted string values using ECC.
Assume there is a fixed secret unavailable private key FPK, and public key FP for it is available to the application.
As user enters a value, a new private key is generated, then shared key is produced from exchanging it fro... |
I got the following question and I really don‘t know how to answer them. My I ask you for your input?
Do you think, that the following adjusted Padding will prevent the classic Bleichenbacher attack
2Byte Random prefix | Random padding bytes unequal 0xff | 0xff | PremasterSecret
In theory I would agree (at least for th... |
How can we analyze the time and space complexity of meet and middle attack on a Triple-DES?
|
Suppose you are given $DES_k(m)$ for some unknown $k$ and $m$, where DES() is the usual DES scheme. With what probability can you predict, for example, the 12-th bit in the output of $DES_{\bar{k}}(\bar{m})$. Here $\bar{m} (resp. \bar{k})$ denotes the bitwise complement of m (resp. k).
In this question, as we know that... |
Ideal cipher is a random permutation for every key in its key space.
And, ideal encryption scheme is the one which has perfect secrecy/indistinguishability.
For an encryption scheme, random permutation from plain text space to cipher text space seems to be a stronger property and is not always needed
I do not understan... |
The standard DDH assumption states that given $(g,g^a,g^b,g^c)$, it is hard to determine whether $c$ is $ab$ or not.
A variant of DDH assumption is:
given $(g,g^a,g^b,g^c, g^{ab} ,g^{bc},g^{ac})$, it is hard to whether the last three terms are random or not.
Is the variant still secure? If then, how to prove this?
|
Assume $g$ is generator of multiplicative group modulo prime $p$.
Assume we know $g^X\bmod p$ and $g^{XY}\bmod p$ and assume we can have access to a Diffie-Hellman oracle.
Can we find $g^Y\bmod p$ in polynomial time?
If we know how to compute $g^{X^{-1}}\bmod p$ then we can use the oracle to compute $g^Y\bmod P$.
So ... |
Assume that one uses two private keys $x_1$ and $x_2$ to generate two public ECDSA keys $y_1$ and $y_2$ (e.g., used as public key for Bitcoin address). The distance between $x_1$ and $x_2$ is small (e.g., less than ${2^{20}}$).
What's bad about it?
I know that if one breaks $x_1$, it certainly leads to the breaking of ... |
Let’s say person A encrypts a message. Now I want both person A and persons B, C, D – A as a single individual – and B, C, D only as a group, to be able to decrypt the encrypted message. The multiparty decryption process should be designed in a way, that it requires no secret sharing between B, C, D. Also the secret th... |
There exist two EC private keys $x_1$ and $x_2$, where their corresponding public keys on the well-known base point $G$ are $X_1=x_1G$ and $X_2=x_2G$ respectively. The order of the cyclic group generated by $G$ is $\ell$.
Those private keys have been chosen such that the distance $d=|x_1-x_2|\ (mod\ \ell)$ is less than... |
I am currently reading the paper: Efficiency Tradeoffs for Malicious Two-Party
Computation. The paper describes a $k$-leak model and gives an example that leaking 1 bit could turn Yao's garbled circuit from semi-honest resistance to malicious resistance.
At page 14, it says that Alice gives it garbled output to Bob --... |
For ElGamal encryption, safe prime $p$ is used such that $p = 2q+1$. However, can someone explain to me, in simple terms, why we would need, in this context, a large order of $G$ and how it will contribute in making $g^{ab}$ more secure such that $a$ and $b$ could be obtained via solving for discrete logarithm problem.... |
I am reading Fast and Secure Three-party Computation:
The Garbled Circuit Approach
And in the introduction section it said that:
the round complexity of these protocols is proportional to the
circuit-depth of the computation being performed
What does this exactly means?
Why does Yao's garbled circuit does not hav... |
Given a keyed pseudorandom function $f: S \times X \rightarrow Y$, where $S$ is the space of secret keys, $X$ is the input domain, and $Y$ is the range, the pseudorandom property says that given any secret key in $S$ the uniform distribution over $Y$ is indistinguishable from the distribution of $f(X)$.
Am wondering, ... |
1. Scenario
Suppose that we have a source that is generating one random value per, say, minute. So we have random value $x_1$ in $1$st minute, $x_2$ in $2$nd minute, $\ldots$, $x_n$ in the $n$th minute, and so forth.
The distribution of values $x_1, x_2, \ldots$ is not entirely uniform random, but follows the followin... |
I saw a paper said RC6 cipher is weak and weakness cause of using 'SINGLE CLASS OF WEAK KEYS'
What is that mean? and could we solve this problem ?
Thank you.
|
If I have a known plaintext and ciphertext pairs and 2 unknown keys of length 24 bits. (Assume encryption method is unknown)
9acb0442f0c5341e 035a85c5772da926
aa209b8e700e0976 f1849958b47fec38
6cb50b02afd3a30c 4e48ca11ee429960
10cd96722811a558 0a18dd10a6b31c5c
18d2fe904d088f48 f84950f2d18dc4e8
83e4f98dd04ab55f 4dc9a896... |
Let's say I have a text file, and I modify it slightly 20 times, and I encrypt each modification using gpg -c (with the same 20 chars secure password). If the attacker has access to the 20 encrypted versions, is the decryption time lower? In this exact scenario, is the encryption breakable?
|
The following is from BGV paper (https://eprint.iacr.org/2011/277.pdf) p. 12.
$\text{FHE.Add}(pk,\textbf{c}_1,\textbf{c}_2)$: Takes two ciphertexts encrypted under the same $\textbf{s}_j$ (If they are not initially, use $\text{FHE.Refresh}$ (below) to make it so.) Set $\textbf{c}_3\leftarrow \textbf{c}_1+\textbf{c}_2 ... |
I'm trying to understand Mitsuru Matsui's "Linear Cryptanalysis Method for DES Cipher", specifically the attack he describes at the end of section 5, on 5-round DES. I followed the attack on 3 rounds, and here's the math for it:
For 5 rounds of DES, I distilled things so that there's only 4 types of variables:
Plaint... |
Say I have a pair of public and private keys associated with some resource (e.g. a TLS certificate for a website mycoolsite.com). I am free to take those keys and reuse them for a different resource (e.g. for anotherneatsite.net). My question is: is there an efficient way to "tag" the original keys with the data "thi... |
As far as I know it is possible to extract the key or key parts using side channel power analysis attack on AES, but we need some strong attacker model in order to do that. The first attack I know about is attacking the first AES round, comparing the first SBOX outcome, where we need to know the plaintext of our traces... |
I recently studied the multivariate Coppersmith algorithm.
Let $f(x)$ be $n$-variate polynomial over $\mathbb{Z}_p$ for some prime $p$.
Informally, the multivariate Coppersmith's theorem stated that if the assumption ($*$) holds, then one can solve the multivariate Coppersmith's algorithm in polynomial time in some par... |
I require an encryption algorithm that requires two parties with two different keys to be able to decrypt it. I could double AES encrypt, but I am instead considering AES encryption followed by a OTP since 1) I would like to hedge against the unlikely possibility of an AES exploit and 2) as the information being encry... |
If you have to generate a sufficiently long keystream, why would the keystream eventually repeat?
If the keystream repeats does it pose the threat of being decrypted by a hacker? How could one use it to that advantage?
|
Let $C(X)$ denote the cardinality of the set $X$. For example, $C(\{0\}) = 1, C(\{0, 2\}) = 2$ etc.
Let $S$ denote a (potentially infinite) sequence of random bits. Split $S$ into $k$-bit words $w_1, w_2, w_3, \ldots$ For example, if $k = 4$ and $S = 0001111010100100\ldots$, then $w_1 = 0001, w_2 = 1110, w_3 = 1010, \l... |
I am currently reading through Secure Distributed Key Generation For Discrete-Log Based Cryptosystems, which describes a secure variant of the Joint-Feldman protocol. In this paper, in section 2 (Preliminaries), it's stated that the communication model assumes the participants have access to a "dedicated broadcast chan... |
Can someone please explain what exactly is the difference between key exchange protocol and key distribution protocol? I looked on the Internet but it was not clear to me. I would be grateful if somebody could either explain it or direct me to some references.
|
I work for an institution where patient data is collected and I am supposed to encrypt it. At the moment I do the following steps (with R):
Randomly assigning an ID to each patient. The procedure avoids duplicates (using sample(), among others)
Create a salt for each patient (using salt <- bcrypt::gensalt(log_rounds= ... |
The only accumulator that I know is the Merkle tree, which has these asymptotic worst:
Space, non-pruned: $O(n)$.
Time insertion/removal: $O(\log_2 n)$.
Time verification: $O(\log_2 n)$.
My question is: Is there any accumulator whose non-pruned version has an asymptotic worst-space that is cheaper than $O(n)$? e.g.,... |
I am learning about symmetric encryption and its security properties. One of the security notion is security against chosen cipher-text attacks (CCA), particularly IND-CCA notion.
Under this notion, adversary has access to both an encryption oracle and a decryption oracle. The IND-CCA game/experiment imposes an importa... |
In the context of ECDSA , given that i have a message and a private key , i can change value of k and i will get different signature , doesn't that mean i can create infinite signatures and all of those will be valid and that means i can forge a signature right as i can assume that random signature that i guessed for a... |
I am studying the Salsa20 algorithm and I was wondering if you could help me understanding the expansion function. I don´t understand what the Pos or stream position as I have read in other places does, is it meant to randomize the data, similar to the nonce? Any help would be greatly appreciated!
|
I was studying the theoretical attacks on ChaCha cipher here (See section 3).
There is one special attack procedure which require key-IV(Initial Vector) pairs. These key-IV pairs are special in the sense that they produce high bias (minimum difference after one round in the differential attack) so that it is helpful in... |
I've been implementing an asymmetric key exchange for creating a symmetric key.
My question is more of a philosophical/legal one in terms of key-exchange responsibility, and what happens when let's say, a commonly known key is used.
I'd like to set these base variables:
The client has the servers public key hardcoded ... |
I'm reading FIPS 197 (AES) to try and understand how the algorithm works but I don't yet have answer for are these two questions:
I see the 256 byte s-box for substituting during the rounds. Do the values in this 256 byte table get updated or is it a static table for the whole transformation?
In key expansion, I see t... |
I have problems with understanding the advanced composition theorem in DP.
Let I have two approximate-DP mechanisms ($k = 2)$ where each satisfies $(\epsilon = 0.5, \delta = 0.1)$-DP. By basic composition, I know that using two queries sequentially will guarantee $(2 \cdot 0.5, 2 \cdot 0.1) = (1, 0.2)$-DP.
Advanced com... |
Let $E$ be an elliptic curve curve $^2 + xy ≡ ^3+^2+$ (a Weierstrass curve) (in this case, with characteristic 2) over a binary extension field $(2^{m})$ with constructing polynomial $()$ be an irreducible, primitive polynomial over $GF(2)$, and let $P(x_p,y_p)$ be a point on the curve.
I have seen various implementati... |
Suppose Alice encrypts a number which indicates her bid on a contract, using textbook ElGamal encryption (malleable). This encryption of produces a ciphertext pair 1 and 2.
How can Eve modify 1 and 2 to make it a modified value of 2 which is an arbitrary value of ? (eg. 1% more than x)
For a modified message two time... |
I have a text that has been XORed with the key "77U" (I am sure of this as it is a file created by a code I have, so I have seen every entry getting XORed by 77U.
However, none of the online decryptors I have tried are giving me any valuable results (error, or something gibberish), some don't have the option to put a s... |
As detailed in a separate question, I thought I had a way to detect the type of ransomware that encrypts files silently, and then decrypts them on the fly, so as to prevent the user from realizing that the files have been encrypted. I thought that a comparison of present vs. past file hashes would detect file changes: ... |
In the LWE symmetric encryption scheme, a ciphertext encrypting a message $\mu \in \{0,1\}$ under the secret key $\mathbf{s} \in \mathbb{Z}_q^n$ is $(\mathbf{a}, \mathbf{b}=\mathbf{a} \cdot \mathbf{s}+e+\frac{q}{2}\mu)$, where $\mathbf{a} \in \mathbb{Z}_q^n$ is a uniformly sampled vector and $e \in \mathbb{Z}_q$ is a n... |
In the ZeroCoin paper, it uses a zk-proof from Camenisch's dynamic accumulator that shows a Pedersen commitment hides an element of an RSA accumulator (https://link.springer.com/content/pdf/10.1007/3-540-45708-9_5.pdf). However, it looks like that the proof can also be used to prove that a subset of elements belong to ... |
I try to use the function
$$C_i=E(M_{2i}, M_{2i+1}) = (M_{2i} + M_{2i+1})\bmod 26.$$
to encode English text.
For example,
Plaintext: The quick brown fox jumps over the lazy dog.
Regrouped Text: TH EQ UI CK BR OW NF OX JU MP SO VE RT HE LA ZY DO G.
$$
T = 19, H = 7, (T + H) \bmod 26 = 26 \bmod 26 = 0 = A.\\
\cdots\\
(D... |
I've looked around but can't find any discussion on using both CP-ABE and KP-ABE by simply wrapping one with the other. It seems like you'd be able to get more fine grained access control with a scheme like that. The lack of any information makes me suspect that I'm missing something. Would this be a advantageous setup... |
I'm learning how CBC works but i don't understand when altering the first 2 bytes of the ciphered text why the 1rst block and ONLY the first 2 bytes of the second block are altered. The first 2 bytes of the cypher text are altered using a xor operation with random values.
Each block is made of 16 bytes.
Those are the r... |
Hi I found this question which I am currently struggling with.
How to handle IKEv1 and IKEv2 diffie-hellman shared secret bits length not multiple of 8?
In ACVP, the input diffe-hellman shared secret bits isn't multiple of 8, for example, 521 in bits.
The given gxy is
9E50F9E86DAF773F657F5F32BA4C84E707284843F422A74DFC6... |
I'm reading about the key expansion for AES but I can't seem to find the answer to this question yet. The book refers to a cipher key and the expanded key (or key schedule). This is the algorithm from the book:
procedure KeyExpansion(byte K[4][Nk], byte W[4][Nb (N r + 1)]) ? Nk ≤ 6
for j = 0 to Nk − 1 do
fo... |
A polynomial hash defines a hash as $H = c_1a^{k-1} + c_2a^{k-2} ... + c_ka^0$, all modulo $2^n$ (that is, in $GF(2^n)$).
For brevity, let $c$ be a $k$ dimensional vector (encapsulating all the individual $c_n$ values).
Are there particular values for $c$ that make the probability of collisions between two randomly cho... |
If I construct a vector pedersen commitment $c = a_1G_1 + a_2G_2 + ... + a_nG_n$ with an arbitrary scalar vector $(a_1, a_2, ..., a_n)$ and group elements $(G_1, G_2, ..., G_n)$, is it possible to create a range proof that proves that each element in this commitment is non-negative?
I understand that it is possible to ... |
Para 3 of Security Requirements for Cryptographic Module (FIPS 140-2) specifies the requirements that will be satisfied by a crypto module protecting sensitive but unclassified information.
What are the standards to protect classified, Secret and Top Secret information?
|
I've been trying to manually decrypt some TLS 1.3 traffic for educational reasons, and have stumbled across a roadblock. So far, I've been able to complete most of the key schedule, including deriving the correct handshake traffic secrets from the ECDHE keys. However, I haven't been able to find much information about ... |
I'm doing sequence-of-game formal security analysis for key exchange protocol. It confuses me a lot how to calculate the adversary's semantic secure (SS) advantage. In Shoup's tutorial "sequences of games: a tool for taming complexity in security proofs", SS-advantage = |Pr[S0]-1/2|; while in other papers like ""Securi... |
I'm learning cryptography recently. I read that for game-based formal security analysis, it is important to embed the hard instance during reduction. Does "hard instance" mean hard-to-solve problems like DDH (Decisional Diffie Hellman) assumption? If so, my understanding of "embedding the "hard instance" during reducti... |
I am not understanding how to compute the output bits of a 6-to-4-SBOX with bitslice technique in DES.
Matthew Kwan made a brief recap in his paper "Reducing the Gate Count of Bitslice DES" of Biham original paper.
He wrote:
Basically, for each S-box, the technique is to take two of the input
bits, expand them to all ... |
It is known that, for an elliptic curves $E$ defined over a prime field $\mathbb{F}_p$ such that $E(\mathbb{F}_p)$ is a prime number, the best algorithms (beside some specific cases) for solving the discrete logarithm are the general ones for an abelian group: Baby-steps Giant-steps, Pollard rho, Kangaroo.
For elliptic... |
I am reading this explanation of zkSnarks written by Maksym Petkus - http://www.petkus.info/papers/WhyAndHowZkSnarkWorks.pdf
My question is about Section 4.6.1
Setup
construct the respective operand polynomial $l(x)$ with corresponding coefficients
sample random $\alpha$ and $s$
set proving key with encrypted $l(s)$ ... |
I was trying to do a simple CPA attack against this scheme, to understand better the concept.
Instead of using a new each time, we decide to use the last block
of the previous ciphertext as an initialization vector. Prove this new scheme is vulnerable to a
chosen-plaintext attack.
So in this case,
the challenger choo... |
Suppose there are two collision-resistant hash functions $h_1$ and $h_2$ with output sizes of $n_1$ and $n_2$ respectively.
Is $H'(x) = h_1(h_2(x))$ collision resistant for the different relationships between $n_1$ and $n_2$?
This has been boggling me and my colleagues for the past few days since two different appro... |
Have there been any publicly known exploits of a cryptographic break in a widely used cryptographic system to actually read encrypted information (or falsely authenticate) since the Ultra program in World War II?
I want to define my terms as precisely as possible to clarify what I mean. An example of what I'm looking f... |
I have been reading crypto_box encryption and have a question. In the details of the algorithm, it uses Key exchange: X25519. However, I don't see why they need to use a key exchange algorithm.
So my question is where and why do they need to key exchange algorithm?
|
At RFC2409, section 5.1, authentication header is like:
HDR*, IDii, [ CERT, ] SIG_I
HDR is an ISAKMP header whose exchange type is the mode. When
writen as HDR* it indicates payload encryption.
IDii is ID of initiator
[CERT] means that sending certificate is optional
SIG_I is signature of initiator.
Why sending certif... |
Background
I'm building a URL shortener, and the URL to shorten may contain a SessionId.
For the URL shortener to not compromise the security of the SessionId, I must use a shortening strategy that fulfills the same requirements as the SessionId.
OWASP states that:
The session ID length must be at least 128 bits (16 b... |
I am currently reading about RS codes. I see that they are using a Galois Fields (Finite Fields) as vector spaces. Is there any other particular reason other than the fact that they simplify binary arithmetic and for example in $GF(2^8)$ each byte can be considered as a vector? Can they work in vector spaces that are d... |
I am doing some research on the BLS12-381 (https://hackmd.io/@benjaminion/bls12-381) and trying to understand if there are endomorphisms that are efficient. Of course, I am looking at this to explore faster multi scalar multiplications :)
I came across this post on Koblitz curves
do koblitz curves over $\mathbb{F}_{P}$... |
I'm thinking let's say you have a smart contract that ensures no double usernames. What's if I generate an ECDSA pair like so:
Accept username and password
Validate username and password
Generate keypair using seed of <username> <some separator> <password>
Return keypair
Would this be cryptographically insecure? I'm ... |
After rigorous testing, it seems that it can possibly be a NIST-level candidate algorithm.
However, explaining or even finding the right people, experts in cryptography to talk about his invention seems to be quite a challenge. It's a time-consuming process to explain and present the material and a hard to believe subj... |
I've been implementing a hobbyist cryptography library, and I'm at the part where elliptic-curve cryptography is being implemented. I've already implemented and tested ECDSA with P-256 and P-384, where static and ephemeral private keys are 256-bit and 384-bit each, so far so good.
What's bothering me is P-521. I'm plan... |
In multivariate public key cryptography, why can not we use the same public key for both signature and encryption?
I read that for signatures the public polynomial $P:\mathbb{F}^n\rightarrow \mathbb{F}^m$ has $n\geq m$ whereas for encryption $m\geq n$.
|
I been trying to solve a particular challenge where we have to sign an admin message.
At first it seems a classic RSA blind signature attack but eventually they didnt give out the public exponents(e,n) and e is of prime(128) length.
The server offers to encrypt anything n number of times but not the admin message and t... |
I understand how this linear approximation board below is produced,
but I can't understand how this second board is produced using the first one
and finally how the pilling-up lemma values are calculated
( o in S 12 the approx. Λ 1 = X5 XOR X7 XOR X8 XOR Y 6 has bias +1/4
o in S 22 the approx. Λ 2 = Y 6‘ XOR Z 6 XOR ... |
For a lot of cryptographic applications, multi-party protocols are used. The idea is to create shares of a key/secret and give them to multiple parties. My question is: Do all parties have to participate in the multi-party protocol or do protocols exist, that only need e.g. >51% of the shares to compute correctly?
|
I'm reading and implementing this tutorial, the author explains everything pretty clearly, the only thing I'm missing is how he decides which trail to use (pg. 12). I understand that one should prefer trails with the least amount of active S-Box and maximize the bias of the trail (in fact, finding the optimal trail see... |
The following details are given:
Partial Key: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX11000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011
Initialization Vector: E898EF8E91F8C9B201E6E29DF87EE152
Ciphertext Block 1: 14B8D1412766A8520BACE4598F8AFAEE
Ciphertext Block 2: 7E687A49015FA6F... |
EDIT: I messed up something (see comments at answer). This question contains some false statements EditEnd.
For tetration modulo prime $P$
$$^{i}g = g\uparrow \uparrow i = \underbrace{g^{g^{\cdot\cdot\cdot^{g}}}}_i\equiv v \mod P$$
with suitable $g,P$ so that
$$|\{^jg \mod P\}| = P-1 \text{ }\text{ , or }\text{ } v\in[... |
Assuming we found a constant $g$ and a prime $P$ which is able to produce all values from $1$ to $P-1$ with it's sequence
$$s_{i} = g^{s_{i-1}} \mod P$$
$$s_0 = g$$
How many steps are needed to compute $i$ for a given value $v$ ($=s_i$) with known $g,P$?
Can it be faster than $i$ steps?
toy example:
With $P=5, g=3$ t... |
Are there moderns (post World War II) and famous protocols that were proven secure (in any model: game-based, UC...) but whose proof was wrong and could have led to real-world attacks?
Note that:
I'm not really concerned about attacks on the mathematical assumptions themself (which seem to be the focus of this thread,... |
In game-based security proof, I found that games are defiend to be played between a PPT adversary and a challenger. The adversary is able to issue queries to different oracles and receives corresponding reponses. Assume A is the participant of the protocol, the queries sent by the adversary could be: Test(A) or hash qu... |
For some $g$ and prime $P$ the sequence
$$x_{i+1} = g^{x_i} \mod P $$
$$ x_0 = g$$
can contain all numbers from $1$ to $P-1$ and with this it is a pseudo-random permutation of those numbers (EDIT: seems to be not the case).
Is there any (quick) way to find big/safe values for $P$ and related $g$ which can still produce... |
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