instruction
stringlengths
32
27.2k
The CLWE problem (and related) talks about the hardness of finding the secret key $\vec{s}$, given polynomially many samples $(\vec{a},t)$, where $\vec{a}$ is sampled from the normal distribution, and $t=\gamma \vec{a}\cdot\vec{s}+e \pmod{1}$, where $e$ is also sampled from the normal distribution. Is the distribution ...
As far as I understand, compressed public keys of secp256k1 can represent points either above or below the X axis, depending on whether they begin 0x02 or 0x03. Am I correct in thinking that if you know a secret key for a public key beginning 0x02 you can trivially find the secret key for the identical public key, but ...
I am interested in the practicality of using generic SNARK techniques to prove the following relation. Let E and E' be two ElGamal ciphertexts. They have the form E = (E1, E2) = (g^r, M*PK^r) and E' = (E1', E2') = (g^r', M'*PK^r'). There is also a hash function H. All of these are public: E, E', PK, H. I want to prove ...
Why can't we use any random elliptic curve? What are the properties that need to be satisfied?
Shamir's Secret Sharing GPL implementation called ssss got removed from Tails OS years back. Is Shamir's secret sharing still secure nowadays? Why was it removed from Tails OS? Is it true that the technical limit is a maximum of 128 characters?
The diffusion model, which is used by products like Midjourney and Dall-E, trains AI systems to de-noise (remove added randomness) from data to infer what the original de-noised data is. That would seem to have direct applications to cryptanalysis. As such, I wonder what views security folks have on the following: Is ...
in the following pdf, several attacks on double key length triple des are deemed feasible at 2 to the power of 88/89 des calculations. if we take the record of cracking des at 2 to the power of 56 calculations in 23 or so hours as the example, according to my estimate, this should take hundreds of years and definitly i...
Could anyone please help me explain this? I am reading the article about TFHE (Guide to Fully Homomorphic Encryption over the [Discretized] Torus). On page 31: I don't understand why we need to scale to module 2N. What is the meaning of "multiplicative element of Zn[X]" and why is X of order 2N?
Are cofactor $4$ and $8$ ECC schemes widely used in practical deployments such as those in cryptocurrencies? Can you name some practical settings where there curves are used and cryptocurrencies where these are used (I checked bitcoin and it uses cofactor $1$ ECC and so I was not sure if other cryptocurrencies also use...
I read somewhere that TRNGs are better than cryptographic algorithms that generate pseudo-random numbers (PRNGs) because these algorithms are more energy intensive than TRNGs. By low power devices, I mean things with limited computational capacity or limited power. Like a small IOT device. Would there be any benefit to...
When I came to the topic of Ansible (Vault), when deploying secrets in Ansible and other passwords up to 128 characters Shamir's Secret Sharing would be an ideal solution I think: The secret is never in one spot The secret can be encrypted "on top" You can place the parts of the secrets on multiple servers with good r...
According to Wikipedia, tropical cryptographic protocols are built upon tropical algebras, i.e., a semiring $(\mathbb{R} \cup \{\infty\}, \oplus, \otimes)$ where $x \oplus y = \min \{x,y\}$ and $x \otimes y = x+y$. Recently, several tropical algebra-based cryptographic protocols have been proposed, and they rely on som...
As I was reading on some encryption schemes the other day, I stumbled upon the Blum–Goldwasser cryptosystem and read that it is vulnerable to adaptive chosen ciphertext attack. I searched for some actual example but could not find any, so I thought asking here for anyone willing to provide a simple proof of concept cho...
I'm decently new to cryptography and am trying to wrap my head around zero-knowledge proofs and applications. One use case that I am trying to figure out a strategy for is the following: I have some plaintext that I'm going to encrypt and give to someone. They can't decrypt the ciphertext but want to verify the hash of...
Let's imagine two entities: Bob and Alice. Bob's public key is $B = bG$. Alice's public key is $A = aG$. Alice encrypts her number $n$ with Bob's public key so Bob could decrypt it ($n$ is small enough to be brute-forced): $$E = nG + r_0B$$ $$R = r_0G$$ where $r_0$ is a random nonce. Alice sends $(E, R)$ to Bob. Bob de...
I am trying to understand the design rationale of in place NTT in Dilithium. I know that how the splitting of polynomials is done but I cant seem to map this approach to the precomputed table of zetas that is present in the authors code. I have attached the array of values as well. Specifically speaking, is there a way...
We can prove the security of a cryptographic scheme in standard model and non-standard model. Standard models like using some computational assumptions, on the other hand, non-standard models like random oracle, generic group model. Right? I've seen in a paper [CGKV18 ,page 10] the term $\color{blue}{static}$ computati...
The MACsec standard (IEEE 802.1AE-2018) states "The number of SCIs (and hence the number of SSCIs) is ultimately limited by the maximum number of current members in a group CA that MKA can support (less than 100) but is likely to be further limited by the port-based network control application (see Clause 7 of IEEE Std...
I am not sure whether "linear decomposition" is appropriate to summary my question: We know that the traditional symmetric encryption/decryption algorithm (like AES, TDES) can be written as: C = FUN_enc(key, P) P = FUN_dec(key, C) Where FUN_enc is the encryption function/algorithm, FUN_dec is the decryption function, C...
I am trying to fully separate RSA key pairs by breaking down $(N,e)$ for public part and $(N,d)$ for private part. From my understanding of RSA signature process, the message to be signed is digested at first (using e.g., SHA256) and the digest is then encrypted using private key. The receiver of the message then calcu...
I am trying to solve a challenge regarding a RSA oracle which allows me to encrypt/decrypt any plaintext/ciphertext I want, but there are a few checks that I have to bypass, and my goal is to decrypt the given flag. The strategy I am using is basically trying to get the N by making the oracle encrypt some small numbers...
I have implemented a ring signature in a Python program, To keep it simple, I have Alice and Bob. Based on this ring equation: $$ v = E_k(y_s⊕E_k(y_i⊕v))$$ I will get: $$ y_s = E_k^{-1}(v)⊕E_k(y_i⊕v) \pmod{n_s}$$ where $y_i$ is the private key of the ring signer However, after calculating, I did not get a value that e...
There are attacks that can extract some information from lookup table access that depends on a secret value, e.g. if we access a[0] or a[255] depending on some property of the secret, and a[255] causes a cache miss. But what if only the order of access changes depending on the secret value? E.g. we could have the a[0],...
For the NTT I know the following preconditions, which must be fulfilled for the primitive $N$-th root of unity: $$ \omega^N \equiv 1 $$ $$ \sum_{i=0}^{N-1} \omega^{ik} \equiv 0 \quad k=1,\ldots,N-1 $$ These are derived from the DFT and adapted to the modular arithmetic of the NNT. So far clear. But what about this cond...
The JSON Web Encryption RFC 7516 says: Encrypt the CEK with the recipient's public key using the RSAES-PKCS1-v1_5 [or RSAES-OAEP] algorithm to produce the JWE Encrypted Key. Assuming a client/server architecture here where the server generates JWE tokens, does this mean that the client must initiate the JWA creation ...
My question is very basic one. Suppose there are two independent boolean variable $X_1$ and $X_2$. It is given that $X_1$ is biased towards $0$ and $X_2$ is biased towards $1$ with same amount of bias. Now will their XOR variable be biased or unbiased ? My try: Since their bias is same, probability that $X_1$ takes $0$...
While working with serial division/remainder method of finding factors, I have found that using knowns such as the known factors of a comparative number, or the difference between a number to be factored and its comparison number, then dividing into each number with the knowns and summing the remainders, the two origin...
Given a password as a seed for a Psuedo Random number generator and Fisher Yates Algorithm to shuffle bytes of a string to random places like Hello World to ldWoeHor ll, is it practically and/or theoretically impossible to break such cipher if plaintext contains enough words like >100? Like for example, a string is shu...
I need to enable hybernation to the LUKS-encrypted drive. My /boot partition is unencrypted hence it stores all kernel images as well as kernel parameters in unencrypted form. For hybernation to work I should specify where the swap file starts off on my drive where the system can write hybernated data to. For this Linu...
In the proof that RSA successfully decrypts the message $x$, we show that $x^{e^{d}}\equiv x \pmod N$. However, I am wondering whether it is a problem that we don't recover $x$ exactly, but merely a number congruent to it in mod $N$. Does this cause problems as far as decrypting the message successfully? Also, the tex...
In an application, a curve25519 private key is the only stable identifier for an individual. I don't have readily have access to the corresponding public key. Would it be safe to generate a public identifier by hashing this private key? E.g. ID = argon2id(K_curve25519_private)
What's the exact meaning of 'Argon2 uses BLAKE2b'? Does it based on BLAKE2b? like chacha20 based on salsa20 kind of meaning or does Argon2 use the BLAKE2b with 12 rounds hash function at the end to generate a hash value? thank you.
In the paper: "Universal One-Way Hash Functions and their Cryptographic Applications". The following is proven: "If 1-1 one-way functions exist, then the one-way based signature scheme described above is secure." For a signature scheme defined in the paper, where by secure they mean "existentially unforgeable under an ...
I want to construct a non-interactive ZK proof that in a set of pairs of group (where the DDH-assumption holds true) elements: $(g_1, Y_1), (g_2, Y_2), ..., (g_n, Y_n)$ , the prover knows at least one private key $x_i$ such that $g_i^{x_i} = Y_i$. The proof should also not reveal $i$. The protocol would be based on $\S...
I have a vector of $n$ elements where each entry is a non-negative integer. Neighboring vectors differ in one element where the absolute value difference between the elements that differ is $1$. I want to release the entire vector differentially privately. We can do this easily using the Laplace mechanism with sensitiv...
I have a question on how to interpret test results of NIST test suite. First, when the asterisk mark appear on the report, what does it mean? I thought it means the random sequence fails the test. However, some p-values are more than 0.01 and it appears second, some tests have p-value lower than 0.01. However, the ast...
I'm making a peer-to-peer game client using an already existing protocol where messages are broadcasted to all people on the network, and messages are already proven to be from a given user. One of the games I want to add is UNO, and I found this paper from the same authors of RSA that describes an algorithm that perfe...
I am currently reading "A Decade of Lattice Cryptography" At page 30, section 4.3.2, it descrip left multiplication by any fixed ring element a It mention something about curcilant matrix whose first column is the coefficient vector a. I am confused why multiply a circulant matrix will yield a SIS instance? Can someo...
If I have three integers $x,y,z\in \mathbb{F}_{2^n}$, How do I convert the modulo addition operation into conjunctive normal form (CNF)? $$ (x+y)\pmod{2^n-1}=z $$
I read that to mitigrate BEAST attack openSSL tried to inject empty TLS record before each real TLS record. and by doing that there is no opportunity to execute an attack but i dont understand way? what the diffrence between normal TLS? the attacker can still xor the block he want to guess with the last block to disabl...
I'm writing a paper for uni about password security, specifically about cracking passwords in the context of a password manager. I've coded a password encryption scheme which uses PBKDF2(SHA512) to hash a master password into a key that AES256 uses to encrypt a password database or vault. I'm trying to estimate the tim...
Setting: Shamir secret-sharing over the field $GF(p)$, $p$ a prime. For $a\in GF(p)$, I would like a protocol that takes a sharing $[a]$ as input, and outputs: $[a^{-1}]$ if $a\neq 0$, and $[0]$ if $a=0$. I cannot think of an easy way to modify the well-known protocol that computes $a^{-1}$ using a multiplicative mask,...
I am currently trying to understand and implement the design of post quantum algorithm signature algorithm Dilithium. I have read the document several times and they have just used uniform random sampling for s1 and s2 and they have not provided any algorithm regarding its calculation. Viewing the reference code, doesn...
Let's say I have the following equation to be arithmetised in PLONK $x^3 + x + 5 = 35$ and the witness is $x = 3$ $3 * 3 = 9$ $9 * 3 = 27$ $27 + 3 = 30$ $30 + 5 = 35$ Now the 4th gate can be expressed as $Q_l\cdot 30 + Q_r\cdot 5 + Q_m(30\cdot 5) + Q_c + Q_o\cdot(35)$ with $Q_l = 1, Q_r = 1, Q_m = 0, Q_c = 0, Q_o = -...
There is a JSON array like this: [ { "date": "28.08.23 10:52", "type": "text", "data": "card number including expiration date and CVC" }, { "date": "29.08.23 10:52", "type": "text", "data": "bank password in the form admin:password" }, { "date": "30.08.23 10:52", "type": "text"...
I am inquiring about the feasibility of calculating the point difference between two distinct secp256k1 elliptic curve points. Given the nature of secp256k1, which is widely used in cryptographic applications such as blockchain technology, I am interested in understanding the process and potential challenges involved i...
What would be an easy way to use the hexadecimal output of a hash function (like md5) to generate n unique numbers from, say 0 to 15. Of course I could generate n numbers by using each digit of the digest, but I need those numbers to be unique.
Consider a BLS signature verification using BLS12-381 where signatures are in $G_1$ and public keys are in $G_2$. Verification is performed by checking that $e(sig, G2) = e(H(m), pk)$ or equivalently (by taking advantage of the bilinearity property to avoid one of the final exponentiations) that $e(sig, -G2) * e(H(m), ...
Hello I am new to lattice cryptography I am reading the paper More Efficient Commitments from Structured Lattice Assumptions They define bound B in page 3 Then In figure 1 in page 9 Can someone kindly explain why the bound increase/decrease will change the LWE/SIS from computation hard to statistical hard? (It ...
In TLS 1.2 and TLS 1.3, does the EC curve used to generate the ephemeral keys at the client side, does it need to be the same as that on the and server sides? For example can I use secp521r1 at the client side and secp256r1 at the server side, and visa-versa? I am asking this question, since in TLS 1.2 you can use fini...
In yet another twist that is the terminology around key establishment I found out that ECIES is often denoted as key encapsulation followed by data encapsulation. I'm wondering how the term "key encapsulation" can be applied to ECIES. ECIES consists of the following: key agreement using ECDH, giving the master secret;...
I just wanted to know for sure that TLS 1.3 does not support DHE_EXPORT cipher suits.
I have a question regarding the operations performed on an elliptic curve, specifically related to point doubling and point addition. I am trying to understand whether it is possible to determine the order in which these calculations were performed in order to obtain the x and y values of a public key. To provide some ...
I had an idea for safely transmitting sensitive data online, and I wanted an expert opinion. Would it be safe to encrypt data (for simplicity at this point just use plain text) with a ruleset (an array with specific instructions on how each letter should be encrypted by any means). Of course, you can guess the ruleset....
I have many questions about the details of using zk-SNARK technology in zk-rollup: How can the validity of signatures in layer-2 transactions be proven in zk-rollup? In zk-rollup, is a single large zero-knowledge proof circuit used to prove the validity of signatures for a batch of transactions, or is it separately pr...
I'm trying to implement X25519 for a little game I'm working on. I knew nothing about this stuff a week ago so it's been a bit of a learning curve (that was really funny). Most of the resources I found online were easy to follow, so I have a seemingly working implementation. While looking around I saw that apparently y...
Obsidian.md claims End-to-end encryption means that the data is encrypted from the moment it leaves your device, and can only be decrypted using your encryption key once it's back on one of your devices. We can't read your data. Neither can any potential eavesdroppers, such as your internet service provider. In the ra...
I've been thinking about creating strong and unique passwords for my online accounts, but I also want them to be memorable. I've come across the idea of using a memorable passphrase as the basis for a complex password generation. Specifically, I'm considering hashing the passphrase to generate the complex password, suc...
I am stuck here and can't map the coding part to the algorithm. $$\underline{\text{Power2Round}_q(r, d)}\\ r := r \bmod^+ q\\ r_0 := r mod^\pm 2^d\\ \textbf{return}\big((r-r_0) / 2^d, r_0\big) $$ What I tried: int32_t power2round (int32_t *a0, int32_t a) { int32_t al; a1 = (a + (1 << (D-1)) - 1) >> D; *a0 =...
When one is computing $E(x) \equiv x^e \pmod N$ (where $N = pq$) in RSA, what is the precedent for which number in the residue class of $x^e$ to have as the result of this computation? Does this mean that we compute $x^e$ and then apply the mod function %$N$ to this, such that $E(x)$ is always in $\{0,1,. . .,N-1\}$? O...
The GOC (Générateur d'Octets Chiffrants, Ciphering Byte Generator) is a PseudoRandom Generator that was used during the late 20th century for content encryption in pre-internet Videotex terminals, mostly in France. One application was encrypting sensitive data (e.g. banking details) while in transit to a Minitel. The G...
As indicated in an earlier Q / A, KEM's do not necessarily directly encrypt a pre-generated random value. However, it is clear that some KEM's do actually do this, with RSA-KEM being an obvious example. Is there a name for the property of a KEM that it relies on both the public key value as well as a generated random v...
Have any good 8-bit S-boxes made using ARX principles been found yet? I found Alzette, but it's a huge S-box at 64 bits. I know that with a combination of addition, rotation, and XOR that any S-box permutation can be achieved, but working backwards would be way too hard for the effort.
In constructing a SHVZK simulator for a sigma protocol I am working on I have encountered some fairly basic questions, but ones which are not often discussed in textbooks and papers - consider the two following probability distributions: $X_n$ - The uniform distribution on $\{1, \dots n\}=[n]$ $Y_n$ - The uniform dist...
I am trying to implement Pei10 and BB13, but I am confused about what concrete parameters to use. In Pei10, Algorithm 1 takes a rounding parameter $r = \omega(\sqrt{\log n})$ as parameter, but it does not specify how to choose it concretely. As in, would $r = \sqrt{\log n}$ or $r = 2\sqrt{\log n}$ work, as long as they...
Is there any formula for deriving the $y$-coordinate using the $x$-coordinate and the slope in the secp256k1 elliptic curve? For example: Calculate the slope: slope = 75359724952757581356787150982223137069297282952438962440225639443485944634025 Calculate the new $x$-coordinates: x = 11271166043971060605674865917392967...
Trying to understand the LPN encryption in this paper: https://eprint.iacr.org/2021/120.pdf. From Definitions 4 and 5, ciphertext is $c=C\cdot s\oplus e\oplus G\cdot m$ and the paper says the LPN encryption scheme is both message homomorphic and key homomorphic, where $s$ is the secret key, $C$ and $G$ are two matrices...
We are doing symmetric Needham-Schroeder protocol in university. We were provided a modified protocol and needed to answer the following questions. Original protocol: Modified protocol: Task a) An attacker is an active MitM and knows an old key $k_{cs_{old}}$ and all transmitted messages from the past. Can the attack...
PKCS#12 contains 2 integrity protection modes: password-based and public-key based. The way this is done in the standard is that data layout wise it appears to be fine to skip integrity protection because the macData field (used for the password-based integrity mode) in the outer structure is OPTIONAL to make way for t...
I am new to cryptography and do not have sufficient background knowledge, and I am sorry for any possible vagueness in my question. I am reading a paper (https://eprint.iacr.org/2019/129.pdf) about homomorphic secret-sharing and is confused by the key generation protocol mentioned (HSS.Gen) in the paper. The key genera...
Let's say we have a point $nP = (x,y)$ on a curve $E$ over a prime $p$. The corresponding Edwards curve coordinates are $(u,v)$. I want to construct the point corresponding to $(u,-v)$ on the Edwards curve. I can construct $(-u,-v)$ easily, that just amounts to $-nP$, flipping the $y$ coordinate. But I don't know about...
How Ciphers, specifically, Substitution Ciphers and Transposition Ciphers manipulate the Entropy of Plaintext w/wo the aid of Entropy Source? Reversely, how Decryption manipulates the entropy of Ciphertext? Link: From Entropy's perspective how a Message was affected by Entropy, specifically, One-time Pad Ciphers and Bl...
The definition of Benaloh encryption scheme can be found here. Does exist an elliptic analogue of this scheme? I want to use this scheme but the length of the key is very big(like $2048$). If you can do something similar for elliptic curves it would be great.
I'm currently taking a course in which we choose a stats-heavy paper and analyse it, summarising our work in the form of a written report and presentation. I have tried to find such a paper in crypto, even asking a professor who works in Information Security, but no success yet. If possible, I'd like to be provided a l...
I would like to get a feeling on how the noise develops in different FHE schemes. So I ran some experiments using HElib for both BGV and CKKS. I wanted to look at the noise of a fresh public key and a fresh secret key ciphertext in both schemes. Curiously, in both schemes the noise I obtained was the same for public ke...
I need to test my server with curl 8.2.1 utility. My server works only with TLS1.3 and cipher 0x1302 - TLS_AES_256_GCM_SHA384. When I run curl it proposes many TLS ciphersuites that are not supported by my server (and TLS1.3) - for example (suites list of TLS-handshaking): 0xC028, 0xC027, 0xC014, 0xC013, etc. I run cu...
The most known example cipher reaching perfect secrecy is One-time Pad, which employs modulus addition for encryption and decryption. Is there any other well-known cipher no less practical than OTP that reachs perfect secrecy? Note: Practical application is necessary. For extempore constructions, See answers here What...
I have a function that generates a random 16 character length (upper + lower case letters plus numbers) seed password: const crypto = require('crypto'); function generateRandomString() { const charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; const length = 16; const randomBytes = cryp...
1. G known - how to decrypt Referring to this question: Basic attacks on McEliece; finding S and P (nobody answered) Take a McEliece cryptosystem with public generator matrix $G′=SGP$ where $G$ is a generator matrix of a secret code with known fast decoding (not necessarily a Goppa code over $\mathbb F_2$), $S$ is rand...
I'm writing a simple small IP hash table on an FPGA for an ARP cache. On the FPGA I need to ensure I can very efficiently calculate the hash due the critical path of the circuit. I have a 32-bit input that I need to reduce to between 2- and 12-bit hash (Compile time configurable). I'm leaning on simply Xoring the bits ...
So I developed this algorithm as RNG, although it looks random to me, I wanted to know the opinion of more experienced persons in the topic. from time import time_ns from math import sqrt class Random: incr = 0 seed = 0 defloat = lambda x: x*(10^(len(str(x))-(str(x).find(".")+1))) def __init__(self,seed...
If $g(x)$ if length preserving one way function, is there a scenario where $h(x) := g(x)_{1\ldots |x|−1}$ . I.e., $h$ returns all bits that g returns, except for the last bit., is not a one way function. I think it has to be one way because the probability of inverse just doubles at most. If the probability of inverse...
I am working on improving my grasp on applied cryptography. Following question is just for learning/understanding purposes.. Lets say I want to generate a 16 byte key that I want to use for some symmetric encryption (leaving aside the specific algorithm, IV etc.) which of the following two is better and for what reason...
First of all a couple of things: I am aware that cascade encryption tries to solve a problem that isn't present often. Attacks are more likely to be mounted against implementation details instead of creating a pure cryptoanalytic break on modern crypto. I am also aware that cascade encryption has at least the security ...
This paper suggests the following approach to oblivious transfer (OT), using asymmetric encryption: Receiver generates keypair $(pk_b, sk)$, selects random $t$, and set $pk_{1 - b} = pk_b \oplus \mathsf{H}(t)$; Receiver gives sender $pk_0, t$, and sender challenges receiver to confirm it knows how to decrypt one of $p...
I don't understand whether they are different or not. Would you mind explaining them all? MK-AC, MK-SMI, MK-SMC MDK Encryption Key, MDK MAC, MDK AC IMK-AC, IMK-SMI, IMK-SMC For example, in the generation of ICC Master Key(=Unique Derived Key), EMV Book 2 on page 129, Option A uses IMK while in Eftlab to generate the ...
Is there a better way than brute forcing (choose $k=\mathrm{rank}(A)$ first columns - test the determinant, if determinant = 0 choose new column set - there are $\binom nk$ many possibilities which is inefficient if the full rank sub matrices are rare!)
In the normal McEliece proposal, the public key G' = SGP is used, with S beeing non-singular, G Generator Matrix and P permutation Matrix In the White Paper on McEliece with Binary Goppa Codes by Michiel Marcus and the lecture of Tanja Lange it says that you do not need P because you can just permute the support L and ...
I am quite new to knapsack cryptosystems (specifically the merkle-hellman cryptosystem) and don't quite understand what exactly is the density $d(a) = \frac{n}{\log_2max_i a_i}$ defined here among other things. The denominator of the formula of $d(a)$ is the largest element of the weights (i.e. the public key)? What ex...
slope (s) = 75359724952757581356787150982223137069297282952438962440225639443485944634025 Qx = 112711660439710606056748659173929673102114977341539408544630613555209775888121 Qy = 25583027980570883691656905877401976406448868254816295069919888960541586679410 Derived x and y-coordinate from performing point doubling usin...
Ok, let me preface this by clarifying that I am not a cryptographer by trade, but I've been using cryptographic suites in the context of signing w3c Verifiable Credentials, and I am not sure if this is the right place to ask this question. In the European framework, eIDAS requires Qualified eSeals for legal entities. W...
I'm building an app that will primarily be iOS or Android based. My plan is for every user to have their own key pair. The public key will be stored on the server along with a 128 bit UUID which is used to identify each user. The private key will obviously stay on the device. When a message is sent to other people the ...
I'm writing a tool for manually collecting entropy from sources like coins and dice, and I'm wondering how to best deal with the case where the desired number of bits of entropy is not representable with a whole number of inputs. For example, when collecting 256 bits of entropy with a D6; log6(2^256) = 99.034318652. Th...
Suppose a prover computes a non-interactive proof which is composed of $k$ parallel repetitions of a sigma protocol with binary challenges (and knowledge error $\frac{1}{2}$), composed in parallel and transformed into a non-interactive proof by Fiat-Shamir. The verifier samples a random subset of $m$-out-of-$k$ of the ...
I am trying to understand theory behind noise budget operation implemented in seal Let the ciphertext be defined as $$ c0=A \in Rq \\c1= As+v+delta*m \in Rq $$ They first calculate noise polynomial $$ c1-c0s = delta*m + v \pmod Q $$ After that they perform multiply by plaintext mod t $$ (Q*m + t v )= tv\pmo...
PORS (PRNG to ORS) is a secure variant of the HORS few-time signature scheme. In PORS, instead of using a hash function, it uses a message (and salt) as a seed of PRNG and query it until obtains k distinct indices. As stated in 6.2 Security of PORS How does a non-adaptive adversary performing a brute-force attack again...
I'm trying to understand benefits of using Twisted Edwards curve over regular Edwards curve. I'm aware of some properties of Twisted Edwards curve that regular Edwards curve missing like isomorphism and fact that every twisted Edwards curve is birationally equivalent to an elliptic curve in Montgomery form. But I can't...
I want to know the state of the art result for proving knowledge of graph isomorphism. As described here, the classical Goldreich-Micali-Wigderson (GMW) protocol is a $\Sigma$-protocol with soundness error $\frac{1}{2}$, so it requires repetition. They then showed a $5$-round protocol for GI, essentially forcing the ve...
I see in many discussion on differential cryptanalysis of SBOX (and others boolean functions, see SIMON-like round functions, SPECK-like round function) the idea of reasoning in terms of weights associated with differentials. Weight is defined as minus the logarithm of the probability of a transition. Some seem to impl...
A (interactive) proof system for a language $\mathcal{L}$ is defined by two algorithms $\mathcal{P}$, a prover, and $\mathcal{V}$, an efficient verifier, with the following requirements: Completeness: For $x\in \mathcal{L}$, $\Pr[\mathcal{V}(x, \mathcal{P(x)}) = 1] \geq c$, for some fix constant $c \in (0,1]$. Soundn...