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Do simulator based proofs still rely on the ROM?

I have seen many game based proofs using the ROM, do simulator based proofs require it? Is it possible to do a simulator based proof for every game based proof? For context: What are the differences ...
10 views

What's the hardest composite for Shor's algorithm?

I do understand Shor's algorithm wants the order of an element to be even so that it can use the factoring identity and find a non-trivial factor. But is there a relationship between safe primes and ...
18 views

hash tree merkle tree

If I have 32 blocks and I have a fault in two blocks, how many pieces should I touch to detect the error? I tried 20 blocks but this does not work? Anyone who knows what is the difference between ...
18 views

Is it safe to store my login credentials in a Veracrypt volume? [migrated]

I have a list of login credentials (usernames and passwords) that I wanna keep safe. I'm planning to keep it in an encrypted Veracrypt virtual drive with AES, SHA-512, and an 8-character password. Is ...
31 views

Collision resistant hash function implies one-way function

I'm struggling to give a formal proof that $CRH \implies OWF$ using the definition below. Intuitively, I see why a $CRH$ would be "hard to predict" and might be used as a $PRF$, but I'm unable to ...
18 views

How many AES 128-bit keys does a MIFARE PLUS tag have?

I know that the question is a bit silly but I dont know how many keys can a MIFARE PLUS tag store in it. Provided that I have a MIFARE PLUS S tag with 4k memory room and the key length is 128 bit, ...
51 views

RSA - What to do when message is greater than N

Exmple: $e=3, n=33$ and $d =7$ and Message is $64$.
48 views

Variant of Pollard rho using small factors of p - 1

Given an integer $N$ to factor which is divisible by some prime $p$, suppose you know (or guess) that $p - 1$ has a few small factors, e.g. $3, 2^2, 5$. Define $B$ as a product of small prime powers ...
43 views

Why are the session keys in DHKE for different values of 'a' the same?

In a DHKE scheme with the a prime p = 467. an element g = 4. The element 4 has order 233 and generates thus a subgroup with 233 elements. after Computing the common key for A. a=400, b=134 B. a=167, b=...
1k views

What systems of robust steganography are out there?

By robust, I mean resistant to common image transforms (reversal, crop a non-multiple of 8 pixels off and recompress, blur, solarize to 64 levels, then interpolate, and sharpen, change compression ...
34 views

Differences and similarities for factoring, GCD method and brute force

I am trying to understand the difference between factoring RSA keys and using the GCD method to find the prime numbers. Does one take longer than the other? Is this what is meant by brute force?
8 views

Zero knowledge proof - Hash [duplicate]

How can I prove that I know the input value of a given hash output without revealing the input? Say for example: sha256("abc123") = "6ca13d52ca70c883e0f0bb101e425a89e8624de51db2d2392593af6a84118090"....
37 views

how decipher youtube url path? [on hold]

whats best approach decipher youtube url? am writing a java application that has to download youtube videos that have help me for my studies.i have tried use many from different developers but it ...
17 views

Steganography Decode [on hold]

I am wondering about the security of a technique of steganography which involves hiding a text (unencrypted) by changing cases. 0 is lowercase and 1 is uppercase and there is data embedded in binary. ...
61 views

Is it possible to translate the RSA accumulator scheme directly to EC without requiring bilinear pairings? In RSA we have: $A_{n+1} = A_n^c$ st. $\{c \: \textrm{prime} \: | \: c \in [\... 1answer 47 views Secure Communication Focus: I have to design a secure keep alive communication protocol and was wondering if it was necessary to sign the ciphertext after the session key has been generated as an attacker will not know ... 0answers 15 views Williams's implementation of Rabin cryptosystem? [duplicate] Williams' implementation of Rabin's Cryptosystem , where b=1/2[(1+m/n)] is being used to verify original decryption message .but my question why this formation likewise , is it any formula for ... 1answer 27 views Why does a transcript which is indistinguishable from a fake one show zero knowledge? Is there an intuitive way to understand why having a transcript that the verifier could have created themselves and is indistinguishable from a real transcript , shows zero knowledge? 0answers 50 views Differences between Gcd and factoring [on hold] please can someone explain to me the difference between the following. Using two different numbers I. E one is the rsa key and the other a number working from 2 upwards to work out the Gcd, until the ... 0answers 32 views Which chipre starts and and with$ [on hold]

I have this cipher but can identify which cipher it is $1vdLMPbtx&quot;*_4S6P@8j.#V,]!$ and this one also ...
25 views

Secret sharing with one smaller share [duplicate]

Given a t-out-of-n shared secret scheme with the message space characterized by binary string of length l, why if one share is smaller than l the scheme is insecure?
31 views

I have a homework question to decipher a piece of text [on hold]

All the info that was given is yorhhufoob lyerlfh wlxgli If anyone solves it please tell me what crypto method was used and the deciphered text, many thanks! :)
26 views

Problem with decode hexadecimal code. Could you help me? [on hold]

Im new here, its my first post here. I don't have strength anymore and I need your help :D. I got wall of the text: ...
48 views

Why there isn't a consistent key transform function of HMAC?

I am currently learning, the internal working of HMAC. There exists a key transformation process in the beginning, which works as follows:- Make the length of $K$ (Key) equal to $B$ (number of bits ...
27 views

How to check the strength of a symmetric key cryptographic algorithm (New/I designed) [on hold]

Reliability/Strength Test Needed I have designed a symmetric key cryptographic algorithm on my own and developed it.(block cipher)I need to test this algorithm's reliability or how much strong or how ...
17 views

Simple Mechanisms For Hiding Data in Images [on hold]

My teacher for extra credit said we can do a paper on cryptography of our chosing. I thought I would chose ways of hiding and passing data without anyone knowing. I figure I may as well ask the ...
39 views

stream ciphering question

If I have the size of the block and the size of the data input, how can I calculate the number of bits to the pad before the data entry process? I tried 2 ^ n (n is a data input byte), but this did ...
31 views

Authentication and encryption using a simplex communication channel

Is it possible to authenticate a client with encryption on a simplex communication channel without the use of authoritative root certs?
77 views

Why is the NIST recommendation for the private key exponent so much smaller than the modulus?

NIST recommends a 256-bit private key exponent for DLP with a 3072-bit modulus. This question answered how the modulus was chosen/calculated, however, why isn't the private key size closer to the ...
65 views

A hash-based pseudorandom function

Let $H()$ be a cryptographic hash function. Question: Can we consider $c= H(r||i)$ as a pseudorandom value, where $i$ is a public value, $1\leq i\leq n$, and $r$ is a large uniformly random value/...
36 views

Alter CBC plaintext by altering IV [duplicate]

I am building on this answer. Essentially I have an initialisation vector $iv$, a ciphetext $c$ and a plaintext $p$. The plaintext was encrypted using AES CBC. The aim is to modify the first 4 ...
21 views

ECIES 1363a-2004 implementation in openssl [on hold]

I'm using openssl library to implement an ETSI standard and, more specifically, to realize communications with a PKI. To do that I must use the ECIES encryption scheme but it isn't implemented in ...
56 views

How to find prime number q in RSA?

To be assumed in RSA key generation algorithm $p$ is a constant prime number and $e$ is an arbitrary prime and also $d$ is an odd number that is relatively prime to $e$. Based on these conditions ...
57 views

What is a good, easy-to-implement hash algorithm for avoiding hash collisions?

I am working on a proxy dll for DirectX 9, and eventually DirectX 11, which dumps textures uploaded via the cpu to files on the disk. Crucial to some of the features I wish to implement is the ability ...
45 views

Interpretation of certain results of NIST Test Suite

I am using NIST Test suite on a PRNG and have a confusion regarding some specific results. Following is the part of the results: ...
28 views

About LFSR based M209 Cipher Machine

Can some one please express M209 Cipher Machine in terms of LFSR with Diagram or any simple method?
44 views

I need to send 16 bytes using ECC keys on a resource-constrained device

I have a system where a resource-constrained device has to send 16 bytes. It has its ECC key pair, and a peer's Public ECC Key. We're using the p256 curve. The device also has an AES-128 hardware ...
45 views

Can an encrypted message be derived from only keys?

I recently started teaching myself cryptography, and had an idea while reading up about basic ciphers. Instead of passing ciphertext between Person A and Person B, which can be broken if intercepted ...
4 views

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Shamir Secret Sharing: Using $a_0 \ldots a_k$ to store secret? [duplicate]

Let's assume I have a truly random secret $s$ that is 256 bits long, and I want to use SSS with e.g. $(k=4,n=8)$. The normal approach is to set $a_0=s$ and choose $a_1 \ldots a_{k-1}$ randomly, ...
33 views

Fastest implementation of SHA256 in software without Intel SHA Extension for a normal Intel CPU based PC [on hold]

I'm implementing SHA256 myself using a normal PC, it never supports SHA256 Extension of Intel. What implementation of SHA256 is the fastest in software without Intel SHA Extension, even faster than ...
541 views

Setting MAC field to all-zero to indicate unencrypted data

I'm currently working on a project where we transmit data between two systems. The data is generally encrypted before transmission, however there are certain transmissions that are unencrypted. We ...
31 views

Differential privacy RAPPOR article proof doubts

Recently I've been trying to understand the RAPPOR proof: \begin{eqnarray*} P(B' = b' | B = b^*) & = & \left(\frac{1}{2}f\right)^{b'_1}\left(1 - \frac{1}{2}f\right)^{1 - b'_1} \times \ldots \\...
45 views

What are the length of ciphertexts when 16 bytes and 18 bytes of plaintext using ECB?

What are the length of ciphertexts when 16 bytes and 18 bytes of plaintext are encrypted with AES using ECB mode?
40 views

Efficient protocols for set membership proofs with private sets

I found the paper on Efficient Protocols for Set Membership and Range Proofs in which efficient protocols for the following problem are discussed: Given a commitment $C_v$ to a value $v$ we want show ...
73 views

Enigma message decode errors, and protocols to prevent them

I was looking at some Enigma messages for some random reasons, and I wondered if there were ever issue pulling the correct words out the strings of characters of if there was a protocol for it. For ...
82 views

Double hash question

I would like a valid Bitcoin address (derived from a private key created by rolling a pair of hexadecimal dice 32 times) to be the private key of any private / public cryptography. So if I encrypt a ...
14 views

Schnorr authentication protocol vs Schnorr signature Scheme

As I understand the schnorr authentication protocol is an interactive protocol where a prover WLOG proves to a Verifier that he possesses the discrete log to some group element. If we use the Fiat-...
I have two ECDSA signatures $(r, s_1, z_1)$ and $(r, s_2, z_2)$ where $s_1 = (z_1 + r*x_1) / k$, and $s_2 = (z_2 + r*x_2) / k$. Can $x_1$ & $x_2$ be computed?
Factorization of the public value $N$ from the RSA cryptosystem
It is mentioned here that the public value $N=p*q$ of the RSA cryptosystem can be factorized if one of the factors is reused. Thus, if $N_1=p*q_1$ and $N_2=p*q_2$ and only $N_1$ and $N_2$ are known, ...