1
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0answers
26 views

Does CP-ABE have any disincentive to share secret keys

I want to use a CP-ABE scheme to encrypt data to be accessed by multiple unknown (at time of encryption) users. Reading the papers related to CP-ABE, there does not appear to be any disincentive for ...
1
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0answers
39 views

How to find the integer multiplicand from given two points?

I have two points on an elliptic curve $P(x_1,y_1)$ and $Q(x_2,y_2)$ and a scalar value $x$, where $P=x \cdot Q$. What is the best way that I could figure out the value of $x$? Given that I know all ...
1
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0answers
53 views

Upper bound on r* on page 7 in the Scale Invariant Fully Homomorphic Encryption over the Integers paper

I was hoping to get some clarification on how the bound on r* was calculated (bottom of page #7). I'm trying to reproduce the results that have been shown, however I keep getting a slightly smaller ...
1
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0answers
40 views

Is this ECC based messaging method secure?

I developing an encrypted messaging for ZeroNet (aP2P file-based network, website: zeronet.io) and would like to have some guidelines if any of this could work. My first idea: In ZeroNet every user ...
1
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0answers
47 views

on broadcast encryption

I've read the following paper and have one question on it. M. Luby and J. Staddon, "Combinatorial Bounds for Broadcast Encryption", EUROCRYPT'98. On page 523 (12th page of the paper) the authors say ...
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0answers
51 views

Grouping in BGN

The below equation is mentioned in Homomorphic Encryption and the BGN Cryptosystem (pdf, page 4): Mult(pk, $C_1$, $C_2$): Choose $u \xleftarrow{R} [1, n]$ and output $D = \hat{e}(C_1, C_2) \cdot ...
1
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0answers
62 views

Calculating Phi(M) and D for RSA decryption given p,q,e

I've been given a message in 4 digit numbers but it doesn't seem to work when I use my calculated values for phi(m) and d. If I'm correct phi(m) = (p-1)(q-1) correct? And d is given by ed = ...
1
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0answers
21 views

Proving for a single input vs several inputs. Is there any difference?

I am working on a new protocol for pattern matching. While defining the ideal functionality, it is possible to say: Alice sends $p$ and Bob sends $T$ to the ideal functionality. i.e. searching for ...
1
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0answers
91 views

When would you use KP-ABE over CP-ABE?

When would you use KP-ABE over CP-ABE or vice versa? I started this question as I am having problems abstracting the pros and cons between KPABE and CPABE. This is not an assignment question. I have ...
1
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0answers
121 views

Are there key collisions in AES-192, AES-256?

Suppose we have a single, fixed plaintext block $p$ of 128 bits. Call the set of all possible 128 bit blocks $B$. We could define fixed plaintext AES-128 as a function $f(k) \to B$ that takes a 128 ...
1
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0answers
16 views

Remotely Verify File Timestamp

I'm working for a professor to build a platform for students to take midterms and finals online. The student downloads the test during class (when the professor makes the test available on the server ...
1
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0answers
39 views

ECDH security when no KDF is used

Let's suppose our device performs ECDH with a fixed, unknown, private key $prv$. It accepts as input any point $Q$ lying in the proper subgroup of the proper ellipict curve, then computes: $P = ...
1
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0answers
15 views

How to calculate LOW(b) and HIGH(b) in spritz cryptography

I try to implement spritz cryptography like this paper . But I don't know how to calculate LOW(b) and HIGH(b). In paper page 7. ...
1
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0answers
43 views

Can you explain “k out of n” from the VCS paper by Naor and Shamir

I am new to visual cryptography. I’ve just read the paper “Visual Cryptography” by Moni Naor and Adi Shamir and I'm stuck on the chapter about the “$k$ out of $n$” construction. I am aware that, on ...
1
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0answers
51 views

Usefulness of ability to calculate $m^{p+q}$ with RSA

I noticed that with only an RSA public key, it is possible/tractable to calculate $m^{p+q} \pmod n$ for any $m$ without knowing $p$ or $q$. Namely, $m^{p+q} \equiv m^{n+1} \pmod n$. (This follows ...
1
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0answers
31 views

How to generate public key for ATV-FHE scheme?

I want to implement the ATV-FHE scheme as it is described here https://eprint.iacr.org/2014/039.pdf. How to generate the public key? Should I compute it as indicated in section 2 : $h(i) = ...
1
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0answers
104 views

Simplest way for strong cryptography in chat

I am a beginner in cryptography and I am interested for several weeks on this for my chat application. Basically, it is a centralized model. All messages are stored and potentially visible by ...
1
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0answers
51 views

equation of mixcolumn in the aes field

$c(y) = (03)y^3 + (01) y^2 + (01) y + (02)$ Let $d = (01)b$ in the AES field $GF(2^8)$. Provide exact equations for the bits $d_i, 0 \leq i \leq 7$, in terms of the bits $b_i$ of b. Can ...
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0answers
116 views

Obtain Enigma key having a encrypted text and the plain text

I have an Enigma message and I know what the original message is (a repetition of the same letter). Is it possible obtain the enigma key? I only know what kind of Enigma machine is it, but I need to ...
1
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0answers
77 views

What is the 'identity function' in AES?

I'm trying to understand how AES works. I got as far as knowing how a password is converted to an unifinished key with the PBKDF2 function. After that RFC3962 says that an AES useable key most be ...
1
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0answers
43 views

Designing an AES-based protocol for controlling and acessing ioT boards via RF

I'm designing an open ioT protocol to be used on ioT boards based on Texas Instruments RF-based MCUs. These MCUs have an AES module to easily encrypt and decrypt AES content, so that's why I choose a ...
1
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0answers
505 views

What is the most secure encryption algorithm to encrypt my password database?

The password manager I use lets me choose an algorithm from the list below in order to encrypt my password database: Microsoft Base Cryptographic Provider v1.0: RC2-128 RC4-128 DES-56 3DES TWO ...
1
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0answers
70 views

What is the lightweight key exchange protocol of choice?

Assume I have to implement a secure channel protocol by myself. Assume further that for some obscure reasons (library restrictions?) I can't use any of the pre-made libraries for SSH, TLS and such. ...
1
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0answers
93 views

Fingerprint RSA public key in PKCS1 format

I can't find anywhere details on how to fingerprint a public RSA key in PKCS1 format. There are a lot of examples on the internet on how to fingerprint an RSA public key in openssh format using ...
1
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0answers
108 views

Solving Vigenére with unknown alphabet

I'm trying to decrypt a cipher that I suppose has been encrypted with Vigenére. However I came about the following thought: The cipher consists of characters from ...
1
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0answers
57 views

Binary equation with encryption

I'm trying to test the ring signature scheme proposed by Rivest Shamir and Tauman in the famous paper "How to leak a secret". One of the step consist in 4) the signer solves the following ring ...
1
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0answers
173 views

Best way to implement secure client/server communication in Python

For a college programming assignment I have to implement a secure communication protocol between a server and one or more clients. Upon instantiation of the server program, a file is generated, call ...
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0answers
44 views

ABE Attributes Based Encryption

I have a question . How the system know the attributes of the users to be after that as a public key in ABE?
1
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0answers
42 views

PKCS#11 Sessions

I am maintaining an application that uses PKCS#11 to talk to a smartcard. Somehow a session gets generated, but i cant figure out where in the code. I am using c# and the PKCS11Interop wrapper. The ...
1
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0answers
36 views

Is it possbile to get same set of public and private keys twice while creating CSR ? If so where does the conflict happens !?

I'm new to cryptography and please clarify if my below assumption is wrong. Lets assume, that two different banks creating CSR and they get identical public and private key pairs of RSA. In such ...
1
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0answers
165 views

Is there specific name for simple XOR with ADD/SUB encoding?

Several years ago a group of malware authors began using code like this: for (j = 0; j < length; j++) ptr[j] = (ptr[j] ^ VALUEA) - VALUEB; for encoding, and ...
1
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0answers
42 views

Are there any existing ASN.1 structures for transferring symmetric keys?

Is there any reasonable ASN.1 standard to encode symmetric keys? I found PSKC, but it seems extremely heavy, and I can't quite find any library (e.g. bouncycastle) that would simplify using it. If ...
1
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0answers
25 views

LFSR, different bits from different initial states

Suppose we useLFSR, which gives output $x_1x_2x_3\dots$ from some particular initial state. From another state, different from previous, same LSFR though, it gives sequence $y_1y_2y_3\dots$ ...
1
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0answers
39 views

Symmetric stream cipher, is it known?

I am thinking on a simple symmetric stream cipher. My first idea is the following: The key is a set of array of random bytes ($\underline{k}_1$ ... $\underline{k}_n$), whose length is $l_1$, $l_2$, ...
1
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0answers
31 views

Where can I find a versatile PKI and library leveraging curve25519?

I note that Things that use Curve25519 provides a long list of protocols, software, and libraries that leverage curve25519, but I'm wondering if there is any such software that more fully implements a ...
1
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0answers
22 views

Is there a system where I can securely store a secret value and compare a semi-ambiguous input to it?

I have an idea for a new kind of mobile phone lock screen. When you first create your pattern, you put together a series of colors and compass directions from the following choices: Red, Blue, Yellow, ...
1
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0answers
55 views

2 round GOST_28147-89 cipher distinguisher

So, here is the scheme of how this will look graphically: The deal is to present distinguisher for this cipher. First of all here is my drafts: Way 1 Assume that distinguisher displays in ...
1
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0answers
640 views

Decrypt using OpenSSL produces packing errors

I am receiving an encrypted file and it's key from a partner. The Key has itself been encrypted using our Digital Certificate Public Key, though I don't know exactly how. The partner has instructed me ...
1
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0answers
47 views

What is the hardness in Decisional Linear Assumption (DLIN)?

I had understood what does the DLIN assumption means and here is a related question. But I fail to understand the 'real hardness' in this problem. I would be grateful if someone can help me to ...
1
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0answers
68 views

In DGHV FHE, why noise $r$ can be in $(-2^{\rho'}, 0)$?

"Fully Homomorphic Encryption over the Integer" described a simple FHE scheme based on the GACD assumption. Its encryption function (on page 6) has the form $c \leftarrow (m + 2r + 2*\sum_{i \in S} ...
1
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0answers
94 views

CPA-security proof of “l-padded RSA” encryption scheme

The 10.9 exercise from the Katz-Lindell textbook creates a lot of confusion, let me state it here. Consider the following experiment for an algorithm $A$ and a function $l$ with $l(n) \leq 2n-2$ for ...
1
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0answers
63 views

Ciphertext size of any CPA-secure public-key encryption scheme

I know that, for any CPA-secure public-key encryption scheme, the size of the ciphertext after encrypting a single bit is superlogarithmic in the security parameter. That is, for $(pk,sk) \leftarrow ...
1
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0answers
83 views

Why is there no 'ECDSA' version of 'DHE-RSA-CHACHA20-POLY1305'?

So I was just checking my TLS cipherlist and noticed that there was a 'DSS' / DSA / ECDSA version of every ...
1
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0answers
131 views

Example describing Baek and Zheng’s threshold identity-based decryption scheme

I am trying to work through an example of Baek and Zheng’s “threshold identity-based decryption scheme” and I tried a lot to solve this, but somewhere I’m doing something wrong. I hope someone can ...
1
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0answers
337 views

How to calculate the avalanche effect in aes-256?

I am a beginner in cryptography. I'm testing AES-128 bit key, AES-256 bit key, and Camellia-256 bit key. I'm using AES-256, 9 character salt, CBC mode, PKCS #5 padding, and the ciphertext using ...
1
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0answers
65 views

Understanding a faulty Needam-Schroeder protocol

Give this mutual-authentication protocol (along with the attack) in which Alice wants to communicate with Bob, I can't understand how the attack works. A chooses $N$ (nonce) and sends to C (trusted ...
1
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0answers
272 views

What are the problems of IKEv1 aggressive mode (compared to IKEv1 main mode or IKEv2)?

I would like to seek confirmation/clarification of the following statements about IKE: IKEv1 aggressive mode is supposed to be “insecure” if used with PSK. But as far as I can see, correct (or more ...
1
vote
0answers
56 views

FFX Encryption over alphabet of arbitrary radix

I understand how standard numeric FPE using a halved string in cycled Feistel networks is constructed and operates. I then read the paper regarding FFX encryption which should allow for any non-binary ...
1
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0answers
84 views

Prove that certain amount of data was stored

I'm looking for a way to prove that a certain amount of data was stored, through some easily verifiable piece of information. Similarly to how proof-of-work can prove through a hash that a certain ...
1
vote
0answers
50 views

What consequences do the plaintext space size has on the performances in the BGV scheme?

In the BGV paper [1], the authors say in §5.4 that you can have $\mathbb{Z}_p$ as plaintext size with a large $p$. What is the impact of the size of $p$ on the ciphertext size and computational work ...

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