0
votes
0answers
23 views

Which parameters of the ATV-FHE scheme should be kept private?

I try to implement the ATV-FHE scheme as it is described in section 2 of this paper. I also read this paper that says how parameters should be chosen. Are there some parameters that must be kept ...
1
vote
0answers
20 views

Is using same key pair for both encryption and signing secure in RSA [duplicate]

In GPG, we can use same key pair for encryption and signing. Can't/Shouldn't we do this in RSA. I am using RSAES-OAEP and RSASSA-PSS, not raw RSA btw.
0
votes
0answers
27 views

what is the difference between one way function and hard core predicate?

Does anyone know what the difference between a one way function is and a hard core predicate? Are they related to each other or different?
0
votes
0answers
23 views

Difference between SHA1 and SHA1HMAC? [duplicate]

Can anyone let me know the difference between SHA1 and SHA1HMAC algo?
2
votes
3answers
919 views

random access stream cipher

Some time ago I was working in a pet project for a type of database engine. And I thought about securing the data in disk with encryption.. and since the main code was already developed.. I had a few ...
2
votes
1answer
52 views

Are private and public key sizes of Elliptic curve related?

I'm new to elliptic curve cryptography. I just want to know in the case where I take a random number (private key) and find its associated public key, does the size of the public key depends upon ...
3
votes
1answer
105 views

A (current or soon-to-be) NIST-recommended alternative to ECC?

So this comes from the professional rumor-mill, and I'm wondering if anyone might either debunk or shed light on this. My understanding is ECC is generally now preferred over RSA simply due to how ...
3
votes
1answer
78 views

gpg --gen-random quality level: is higher “better”?

The GNU Privacy Guard manual pages have this to say about using the gpg --gen-random 0|1|2 count command: Emit count random bytes of the given quality level 0, ...
0
votes
1answer
52 views

Is there a library-less implementation of DSA available to read? [closed]

Is there a pedagogical library-less implementation of DSA available to read? (Not ECDSA.) Obviously BigInteger and hash functions may be from libraries, but I want to read the implementation of all ...
2
votes
0answers
77 views

Why is SSL/TLS so complicated?

I'm new to SSL/TLS and I'm staring as a new security researcher. It appears to me that SSL/TLS protocol is needlessly complex for arriving at a shared secret. The complexity results in so many bugs ...
4
votes
2answers
108 views

How to compare performances of lattice-based and pairing-based IBE schemes

I try to compare the performances (cost of Enc, Dec, ... size of keys, ciphertexts, ...) of IBE schemes using lattices (LWE hardness assumption) or pairing (Diffie-Hellman hardness assumption). I've ...
3
votes
1answer
25 views

What communications security protocols exist that aren't based on PKC?

Lets say that you have two devices that need to communicate in a secure manner. These devices can share secrets before communication takes place (This sharing of secrets occurs over another secure ...
0
votes
0answers
39 views

In FHE over integers is each bit of the cyphertext encrypted under the new key?

In the paper Fully Homomorphic Encryption over the Integers, a method is shown for doing homomorphic encryption using only integers. The basic idea is that a bit m is encoded as a large integer c. ...
0
votes
1answer
26 views

How to compare two CSPRNGs? [duplicate]

Let's say I am given to CSPRNGs: RNG1 and RNG2. I want to select the best one of the two for cryptography. How should I do it? Any of the two RNGs can be initialized with a secret key during tests and ...
0
votes
0answers
77 views

How to decrypt RSA cipher text? [closed]

How can I decrypt an RSA cipher text in which I am only provided with a public key and the cipher text. The person who encrypted it made a mistake in taking the exponent.
1
vote
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
vote
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. ...
2
votes
1answer
39 views

Is there a single-use signature scheme, where a second use of the private key discloses it to the world?

With ECDSA (and possibly DSA too) I'm aware that if the same value for $k$ is used with the same private key $D_A$ to sign two different messages, then anyone possessing the two messages $m_0$ and ...
2
votes
1answer
161 views

Best practises to generate IV for AES-CTR in this scenario

I'm building a cloud storage application that will store files on my servers. I want these files to be encrypted with AES in CTR mode and the key will be always the same. I'm wondering what would be ...
2
votes
2answers
37 views

With EC secp256k1 is there a way of transforming a function of the private key to a function of the public key?

A key pair has a private key $D_A$ and a public key $Q_A$. $D_A$ is an integer less than the curve's $n$. Is there any (boolean) function of the private key $f(D_A)$ which can be transformed into a ...
4
votes
1answer
121 views

What is scale-invariance notion of a fully homomorphic encryption scheme?

I read this paper https://eprint.iacr.org/2012/078.pdf and I didn't understand what does the author mean with scale-invariance perspective. The perspective in which we view the ciphertext is ...
3
votes
1answer
43 views

How many bits of an exponent are leaked when doing a powmod?

How many bits of the exponent $x$ are leaked when you calculate and reveal $g^x \pmod p$ for some generator $g$ of $\mathbb Z^∗_p$? The low bit of $x$ is obviously leaked: the low bit equals ...
2
votes
2answers
106 views

Is it possible to recover an RSA modulus from its signatures?

Let's say that you have some small number of RSA signatures of known data: you know some pairs $(m_k, c_k)$ such that ${c_k}^e \equiv m_k \pmod n$. If you know $e$, because probably it's one of $\{3, ...
6
votes
1answer
115 views

Is there any reason not to use Single-Key EM with AES and a constant key?

I've read recently the paper "Minimalism in Cryptography: The Even-Mansour Scheme Revisited" by Dunkelman, Keller and Shamir where it is claimed that the following construction (Single-Key EM) is ...
0
votes
3answers
61 views

Which method to generate one time password?

I'm looking for a concrete algorithm to generate one time passwords. The situation is as follows: Alice and Bob exchanged a passphrase over a secure channel in the beginning. They want to ...
2
votes
1answer
66 views
1
vote
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 ...
8
votes
4answers
376 views

Is there a public key encryption scheme with optimal key size?

Symmetric encryption schemes such as AES have known security levels equal to their key sizes (i.e. breaking an encryption with an $n$ bit key needs about $2^n$ work steps). Elliptic curve encryption ...
0
votes
0answers
23 views

Intermediate values for testing Blowfish

I am trying to implement the Blowfish algorithm in VHDL. To debug my code, I need the intermediate values of s-box and P vectors after each iteration. Where can I find this data set? p.s :- I know ...
0
votes
1answer
140 views
1
vote
1answer
114 views

With ECDSA is there a way for the verifier to calculate any properties of $k$?

With ECDSA, given $(r,s)$ and $m$, is there a way for a verifier to calculate any (boolean) properties of $k$, without knowing $k$ or the private key $D_A$? (I understand that $k$ should be random, ...
3
votes
2answers
58 views

How does the size of the prime affect Elliptic Curve Bit Security?

I am using the MIRACL Library to implement an Elliptic Curve Diffie Hellman based Key Exchange according to ECDH-Scheme-Wikipedia. Referring to the Miracl Docs they suggest a few curves. Each curve ...
4
votes
3answers
171 views

Is there a way to prove equality of plaintext that was encrypted using different public keys?

Imagine if Alice encrypts message to Bob (using public key $P_{bob}$) and then Bob encrypts the same message to Carol (using $P_{carol}$). Is there a way for Bob to prove that: $P_{carol}$ was ...
4
votes
0answers
160 views

Salary Negotiation Problem

Imagine Alice is applying for a new job. Alice has an idea of the minimum salary that she is willing to accept—let's call this value A. Bob, the hiring manager for ...
2
votes
3answers
197 views

One Time Pads and reuse of the decrypted message?

How is it insecure when Alice encrypts a message with a One-Time-Pad to Bob, and Bob then uses the decrypted message from Alice as the next One-Time-Pad? For example: Alice sends Bob a message ...
1
vote
1answer
100 views

Storing a secure key in an embedded device's memory

I am working on an embedded device which send/receive data and stored them in ciphertext mode (encrypted mode ). Now what's best approach for storing Keys (I used ARM CORTEX M series MCU) ? Storing ...
2
votes
2answers
273 views

Reusing message in One Time Pad

One of the main rules of the OTP is, that a key should never ever be reused. But if we use some commutative operation (XOR for example) for generating the cipher text, then I don't see any difference ...
3
votes
1answer
118 views

How can you produce visual cryptography?

I would like to be able to "code" images such as the one seen here on Wikipedia. Is this generally produced with software, or does this require complex programming? Ideally, I would love to be able ...
4
votes
0answers
123 views

Explanation of part of a visual cryptography algorithm

I have been working on a project involving visual cryptography and I am stuck with the following problem. My question is related to this paper, AN IMPROVED VISUAL CRYPTOGRAPHY SCHEME FOR SECRET ...
1
vote
1answer
44 views

Explanation of vector in Visual Cryptography

I'm starting to study about visual cryptography, but I am stuck with the following problem. On paper "Visual Cryptography" by Moni Naor and Adi Shamir, on page 6. How to read/what is the meaning of ...
1
vote
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 ...
2
votes
1answer
230 views

Public Key Encryption using ECDHE and AES-GCM

Using a text book example, Alice and Bob want to communicate securely using encrypted messages over an insecure channel (the Internet). Alice and Bob have decided to use ECDH (using ephemeral keys ...
0
votes
1answer
38 views

Understanding SSL vulnerability within Apple's GOTOFAIL

Currently learning and reading about the fascinating SSL Key Exchange and came upon the Apple GOTOFAIL incident back in 2014. I'm going through the code during that time and came across this section. ...
3
votes
2answers
400 views

Algorithm for generating OAuth tokens

I'm trying to find a good algorithm for generating authorization codes, access tokens and refresh tokens in an API. Currently, I am looking into the following setup: Tokens are generated using the ...
3
votes
3answers
683 views

Is it usual for a signed message to contain the public key of the signer?

In protocols/systems which use ECDSA, is it common for the message to contain the public key of the message signer? If not, how do recipients know that the message has been signed by the correct ...
2
votes
1answer
203 views

Hashing passwords

The common way to store passwords in web applications is this form: $$hash(password||salt)$$ Does it make sense to store them in the following form instead:? ...
2
votes
2answers
104 views

How do you communicate the hash function used with RSA signing?

When it comes to RSA signing, I understand why you need to hash the data before signing it, but don't you need to communicate what hash algorithm you use to whoever will need to verify the signature? ...
-2
votes
2answers
121 views

Why are there so many stream ciphers out there and even ongoing research?

What make them better than OTP using a CSPRNG initialized with a secret key?
1
vote
0answers
21 views

EC algorithm to derive bits/keys and sign/verify [duplicate]

Looking at the question “ECDSA vs ECIES vs ECDH” it appears that you can either have a tool that can derive keys or bits, or can be used to sign and verify something. Is there an EC way to do both ...
2
votes
2answers
125 views

Possible to guess RSA public key $e$ using $n$ and $\phi$

We know that if $n$ and $\phi$ is known, then it is possible to find $p$ and $q$ (initial prime numbers). I have following the questions: Assume the public key $e$ is not known, how difficult would ...

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