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# Questions tagged [public-key]

An asymmetric cipher is an encryption scheme using a pair of keys, one to encrypt and a second to decrypt a message. This way the encrypting key need not be kept secret to ensure a private communication. Similarly in public key authentication, the verification key can be public and the signing key private.

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### Given a 'good' basis for a lattice, how can we solve the CVP?

I'm doing a little bit of reading about lattices. I read that if we can find a 'short' basis for our given lattice, we can solve CVP and SVP very efficiently. However, the paper didn't describe an ...
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### Why is recipient hashed in this Sign/Encrypt/Sign proposal?

Own research In my journey into trying to understand PGP, and public key singing and encryption as a whole, I came across this answer on CE. It is an answer to a question with the title: Should we ...
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### Where do the PKs come from in Bluetooth device?

I am studying the Elliptic Curve Diffie-Hellman (ECDH) on Bluetooth 4.2. There are some questions about the PK.. Where do these public and private keys come from? Who defines them? and Will it ...
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### What public-key encryption protocol can use the same key pair as ECDSA?

Assume we wanted to use the same ECDSA public/private key pair (drawn for standard ECC parameters, perhaps P-256) for both its intended use (public-key signature), and for public-key encryption; this ...
241 views

### Zero knowledge proof for Paillier addition under multiple keys

Suppose $m_0, m_1, m_2 \in \mathbb{N}$ such that $m_0 = m_1 + m_2$, $m_i > 0$ (none of them can be 0 or lower) Under a Paillier cryptosystem, set $e_0 = E(m_0, r_0)$ for a public key $(g_0, n_0)$ ...
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### Montgomery modular multiplication – confusion with subtraction of modulus

I'm reading the paper “COMPARISON OF SCALABLE MONTGOMERY MODULAR MULTIPLICATION IMPLEMENTATIONS EMBEDDED IN RECONFIGURABLE HARDWARE” (PDF) on hardware algorithms for montgomery multiplication for ...
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### show how LWE errors can have a greater impact on result

Hi weve been given the following question in one of our classes but have not been taught anything about it and is worded strangely. It is to show how the LWE problem works by showing how small errors ...
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### Chosen Plaintext Attack and Chosen Multiple-Plaintext Attack

The original CPA game: The adversary gives two arbitrary messages $m_0$ and $m_1$ to a challenger; The challenger encrypts an arbitrary message $m_u$, $u∈\{0,1\}$ , and sends the ciphertext to the ...
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### How long does it take to brute force Blowfish-448?

I am conducting an investigation on the efficiency of AES and Blowfish with regards to memory when encrypting data of varying sizes. I open my essay with an introduction as to what encryption is and ...
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### Can “PrivateKey+MagicValue” decode pre-encoded data without intermediate key?

Let's say I want to build a public repository of encrypted files. EncA(FileA) EncB(FileB) ...
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### How to safely double-encrypt a secret?

Imagine two persons: Alice and Bob. We have a generated secret value that is valuable and has to be encrypted in a way that both can't reveal the value on their own but only when they both confirm. ...
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### Feasible attacks on ECRSA cryptosystem

In ECRSA cryptosystem, I want to know the feasible attacks. For illustrations we have two prime $p$ and $q$ such that $p \equiv 2 \pmod 3$, $q \equiv 2 \pmod 3$ and generate key pair as follows: n = ...
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### MITM Attack on Key Exchange Protocols

I was doing research on this attack and I am wondering, why is Diffie-Hellman always associated with such an attack? ​ Aren't other public key cryptography schemes vulnerable to the same kind of ...
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### How do I prove that a bit by bit PKE scheme (that is IND-CPA secure) for an n-bit message is not IND-CCA-2 secure?

Gen generates Pk and Sk (l bits each), Enc encrypts m (length l) but by bit using each bit of Pk respectively, Dec decrypts ciphertext bit by bit using each bit of Sk respectively. How do I prove this ...
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### Signing integers and UUIDs and restoring them from a third party server without tampering

I'm educating myself about cryptography. I know this is a long one, but please, bear with me. :) Now I have a scenario in my mind and I'd like to ask if what I've thought is sound (enough), what more ...
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### How can I make a message into a blocks for NTRU?

I have more bits than the degree of the NTRU polynomial. For example: $x^{11}-1$ message: Hello (I am using ascii, 8 bits for 1 symbol) got: ...
275 views

### Threshold signatures vs. certificate authority+voting verification

Perhaps a silly question, but I am wondering what the advantages are of threshold signatures. Let's consider the following two signature schemes: $(t,n)$-threshold signature with a trusted dealer, i....
136 views

### Prevent/minimize replay attacks in public message board

Assume we have a public message board where anyone can send a message to. If plain messages are used, anyone can impersonate anyone. The goal is to disallow impersonations. We can use public key ...
I'm Implementing a protocol that uses masking techniques (or blinding factors), so we can mask a value $y_0$ as $m_0=y_0 \cdot r_0$ where $y_0 \in \mathbb{Z}_p$ and \$r_0 \stackrel {R}\leftarrow \...