# Tagged Questions

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 ...

750 views

### Is it possible to reduce the size of an RSA key?

The details about what an RSA key is made up of are explained succinctly here. Is it possible to reduce the amount of data that's usually packaged with the (private) key and then derive it later?
40 views

### How to use a secret to allow the generation of public keys, where the private keys can be calculated later

Alice has a secret S and publishes some public information P, about S which is insufficient ...
46 views

### 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 ...
36 views

### Can I expand the modular of an encryption scheme?

Take the lifted ElGamal as an example: suppose the original ciphertext is $<g^y ~mod~q,~g^m~mod~q>$. After some calculations, $m$ could be large enough to do modular. But I don't want $m$ to be ...
219 views

### Signature to prove of ownership of arbitrary sized data

I am familiar with public key signatures, but I was wondering if there is a method to accomplish the following. Suppose I publish a file (say a PDF article) on a peer to peer network. How can I ...
52 views

### What is the most an adversary can do in the context of public key masquerading?

Suppose two parties A and B are using a public-key encryption scheme in order to communicate securely. A and B both have a public/private key pair: $$A: (P_A, S_A), B: (P_B, S_B)$$ and A already ...
90 views

### public/private key: is it possible to have master public/private key

This may be a very primitive question which might not be possible but I have this question to understand. Assume Yahoo provides a messenger where yahoo users can chat in secure way (end-end ...
142 views

### How to use CRT to compute 4 square roots while decryption in Rabin Cryptosystem

I'm reading Rabin Cryptosystem which requires to compute 4 square roots $r, -r, s,- s$ while decryption of cipher text $c$ such that $$r = (y_p \times p \times m_q + y_q \times q \times m_p) \mod n$$...
293 views

### Is there a difference between asking for a signature and asking for a decryption in challenge-response authentication?

Consider the following two authentication schemes. In both cases the server knows a public key of the client (for a signature system in the first and an encryption system in the second case). Scheme ...
931 views

553 views

### How feasible would it be to generate 300 million public key pairs in 8 hours?

Assume there is a hypothetical situation where one would need to generate hundreds of millions of public key pairs of reasonable strength in a limited time. What would be required in terms of ...
3k views

### Why is RSA encryption significantly faster than decryption?

I am designing an implementation of RSA . I recorded computation times in Java by using System.currentTimeMillis(). It returned an encryption time of 0.05 ms and ...