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.

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.

Public key cryptography describes all cryptographic algorithms which have a pair of keys, one key that performs encryption and one key that performs decryption. One of these keys is made available publicly, allowing anyone to send messages that only the holder of the private key can read. You should use this tag for questions on any such system, for example RSA or Elliptic Curve Cryptography.

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How does asymmetric encryption work?

I've always been interested in encryption but I have never found a good explanation (beginners explanation) of how encryption with public key and decryption with private key works. How does it encrypt something with one key and decipher it with…
Senad Meškin
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Multiple private keys for single public key

I am currently working in security in mobile ad-hoc networks. I have several clusters, and I want to send some data encrypted with its public key, from the cluster head to the cluster members. I assume that each member has its own private key so it…
yomna
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Is there an asymmetric encryption protocol which provides arbitrarily many seemingly unrelated public keys for a single private key?

I am looking for an encryption protocol with the following properties. Alice has a private key $x$. Using this private key, she chooses public key $p$ corresponding to this private key. She let's Bob know about this public key. Bob then uses this…
zabop
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Which public key cryptosystems are not based on number theory?

Are there any public key cryptographic systems whose hardness assumptions don't involve number theoretic problems?
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Suppose I capture encrypted data that I want to decrypt. Could I use a server farm to decrypt?

For argument's sake, let's say that I'm a bad actor who produces malware. I've infected around 10,000 computers and smartphones with my malware, which runs in the background and can be used to make someone else's machine run calculations for…
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Modular Inverse as a Problem

Given a modulus $N$ and a number $a$, a multiplicative inverse exists for $a$ if $a$ and $N$ are coprime. Why isn’t there a cryptosystem that uses this as a computational problem? Example Alice and Bob agree on a public modulus $N$ and a public…
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Why are key lengths in asymmetric algorithms typically longer than key lengths in symmetric algorithms?

Apologies if this is a duplicate question. I did search prior to posting :-) I think it may be somewhat related to my other question here but I think it's different enough to warrant a separate question page. Symmetric algorithm key lengths seem…
Mike B
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The relationship between a private and public key?

It's known that the relationship between public and private key allows data encrypted by the public key to be decrypted only by the corresponding private key. As I understand it, this means that normally there is a relation between them (regarding…
TooCool
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Do public/private pairs work both ways?

Public/private key algorithms such as RSA encrypt a message with a private key but only decrypted with another (mathematically related) key. Can the public key decrypt the messages encrypted with the private key and the private key decrypt messages…
Filip Haglund
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Does any public key crypto support and/or allow a 3rd party "control-key"?

My question is based on the following situation: Bob and Alice work for a company that expects them to exchange data encrypted. They could do so using regular public-key cryptography, but Joe (their boss) wants to be part of the procedure to ensure…
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In a lattice, how can one define a good basis and a bad basis?

When it comes to lattice based cryptographic systems, all the literature talks about, good bases and bad bases. How does one define what a good basis is and what a bad basis is?
sashank
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Why is a 2048-bit public RSA key represented by 540 hexadecimal characters in X.509 Certificates?

In the public certificate, an RSA public key specified as 2048 bits long is represented by 540 hexadecimal characters. Converted to base-2, this yields 2160 bits, 112 more than the stated 2048.
sentinel
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What kind of attack could one perform if you generate private keys using SHA3(master_key || nonce)?

I'm aware HMAC is more appropriate than SHA3(master_key || nonce), but I do not understand what kind of attack could be performed against that strategy. How could an attacker use this fact to figure out your private keys?
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Can an RSA public key be generated without ever knowing the factors?

Context: http://blog.cryptographyengineering.com/2013/12/a-few-more-notes-on-nsa-random-number.html Assume I wanted to use RSA as the basis for a hash function or DRBG. Also assume that my construct would be insecure if someone were to have the…
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Can one tell private key entropy from a public key?

Given a weak entropy private key and its associated public key. Can we predict low entropy from the private key by examining the public key? In other words, is the low entropy from the private key in some ways 'reflected' in the public key? What…
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